MRI compatible interventional medical devices, and methods of manufacture and use

Abstract

The disclosure relates to methods of imaging a portion of a body vessel using magnetic resonance imaging (MR.I), methods of performing interventional medical treatment under MRI, interventional medical devices, such as wire guides, useful in performing treatment under MRI, and methods of making interventional medical devices. A method of imaging a portion of a body vessel of a patient using MRI includes advancing through a body vessel an end of a wire guide comprising a continuous metal core member and a continuous jacket disposed over the entire core member through a body vessel and scanning the portion of the patient that is positioned within an MRI scanner and that includes a portion of the body vessel within which the end of the wire guide is disposed. A secondary medical device, such as a catheter, can be disposed over the wire guide and manipulated in the method.

Description

MRI COMPATIBLE INTERVENTIONAL MEDICAL DEVICES, AND METHODS OF MANUFACTURE AND USECROSS REFERENCE TO RELATED APPLICATION

[0001] I 'his application claims the benefit of US Pro visional Application No. 63 / 554,943 filed February 16, 2024, entitled MR! COMPATIBLE INTERVENTIONAL MEDICAL DEVICES, AND METHODS OF MANUFACTURE AND USE, which is hereby incorporated by reference.FIELD

[0002] The disclosure relates generally to the field of medical devices. More particularly, the disclosure relates to interventional medical devices, such as wire guides, useful in interventional procedures performed under magnetic resonance imaging (MRI), methods of imaging a portion of a body using MRI, methods of performing interventional medical treatment under MRI, and methods of making interventional medical devices.BACKGROUND

[0003] Interventional procedures conducted under MRI have several benefits over X-Ray- guided interventions. For example, the patient is not exposed to ionizing radiation. Also, MRI provides (he ability to characterize tissue and fluid flow during an interventional procedure. For at least these reasons, the use of interventional MRI is gaining wider acceptance and the number of procedures that can be performed under MRI is generally increasing.

[0004] The art provides only a limited number of interventional medical devices suitable for use under MRI, however, which continues to limit growth of the use of interventional MRI procedures. As a result, patients have not yet benefitted fully from interventional MRI technologies and, indeed, are often still limited to less convenient, and potentially less effective, options for certain treatments.

[0005] Wire guides are fundamental to the performance of interventional procedures, making the development of an MRI compatible wire guide a critical step in the wider adoption of interventional MRI proced ures. To date, development of MRI compatible wireguides has been limited. Needs remain, therefore, for new and -or improved MRI compatible wire guides and related methods, including methods of imaging a portion of a body vessel using MRI, methods of performing interventional medical treatment under MRI, and methods of making interventional medical devices. BRIEF SUMMARY OF SELECTED EXAMPLES

[0006] V arious example interventional medical devices useful in interventional procedures performed under MRI are described.

[0007] One example interventional medical device of the present disclosure is an MRI compatible wire guide. The wire guide includes a core member having a proximal end, a distal end. and a length between the proximal end and the distal end. The wire guide includes a first passive MRI marker disposed along the length of the core member, and a second passi ve MRI marker disposed along (he length of the core member and longitudinally spaced from the first passive MRI marker. One or more additional passive MRI markers can also be incorporated. The wire guide further includes a polymeric jacket that encapsulates the core member. In some forms, the wire guide has separate groups of markers, visibly distinct. In other forms, the wire guide has selections of passive MRI marker Tonning materials, volumes and / or arrangements thereof, designed to provide advantageous functionalities to the wire guide under MRI. In still other forms, a distal-most region of the wire guide bears one or a plurality of passive MR! markers, and is configured in the presence of the markers to exhibit desired mechanical properties,

[0008] Another example wire guide comprises a continuous core member formed of a metallic material and having an outer surface; and a jacket disposed on the core member such that the outer surface of the core member is fully encapsulated by the jacket.

[0009] Another example wire guide comprises a continuous core member formed of a metallic material and having an outer surface, the core member having a first susceptibility; a marker disposed on the outer surface of the core member and formed of a second metallic material having a second susceptibility that is different from the first susceptibility; and a jacket disposed on the core member and the marker such that no portion of the outer surface of the core member is exposed to the external environment surrounding the wire guide.

[6010] Another example wire guide comprises a continuous core member formed of a metallic material and having an outer surface, the core member having a first susceptibility; a jacket disposed on the core member such that no portion of the outer surface of the coremember is exposed to the external environment surrounding the wire guide; and a marker disposed within the thickness of the jacket and formed of a second metallic material having a second susceptibility that is different from the first susceptibility.

[0011] Various example methods of imaging a portion of a body vessel of a patient using MR.T are described.[00 U] An example method of imaging a portion of a body vessel of a patient using MRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of (he scanner of the MRI system will be present once the scanner of the system is activated; grasping a wire guide comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the distal end of the wire guide into the body vessel: advancing the distal end of the wire guide through the body vessel until the distal end of the wire guide is disposed at a first position within a first portion of the body vessel that is located within the scanner of (he MRI system; operating the scanner of (he MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel: obtaining a magnetic resonance image of the first portion of the body vessel; and withdrawing the wire guide from the body vessel.

[0013] Another example method of imaging a portion of a body vessel of a patient using MRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the M.R1 system will be present once (he scanner of the system is activated; grasping a wire guide comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the distal end of the wire guide into the body vessel; advancing the distal end of the wire guide through the body vessel until the distal end of the wire guide is disposed at a first position within a first portion of the body vessel that is located within the scanner of the MR! system: while advancing the distal end of (he wire guide through the body vessel of the patient, operating the scanner of the MRI system to scan the portion of the patient that Is positioned within the scanner and that includes the firstportion of the body vessel and obtaining a magnetic resonance image of the first portion of the body vessel; and withdrawing the wire guide from the body vessel.

[0014] Another example method of imaging a portion of a body vessel of a patient usingMRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the .MRI system will be present once the scanner of the system is activated; grasping a wire guide comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the distal end of the wire guide into the body vessel; advancing the distal end of the wire guide through the body vessel until the distal end of the wire guide is disposed at a first position within a first portion of the body vessel that is located within the scanner of the MRI system; while advancing the distal end of the wire guide through the body vessel of the patien t, repeatedly operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and repeatedly obtaining a magnetic resonance image of the first portion of the body vessel; and withdrawing the wire guide from the body vessel.

[0015] Various example methods of performing interventional medical treatment under MRI are also described.

[0016] An example method of performing interventional medical treatment under MRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated; grasping a wire guide ha ving a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over the wireguide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within said body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel; obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel.

[0017] Another example method of performing interventional medical treatment under MRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of (he system is activated; grasping a wire guide having a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over the wire guide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within said body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; while advancing the distal end of the wire guide through the body vessel of the patient, repeatedly operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and repeatedly obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel. Another example method of performing interventional medical treatment under MRIcomprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the sy stem is activated; grasping a wire guide ha ving a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting lhe wire guide distal end into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen: passing the medical device distal end over the wire guide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end .reaches said point of treatment within the body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; while advancing the medical device distal end over the wire guide and into the body vessel, repeatedly operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and repeatedly obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel.

[0018] Another example method of performing interventional medical treatment underMRI comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated; grasping a wire guide having a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and (he jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel: advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; graspinga medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over the wire guide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within the body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; while manipulating the medical device proximal end to produce a manipulation of the medical device distal cud a t the point of treatment, repeatedly operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and repeatedly obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel.

[0019] Another example method of performing interven tional medical treatmen t under MR1 comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated; grasping a wire guide having a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel; advancing the distal cud of the wire guide through said body vessel until (he distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MR! system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over the wire guide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within the body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; while advancing the wire guide distal end through the body vessel, advancing the medical device distal end over the wire guide into the body vessel, and manipulating the medical deviceproximal end, repeatedly operating the scanner of the M.RI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and repeatedly obtaining a magnetic resonance image of the first portion of the body vessel: withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel .

[0020] Various example methods of making wire guides are also described.

[0021] An example method of making a wire guide comprises forming a continuous core member of a metallic material, the continuous core member having an outer surface: and disposing a jacket on the continuous core member such that the outer surface of the core member is in continuous contact with the jacket and such that no portion of the outer surface of the core member is exposed to the ex ternal en vironment surrounding the wire guide. In these or other methods herein, a marker material can be adhered to an outer surface of the core member before disposing the jacket (e.g. by over-extrusion or heat shrinking), and / or a marker malerial can be disposed within the thickness of the jacket, e.g. after it is disposed on the core member.

[0022] Another example method of making a wire guide comprises forming a continuous core member formed of a metallic material and having an outer surface; disposing a jacket on the continuous core member such that the outer surface of the core member is in continuous contact with the jacket and such that no portion of the outer surface of the core member is exposed to the external environment surrounding the wire guide; evaluating the jacket to determine if the outer surface of the core member is in continuous contact with the jacket; and transferring the wire guide to an intended user of the wire guide only if the evaluating step results in a determination that the outer surface of the core member is in continuous contact with the jacket.

[0023] An example method of making a plurality of wire guides comprises forming a plurality of continuous core members, each continuous core member of the plurality of continuous core members formed of a metallic material and having an outer surface; disposing a jacket on the outer surface of each continuous core member such that the outer surface of each continuous core member is in continuous contact with the jacket and such that no portion of the outer surface of each continuous core member is exposed to the external environment surrounding the wire guide of the plurality of wire guides; evaluating each jacket to determine if the outer surface of each continuous core member is in continuous contact with the jacket disposed on the outer surface of the continuous core member. Anoptional step includes destroying any wire guides from the plurality of wire guides for which the evaluating step results in a detennination that the outer surface of the continuous core member is not in continuous contact with the jacket disposed on the continuous core member.

[0024] Additional understanding of these and other example methods of imaging a portion of a body vessel using MRI, methods of performing interventional medical treatment underMRI, interventional medical de vices, such as wire guides, useful in performing treatment under MRI, and methods of making interventional medical devices can be obtained by review of the detailed description of selected examples, below, and the referenced drawings.DESCRIPTION OF FIG U RES

[0025] FIG. I is a perspec tive view of an example interventional medical device.

[0026] FIG. 2 is a side view of the example interventional medical device illustrated in FIG. 1.

[0027] FIG. 3 is a lengthwise sectional view of the example interventional medical device illustrated in FIG. 1 , taken along line 3-3 in FIG. 2.

[0028] FIG, 4 is a magnified sectional view of the interventional medical device illustrated in FIG. 1 , taken along line 4-4 in FIG. 2.

[0029] FIG. 5 is a magnified sectional view of the interventional medical device illustrated in FIG. 1, taken along line 5-5 in FIG. 2,

[0030] FIG. 6 is a lengthwise sectional view, partially broken away, of another example interventional medical device.

[0031] FIG. 7 is a side view, partially device broken away, of another example interventional medical device.

[0032] FIG. 8 is a side view, partially broken away, of another example interventional medical device.

[0033] FIG. 9 is a side view, partially broken away, of another example interventional medical device.

[0034] FIG. 10 is a flowchart illustration of an example method of imaging a portion of a body vessel.

[0035] FIG, 1 1 is a flowchart illustration of an example method of performing interventional medical treatment under MRI.

[0036] FIG. 12 is a flowchart illustration of another example method of performing interventional medical treatment under MRI.

[0037] FIG. 13 is a flowchart representation of an example method of making a wire guide.

[0038] FIG, 14 is a flowchart representation of an example method of making a plurality of wire guides.

[0039] FIG. 15 illustrates graphical representations of raw RF-induced heating for various lest wire guide constructions over 2-7 m inutes of scanning in a 1.5T MRI system. Panels on the left represent measured temperature for scans of a wire guide having a continuous mtinolcore; panels on the right represent temperature rise normalized to the initial temperature for the corresponding panel on the left.

[0040] FIG. 16 presents data referenced in an Example described herein in tabular format.

[0041] FIG. 17 presents data referenced in an Example described herein in tabular format.

[0042] FIG. 18 presents data referenced in an Example described herein in tabular format.

[0043] FIG. 19 presents data referenced in an Example described herein in tabular format.

[0044] FIG, 20 presents an equation referenced in an Example described herein.

[0045] FIG, 21 presents an equation referenced in an Example described herein.FIG. 22 presents an equation referenced in an Example described herein.

[0046] FIG. 23 is a side view, partially broken away, of another example interventional medical device.

[0047] FIG. 24 is a side view, partially broken away, of another example interventional medical device.

[0048] FIG, 25 is a side view, partially broken away, of another example interventional medical device.

[0049] FIG. 26A is a cross-sectional view taken along line 26A-26A of FIG. 23 illustrating one embodiment of FIG. 23.

[0050] FIG. 26B is a cross-sectional view taken along line 26B-26B of FIG. 23 of the embodiment of FIG. 23 shown in FIG. 26A.

[0051] FIG. 27A is a cross-sectional view taken along line 26A-26A of FIG. 23 illustrating another embodiment of FIG, 23.

[0052] FIG, 27B is a cross-sectional view taken along line 26B-26B of FIG. 23 of the embodiment of FIG. 23 shown in FIG. 27A.

[0053] FIG. 27C is a cross-sectional view taken along line 26B-26B of FIG. 23 illustrating another embodiment of FIG. 23.

[0054] FIG. 28 is a cross-sectional view taken along line 26B-26B of FIG. 23 illustrating another embodiment of FIG. 23.

[0055] FIG, 29 is a side view, partially broken away, of another example interventional medical device.

[0056] FIG. 30 is a cross-sectional view taken along line 30-30 of FIG. 29.

[0057] FIG. 31 is a perspective view, partially broken away, of another example interventional medical device.DETAILED DE SCRI PTION OF SELECTED EXAMPLES

[0058] The following detailed description and the appended drawings describe and illustrate various example methods of imaging a portion of a body vessel using MRI, methods of performing interventional medical treatment under MRI, wire guides useful in performing interventional treatment under MRI, and methods of making wire guides. The description and illustration of these examples are provided to enable one skilled in the art to perform methods of imaging a portion of a body vessel using MRI, methods of performing interventional medical treatment under MRI, and methods of making interventional medical devices, and to make and use interventional medical devices, such as wire guides. The inclusion of detailed descriptions of these examples is not in tended to limit the scope of the invention, or its protection, in any manner. The invention is capable of being practiced or carried out in various ways and the examples described and illustrated herein are not considered exhaustive .

[0059] As used herein, the term "attached" refers to one member being secured to another member such that the members do not completely separate from each other during use performed in accordance wi th the intended use of an i tem that includes the members in their attached form.

[0060] As used herein, the term ’’circumference” refers to an external enclosing boundary of a body, element, or feature and does not impart any structural configuration on the body, element, or feature.

[0061] As used herein, the term "continuous" refers to a structural configuration of an element in which the element extends from a first terminal end of the element to a second terminal end of the element in an uninterrupted manner such that no additional terminal ends exist between the first and second terminal ends. The term includes structural configurations in which two structural members, such as segments of the same or different materials, are joined end-to-end such that: no internal terminal ends exist in the combined structure.

[0062] As used herein, the term "magnetic susceptibility" refers to the intrinsic property of a material that relates to how much the material will become magnetized in an applied magnetic field. When numeric values for magnetic susceptibility are provided herein, they refer to volume-based magnetic susceptibility in International System of Units (SI) values at 25°C. Some magnetic susceptibility values are given herein as parts per million ("ppm"), and personsskilled in the pertinent art will understand that the reference to ’’ppm" is equivalent to a reference to "x 1 O'S".

[0063] As used herein, the term "marker” refers to a discrete deposit of a first material on a second material such that the first material is visible under MRI and is distinguishable from the second material under MRI, a portion of an interventional device in which a first material has been incorporated into a second material such that the combination of the first and second materials is visible under MRI and is distinguishable from the second material under MRI, and a portion of an interventional device in which a material that forms a portion of an interventional device has been manipulated such that the portion is visible under MRI and is distinguishable from the remainder of the interventional device under MRI,

[0064] As used herein, the term ’’MRI system” refers to magnetic resonance equipment that includes a magnet and scanner and that is suitable for medical imaging purposes. The term incl udes MRI systems that define a bore within which a patient, or a portion of a patient, can be positioned, open MRI systems, and portable MRI systems that can be moved relative to a patient to position the patient, or a portion of the patient, relative to the scanner of the MRI system prior to initiation of an imaging procedure.

[0065] As used herein, the term ’’passive," in relation to a marker, refers to a marker that is either unpowered or powered exclusively by the electromagnetic field of a magnetic. resonance scanner.

[0066] As used herein, the term "susceptibility," when not immediately preceded by "magnetic," refers to the ability of an element to influence an external magnetic field.Susceptibility is dependent on various properties of an element, including the size, density, geometric configuration, volume, and other physical properties of the element, and the magnetic susceptibility of the material of which the element is formed.

[0067] As used herein, the term ’’treatment" refers to a medical procedure performed on or in a portion of a body of a patient. Examples of treatments include delivery of an agent to a site within a body vessel, modification of a local environment inside of a body vessel such as by heating or cooling, and removal of a tissue or portion of a tissue from a site within a body of a patient (i.e., biopsy).

[0068] As used herein, the term "wire" and refers to a strand or rod of material. The term does not require any particular cross-sectional shape, composition, physical properties, or production method by which a referenced element was made.

[0069] As used herein, the "maximum dimension" of a visible artifact refers to the maximum edge-to-edge distance of the visible artifact under MRI. Where a numeric value for the maximum dimension of a visible artifact is referenced or required to determine a feature disclosed herein, it is as determinable according to ASTM F2119-07 (2013) and using a primary field strength of 0.55T and the following parameters:

[0070] FIGS. 1 , 2, 3, 4, and 5 illustrate an example wire guide 100. The wire guide is an interventional medical device useful in interventional procedures performed under MRI. The wire guide 100 includes a core member 1 10 formed of a first materia! having a first susceptibility and a jacket 130 disposed on the core member 110. An optional marker 150 is attached to the core member 1 10 and, if included, is formed of a second material having a second susceptibility that is different from the first susceptibility. In embodiments in which a marker 150 is included, the first and second materials can be the same or different. Thus, the first and second materials can have the same or different magnetic susceptibility. If included, the marker 150 can be attached to the core member I 10 in any suitable manner, such as with an adhesive, swaging, plating or otherwise depositing the second material to adhere to the core member, or other suitable forms of attaching one member to another. Also if included, the jacket 130 is advantageously disposed over the external surface of the marker 150 to provide a desirable fully encapsulated structure, as described above,

[0071] T he core member 1 10 is a continuous elongate member having a proximal end 1 12, a distal end 1 .14, a lengthwise axis 102 extending between the proximal end 1 12 and the distal end. 1 14, and an axial length that extends from the proximal end 112 to the distal end 114, In this example, the core member 110 has an outer surface I 16 that is in continuous contact with the jacket 130. Importantly, the entire outer surface 1 16 is fully encapsulated bythe jacket 130. That is, no portion of the outer surface 1 16 of the core member 1 10 is exposed to the external environment surrounding the wire guide 110.

[0072] The core member 1 10 is preferably formed of a metallic material, such as a metal or an alloy, and can for example be a single, continuous wire of the metallic material. The core member 1 10 can be formed of any suitable metallic material and selection of a suitable metallic material for a core member in a wire guide according to an embodiment can be based on various considerations, including any desired handling characteristics and any material selected for a marker, if included. Examples of metallic materials considered suitable for the core member include, but are not limited to, shape memory alloys, including nickel-titanium alloys such as Nitinol, superelastic Nitinol, Superelastic Nitinol SB508 straight with black oxide, matte finished Nitinol, polished Nitinol, nickel chromium, nickel cobalt, tungsten, titanium, nickel oxide, cobalt chromium nickel molybdenum alloys, such as the alloy available under the trade name Blgiloy from Elgiloy Specially Metals (Elgin, IL), combinations of those described herein, and any other metallic materials considered suitable for a particular embodiment.

[0073] As described hi detail below, jacket 130 is a continuous jacket disposed over the entire length 104 of the core member 110. The continuous nature of the jacket 130 over the entire length 104 of the core member 1 10 is highly preferred in embodiments herein. Core member 1 10 can include features that aid in the detection of disruptions in the continuous nature of the jacket 130, which may aid in assuring use of wire guides having a truly continuous jacket 130, For example, core member 1 10 can include a high contrast color jacket on its surface, disposed under jacket 130. The high contrast color of this underlayment jacket is relative to any color of jacket 130. For example, if jacket 130 is a dark color, such as a black or grey, a bright underlayment jacket, such as a yellow jacket, provides a high contrast color that, if visible upon inspection prior to use of a wire guide, can alert a user to a disruption in the continuous nature of jacket 130, allowing the user to assess whether the wire guide should be used in a contemplated procedure. Also, the core member 110 can include a coating that is responsive to exposure to an external substance other than the jacket 130, such as water. For example, the core member 1 10 can include a coating that changes color if it contacts an external substance, such as water. The color change can be visible under ambient light or another wavelength, such as under ultraviolet or another wavelength. Inspecting a wire guide or plurality of wire guides for suitable color changes, under appropriate lightwavelengths, can be incorporated into methods of making a wire guide or a plurality of wire guide when the core member includes such a coating.

[0074] The core member 110 can have any suitable form and a skilled artisan will be able to select a suitable form for a wire guide according to a particular embodiment based on various considerations, including the intended use of the wire guide and the nature of anybody vessel within which the wire guide is intended to be placed. In the illustrated example, the core member 110 is a wire having a substantially continuous outer diameter along its length 104. A core member having a taper along a length at its distal end is also considered suitable.

[0075] The core member 1 10 can have any suitable axial length and a skilled artisan will be able to select a suitable length for a core member in a wire guide according to a particular embodiment based on various considerations, including the intended use of the wire guide and the nature of any body vessel within which the wire guide is intended to be placed. Examples of lengths considered suitable for a core member in a wire guide according to the present disclosure include, but are not limited to, lengths equal to, greater than, less than, or about 100 centimeters, 110 centimeters, 120 centimeters, 130 centimeters, 140 centimeters, 150 centimeters, 240 centimeters, 250 centimeters, 260 centimeters, 270 centimeters, 280 centimeters, between about 50 centimeters and about 350 centimeters, between about 100 centimeters and about 280 centimeters, between about 120 centimeters and about 260 centimeters, and any other length considered suitable for a wire guide according to a particular embodiment. The core member 1 10 can have any suitable outer diameter. The outer diameter of the core member 1 10 may be constant, or may vary'. In some forms, the core member 110 will have a segment of constant diameter extending from its proximal end that extends to a distal region having a tapered segment of decreasing outer diameter in the distal direction, to provide increasing flexibility to the distal region of the wire guide incorporating the core member 110. For example, in some forms, a distal-most 50 cm-long segmen t of the core member can include such a tapered portion, e.g. where the tapered portion has a length in the range of about 3 cm to about 50 cm, or about 3 cm to about 40 cm. In some forms, the tapered portion can continue to the distal end of the core member 1 10. In other forms, the tapered portion may terminate proximal of the distal end of the core member 110, and the core member 1 10 can have a distal smaller constant diameter segment that extends between the distal end of the tapered diameter segment and the distal end of the core member 1 10. Such a distal constant diameter segment in typical forms can have a length ofabout I cm to about 5 cm, or about 2 to about 4 cm. In some forms, the core member 1 10 will have a greatest outer diameter, typically occurring in a constant diameter segment extending from its proximal end as discussed above, in the range of about 0,2 mm to about 0,8 mm.

[0076] The jacket 130 is a continuous jacket disposed over the entire length 104 of the core member 1 10. As such, jacket fully encapsulates the core member 1 10. The jacket 130 has a proximal end 132, a distal end 134, and an axial length that: extends from the proximal end 132 to the distal end 134. The length of the jacket 130 is greater than the length of the core member 110, ensuring that each of the terminal surface 122 of the proximal end 132 and the terminal surface 124 of the distal end 134 of the core member 1 10 are fully covered by the jacket 130. As is shown, the proximal end 132 is provided by a proximal end wall of the jacket 130, the distal end 134 is provided by a distal end wall of the jacket 130, the proximal end terminal surface 122 of the core member 110 is received against an inner surface of the proximal end wall of the jacket 130, and the distal end terminal surface 124 is received against an inner surface of the distal end wall of the jacket 130,

[0077] The jacket is formed of one or more dielectric materials. In the illustrated embodiment, the jacket 130 is formed of a polymeric material. Any polymeric material that is a dielectric material can be used and a skilled artisan will be able to select a suitable polymeric material for the jacket in a wire guide according to a particular embodiment based on various considerations, including any desired handling and performance characteristics of the wire guide, such as torqueability, pushability, and / or other mechanic properties of the wire guide 100, Examples of suitable polymeric materials include, but are not l imited to, heat-formable polymeric materials, such as polyamide materials. These polymeric materials are considered desirable at least because of their ability to melt and flow between and around elements during a heat forming or heat shrinking process. Nylon is considered particularly advantageous at least because of its ready availability and well-characterized nature. Fluoropolymers, such as polytetrartuoroethylene, are also considered particularly advantageous as they have some of the highest characterized dielectric properties. Polyurethane, polyether-block amide, and other polymeric materials are also considered advantageous. Additional jackets or other materials can be applied to the jacket 130 if desired. For example, a lubricious jacket can be applied as a topcoat on the jacket 130. The jacket 130 can have varying composition along the axial length of the wire guide 100. For example, a different polymer composition can be used at one or both ends relative to a polymer composition present in the jacket disposed over the axial midpoint of the wire guide.Polymer compositions that provide a more rigid, durable, or both jacket can be used at one or both ends to provide resistance to tearing or other disruptions in the continuous nature of the jacket 130, which is critical to desirable performance of the wire guide 100, In other embodimen ts, two or more dielectric materials can form the jacket. For example, a jacket having a first axial portion formed of a first polymer that is a dielectric material and a second axial portion formed of a second, different polymer that is a dielectric material can be used. Indeed, the two different polymers, while both providing the desired dielectric properties, cart provide different properties, such as flexibility, hardness, and other properties. Furthermore, as described in more detail below, a jacket on a wire guide according to embodiments can comprise a first axial portion formed of a polymer tha t is a dielectric material and a second axial portion formed of a non-polymer that is a dielectric material, such as a ceramic or other nonpolymeric dielectric material.

[0078] In some forms, the jacket 130 can include a radiopaque material and / or an M.RI- artifacl-generating material dispersed through the polymeric material or other dielectric material of the jacket 130. Potential radiopaque materials include as examples particulate materials such as bismuth oxychloride, bismuth subcarbonate, bismuth (rioxide, and barium sulfate. If present, the radiopaque agent preferably has a magnetic susceptibility of less than about 500 ppm. Potential .MRI-artifact-ge.nerating materials include as examples particles of a material that has a magnetic susceptibility greater than about 500 ppm, and preferably greater than about 7000 ppm, or greater than 1. Examples of MRJ -artifact-generating particles include particles of nickel, a nickel alloy, iron, an iron alloy, or titanium. The incorporation of a radiopaque material along with the passive MRI markers can provide a catheter that can be beneficially used in both X-ray guided and MRI-guided interventional procedures. The incorporation of MR 1-artifact -generating materials dispersed in the polymeric or other dielectric material of the jacket 130 along with the discrete passive MRI markers discussed herein can provide a catheter that both generates an elongate, continuous visible artifact longitudinally along the wire guide 100 as well as discrete artifacts that positionally mark locations along the wire guide 100, with the discrete MRI marker artifacts preferably having a larger maximum dimension than the continuous artifact in a direction perpendicular to the longitudinal axis of wire guide 100, that further aid in tracking and / or identifying a position of the wire guide 100,

[0079] A continuous nature of the jacket 130 over the entire length 104 of the core member 1 10 is highly preferred in many forms. As such, jacket 130 can include elements thatresist formation of disruptions in the continuous nature of the jacket 130, such as fibers and other additives. Also, jacket 130 can be treated in a manner during manufacturing of the wire guide that renders jacket 130 relatively more resistant to such disruptions than if such treatment had not been performed. For example, jacket 130 can be subjected to electron beam irradiation, gamma irradiation, or other suitable treatments to cross-link the polymer of the jacket 130 to render jacket 130 more resistant to disruptions in the continuous nature of the jacket 130.

[0080] W ire guide 100 can include one or more markers 150. If included, the marker I 50 can be disposed directly on the core member 110 such that the jacket 130 is disposed over the marker 150 and the core member 110, Alternatively, an included marker can be structurally positioned on the wire guide 100 in a manner such that the marker 150 has no direct structural contact with the core member 1 10. In the example wire guide 100 illustrated in FIGS. 4 through 8, the marker 150 is disposed directly on the core member such that no portion of jacket 130 is positioned between the marker 150 and the core member 110, As an alternative, a marker can be disposed within the thickness of the jacket such that a portion of the jacket is disposed between the inner surface of the marker and the external surface of the core member. In these embodiments, the marker is not in direct contact with the core member. If included, marker 150 is a passive marker and is formed of a metal or an alloy and has a susceptibility that is different from the susceptibility of the core member 110. Also alternatively, an outer surface of the jacket and an outer surface of one or more markers included in a wire guide according to an embodiment can be continuous with each other, such that the core member is fully encapsulated by the combination of the jacket and one or more markers. In these embodiments, the outer surface of the jacket and the outer s urface of the one or more markers are advantageously flush with each other. Also alternatively, a marker can be disposed on a previously placed jacket.

[0081] Marker 150 can have any structural configuration, and a skilled artisan will be able to select a suitable structural configuration for a medical de vice according to a particular embodiment based on various considerations, include any desired visualization characteristics when the medical device is used with imaging modalities, such as MR'l, Examples of suitable configurations include, but are not limited to, a ring, a strip, a plug, a twisted band, a twisted ring, multiple bands attached to each other, multiple rings attached to each other, and other configurations. A circumferential band of material, e.g. as illustrated in FIGS. 4, 5, and 6, is considered particularly advantageous. A wire guide according to anembodiment can include any number of markers, too, and a skilled artisan will be able to select a suitable number of markers for a medical device according to a particular embodiment based on various considerations, including any desired visualization patterns when the wire guide is used with imaging modalities, such as MRI. Examples of suitable numbers include, but are not limited to, one, more than one, two, a plurality, three, more than three, four, five, six, seven, eight, nine, ten, and more than ten.

[0082] The marker 150 can be disposed at any suitable axial position relative to the lengthwise axis 102 of the core member 110 and a skilled artisan will be able to select a suitable position for a marker relative to (he lengthwise axis of the core member in a wire guide according to a particular embodiment based on various considerations, including any desired visualization patterns when the medical device is used with imaging modalities, such as MRI. As illustrated in FIGS. 4, 5, and 6, the marker 150 in the example wire guide 100 is positioned proximal to the distal end 114 of the core member 110, but axially within a distal portion 120 of the wire guide 100 that extends from a point beyond the longitudinal midpoint on the lengthwise axis 102 of the core member 110 to the distal end 1 14 of the core member1 10. Other examples of suitable positions include, but are not limited to, within an axial portion of the wire guide 100 that is proximal to the longitudinal midpoint of the core member 1 10, at the distal end 114 of the core member 110, at the proximal end 1 12 of the core member 1 10, at the distal end 134 of the jacket 130, and the proximal end 132 of the jacket 130, and combinations of these positions with multiple markers.[0083 [ The marker 150 has a susceptibility that is different from the magnetic susceptibility of the core member 110. .Accordingly, the marker can be formed of any metal, alloy, or other material that provides the desired relative susceptibility as compared to the susceptibility of the core member 1 10. A skilled artisan will be able to select a suitable material for the marker in a medical device according to a particular embodiment based on various considerations, including the composition of the reinforcement member in the medical device. Suitable pairings of materials for the core member and the marker in wire guides according to the invention are described in detail below . Examples of suitable materials for the marker include, but are not limited to, metals, such as Titanium, Nickel, and other metals, alloys, such as stainless steel alloys, including 304V stainless steel and316LVM stainless steel, nickel iron alloys, such as mu-metal, including mu-metal according to ASTM A753 Alloy 4, MUMETAL® magnetic shielding alloy available from Magnetic Shield Corporation of Bensenville, IL, MUMETALL® alloy available fromV ACIIUMSCHMELZE GmbH & Co. KG of Hanau, Germany, and MUSHIELDTM magnetic shielding alloy according to ASTM A753, Alloy 3 available from The MuShield Company of Londonderry, New Hampshire, ferromagnetic materials, paramagnetic materials, alloys containing at least 50% Iron by weight, 316 Stainless Steel, and any other material considered suitable for a particular embodiment. Alternative embodiments include a marker disposed on an external surface of the jacket: of the wire guide. For example, a marker can be printed onto or adhered to an external surface of a wire guide. For example, an ink containing a material having a magnetic susceptibility that is greater than the magnetic susceptibility of the core member in a wire guide, such as an ink containing magnetic particles, an ink containing Iron Oxide nanoparticles, or an ink containing Iron Oxide nanoparticles bound to phospholipids, can be printed onto an external surface of the jacket to form a marker in a wire guide according to an embodiment. A marker can be disposed on a surface by other suitable processes, too, such as chemical vapor deposition and plating. Also alternatively, a (ape including a material having a magnetic susceptibility that is greater than the magnetic susceptibility of the core member in a wire guide, such as magnetic tape, can be adhered to an external surface of a covering in a wire guide to form a marker in a wire guide according to an embodiment. Selection of a marker, or markers, to include in a wire guide according to a particular embodiment can also be based upon the field strength, or field strengths, within which the wire guide is intended to be used. For example, a wire guide that includes a marker can be utilized to complete one, or more than one, interventional procedure under MRI utilizing one or more field strengths (0.55T, 1.5T, or 3.0T). Material or materials can be selected for a marker or markers in a wire guide according to an embodiment based on these expected field strengths and the expected visual artifacts produced by a marker or markers formed of a particular material and having a particular structural configuration.

[0084] The core member in a wire guide according to the present disclosure has a susceptibility that is different from the susceptibility of a marker in the wire guide. Thus, the marker in a wire guide according to the invention has a susceptibility that is different from the susceptibility of the core member in the wire guide. Any pairing of materials for these elements that provides this relative relationship of the susceptibilities for these elements, which is considered critical to the performance of wire guides according to the invention, can be used in a wire guide according to a particular embodiment. Indeed, the core member and the marker can be formed of the same or different materials as long as the relative relationship of the susceptibilities for these elements is provided. In some embodiments,different materials having different magnetic susceptibilities are used for the core member and the marker. In these embodiments, the core member and the marker have different susceptibilities and are formed of materials having differen t magnetic susceptibilities For these embodiments, a skilled artisan will be able to select a material for one of these elements in a wire guide according to a particular embodiment based on various considerations, including the composition of the other of these elements and any desired performance characteristics or imaging characteristics for the wire guide. Examples of suitable pairings of different materials for the core member and the marker include, but are not limited to, a first material for the core member and a second, different material for the marker, such as a paramagnetic material for the core member and a ferromagnetic material for the marker, an alloy containing less than or equal to 1 % Iron by weight for the core member and an alloy containing at least 50% Iron by weight for the marker, a Cobalt Chromium alloy for the core member and a stainless steel for the marker, and a Nickel Cobalt alloy, such as MP35N, for the core member and a stainless steel, such as 304V stainless steel of 3161. VM stainless steel, for the marker. In other embodiments, the core member and the marker are formed of the same material. In these embodiments, while the reinforcement member and the marker have different susceptibilities, the core member and the marker have the same magnetic susceptibility. For example, in the illustrated embodiment, the core member 1 10 and the marker 150 can be formed of the same material, giving the core member 1 10 and the marker 150 the same magnetic susceptibility. To provide the different susceptibilities for these elements 1 10, 150, one element, such as the marker 150, can be work-hardened or manipulated in some manner that provides a susceptibility that is different from the susceptibility of the other.

[0085] Passive ,MRl markers herein can be formed from any suitable material, herein sometimes referred to as a "passive MRI marker-forming material". In certain forms, a marker or markers described herein will be formed of a passive MRI marker-forming material, such as a metal or metal alloy, having an absolute magnetic susceptibility value (positive or negative, i.e. including diamagnetic materials with a negative value and paramagnetic or ferromagnetic materials with a positive value) of at least about 10 ppm. In certain preferred forms, the passive MRI marker-forming material will have a magnetic susceptibility of at least about 500 ppm, or at least about 2000 ppm, or at least 7000 ppm, and typically in the range of about 500 ppm to about 1 ,000,000 and more preferably in the range of about 7000 ppm to about 100,000 (these values will be understood as positive values).

[0086] In some forms, such a passive MRI marker-forming material, configured to provide an individual discrete marker, will be provided on the medical device within a longitudinal length along the device that does not exceed about 10 mm, or that does not exceed about 5 mm, or that does not exceed about 2mm, and typically in the range of about 0-2 to about 5 mm; and'or such a marker-forming material, configured to provide an individual discrete marker, will be provided on the device in a volume not exceeding 3 nnntr, or not. exceeding 1 nnnn', or not. exceeding 0.1 nrinn', and in each of these aspects, the volume may be at least 0.00005 mmi?, or at least about 0.0001 nnnn’. In certain embodiments, the passive M.R1 marker-forming material has a magnetic susceptibility of at least about 1 and is present in the passive MRI marker in a volume not exceeding 0.1 nrinn3, or in the range of 0.00001 nrinn3to 0.1 nrinn3, or in the range of 0.00005 nnnn3to 0.05 nnnn3.

[0087] In addition or alternatively, in certain particularly beneficial embodiments herein, a passive MRI marker- forming material, configured to provide an individual discrete marker, will be provided on the guide wire in an amount sufficient to generate a visible artifact underMRI that has a maximum dimension that is at least 10 times, or at least .15 times, the greatest outer diameter of the polymeric jacket, or in some forms in the range of about 15 to 100 times, or about 15 to 50 times, the greatest outer diameter of the polymeric jacket: and / or such a maximum dimension of the visible artifact can be in the range of about 0,5 cm to about 3 cm, or about I cm to about 2 cm. Preferred marker-forming materials for these or other purposes herein include, for example: nickel, alloys of nickel, iron, alloys of iron, cobalt, alloys of cobalt, or other suitable metals. These may be selected to have magnetic susceptibility values as discussed herein and / or in some forms may be paramagnetic or ferromagnetic materials,

[0088] In certain preferred forms, a layer of magnetically susceptible material applied to the wire guide, e.g. on the outer surface of the core member, to provide a passive MRI marker, is a plated layer of magnetically susceptible ma terial, such as a plated layer of metal. Such a plated layer in some preferred forms is a plated layer of a pure metal, such as pure nickel, rhodium, palladium, platinum, or aluminum. The plated layer, or any other layer provided herein to form a passive MRI marker, can in some embodiments have a thickness not exceeding about. 0.1 mm, or not exceeding about 0.05 min, and typically being in the range of about 0.00025 mm to about 0.02 mm, or about 0.001 mm to about 0.015 mm, or about 0.0025 to about 0.015 mm; and / or can include a volume of the passive MR! marker-forming materia! not exceeding 1 nrini5, or not exceeding 0.2 nrini , or in the range of about 4 x 10” mrn’ to about 0.05 mrn’; and / or can have a maximum longitudinal length along the wire guide (e.g. along the core member) of no greater than about 10 mm, or no greater than about 5 mm, and in some forms about 0.2 mm to about 3 mm or about 0.2 mm to about 2 mm. For some preferred plated nickel passive MRI markers, a plated circumferential band of nickel having a longitudinal length of 0.25 mm to about 2 mm, or about 0.25 mm to about 1.5 mm, and a thickness not exceeding about 0,05 mm, e.g. in the range of about 0.005 mm to about 0.05 mm or about 0.005 mm to about 0.02 mm, will be used. In these plated or other passive MRI markers using nickel as the passive MR] marker-forming material, in certain preferred aspects the passive MRI marker will contain a volume of nickel of ai least about 0.01 mm3, for example in the range of 0.01 nrini ' to about 0.1 mm3, or about 0.015 m mm3to about 0.075 mm3, or about 0.02 mm3to about 0.05 mnr’. It will be understood that multiple plated layers can be included to provide multiple passive MRI markers along the length of the wire guide, as described for many device embodiments herein. The plated layer or layers can be applied by any suitable plating method, and beneficially in some aspects by electroplating or electroless plating. The plated iayer(s) of the completed medical device can be as-applied, for example in a simultaneous or sequential selective plating of multiple discrete regions of the medical device (e.g. elongate member) with or without utilizing masking, or may be the result of a subtractive process in which amounts of plated material are removed to provide the plated layeris) of the completed medical device.

[0089] Shown in FIG, 23 is one illustrative example of a wire guide 1100 having a plurality of passive MRI markers provided by respective layers, for example plated layers, of magnetically susceptible material adhered to the outer surface of a core member, and encapsulated by the polymeric jacket along with the core member. Wire guide 1100 can have features that are the same as wire guide 100 discussed above, except has otherwise described.Wire guide 1100 includes a continuous core member 1110 encapsulated by a jacket 1130.Core member 1 1 10 includes a proximal constant outer diameter segment 1 1 12 and a distal region including a tapered core member segment 1 1 14 having a decreasing outer diameter in a direction toward the distal end of the core member 1 1 10 and, in the specific illustrated form, a distal constant outer diameter segment 1 1 16 distal of the distally -decreasing outer diameter segment 1 1 14. Distal constant outer diameter segment 1 16 can, for example, have a longitudinal length of about 1 cm to about 5 cm, or about 2 cm to about 4 cm. Wire guide 1100 includes a plurality of passive MRI markers 1 150, 1152, 1 154, 1 156 and 1158longitudinally spaced from one another along the length of wire guide I 100, preferably provided by layers of passive M.RJ marker-forming material in the form of circumferential bands adhered to and extending completely around the outer surface of the core member1 110. In particular, markers 1 150 and 1 158 are each positioned on a constant outer diameter segment of the core member 1 1 10 (segments 1112 and 1 S 16, respectively), and markers1152, 1 154 and 1156 are each positioned on the tapered core member segment 1114 of the core member 11 I 0. In certain preferred forms, at least markers 1152, 1154, 1 156 and 1158 are configured to generate discrete visible image artifacts. In this regard, a discrete visible image artifact generated by a passive MRI marker herein may not overlap any other visible image artifact generated by any adjacent passive MRI marker to any extent, or may partially (e.g. up to about 75%, or up to about 50%) overlap one or more visible image artifacts generated by one or more respective adjacent passive MRI markers but nonetheless be visually discernable as separately generated from the one or more other image artifacts. In certain preferred forms, at least, markers 1152, 1 154, 1156 and 1158 are configured to generate respective visible image artifacts that are the same size as one another. For these purposes, markers 1 152, 1154, 1 156 and 1 158 can be formed from the same passive MRI marker-forming material, and can have substantially the same volume (i.e. each within about 10% of the others) of the passive MRI marker-forming material. In the illustrated form, the passive MRI marker-forming material layers providing markers 1152, 1 154, 1 156 and 1158 can have the same volume of passive MR! inarker-forming material, and in doing so can have substantially the same thickness (i.e. each within about 10% of the others), while marker1 152 has a longitudinal length that is substantially less (i.e. at least 10% less), and thus outer surface area that is substantially less (i.e. at least 10% less), than that of marker 1154 which in turn is substantially less than that of marker 1156 which in turn is substantially less than that of marker 1 158. In other forms, at least one of markers 1152, 1 154, 1156, and 1158 can be configured to generate a visible artifact with a greater maximum dimension than at least one other of such markers. 'This includes embodiments in which each respective artifact of markers 1152, 1 154, 1156, and 1 158 differs in greatest maximum dimension from that of at least two of, or each of, the others (e.g. where such respective greatest maximum dimensions can decrease in a distal direction along the guide wire 1 1 I 0). Marker 1150, on the constant outer diameter segment 1 112 of the core member 11 10, can be configured, to generate a visible image artifact having the same size as, or having a different size than, one, some or all of those generated by markers I 152, 1 154, 1156 and 1 I 58. Also, while only one marker 1 150on the constant outer diameter segment 1 112 is shown, it will be understood that a plurality of such passive MRI markers can be provided (e.g. 2 to 20 markers, or 4 to 10 markers), for example at regular distance intervals along the length of the wire guide 1 100.

[0090] Shown in FIG. 24 is another illustrative example of a wire guide 1200 having a plurality of passive MRI markers provided by respective layers, for example plated layers, of magnetically susceptible material applied to the outer surface of a core member. Wire guide 1200 can have features that are the same as wire guide 100 discussed above, except, has otherwise described. Wire guide 1200 includes a continuous core member 1210 encapsulated by a jacket 1230. Core member 1210 includes a proximal constant outer diameter segment 1212 and a distal region .including a distally-decreasing outer diameter segment 1214 and, in the specific illustrated form, a constant outer diameter segment 1216 distal of the distally- decreasing outer diameter segment 1214. Wire guide 1200 includes a plurality of passive MRI markers 1250, 1252, 1254, and 1256 longitudinally spaced from one another along the length of wire guide 1200, preferably provided by layers of passive MRI marker-forming material in the form of circumferential bands adhered to and extending completely around the outer surface of the core member 1210. In certain preferred forms, at least markers 1252 and 1254 are configured to generate respective visible image artifacts that are the same size as one another. For these purposes, markers 1252 and 1254 can be formed from the same passive MRI marker-forming material, and can have substantially the same volume (i.e. each within about 10% of the others) of the passive MRI marker-forming material. In the illustrated form, the passive MRI marker-forming material layers providing markers 1252 and 1254 have substantially the same thickness (i.e. each within about 10% of the others), and marker 1252 has a longitudinal length less than that of marker 1254. Marker 1256 has a longitudinal length greater than that of marker 1252 and that of marker 1254, and in some forms can have a longitudinal length that is at least two times, at least three times, or at least for times, that of marker 1252 and / or that of marker 1254. In some forms, marker 1256, e.g. when axially aligned with die primary magnetic field of an MRI system, can generate a dipole image artifact having a first enlarged artifact region at a proximal end of marker 1256, a second enlarged artifact region at a distal end of marker 1256, and a narrower artifact region extending between the first and second artifact regions, hi certain aspects, elongate marker 1256 can be configured to facilitate a physical ly-reshapable distal end region of the wire guide 1200, as discussed further below. In beneficial forms, markers 1250, 1252, 1254,and 1256, and any other passive MRI markers on the wire guide 1200, will be formed from the same passive MRI marker-forming material.

[0091] Shown in FIG. 25 is one illustrative example of a wire guide 1300 having a plurality of passive MRI markers provided by respective layers, for example plated layers, of magnetically susceptible material adhered to the outer surface of a core member. Wire guide 1300 can have features that are the same as wire guide 100 discussed above, except has otherwise described. Wire guide 1300 includes a continuous core member 1310 encapsulated by a jacket 1330. Core member 1310 includes a proximal constant outer diameter segment 1312 and a distal region including a distally-decreasing outer diameter segment 1314 and, in the specific illustrated form, a constant outer diameter segment 1316 distal of the distally- decreasing outer diameter segment 1314. Wire guide 1300 includes a plurality of passive MRI markers 1350, 1352, 1354, 1356 and 1358, each configured to generate a discrete visible artifact under MRI, longitudinally spaced from one another along the length of wire guide 1300, preferably provided by layers of passive MRI marker-forming material in the form of circumferential bauds adhered to and extending completely around the outer surface of (he core member 1310. In particular, markers 1350 and 1358 are each positioned on a constant outer diameter segment of the core member 1310 ( segments 1312 and 1316, respectively), and markers 1352, 1354 and 1356 are each positioned on the decreasing outer diameter segment 1314 of the core member 1.310. In certain preferred forms, at least markers 1352, 1354, 1356 and 1358 are configured to generate respective visible image artifacts that are the same size as one another. For these purposes, markers 1352, 1354, 1356 and 1358 can be formed from the same passive MRI marker-forming material, and can have substantially the same volume (i.e. each within about 10% of the others) of the passive MRI marker-forming material. In (he illustrated form, the passive MRI marker- forming material layers providing markers 1352, 1354, 1356 and 1358 have substantially the same thickness (i.e. each within about 10% of the others). Marker 1352 has a longitudinal length less than that of marker 1354. Marker 1356, positioned on the deceasing outer diameter segment 1314, is provided by a pl urality of lay ers 1356a, 1356b, and 1356c, in the form a circumferential bands, that are closely spaced so as to generate a single combined image artifact. The longitudinal length of each of the layers 1356a, 1356b and 1356c is less than (hat of the layer of marker 1354, and the sum of the longitudinal lengths of layers 1356a, 1356b, and 1356c is greater than the longitudinal length of the layer of marker 1354. Marker 1358, positioned on the constant outer diameter segment 1316, is provided by a plurality of layers 1358a, 1358b, and 1358c that areclosely spaced so as to generate a single combined image artifact. The sum of the longitudinal lengths of layers 1358a, 1358b, and 1358c is greater than the sum of the longitudinal length of layers 1356a, 1356b and 1356c. Marker 1350, on the proximal constant diameter outer segment 1312 of the core member 1310, can be configured to generate a visible image artifact having the same size as, or having a different size than, those generated by markers 1352, 1354, 1356 and 1358. Also, while only one marker 1350 on the proximal constant outer diameter segment 1312 is shown, it will be understood that a plurality of such passive MRI markers can be provided (e.g, 2 to 20 markers, or 4 to 10 markers), for example at regular distance intervals along the length of the wire guide 1300. The incorporation of markers 1356 and 1358 that are provided by a plurality of closely spaced (e.g, within about 2 .mm of one another) but separate layers of passive MRI marker-forming material can minimize or eliminate mechanical property changes relative to the corresponding core member without the layer) s), which in some aspects herein can facilitate providing embodiments in which the distal region of the wire guide 1300 exhibits the capacity to resiliently return to its original set (e.g. straight) configuration after forcible bending therefrom, as discussed further below.

[0092] Referring now to FIGs. 26A and 268 for additional details regarding exemplary markers, FIG. 26A provides a cross-sectional view taken along line 26-26 of FIG. 23 and FIG. 26B provides a cross-sectional view taken along line 27-27 of FIG. 23. Shown is passive MRI marker 1150 provided by a layer of passive MRI marker-forming material in the form of a circumferential band adhered to and extending completely around the outer surface of core member 1110. In this illustrated form, the layer of passive MRI marker- forming material has an outer surface 1 160 that is positioned radially outward with respect to longitudinally adjacent proximal and distal outer surfaces 1 164 and 1166 of the core member 1110. For example, when the layer of passive MRI marker- forming material is a circumferential band as shown, the outer diameter of the circumferential band can be greater than the outer diameter of the respective segments of the core member 1110 occurring immediately proximally and distally of die marker 1 150. It will be understood that: while only marker 1150 is specifically shown, markers 1 152, 1154, 1 156 and 1 158 can have corresponding features. In addition, while the layer of MRI marker 1 150 is shown with a constant thickness, in other forms, the layer will have peripheral edges (e.g. proximal and distal edges) with a thickness less than a maximum thickness occurring therebetween,

[0093] Referring now to FIGs. 27 A and 27B, shown are a cross-sectional views taken along line 26A-26A and along 26B-26B of FIG. 23, respectively, illustrating an alternativewire guide embodiment that is the same as that of FIGs. 26A and 26B, except also including directly visible indicia on the outer surface of the polymeric jacket 1130 marking the position of one, some or all of the passive MRI markers of the wire guide I 100. In the particular illustrated embodiment, visible indicia 1132 are provided by a layer of a visible marking material, for example in the form of a circumferential band, on the outer surface of the polymeric jacket 1 130, The visible marking material may for example be an ink that visibly contrasts relative to the color of the outer surface of the polymeric jacket 1130, It will be understood that while the region of only marker 1150 is specifically shown, the regions of markers 1 152, 1 154, 1156 and 1 158 can have corresponding features.

[0094] Referring now to FIG. 27C, shown is a cross-sectional view taken along line 26B- 2613 of FIG. 23 illustrating another alternative wire guide embodiment that is the same as that of FIGs. 27 A and 27B, except that the layer 1 I 50t of passive MRI marker-forming material has a varied thickness. In particular, (he layer 11501 is tapered, having peripheral edges (e.g. proximal and distal edges to a circumferential band as shown) with a thickness that is less than a maximum thickness of the layer 1150t occurring between the peripheral edges. In some forms, the thickness of the layer 1150t can continuously decrease to provide an outer surface 1 160 that tapers smoothly to the adjacent outer surfaces 1 164 and 1 166 of the core member 1 110. The thickness profile of the layer 1 150t can be achieved by any suitable means. In some forms, such thickness profile can be as-applied. For example, the conditions of a deposition process, such as a plating process, can be controlled so as to deposit a layer with the described thickness profile features herein. As an example, the conditions of an electroplating process can be controlled to result in a varied thickness layer by varying the current density across the surface of the area io be plated, by varying the residence lime of a plating medium across the surface of the area to be plated, by varying the metal ion concentration of the plating medium across the surface area to be plated, and- or by other means. In other embodiments, the thickness profile of the varied thickness marker(s) of the wire guide can be the result of a subtractive process, such as polishing (e.g, electropolishing) or etching, that selectively removes deposited material to provide a layer with the described thickness profile features herein. It will be understood that while the region of only marker 1 150 is specifically shown, the regions of markers 1 152, 1 154, 1 156 and 1158 can have corresponding features. Additionally, it. will be understood that the directly visible indicia 1132 is.'are optional, and in other embodiments the outer surface of the polymeric jacket 1130can be free of any directly visible marker(s) marking the position(s) of the passive MRI marker(s).

[0095] Referring now to FIG. 28, shown is a cross-sectional view taken along line 26B- 26B of FIG. 23 in an alternative marker configuration embodiment. Shown is passive MRI marker 1 150 provided by a layer of passive MRI marker-forming material in the form of a circumferential band adhered to and extending completely around the outer surface of core member 1 1 10'. In this illustrated form, the layer of passive MRI marker-forming material has an outer surface 1 160 that flush with respect to longitudinally adjacent proximal and distal outer surfaces 1164 and 1 166 of the core member 1 1 10*. For these purposes, the core member 11101 has a depression therein, such as a groove, and the material of the passive MRI marker1 150 is positioned in the depression. It will be understood that while only marker 1150 is specifically shown, markers I 152, 1154, 1156 and 1 158 can have corresponding features.Additionally , it will be understood that the directly visible indicia .1 132 is / are optional, and in other embodiments the outer surface of the polymeric jacket 1 130 can be free of any directly visible markerfs) marking the position(s) of the passive MRI markerfs).

[0096] As discussed above, in certain forms, wire guides herein will have a core member that has a tapered, or otherwise smaller diameter, distal region that provides increased flexibility to the corresponding region of the wire guide as compared to that provided by a constant outer diameter proximal region. In some embodiments herein, one or more passive MRI markers in the distal region provided by passive MRI marker-forming material adhered to an outer surface of fee core member will be configured such feat fee corresponding distal region of the wire guide exhibits the capacity to resihently return to its relaxed configuration (in the absence of externally applied force), e.g. a straight configuration, after release of a force bending the distal region from its relaxed configuration. The particular passive MRI marker-fanning material, fee thickness of the layer, and the longitudinal length of fee layer, can be controlled for these purposes. For example, in some aspects, the layer can have a thickness not exceeding about 0.05 mm, or not exceeding about 0.03 mm, and / or a longitudinal length not exceeding about 5 mm, or not exceeding about 3 mm, Such relatively minor thicknesses and / or small longitudinal lengths can be controlled with a given marker- forming material to ensure (hat any plastic deformation of the marker layer to a new shape caused by bending the corresponding distal region of the wire guide away from its preset shape does not prevent resilient return of the distal region to the preset shape (e.g. where the resilient return force of the corresponding distal core member region may again plasticallydeform the layer during its return to the relaxed configuration). In certain forms, as illustrated in conjunction with guide wire 1300 of FIG. 25, one or more, or two or more, passive MRI markers can be provided in such a distal region by a plurality of separate layers that are closely spaced so as to generate a single visible image artifact. The use of such separate layers, with uncoated segments of the core member 1310 between them, can facilitate configurations that exhibit resilient return io the initial relaxed configuration.

[0097] In alternative embodiments herein, one or more passive MRI markers in a tapered or otherwise smaller diameter distal region of a core member, provided by passive MRI marker-forming ma terial adhered to an ou ter surface of the core member, will be sized and configured such that the corresponding distal region of the wire guide exhibits the capacity io substantially hold a shape to which its initial relaxed configuration (e.g. a straight configuration) has been forcibly bent, even upon release of the bending force. Again, the particular passive MRI marker-tonning material, the thickness of the layer, and the longitudinal length of the layer, can be controlled for these purposes to ensure that plastic deformation of the marker layetfs) to a new shape caused by resiliently bending the corresponding distal region of the wire guide away from its preset shape prevents resilient return of the distal region to the preset shape (e.g. where the resilient return force of the core member in the distal region is less than that required to again plastically deform the layoffs)). In this manner, a selectively shape-settable distal region is provided to the guide wire, where a user can bend the distal region to a desired shape which it will retain (e.g. for navigation within a vasculature). In some forms, e.g. as may be provided by wire guide 1200 and its elongate marker 1256 illustrated in FIG. 24, at least one layer (e.g. circumferential band layer) having a relatively large longitudinal length, for example at least about 2 cm, or at least about 3 cm, or at least about 7 cm, can facilitate providing such a shape-settable distal region to a wire guide. As well, while it is considered beneficial that the layer or layers providing the shape-settable property also provide the function of a passive MRI marker(s), in other forms, similar deposited (e.g. plated) layers of other materials that do not provide the function of a passive MRI marker(s) can be incorporated in a wire guide to nonetheless provide an advantageous shape-settable distal region thereof,

[0098] The above-mentioned aspects for configuring distal regions that do or do not resiliently return to their preset shape are particularly applicable where the diameter of the distal region of the core member on which the passive MRI marker(s) is / are located is relatively small, for example less than about 0.4mm, or less than about 0.3 mm, or less thanabout 0.2 mm. Core members formed of superelastic nitinol having these dimensions are preferred for these purposes.

[0099] The embodiments illustrated and described in connection with FIG. 23 to 28 above include layers of passive MRI marker forming material adhered to an outer surface of the core member of the wire guide. While in the illustrated forms the layers are shown as directly adhered to the outer surface of the core member, in other forms the layers may be indirectly adhered, for example adhered to an underlayer that is directly adhered io the outer surface of the core member (e.g.to promote adhesion of the combined layered structure to the core member. As well, while in the specific embodiments illustrated there is no shown layer overfop the layers of passive MRI marker-providing material (other than that provided by the guide wire jacket), in other forms there may be such respective layers or a continuous layer overtop the layers of passive MRI marker-forming material. Such an overlying layer or layers can, for example, provide a barrier (e.g. oxygen barrier) protecting the layers of passive MRI marker forming material. Additional layers below and / or above the noted layers of passive MRI marker-forming material may be selected so as to not contribute significantly to the passive MRI marker function at the position on the wire guide. In certain forms, where the layer of passive MRI marker-forming material is a deposited metallic layer, such as a plated nickel or other metallic layer, so too can be any layer underneath or overtop the layers of passive MRI marker-forming material. For example, if desired, a layer of gold can be plated overtop a plated layer of metallic passive MRI marker- forming material,

[0100] Shown in FIGs. 29 and 30 are views depicting another exemplary wire guide 1400 herein, having passive MRI markers disposed within a polymeric jacket thereof. Wire guide 1400 can have features that are the same as wire guide 100 discussed above, except has otherwise described. Wire guide 1400 includes a continuous core .member 1410 encapsulated by a jacket 1430. Core member 1410 includes a proximal constant outer diameter segment 1412 and a distal region including a distally-decreasing outer diameter segment 1414 and, in the specific illustrated form, a constant outer diameter segment 1416 distal of the distally- decreasing outer diameter segment 1414. Wire guide 1400 includes a plurality of passive MRI markers 1450, 1452, 1454, 1456 and 1458 disposed within the jacket 1430 and longitudinally spaced from one another along the length of wire guide 1400. Markers 1450, 1452, 1454, 1456 and 1458 can each be in the form of a discrete volume of the passive MRI marker-forming material, e.g. a plug. In providing such markers, a respective holes cau be created in the material of jacket 1430 and the respective plugs of the passive MRI markerforming material inserted into the holes and potentially positionally secured, e.g. with an adhesive. In certain preferred forms, at least markers 1452, 1454, 1456 and 1458 are configured io generate respective visible image artifacts that are the same size as one another. For these purposes, markers 1452, 1454, 1456 and 1458 can be formed from the same passive MRI marker-forming material, and can have substantially the same volume (i.e. each within about 10% of the others) of the passive M.RI marker-forming material. Marker 1450, on the constant diameter outer segmen t 1412 of the core member 1410, can be configured to generate a visible image artifact having the same size as, or having a different size than, those generated by markers 1452, 1454, 1456 and 1458. Also, while only one marker 1450 on the proximal constant outer diameter segment 1412 is shown, ii will be understood that a plurality of such passive MRI markers can be provided (e.g. 2 to 20 markers, or 4 to 10 markers), for example at regular distance intervals along the length of the wire guide 1400. It has been found that relatively small amounts of suitable materials can be used for these market's positioned wi thin foe jacket 1430, Preferred materials for these purposes will have a magnetic, susceptibility of at least about 500 ppm, or at least about 2000 ppm, and typically in the range of about 500 ppm to about 1,000,000, and more preferably in foe range of about 7000 ppm to about 100000. In some forms, the marker-forming material will have a volume not exceeding 5 nnrn3, or not exceeding 3 nnnn3, or not exceeding 1 nnnn3, or not exceeding 0.1 nnnn3; in each of these aspects, the volume may be at least 0.00005 irnnr5, or at least about 0.0001 nnnn3. In more preferred forms where a relatively high magnetic susceptibility material is used, for example a magnetic susceptibility of at least about 1 (nickel, for example, as a magnetic susceptibility of about 1, 1), a volume of the passive MRI marker-forming material not exceeding 0.1 mimF, for example in the range of 0.00001 nnnn3to 0.1 nnnn3, or in the range of 0.00005 nnnn3to 0.02 nnrn3, can be used in forming the passive MRI marker) s). Particular materials that may be used are discussed elsewhere herein. It will be understood that generally the higher the magnetic susceptibility exhibited by an MRI marker forming material, the lower the volume of that material that will be needed to form a visible image arti fac t of a given size. These aspects can be selected and controll ed by persons of skill in the art to provide passive MRI markers configured to generate visible artifacts of a size, or relative size, as discussed herein.

[0010] ] In certain advantageous forms herein, the passive MRI marker- forming material will be incorporated as a continuous volume of the passive MRI marker-forming material, for example as a plug or layer (e.g. plated layer), within a length of the guide wire herein. Such continuous volume-forms of passive MRI markers herein can facilitate minimizing thevolume of material needed to be incorporated to provide a passive MRI marker, for example as compared to forms of passive MRI markers that include particles of the passive MRI marker-forming material dispersed in a volume of another material providing a solid matrix. Layers or plugs of the passive MRI marker-forming material that are free of any polymer matrix material are thus advantageously used in some embodiments herein,

[0102] With reference now to FIG. 31 , shown is a view of another exemplary wire guide1500 herein. Wire guide 1500 can have the features of any of the wire guides exemplified herein (e.g. wire guides 100, 1 100, 1200, 1300 or 1400), except as otherwise described. Wire guide 1500 includes a distal-most segment 1515 on which is positioned a first group of passive MRI markers located distally of a proximal segment 1525 upon which is positioned a second group of passive MRI markers. Tire passive MRI markers of the first group can generate a group of visible artifacts that is distinguishable from a second group of artifacts generated by the passive MRI markers of the second group, for example based on the size and / or spacing of the artifacts. Distal-most segment 1515 can have a longitudinal length of about 3 cm to about 40 cm. Proximal segment 1525 can have a longitudinal length that is greater than that of the distalmost segment 1515, Distalmost segment 1515 has a first group of two or more, for example two to ten, or two to five, passive MRI markers positioned thereon, configured to generate image artifacts that are discrete from one another. In the specific illustrated form, first group of marker on the distal-most segment 1515 has four markers 1550, 1552, 1554 and 1556 therein. In certain preferred forms, the distal-most 10 cm of the wire guide 1500 will include two, three, four (e.g, markers 1550, 1552, 1554 and 1556), five, or six passive MRI markers of the first group, which in some preferred forms will be provided by respective layers of passive MRI marker-forming material plated or otherwise deposited on the distal-most 10 cm of the core member (e.g, core member 1 10, 310, 410, 510, 11 10, 1210, or 1310 herein) as discussed herein, and in other forms will be provided by respective volumes (e.g. plugs) of passive MRI marker-forming material disposed within the thickness of the distal-most 10 cm of the polymeric or other dielectric material jacket of the wire guide, for example as disclosed in FIGs. 29 and 30 and descriptions thereof. Proximal segment 1525 has a second group of two or more, for example two to twenty, passive MRI markers positioned thereon, configured to generate image artifacts that are discrete from one another. While four markers 1560, 1562, 1564 and 1566 are shown in the second marker group positioned on the proximal segment 1525 in FIG. 31 , it will be understood that in some forms one or more additional markers could occur betweenmarkers 1562 and 1564 (i.e. in the cutaway region of the wire guide 1500). The average longitudinal distance between the passive MRI markers in the second marker group on the proximal segment 1525 is greater than, for example at least 1.5 times, or at least 2 times, the average longitudinal distance between the passive MRI markers in the first marker group on the distal-most segment 1515. The passive MRI markers in the proximal segment 1525 can be provided at regular longitudinal distance intervals along the proximal segment 1525, for example with the longitudinal distance interval between each of the markers being in the range of about 10 cm to about 30 cm; and / or the passive MRI markers in the distahnost segment 1515 can be provided at regular longitudinal distance intervals along the distahnost segment 1515, for example with the longitudinal distance interval between each of the markers being in the range of about 1 cm to about 5 cm, or about 1.5 cm to about 5 cm, or about 1.5 cm to about 3 cm. In addition or alternatively, each given passive MRI marker in the distahnost segment 1515 can be spaced from each other adjacent passive MRI marker by a longitudinal distance that is at least 75% of, at least 90% of, or at least 100% of, or exceeds, the maximum dimension of the visible artifact generated by such given passiveMRI marker. The number of passive MRI markers along the proximal segment 1525 can be greater than the number of passive MRI markers along the distalmost segment 1515. Such arrangements can beneficially aid in determining the position and travel of the wire guide 1500 as a whole in the patient while also providing an increased longitudinal frequency of markers in the distal region 1515 io more particularly discern a configuration taken by, and a position of, the distal region 1515 within the anatomy of the patient.

[0103] FIG, 6 illustrates another example wire guide 200. Wire guide 200 is similar to wire guide 100 described above and illustrated in FIGS. 1 , 2, 3, 4, and 5, except as detailed below. In this embodiment, wire guide 200 includes a core member 210 formed of multiple core segments 210a, 210b, 210c, each of which has an axial length that is different from the axial length of the other core segments 210a, 210b, 210c. A jacket 230 formed of a dielectric material is disposed over all of the core segments 210a, 210b, 210c. Thus, each of the core segments 210a, 210b, 210c is fully encaps ulated by the jacket 230.

[0104] C ore segment 210a has first 260 and second 262 terminal ends. Core segment 210b has first 264 and second 266 terminal ends. Core segment 2I0c has first 268 and second 270 terminal ends. Thus, in this embodiment, core member 210 is not a continuous core member, but is rather an interrupted core member with internal terminal ends. This structural arrangement may be desirable in wire guides according to particular embodiments, forexample. Each of the core segments 210a, 210b, 2.10c is formed of a first material having a first susceptibility. It is noted, though, that the core segments 210a, 210b, 210c may have different susceptibilities and can be formed of different materials. Also, while wire guide 200 includes multiple core segments 210a, 210b, 210c arranged end-to-end, it is noted that, in other example embodiments, wire guides can include multiple core members that co-extend along a length or portion of a length of the wire guide. For example, a wire guide can include multiple core members arranged side-by-side, wound helically around a central longitudinal axis, or arranged in another suitable structural configuration.

[0105] FIG. 7 illustrates another example wire guide 300. Wire guide 300 is similar to wire guide 100 described above and illustrated in FIGS. 1 , 2, 3, 4, and 5, except as detailed below. Thus, wire guide 300 includes a continuous core member 310 formed of a material having a first susceptibility. A jacket 330 formed of a first dielectric material is disposed over the continuous core member 310 and includes first 330a and second 330b jacket portions. A circumferential band 380 formed of a second dielectric material that is different from the first dielectric material is disposed around the continuous core member 310 and axially between the first 330a and second 330b jacket portions. The circumferential band 380 is attached to the first 330a and second 330 jacket portions, such as with an adhesive or other suitable attachment, and forms a substantially continuous outer surface with the first 330a and second 330b jacket portions. Any suitable dielectric materials can be used for the first and second dielectric materials, as long as they are different materials. For example, the first dielectric material can be a first polymer and the second dielectric material can be a second polymer. Advantageously, the first dielectric material is a polymer and the second dielectric material is a non-polymer. Particularly advantageously, the first dielectric material is a polymer and the second dielectric material is a ceramic.

[0106] FIG. 8 illustrates another example wire guide 400. Wire guide 400 is similar to wire guide 300 described above and illustrated in FIG. 7, except as detailed below. Thus, wire guide 400 includes a continuous core member 410 formed of a material having a first susceptibility. A jacket 430 formed of a first dielectric material is disposed over the continuous core member 410. A. circumferential band 480 formed of a second dielectric material that is different from the first dielectric material is disposed around the continuous core member 410. Any suitable dielectric materials can be used for the first and second dielectric materials, as long as they are different materials. For example, the first dielectric material can be a first polymer and the second dielectric material can be a second polymer.Advantageously, the first dielectric material is a polymer and the second dielectric material is a non-polymer. Particularly advantageously, as described below, the first dielectric material is a polymer and the second dielectric material is a ceramic.

[0107] In this embodiment, the circumferential band 480 extends from one end 482 of the wire guide 400 toward the other end 484 of the wire guide 400 along an axial length 486 that is less than the full axial length of the wire guide 400. Also in this embodiment, circtimferenlial band 480 is a cap that defines a terminal surface 488 at the end 482 of the wire guide 400, The axial length 486 can be any axial length relative to the full axial length of the wire guide and a skilled artisan will be able to select a suitable axial length for a circumferential band 482 in a wire guide according to a particular embodiment based on various considerations, including the nature of the material from which the circumferential band 482 is formed. Examples of suitable axial lengths relative to the full axial length of the wire guide included, but are not limited to, about 5%, about 10%, about 15%, about 20%, about 25%s, about 40%, and about 50%, Advantageously, the axial length of the c ircumferential band is less than about 20% of the full axial length of the wire guide. Also advantageously, the axial length of the circumferential band is less than about 10% of the full axial length of the wire guide. Inclusion of circumferential band 486, particularly a ceramic circumferential band, in accordance with this embodiment is considered particularly advantageous at least because the ceramic material, positioned on one end of the wire guide, provides the desired dielectric material while also providing a material that is less susceptible to integrity disruptions that a polymer during manual handling of the wire guide at an end during use of the wire guide.

[0108] FIG. 9 illustrates another example wire guide 500. Wire guide 500 is similar to wire guide 400 described above and illustrated in FIG. 8, except as detailed below. Thus, wire guide 500 includes a continuous core member 510 formed of a material having a first susceptibility. A jacket 530 formed of a first dielectric material is disposed over the continuous core member 510. A circumferential band 580 formed of a second dielectric material that is different from the first dielectric material is disposed around the contimious core member 510. Any suitable dielectric materials can be used for the first and second dielectric materials, as long as they are different materials. For example, the first dielectric material can be a first polymer and lhe second dielectric material can be a second polymer. Advantageously, the first dielectric material is a polymer and the second dielectric material isa non -polymer. Particularly advantageously, as described below, the first dielectric material is a polymer and the second dielectric material is a ceramic.

[0109] In this embodiment, the circumferential band 580 extends from one end 584 of the wire guide 500 toward the other end 582 of the wire guide 500 along an axial length 586 that is less than the full axial length of the wire guide 500. Also in this embodiment, circumferential band 580 is a cap that defines a terminal surface 588 at the end 584 of the wire guide 500, The axial length 586 can he any axial length relative to the full axial length of the wire guide and a skilled artisan will be able to select a suitable axial length for a circumferential band 582 in a wire guide according to a particular embodiment based on various considerations, including the nature of the material from which the circumferential band 582 is formed. Examples of suitable axial lengths relative to the foil axial length of the wire guide included, but are not limited to, about 5%, about 10%, about 15%, about 20%, about 25%, about 40%, and about 50%. Advantageously, the axial length of the circumferential band is less than about 20% of the full axial length of the wire guide. Also advantageously, the axial length of the circumferential band is less than about 10% of the full axial length of the wire guide. Inclusion of circumferential band 586, particularly a ceramic circumferential band, in accordance with this embodiment is considered particularly advantageous at least because the ceramic material , positioned on one end of the wire guide, provides the desired dielectric material while also providing a material that is suitable for advancing the end 584 of the wire guide 500 through biological matter, such as blockages within a body vessel, tissue, or other biological matter. Also in this embodiment, circumferential baud 580 defines a taper 590, providing a reduced diameter at. the end 584 of the wire guide.

[0110] Wire guides according io embodiments are useful in performing interventional procedures under MR!

[0111] FIG. 10 illustrates an example method 600 of imaging a portion of a body vessel.

[0112] An initial step 610 comprises placing a portion of a patient within or adjacent anMR1 system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated. Another step 612 comprises grasping a wire guide having a continuous metallic core member and a continuous jacket disposed over the entire core member. Another step 614 comprises inserting the distal end of the wire guide info a body vessel of the patient. Another step 616 comprises advancing the distal end of the wire guidethrough the body vessel of the patient unti l the distal end of the wire guide is disposed at a first position within a first portion of the body vessel that is located within the scanner of the MRI system. Another step 6.18 comprises operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel. .Another step 620 comprises obtaining a magnetic resonance image of the first portion of the body vessel. Another step 622 comprises withdrawing the wire guide from the body vessel.

[0113] Step 610 can be performed by any suitable technique and the technique used in a method according to a particular embodiment will depend on various considerations, including the nature and configuration of the MRI system and scanner used and the nature and position of the body vessel to for which imaging is to be performed. Conventional MR! systems typically include a patient support surface, such as a table or bed, that can be moved relative to a bore defined by (he MR! system to position a desired portion of the patient within the magnetic field of the scanner. For these MRI systems, step 610 can be performed by moving the patient support system relative to the scanner of the MRI system until the desired portion of the patient is located within the bore of the MRI system. For open, portable, and other MRI systems that do not define a bore within which the patient or portion of the patient can be placed, step 610 can be performed by placing the desired portion oftbe patient within the area within which the magnetic field of the scanner of the MRI system which will be presen t once the scanner of the system is activated. For example, for a portable MRI system, the system can be moved to the patient, such as by transporting the portable MRI system to the bedside of a patient, and then moving the portable MRI system relative to a patient support surface on which the patient is positioned, such as a hospital bed, such that the portion of the body vessel is located within the magnetic field of the scanner, or will be located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the MRI system is activated.

[0114] For step 610, any sui table portion of a patient can be used, and selection of a suitable portion of a patient during performance of a method according to a particular embodiment can be based on various considerations, including desired images, any treatment intended to be performed, and other considerations. Examples of portions of a patient considered suitable Include, but are not limited to, the extremities (e.g., arms, legs), chest, breast, spine, neck, head, abdomen, pelvis, prostate, peri-prostatic structures, tissues surrounding the portions of a patient described herein, and / or any other portion of the patientconsidered suitable for a method according to a particular embodiment. Also for this step, the patient can be any animal for which imaging is desired, including human beings and other mammals.

[0115] Step 612 can be performed by grasping an appropriate wire guide by the hand or using a suitable tool or equipment, such as a robotic arm. Selection of an appropriate wire guide for performance of step 612 is considered important to the performance of the method 600. The wire guide selected should have a continuous metal core member with a jacket that fully encapsulates the core member, such as a jacket that is disposed over the entire length of the core member and that has a length (hat is greater than the length of the core member. Examples of wire guides suitable for use in performance of step 612 include the example wire guides described in detail below and illustrated in the Figures.

[0116] Step 614 can be performed using conventional interventional techniques, such as the Seidinger technique, to introduce (he distal end of the wire guide into any suitable body vessel at a point of insertion. For example, a needle can be used to puncture the skin and enter the body vessel Once access to the body vessel is established in this way, the distal end of (he wire guide can be passed through the lumen of the needle and into the body vessel. The needle can then be withdrawn over the proximal end of the wire guide, leaving the distal end of the wire guide extending into the body vessel. Also, the distal end of the wire guide can be inserted into any suitable body vessel. The body vessel into which the distal end of the wire guide is inserted during performance of a method according to a particular embodiment can be selected based on a desired location for scanning, imaging, treatment, or other considerations. Examples of suitable body vessels include, but are not limited to vessels of the peripheral vasculature. Step 614 can be performed before or after step 610 is performed, or while step 610 is being performed. A skilled artisan will be able to select an appropriate relative ordering of steps 610 and 614 based on a variety of considerations, including the nature of the MRI system and scanner and other considerations.

[0117] Step 616 can be performed by applying a distal ly directed force on a portion of the wire guide that remains external to the body of the patient, s uch as the proximal end of the wire guide or an intermediate portion of the wire guide, such that the distal end of the wire guide moves axially within foe lumen of the body vessel, away from the point of insertion into the body vessel. Step 616 is performed until the distal end of foe wire guide is disposed at a first position within a first portion of the body vessel, the first portion being a portion ofinterest for subsequent step 618 of operating the scanner of the MR! system and step 620 of obtaining an image.

[0118] Step 618 can be performed by operating the MRl system io scan the portion of the patient located within the scanner of the MRI system by performance of step 610. Step 618 can be performed using any suitable MRI parameters applicable for the scanner of the MRI system, such as gradient refocusing echo imaging, spin echo imaging, true fast imaging with steady-state precession, fast low flip angle shot spoiled gradient-echo imaging, field strength, such as 0.55T, 1.5T, 3T, between about ,055T and 1.5T, and a field strength less than IT, slice thickness, flip angle, field-of-view, resolution, gradient fields, and any other MRI parameter or parameters considered suitable for a method according to a particular embodiment.

[0119] Step 620 can be performed by obtaining the image from the scanner of the MRI system used in step 618. For the step 620 of obtaining a magnetic resonance image of the first portion of the body vessel, a single still image can be obtained. Also, and optionally, this step 620 can be repeated any desired number of times to obtain multiple magnetic resonance images that can be grouped as a cine to show motion. Furthermore, as an alternative to, or in addition to, obtaining an image, a step of visualizing the wire guide, a step of visualizing a marker or markers associated with the wire guide, or both, can be included in the method 600.

[0120] Step 622 can be performed by applying a proximally directed force on a portion of the wire guide that remains external to the body of the patient, such as the proximal end of the wire guide or an intermediate portion of the wire guide, such that the distal end of the wire guide moves axially within (he lumen of the body vessel, toward the point of insertion into the body vessel. This step 622 is performed until the distal end of the wire guide passes through the point of insertion and the wire guide completely exits the body lumen. Ultimately, this step 622 results in the wire guide exiting the body of the patient. At this point, performance of the method 600 is complete.

[0121] Step 616, 618, and 620 can be performed discretely and sequentially. For example, performance of step 618 can be initiated after step 616 is completed. Also, performance of step 620 can be initiated after step 618 is completed. Other sequencing of these steps is possible, though, and are considered advantageous for methods according to particular embodiments. For example, if multiple images are desired to aid in navigation of a wire guide through a body vessel, each of steps 618 and 620 can be performed multiple timeswhile step 616 is being performed. That is, the step 618 of operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and the step 620 of obtaining a magnetic resonance image of the first portion of the body vessel can be performed multiple times while the step 616 of advancing the distal end of the wire guide through the body vessel of the patient is being performed. Ln these examples, steps 618 and 620 can be performed any suitable number of times during the performance of step 616, and a skilled artisan will be able to select an appropriate number of times for each step for inclusion in a method according to a particular embodiment based on various considerations, including (he capabilities of the MRI system, the nature of the body vessel and any navigation challenges it presents, and other considerations. Examples of suitable numbers of times for the performance of step 618 and 620 while step 616 is being performed include, but are not limited to, one, two, more than two, three, a plurality, four, five, six, seven, eight, nine, ten, more than ten, eleven, twelve, more than twelve, twenty, fifty, one hundred, and one thousand,

[0122] Performance of the method provides one or more images of the portion of the body vessel that can be used for various purposes, including educational purposes, research purposes, diagnostic purposes, treatment purposes, and informational purposes.

[0123] FIG. 11 illustrates an example method700 of performing interventional medical treatment under MRI.

[0124] An initial step 710 comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated. Another step 712 comprises grasping a wire guide having a continuous metallic core member and a continuous jacket disposed over the entire core member. Another step 714 comprises inserting the distal end of the wire guide into a body vessel of the patient. Another step 716 comprises advancing the distal end of the wire guide through the body vessel of the patient until the distal end of the wire guide is disposed within a first portion of the body vessel having a first position. Another step 718 comprises operating the scanner of the MRI system to scan the portion of the patient that is positioned within die scanner and that includes the first portion of the body vessel. Another step 720 comprises obtaining a magnetic resonance image of the first portion of the body vessel.Another step 722 comprises grasping a medical device having a medical device proximal end and a medical device distal end and includes an elongate member defining a lumen. Anotherstep 724 comprises advancing the distal end of the medical device over the wire guide into the body vessel of the patient until the distal end of the medical device reaches the point of treatment within the body vessel. Another step 726 comprises manipulating a proximal end of the medical device to produce a manipulation of the distal end of the medical device at the point of treatment. Another step 728 comprises withdrawing the medical device from the body vessel. Another step 730 comprises withdrawing the wire guide from the body vessel. [0125 J Step 710 can be performed by any suitable technique and the technique used in a method according to a particular embodiment will depend on various considerations, including the nature and configuration of (he MRI system used and the nature and position of the body vessel for which imaging is to be performed. Conventional MRI systems typically include a patient support surface, such as a table or bed. that can be moved relative to the scanner of the MRI system to position a desired portion of the patient within the scanner. For these MRI systems, step 710 can be performed by moving the patient support system relative to the scanner of the MRI system until the desired portion of the patient, is located within the scanner of the MRI system. As described above with method 700, this step 710 can be performed with other, non-bore defining MRI systems, such as open MRI systems and portable MRI systems, too. For example, for portable MRI systems, step 710 can be performed by moving the portable MRI system relative to the patient to place the desired portion of the patient within the area within which the magnetic field of the scanner of the MRI system will be presen t once the scanner of the system is activated.

[0126] For step 710, any suitable portion of a patient can be used, and selection of a suitable portion of a patient during performance of a method according to a particular embodiment can be based on various considerations, including the location of the desired point of treatment, the nature of the treatment intended to be performed, and other considerations. Examples of portions of a patient considered suitable include, but are not limited to, the extremities (e.g., arms, legs), chest, breast, spine, neck, head, abdomen, pelvis, prostate, periprostatic structures, tissues surrounding the portions of a patient described herein, and / or any other portion of the patient considered suitable for a method according to a particular embodiment. Also for this step, the patient can be any animal for which imaging is desired, including human beings and other mammals,

[0127] Step 712 can be performed by grasping an appropriate wire guide by the hand or using a suitable tool or equipment, such as a robotic arm. Selection of an appropriate wire guide for performance of step 712 is considered important to the performance of the method700. The wire guide selected should have a continuous metal core member with a jacket that fully encapsulates the core member, such as a jacket that is disposed over the entire length of the core member and that has a length that is greater than the length of the core member.Examples of wire guides suitable for use in performance of step 712 include the example wire guides described in detail below and illustrated in the Figures.

[0128] Step 714 can be performed using conventional interventional techniques, such as the Seidinger technique, to introduce the distal end of the wire guide into any suitable body vessel at a point of insertion. For example, a needle can be used to puncture the skin and enter the body vessel. Once access to the body vessel is established in this way, the distal end of the wire guide can be passed through the lumen of the needle and into the body vessel. The needle can then be withdrawn over the prox imal end of the wire guide, leaving the distal end of the wire guide extending into the body vessel. Also, the distal end of the wire guide can be inserted into any suitable body vessel. The body vessel into which the distal end of the wire guide is inserted during performance of a method according to a particular embodiment can be selected based on a desired location for scanning, imaging, treatment, or other considerations. Examples of suitable body vessels include, but are not limited to vessels of the peripheral vasculature. Step 714 can be performed before or after step 710 is performed, or while step 710 is being performed. A skilled artisan will be able to select an appropriate relative ordering of steps 710 and 714 based on a variety of considerations, including the na ture of the MRI system and scanner and other considerations.

[0129] Step 716 can be performed by applying a distally directed force on a portion of foe wire guide that remains external to the body of the patient, such as the proximal end of the wire guide or an intermediate portion of the wire guide, such that the distal end of the wire guide moves axially within the lumen of the body vessel, away from the point of insertion into the body vessel. Step 716 is performed until the distal end of the wire guide is disposed at the a first position within a first portion of the body vessel, the first portion being a portion of in terest for subsequent step 718 of operating the scanner of the MRI sy stem and step 720 of obtaining an image.

[0130] Step 718 can be performed by operating the MRI system to scan the portion of the patient located within the scanner of the MRI system by performance of step 710. Step 718 can be performed using any suitable MRI parameters applicable for the scanner of the MRI system, such as gradient refocusing echo imaging, spin echo imaging, true fast imaging with steady-state precession, fast low flip angle shot spoiled gradient-echo imaging, field strength,such as 0.55T, 1.5T, 3T, between about ,055T and 1.5T, and a field strength less than IT, slice thickness, Hip angle, field-of-view, resolution, gradient fields, and any other MRI parameter or parameters considered suitable for a .method according to a particular embodiment.

[0131] Step 720 can be performed by obtaining the image from the scanner of the MRI system used in step 718. For the step 720 of obtaining a magnetic resonance image of the first portion of the body vessel, a single still image can be obtained. Also, and optionally, this step 720 can be repeated any desired number of times to obtain multiple magnetic resonance images that can be grouped as a cine to show motion. Furthermore, as an alternative to, or in addition to, obtaining an image, a step of visualizing the wi re guide, a step of visualizing a marker or markers associated with the wire guide, or both, can be included in the method 700.

[0132] Step 722 can be performed by grasping an appropriate medical device by the hand or using a suitable tool. Any suitable medical device can be used in step 722 as long as the medical device includes an elongate member that defines a lumen configured to receive the wire guide. The medical device selected for use in a method according to a particular embodiment will depend on various considerations, including the nature of the body vessel, the point of treatment, and the effect desired by performance of the m ethod. Examples of suitable medical device include, but are not. limited to, catheters, balloon catheters, cannula, biopsy device, retrieval devices, and other medical devices. Furthermore, the medical device can include a deployable medical device that can be deployed from the medical device in step 726, described below, and left within the body vessel after performance of the method 700. For example, a medical device used in this step 722 can include a stent, such as a selfexpandable stent, a balloon expandable stent, or other stent, a graft device, such as a stent graft, a valve, such as a prosthetic heart valve or other valve device, a filter, or any other type of deploy able medical device.

[0133] Step 724 can be performed by applying a distally directed force on a portion of the medical device that remains external to the body of the patient, such as the proximal end of the medical device or an intermediate portion of the medical de vice, such that the distal end of the medical device moves axially within the lumen of the body vessel, away from the point of insertion into the body vessel. Step 724 is performed until the distal end of the medical device reaches the desired point, of treatment within the body vessel.[01.34] Step 726 can be performed in any suitable manner that is appropriate for the medical device advanced through the body vessel in step 724. For example, if the medicaldevice is a balloon catheter, step 726 can be performed by passing an inflation fluid into a connector on the proximal end of the device and through an inflation lumen of the medical device such that the balloon on the distal end inflates at the point of treatment. Additional manipulations can be included in the performance of step 726 as appropriate for the medical device, too.

[0135] Step 728 can be performed by applying a proximally directed force on a portion of the medical device that remains external to the body of the patient, such as the proximal end of the medical device or an intermediate portion of the medical device such that the distal end of the medical device moves axially within the lumen of (he body vessel and along the wire guide, toward the point of insertion into the body vessel. This step 728 is performed until the distal end of the medical device passes through the point of insertion and the medical device completely exits the body vessel. Ultimately, this step 728 results in the medical device exiting the body of the patient.

[0136] Step 730 can be performed by applying a proximally directed force on a portion of the wire guide that remains external to the body of the patient, such as the proximal cud of the wire guide or an intermediate portion of the wire guide, such that the distal end of the wire guide moves axially within (he lumen of the body vessel, toward the point of insertion into the body vessel. This step 730 is performed until the distal end of the wire guide passes through the point of insertion and the wire guide completely exits the body lumen. Ultimately, this step 730 results in the wire guide exiting the body of the patient. Al (his point, performance of the method 700 is complete. Various steps of method 700 can be performed discretely and sequentially. For example, performance of step 718 can be initiated after step 716 is completed. Also, performance of step 720 can be initiated after step 718 is completed. Also, performance of step 724 can be initiated after step 720 is completed. Other sequencing of these steps is possible, though, and are considered advantageous for methods according to particular embodiments. For example, if multiple images are desired to aid in navigation of a wire guide through a body vessel, each of steps 718 and 720 can be performed multiple times while step 716 is being performed. That is, the step 718 of operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and the step 720 of obtaining a magnetic resonance image of the first, portion of the body vessel can be performed multiple times while the step 716 of ad vancing the distal end of the wire guide through the body vessel of the patient is being performed. In these examples,steps 718 and 720 can be performed any suitable number of times during the performance of step 716, and a skilled artisan will be able to select an appropriate number of times for each step for inclusion in a method according to a particular embodiment based on various considerations, including the capabilities of the MRI system, the nature of the body vessel and any navigation challenges it presents, and other considerations.

[0137] Also, if multiple images are desired to aid in navigation of the medical device over the wire guide and through the body vessel, each of steps 718 and 720 can be performed multiple times while step 724 is being performed. That is, the step 718 of operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and the step 720 of obtaining a magnetic resonance image of the first portion of the body vessel can be performed multiple times while the step 724 of advancing the distal end of a medical device over the wire guide into the body vessel of the patient is being performed. In these examples, steps 718 and 720 can be performed any suitable number of times during the performance of step 724, and a skilled artisan will be able to select an appropria te number of times for each step for inclusion in a method according to a particular embodiment based on various considerations, including the capabilities of the MRI sys tem, the nature of the body vessel and any navigation challenges it presents, and other considerations. Examples of suitable numbers of times for the performance of step 718 and 720 while step 724 is being performed include, but are not limited to, one, two, more than two, three, a plurality, four, five, six, seven, eight, nine, ten, more than ten, eleven, twelve, more than iwel ve, twenty, fifty, one hundred, and one thousand.

[0138] Also, if multiple images are desired to monitor manipulation of (he distal end of the medical device at the point of treatment, each of steps 718 and 720 can be performed multiple times while step 726 is being performed. That is, the step 718 of operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel and the step 720 of obtaining a magnetic resonance image of the first portion of the body vessel can be performed multiple times while the step 726 of manipulating a proximal end of the medical device to produce a manipulation of the distal end of the medical device at the point of treatment is being performed. In these examples, steps 718 and 720 can be performed any suitable number of times during the performance of step 726, and a skilled artisan will be able to select an appropriate number of times for each step for inclusion in a method according to a particularembodiment based on various considerations, including the capabilities of the MRI system, the nature of the body vessel and any navigation challenges it presents, and other considerations. Examples of suitable numbers of times for the performance of step 718 and 720 while step 726 is being performed include, but are not limited to, one, two, more than two, three, a plurality, four, five, six, seven, eight, nine, ten, more than ten, eleven, twelve, more than twelve, twenty, fifty, one hundred, and one thousand.

[0139] Performance of the method provides one or more images of the portion of the body vessel that can be used for various purposes, including educational purposes, research purposes, diagnostic purposes, treatment purposes, and informational purposes.

[0140] FIG. 12 illustrates an example method 800 of performing interventional medical treatment under MRI. The method 800 is similar to the method 700 described above, except as detailed below'.

[0141] An initial step 810 comprises placing a portion of a patient within or adjacent an MRI system having a scanner such that a portion of the body vessel is located within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is activated. Another step 812 comprises grasping a wire guide having a continuous metallic core member and a continuous jacket disposed over the entire core member. Another step 814 comprises inserting the distal end of a wire guide into a body vessel of the patient. Another step 816 comprises advancing the dista l end of the wire guide through the body vessel of the patient until the distal end of the wire guide is disposed within a first portion of the body vessel having a first position. Another step 818 comprises operating the scanner of the MRI system to scan the portion of the patient that is positioned within (he scanner and that includes the first portion of the body vessel. Another step 820 comprises obtaining a magnetic resonance image of the first portion of the body vessel. Another step 822 comprises grasping a medical device having a medical device proximal end and a medical device distal end and includes an elongate member defining a lumen. Another step 824 comprises advancing the distal end of the medical device over the wire guide into the body vessel of the patient until the distal end of the wire guide reaches the point of treatment within the body vessel. Another step 826 comprises manipulating a proximal end of the medical device to produce a manipulation of the distal end of the medical device at the point of treatment. Another step 828 comprises wi thdrawing the medical device from the body vessel. Another step 830 comprises grasping a second medical device having a second medical device proximal end and a second medical device distal end and includes an elongatemember defining a lumen. Another step 832 comprises advancing the distal end of a second medical device over the wire guide into the body vessel of the patient until the distal end of the second medical device reaches the point of treatment within the body vessel. Another step 834 comprises manipulating the proximal end of the second medical device to produce a manipulation of the distal end of the second medical device at the point of treatment. Another step 836 comprises withdrawing the second medical device from the body vessel. Another step 838 comprises withdrawing the wire guide from the body vessel.

[0142] As described above with method 600 and method 700, step 810 can be performed by moving the patient relative to the MRI system, such as with MRI systems that define a bore into which the patient is positioned for an imaging procedure. Also, step 810 can be performed by moving a portable MRI system relative to the patient to position the patient, or a portion of the patient, within the area within which the magnetic field of the scanner of the MRI system will be present once the scanner of the system is acti vated.

[0143] Step 814 can be performed before or after step 810 is performed, or while step 814 is being performed. A skilled artisan will be able to select an appropriate relative ordering of steps 810 and 814 based on a variety of considerations, including the nature of the MRI system and scanner and other considerations.

[0144] In some methods, it may be desirable to pre-load a wire guide into a medical device having an elongate member defining a lumen. In these methods, the distal end of the medical device can be advanced substantially over the wire guide prior to inserting the distal end of the wire guide into the body vessel. In these methods, the distal end of the medical device is advanced over the wire guide until only a relatively small portion of the wire guide extends beyond (he distal end of (he medical device. The wire guide and medical device are then inserted into the body vessel and navigated through the body vessel together.

[0145] As discussed herein, in some embodiments, wire guides are provided that include a plurality of passive MRI markers, for example as described in connection with FIGs. 23 to 31 above. Beneficial embodiments are provided wherein the pattern of passive MRI markers enables visual observation by a user and / or enables detection by the MRI system, for example based on the size(s), relative positionfs), or movements) of the markers, and where the MR1 system is configured to execute at least one function based on such detection. The MRI system can be configured to delect such patterns using a computer processor. For these purposes, the MRI system can include software, for example software with artifact recognition, localization, tracking, image processing, and / or machine learning. The MRIsystem can also include a database that correlates a unique pattern of image artifacts generated by the wire guide, and / or its combination with another medical device, that when a pattern of image artifacts is identified by the MR scanner during use the MR scanner can identify and / or track the wire guide, or its combination with another medical device, alter a first set of MR image parameters and / or sequence to a second set of MR image parameters and / or sequence, e.g. as described herein, and / or alter the image created by the MRI system to create an altered MR image. The database can include features of each pattern of image artifacts produced by the wire guide, or its combination with another medical device, such as characteristics, such as size, shape, pattern, and-or intensity, to identify the specific wire guide. For example, each of the medical devices of FIGs. 23 to 31 has a distinct pattern of markers. As a result, each of the wire guides or its combination with another medical device, will produce a distinct image artifact pattern (e.g., code) under MRI that can be identified using the database included in the MRI system. Image processing software or machine learning can optionally be used to determine the state of these markers, or image artifacts, in real or near .real-time (e.g. with a new image being generated and displayed about every 0. 1 to 7 seconds), aiding in the estimation of device positioning through automated sequence selection and allowing for path planning to targeted locations during treatment to avoid critical or sensitive anatomy.

[0146] As noted above, the pattern of the passive MRI markers on the wire guide can enable various functions to be automatically executed by the MRI system based on the detection of the passive MRI markers or their artifacts. As an example, based on such detection, the MRI system can, using the computer processor, identify the wire guide, locate it in three-dimensional space, and adjust the imaging plane of the MRI system to be optimal for visualizing the wire guide. In some forms, as the wire guide is navigated through the vasculature, the MRI system can, using the computer processor, continuously detect and track the passive MRI markers and maintain optimal imaging of the moving wire guide by continually adjusting the imaging plane. The ability to automatically locate and track the wire guide reduces the burden on a user (e.g. MR technician or physician) to allow focus on navigating and performing treatment. Clear visualization of the wire guide provides greater accuracy and speed and treatment procedure time can be reduced.

[0147] In another example, the MRI system, using the computer processor, can alter an MRI image being displayed on an electronic display of the MRI. system, for example by adding visible graphic, with the .graphic potentially provided as an overlay of the MRIimage(s). Such a graphic overlay may, for example, estimate a shape a distal region of the wire guide, and / or provide an indicator of the distal end of the wire guide, A user inpu t device such as a keyboard of the MR! system may be used as a control to display or not display the graphic, as desired.

[0148] In another example, a code for the wire guide can be uploaded to the computer processor of the MRI system (e.g., by optically scanning a bar code on the wire guide). The MRI system can identify the wire guide, for example by reference to a database correlating the code to the wire guide and its passive MRI marker patern, and can execute a function based thereon. For instance, the MR Y system can overlay a graphic on displayed MRI image, for example where the graphic can identity and distinguish the wire guide from another device, e.g. by overlaying a graphic substantially matching the profile of the wire guide. During the procedure the graphic overlays may be made by the MRI system to appear more or less bright on the MR images as the device is focused upon through the course of the treatment procedure.

[0149] In another example, the pattern of MRI markers can be configured such that MRI system, apart from genera ting MR images, detects signals in K-Space (an array of numbers representing spatial frequencies in an MR image) based on the presence of passive MRI markers on the wire guide. For example, while other medical devices are being visually displayed and / or tracked using the computer processor of the MRI system, for example catheters positioned or being advanced over the wire guide with the wire guide in a fixed position, the K-space data in the region the wire guide can be continually monitored using the computer processor to confirm that the wire guide maintains its intended fixed position. The MRI system can signal a user (e.g. audibly through a speaker and / or visually on an electronic display) if the position of the wire guide changes more than a predetermined amount (e.g. 5 cm from the intended anchored position). If needed the user can then refocus the MR image display on the wire guide to reposition it prior to continuing the procedure to prevent access from being lost to the intended treatment location.

[0150] Methods of making a wire guide and methods of making a plurality of wire guides are also provided.

[0151] FIG. 13 illustrates an example method of making a wire guide 900. An initial step 910 comprises forming a continuous core member of a metallic material, the continuous core member having an outer surface. Another step 912 comprises disposing a jacket on the continuous core member such that the outer surface of the core member is in continuous contact with the jacket and such that no portion of the outer surface of the core member isexposed to the external environment surrounding the wire guide. An optional step 914 comprises evaluating the jacket to determine if the outer surface of the core member is fully encapsulated by the jacket, in continuous contact with the jacket, or both. Another optional step 916 comprises transferring the wire guide to an intended user of the wire guide only if the evaluating step 916 results in a determination that the outer surface of the core member is in continuous contact with the jacket.

[0152] Step 910 can be performed using any suitable process or technique, including cuting a length of a core member from a stock supply of core member material. Furthermore, any suitable material can be used in the performance of step 910, as described above in relation to the core member of the example wire guides described herein. To form a wire guide according to an embodiment, the material should be a metallic material. Examples of metallic materials considered suitable for forming the core member during the performance of step 910 include, but are not limited to, shape memory alloys, including nickel-titanium alloys such as Nitinol, Superelastic Nitinol SE508 straight with black oxide, matte finished Nitinol, polished Nitinol, combinations of those described herein, and any other metallic materials considered suitable. Step 910 can include various processes and techniques commonly used in the formation of metallic wire guides, including grinding an end to form a desirable tip shape.

[0153] Step 912 can be performed using any suitable process or technique, including extruding a polymeric material over the continuous core member to form the jacket, reflowing a polymeric material over the continuous core member to form the jacket, and other suitable processes and techniques. If included, step 914 can be performed by performing a visual inspection of the j acket to identify any disruptions in the continuous nature of the jacket, performing a visual inspection of the jacket to determine if any portion of the continuous core member is visible; hydrating the continuous core member and determining if any fluid leaks through the jacket, evaluating conduction, induction, or both properties of the core member, and other suitable visual inspection, leak testing, or other suitable quality control techniques. Multiple steps can be included for evaluating the jacket, if desired, such as the leakage testing steps described in detail below.

[0154] If included, step 916 can be performed by shipping a wire guide to a purchased, an end user, or an agent of an end user, after determining that the outer surface of the core member is in continuous contact with the jacket.

[0155] In alternative methods of making a wire guide, two or more segments that each include a continuous core member and a jacket surrounding the continuous core member can be joined by placing the segments end to end relative to each other, as in a series, and reflowing the jackets by heat treatment to for a continuous wire guide having a continuous jacket that fully encapsulates the series of continuous core members from the previously individual segments. The positioning of the segments and the reflowing of the jackets can be performed in a manner such that the individual continuous core members are abutting each other in the final wire guide, with no insulating material between them, or such that a portion of the jacket is disposed between the individual continuous core members following the reflowing of the jacket. This alternative method can be advantageous for inclusion of distal ends having a jacket comprising a different dielectric material than a jacket of another segment used for the main body of a wire guide, for example,

[0156] FIG. 14 illustrates an example method of making a plurality of wire guides 1000, An initial step 1010 comprises forming a plurality of continuous core members, each continuous core member of the plurality' of continuous core members formed of a metallic, material and having an outer surface. Another step 1012 comprises disposing a jacket comprising one or more dielectric materials on the outer surface of a continuous core member such tha t the continuous core member is fully encapsulated by the jacket. This step 1012 can be performed such that the outer surface of the core member is in continuous contact with the jacket. This step 1012 is repeated for each continuous core member formed in step 1010.Another step 1014 comprises evaluating each jacket to determine If the continuous core member associated with the jacket i n step 1012 is fully encapsulated by the jacket. An optional step 1016 comprises destroying any wire guides from the plurality of wire guides for which the evaluating step results in a determination that the continuous core member is not fully encapsulated by a jacket. Another optional step 1018 comprises transferring a first wire guide to a first intended user only if the evaluating step 1014 results in a determination that the continuous core member is fully encapsulated by a jacket. Another optional step 1020 comprises transferring a second wire guide to a second intended user only if the evaluating step 1014 results in a determination that the continuous core member is fully' encapsulated byra jacket

[0157] Methods of making a wire guide and methods of making a plurality of wire guides can leverage the metal of the continuous core member and the dielectric nature of the jacket in a step or steps for evaluating the encapsulation of the continuou s core member by thejacket in each wire guide made by the relevant method. For example, a method can include steps applying an electric current to one end of the continuous core member and measuring the current at the opposite end of the continuous core member to determine if leakage of the applied current is occurring. If leakage is detected, the wire guide can be rejected as likely having a jacket that does not fully encapsulate the continuous core member. One particular method includes the steps of submerging a wire guide in a conductive fluid, such as physiological sal ine, electrically coupling the continuous core member of the wire guide to a source of electric current to induce current flow in the continuous core member, and measuring current in the conductive fluid to determine if leakage of the applied current into the conductive fluid is occurring. A step of rejecting the wire guide if leakage of current is detected can be included. Detecting leakage of current is considered particularly advantageous as a quality control measure in methods of making a wire guide and methods of making a plurality of wire guides at least because it is believed that leakage of current will correlate with temperature rise of the wire guide under MRI. Identification of a wire guide that demonstrates leakage of electrical current is believed to be a reliable indicator of a wire guide (hat will demonstrate elevated heating under MRI due to less than full encapsulation of the continuous core member by the jacket.

[0158] As disclosed above, in some methods of wire guide manufacture, a polymeric jacket is disposed on a continuous core member. In making wire guides in which passive MRI marker(s) is / are provided by a passive MRI marker-forming material adhered to the outer surface of the core member, the marker-forming material can be deposited on the outer surface of the core member prior to disposing the pol ymeric j acket thereon. For example , a continuous core member bearing passive MRI markers, e.g. as discussed in conjunction with wire guide 1100, 1200, or 1300 hereinabove, can be prepared. The polymeric jacket (e.g. 1 130, 1230 or 1330) can then be disposed on the marker-bearing continuous core member. In some preferred forms, the polymeric jacket will be over-extruded onto the marker-bearing continuous core member. For instance, such an over-extrusion process can include the steps of advancing the marker-bearing continuous core member in to an ex trusion apparatus, pulling the marker-bearing continuous core member through the extrusion apparatus, extruding a molten polymeric material onto an outer surface of the marker-bearing continuous core member, and causing the molten polymeric material to solidify (e.g. by cooling) to form the polymeric jacket as described herein. The pulling can be conducted witha gripping apparatus in some forms, which can for example grip a portion of the markerbearing continuous core wire, or a portion of an already-solidified polymeric jacket portion, that has already passed through the extrusion apparatus. After completion of the over-extrusion with the extrusion apparatus, the prox imal and / or distal end(s) of the over- extruded product can be processed, if and as necessary, to ensure closed proximal and distal ends of the polymeric jacket over the proximal and distal ends of the marker-bearing continuous core member.

[0159] In other methods of manufacture, a continuous core member bearing passive MRI markers, e.g. as discussed in conjunction with wire guide 1 100, 1200, or 1300 hereinabove, can be prepared. The polymeric jacket (e.g. 1 130, 1230 or 1330) can then be disposed on the marker-bearing continuous core member by a heat shrink process. In particular, the markerbearing continuous core member can be placed within a length of heat-shrinkable polymeric tubing, for example heat-shrinkable polytetrafluoroethylene (PTFE) tubing, and the heat- shrinkable tubing can be heated to cause it to shrink to fit snugly against the outer surface of the marker-bearing continuous core member. The proximal and / or distal end(s ) of the heatshrink jacketed product can be processed, if and as necessary, to ensure closed proximal and distal ends of the polymeric jacket over the proximal and distal ends of the marker-bearing continuous core member. In some forms, such end processing can include adding a volume of polymeric material to close the proximal and / or distal end of the heat-shrink jacketed product,

[0160] The above-described over-extrusion jacketing method steps, or the above- described heat shrink jacketing method steps, can be incorporated in any of those more generalized manufacturing methods discussed herein above.SPECIFIC EXAMPLES

[0161] FIG. 15 includes graphical representation of raw RF-induced heating for various test wire guide constructions over 2-7 minutes of scanning in a 1.5T MRI system. Measured temperature for the four scans of a wire guide having a continuous Nitinol core covered entirely by a jacket (Mi Wire® Nitinol core wire guide available from Cook Medical of Bloomington, IN) is shown in the panels on the left and temperature rise normalized to the initial temperature is shown on the panels on the right. The top three sets of panels reflect data for wire guides having fully intact jackets; (he bottom two panels reflect data for wire guides in which the proximal end was cut to expose the proximal terminal surface of the wire guide prior to scanning in the MRI system. Data from four separate temperature probes are included.

[0162] FIG. 16 presents a table of experimental data showing maximum temperature rise for a) a wire guide having a continuous Nitinol core covered entirely by a jacket (fit Wire® Nitinol core wire guide available from Cook Medical of Bloomington, IN), and b) a wire guide having a segmented construction. Considering the teaching of the art, which suggests that a segmented construction is necessary to avoid undesirable RF heating under MRI, this data surprisingly reveals that a wire guide having a fully intact jacket on a continuous nitinol core did not show the expected significant RF heating in an MRI scanner. Data from four separate temperature probes are included.

[0163] Also surprisingly, the data reflected in the bottom two panels of FIG, 15 demonstrate tha t partial insulation in a wire guide by a jacket (i.e., the test wire guides in which the proximal end was cut to expose the proximal terminal surface of the wire guide prior to scanning in the MRI system) results in increased heating, which is believed to be due to a concentration of all electromagnetic propagating waves on the small area of the exposed terminal surfaces of the core member, and the inability of these waves to escape the insulation provided by the jacket along the length of the continuous core member. Based on this, the inventors believe that a wire guide having a continuous core that is folly covered by a jacket will exhibit less heating than that exhibited by a bare continuous core in foe same environment, and that a continuous core that is covered by a jacket but that has a hire end of foe core member exposed will exhibit even greater temperature rise tn the same environment. For at least this reason, inspection of foe jacket in wire guides according to the invention, and forpotential exposure of the core member to the external environment surrounding the wire guide, is considered important.

[0164] Computational modeling and simulation (CM&S) was used to evaluate normalized heating of biological tissue due to radiofrequency (RF) hea ting. MR! scanners create images using a large static magnetic field (typically 1 ,5 T but also include 3 T, 1 .2 T and low field scanners 0.7 T and 0.55 T), three gradient magnetic fields, and a set of coils that: transmit and receive radiofrequency (RF) waves. Clinical MRI systems typically use an RF body coil to transmit RF energy which in tum heats the surrounding tissues. Finite Element Analysis (FEA) of a typical covered wire guide in an ASTM F2182 gel phantom was conducted using COMSOL Multiphysics®' v6.0 to quantify the normalized heating of tissue as a function of insulated covering thickness and electrical conductivity as presented in the tables illustrated in FIGS. 17 and 18. The table illustrated in FIG. 19 presents electrical conductivity for some typical wire guide insulating materials.

[0165] COMSOL's RF module solves Maxwell's equations subject to initial and boundary- conditions and constitutive material properties. A frequency-domain wave equation is solved lor the electric field (E) shown in Equation 1 presented in FIG. 20. The eigenvalue problem is solved at frequency (co), given the magnetic permeability of a vacuum (po), the relative magnetic permeability (Pr= p / po), the electrical permittivity of a vacuum (Eo), the relative electrical permittivity (Er - £ / £0), and the electrical conductivity (a) of the material,

[0166] COMSOL's heat transfer module solves the heat equation for heat conduction in a solid (Equation 2, presented in FIG. 21) subject to initial and boundary conditions. The transient heat equation is solved for temperature (T), given time (t) , a heat source (q) solved for in the electromagnetic simulation, the density (p) , the specific heat (ep), and the thermal conductivity of the material. Only in-vivo simulations included the perfusion term in the bioheat equation.

[0167] Maxwell’s equations and the heat equation are coupled in COMSOL using Joule heating, also known as resistive heating, as the heat source in the heat equation. Joule heating is the process by which the passage of electric current (J) through a conductor releases heat(q) as shown in Equation 3, presented tn FIG. 22, given the electric field (E) from Equation 1.LISTING OF CERTAIN DISCLOSED EMBODIMENTSThe following provides an enumerated listing of some illustrative Embodiments disclosed herein. It will be understood that the following listing is non-limiting, and thatother embodiments are disclosed herein, including for example embodiments in which one, two, or three or more features disclosed hereinabove in the Detailed Description are combined with features of the enumerated Embodiments below.

[0168] 1. An MRI compatible wire guide, comprising: a core member having a proximal end, a distal end, and a length between the proximal end and the distal end; a first passive MRI marker disposed along the length of the core member; a second passive MRI marker disposed along the length of the core member and longitudinally spaced from the first passive MRI marker; and a polymeric jacket that encapsulates the core member.

[0169] 2. The wire guide of Embodiment 1 , wherein:

[0170] the elongated core member has a proximal end, a distal region extending to the distal end, and a longitudinal axis, wherein the distal region includes a tapered core member segment having a decreasing outer diameter in a direction toward the distal end;

[0171] at least the first passive MRI marker is disposed along the tapered core member segment and includes a first layer comprising a first passive MRI marker-forming material adhered to an outer surface of the tapered core member segment of the core member;

[0172] the second passi ve MRI marker includes a second layer comprising a second passive MRI marker-forming material adhered to an outer surface of the core member; and

[0173] the polymeric jacket encapsulates the core member, the first layer and the second layer,

[0174] 3, The wire guide of Embodiment 2, wherein:(he first layer is in (he form of a circumferential band extending completely around the outer surface of the tapered core member segment; and the second layer is in the form of a circumferential band extending completely around the outer surface of the core member,

[0175] 4, The wire guide of Embodiment 2 or 3, wherein the second layer is adhered to aa outer surface of the tapered core member segment of the core member,

[0176] 5. The wire guide of Embodiment 3, wherein the core member includes a first constant diameter core member segment distal of the tapered core member segment, and wherein the second layer is adhered to an outer surface of the first constant diameter core member segment.

[0177] 6. The wire guide of Embodiment 4, also comprising:a third passive MRI marker including a third layer comprising a third passive MRI marker-forming material, the third layer adhered to an outer surface of the core member,7, The wire guide of Embodiment 6, wherein: the core member includes a first constant diameter core member segment distal of the tapered core member segment; and the third layer is adhered to an outer surface of the first constant diameter core member segment.

[0178] 8. The wire guide of Embodiment 7, also comprising: a fourth passive MRI marker including a fourth layer comprising a fourth passiveMRI marker-forming material, the fourth layer adhered to an outer surface of the core member.

[0179] 9. The wire guide of Embodiment 8, wherein: the fourth layer is adhered to an outer surface of the first constant diameter core member segment.

[0180] 10. The wire guide of any of Embodiments 7 to 9. wherein: the third layer is in the form of a circumferential band extending completely around the outer surface of the first constant diameter core member segment; and the fourth layer is in the form of a circumferential band extending completely around the outer surface of the first constant diameter core member segment.

[0181] 11. T he wire guide of Embodiment 1 , also comprising: a third passive MRI marker disposed along the length of the core member and longitudinally spaced from the first and second passive MRI markers; and a fourth passive MRI marker disposed along the length of the core member and longitudinally spaced from the first, second and third passi ve MRI markers; wherein the first and second passive MRI markers are disposed along a distal-most segment of the core member that terminates in the distal end of the core member, the distal- most segment having a length of 10 cm; wherein the first passive MRI marker is distal of the second passive MRI marker along the distal-most segment of the core member: wherein the third passive MRI. marker is disposed along the core member proximal of the distal-most segment; wherein the fourth passive MRI marker is disposed along the core member proximal of the third passive MR! marker;wherein the first and second passive MRI markers are longitudinally spaced from one another a first longitudinal distance along the length of the core member; wherein the third and fourth passive MRI markers are longitudinally spaced from one another a second longitudinal distance along the length of the core member; and wherein the second longitudinal distance is greater than the first longitudinal distance.

[0182] 12. The wire guide of Embodiment 1 1 , also comprising: a fifth passive MRI marker disposed along the length of the core member and longitudinally spaced from the first, second, third and fourth passive MRI markers along the length of the core member.

[0183] 13. The wire guide of Embodiment 12, wherein; the fifth passive MRI marker is disposed along the length of the core member proximal of the fourth passive MRI marker, the fourth and fifth passive MRI markers longitudinally spaced from one another a third longitudinal distance along the length of the corer member, wherein the third longitudinal distance is equal to the second, longitudinal distance.

[0184] 14. The wire guide of Embodiment 12, wherein: the fifth passive MRI marker is disposed along the distal-most segment of the core member distal of the first passive MRI marker, the first and fifth passi ve MRI markers longitudinally spaced from one another a third longitudinal distance along the length of the core member, wherein the third longitudinal distance is equal to the first longitudinal distance.

[0185] 15. The wire guide of Embodi ment 13, also comprising: a sixth passive MRI marker disposed along the distal-most segment of the core member distal of the first passive MRI marker, the first and sixth passive MRI markers longitudinally spaced from one another a fourth longitudinal distance along the length of the core member, wherein the fourth longitudinal distance is equal to the first longitudinal distance.

[0186] 16. The wire guide of Embodiment 15, also comprising: a seventh passive MRI marker disposed along the distal-most segment of the core member distal of the sixth passive MRI marker, the sixth and seventh passive MRI markers longitudinally spaced from one another a fifth longitudinal distance along the length of the core member, wherein the fifth longitudinal distance is equal to the first longitudinal distance.

[0187] 1 7. The wire guide: of Embodiment 11 , wherein the first, second, third and fourth passive MRI markers(j) each include a layer comprising a passive MRI marker-fonning material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker- forming material disposed within a thickness of the polymeric jacket; or of any one of Embodiments 12 to 14, wherein the first, second, third, fourth and fifth passive MRI markers (i) each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket; or of Embodiment 15, wherein the first, second, third, fourth, fifth and sixth passiveMRI markers (i) each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket; or of Embodiment 16, wherein the first, second, third, fourth, fifth, sixth and seventh passive MRI markers (i) each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket.

[0188] 18. The wire guide of any one of Embodiments 11 to 16, wherein the first longitudinal distance is less than 3 cm.

[0189] 19. The wire guide of Embodiment 18, wherein the first longitudinal distance is in the range of about 1.5 cm to about 2.5 cm,

[0190] 20. The wire guide of any one of Embodiments 1 1 to 19, wherein the second longitudinal distance is at least about 8 cm.

[0191] 21 . The wire guide of Embodiment 20, wherein the second longitudinal distance is in the range of about 8 cm to about 30 cm.

[0192] 22. The wire guide of Embodiment 21 , wherein the second longitudinal distance is in the range of about 10 cm to about 20 cm.

[0193] 23. The wire guide of; any one of Embodiments 1 to 22, wherein the first passive MRI marker and the second passive MRI marker are each configured to generate a visible artifact having a maximum dimension in the range of about 1 .5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; orany one of Embodiments 6 to 22, wherein the first, second and third passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of Embodiments 8 to 22, wherein the first, second, third and fourth passiveMRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1 .5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket: or any one of Embodiments 12 to 22, wherein the first, second, third, fourth and fifth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a max imum outer diameter of the polymeric jacket; or any one of Embodiments 15 to 22, wherein the first, second, third, fourth, fifth and sixth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm atid-or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket: or any one of Embodiments 16 to 22, wherein the first, second, third, fourth, fifth and sixth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1 .5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket.

[0194] 24. The wire guide of any one of Embodiments 2 io 23, wherein: the first passi ve MRI marker includes a first layer comprising a first volume of a first passive MRI marker-forming material adhered to an outer surface of the core member; the second passive MRI marker includes a second layer comprising a second volume of a second passive MRI marker forming material adhered to an outer surface of the core member; the first passive MRI marker forming material and the second passive MRI marker forming material are the same: the first volume and the second volume are substantially the same; and the first layer differs at least 10% from (he second layer in at least one of thickness and outer surface area.

[0195] 25. The wire guide of Embodiment 24, wherein:the first layer is in the form of a first circumferential band that extends completely around the outer surface of the core member; and the second layer is in the form of a second circumferential band that extends completely around the outer surface of the core member.

[0196] 26. The wire guide of Embodiment 25, wherein: the first layer and the second layer have substantially the same thickness; and the first circumferential band has a longitudinal length along the core member that differs at least .10% from that of the second circumferential band.

[0197] 27. The wire guide of Embodiment 25, wherein: the first layer and the second layer differ substantially in thickness: and the first circumferential band has a longitudinal length along the core member that is substantially the same as that of the second circumferential band.

[0198] 28. The wire guide of any one of Embodiments 1 to 27, wherein: the core member is a continuous length of wire made from a metal alloy and extending from the proximal end to the distal end of the core member.

[0199] 29. The wire guide of Embodiment 28, wherein the metal alloy is a superelastic nitinol alloy.

[0200] 30. The wire guide of Embodiment 28 or 29, wherein the first passive MR1 marker comprises a first marker-forming material and the second passive MR1 marker comprises a second marker-forming material, wherein the first marker-forming material and the second marker-forming material both have a magnetic susceptibility greater than that of the metal alloy.

[0201] 31 . The wire guide of Embodiment 30, wherein the first marker-forming material and the second marker-forming material are each a metallic material.

[0202] 32. The wire guide of Embodiment 31 , wherein the metallic material is a plated metallic material plated over the outer surface of the elongate member.

[0203] 33. The wire guide of Embodiment 31 or 32, wherein the metallic material has a magnetic susceptibility of at least about 7000 ppm, or in foe range of about 7000 ppm to about 1 ,000,000, or in the range of about 7000 ppm to about 100,000.

[0204] 34. The wire guide of Embodiment 31 or 32, wherein the metallic material is selected from nickel, alloys of nickel, iron, alloys of iron, cobalt, and alloys of cobalt.

[0205] 35. The wire guide of Embodiment 34, wherein the metallic material is nickel or an alloy containing nickel, molybdenum, and iron.

[0206] 36. The wire guide of Embodiment 35, wherein the metallic material is nickel.

[0207] 37. The wire guide of Embodiment 36, wherein: the first passive MRI marker contains a first volume of nickel of at least about 0.01 mm3; and the second passive MRI marker each contains a second volume of nickel of at least about 0,01 mm3: when present, the third passi ve MRI marker contains a third volume of nickel of at least about. 0.01 mm3; when present, the fourth passive MRI marker contains a fourth volume of nickel of at least about 0.01 mnr1; when present, the fifth passive MRI marker contains a fifth volume of nickel of at least about 0.01 mm3; when present, the sixth passive MRI marker contains a sixth volume of nickel of at least about 0.01 mm’; and when present, the seventh passive MRI marker contains a seventh volume of nickel of at least about 0,01 mm3.

[0208] 38. The wire guide of Embodiment 37, wherein the first volume, second volume, third volume, fourth volume, fifth volume, sixth volume and seventh volume are each in the range of about 0.01 mm3to about 0.1 mm3, or about 0.02 mm3to about 0.075 mm3, or about 0,03 mm3to about 0.05 mm3.

[0209] 39. The wire guide of Embodimen t 37 or 38, wherein the first volume, second volume, third volume, fourth volume, fifth volume, sixth volume and seventh volume are each a plated volume of nickel plated onto the outer surface of the core member.

[0210] 40. The wire guide of any one of Embodiments 1 to 39, wherein: the wire guide lias distal-most wire guide segment with a relaxed configuration in the absence of externally applied force, the distal-most wire guide segment having a length of 10 cm; at least the first passive MRI marker is positioned in the distal-most wire guide segment and includes a layer of passive MRI marker-forming material adhered to an outer surface of the core member; the segmen t of the core member within the distal-most wire guide segment, is sized and confi Sg--ured such that when the distal-most wire S g--uide se Sa-'ment is fbrcib.lv and resilientlv ** deformed from the relaxed configuration to a deformed configuration, the segment of thecore member exerts a resilient return force that urges a resilient return of the distal-most wire guide segment to the relaxed configuration; any layer or layers of passive MRI marker forming material adhered to the outer surface of the distal-most segment of the core member is / are sized and configured to plastically deform during movement of the distal-most segment of the core member from the preset relaxed configuration io the deformed configuration; and said any lay er or layers of passive MRI marker forming material are sized and configured so as to again plastically deform in response to said resilient return force during resilient return of the distal-most wire guide segment to the set relaxed configuration,

[0211] 41. The wire guide of Embodiment 40, wherein the distal-most segment of the core member is free from any layer of passive MRI marker-forming material having a longitudinal length of greater than 2 mm, or greater than 1 mm.

[0212] 42, The wire guide of Embodiment 40 or 41 , wherein the distal-most segment of the core member is free from any layer of passive MRI marker-forming material having a thickness greater than 0.05 mm.

[0213] 43. The wire guide of any one of Embodiments 1 to 39, wherein: the wire guide has distal-most wire guide segment with a relaxed configuration in the absence of externally applied force, the distal-most wire guide segment having a longitudinal length of 10 cm; at least the first passive MRI marker is positioned in the distal-most wire guide segment and includes a layer of passive MRI marker- forming material adhered to an outer surface of the core member:(he segment of the core member within the distal-most wire guide segment, when the distal-most wire guide segment is forcibly and resiliently deformed from the set relaxed configuration to a deformed configuration, is sized and configured to exert a resilient return force to urge resilient return of the distal-most wire guide segment to the relaxed configuration; any layer or layers of passive MRI marker forming material adhered to the outer surface of the distal-most segment of the core member is / are sized and configured to plastically deform during movement of the distal-most wire guide segment from the relaxed configuration to the deformed configuration;said any layer or layers of passive M'Rl marker forming material are sized and configured so as to not plastically deform in response to said resilient return force, thereby providing a selectively shape-settable character to the distal-most wire guide segment,

[0214] 44. The wire guide of Embodiment 40, wherein the distal-most segment of the core member has at least one layer of passive MR.I marker-forming material having a longitudinal length of at least 7 mm.

[0215] 45. The wire guide of any one of Embodiments I io 44, wherein the distal-most segment of the core member has a maximum diameter of less than about 0.4mm, or less than about 0.3 mm, or less than about 0.2 mm,

[0216] 46. The wire guide of any one of Embodiments 21 to 29, wherein a distal-most 50 crn segment of the core member includes a tapered portion having a decreasing outer diameter in a direction toward the distal end of the core member, and the tapered portion has a longitudinal length of about 3 cm io about 40 crn.

[0217] 47. The wire guide of any one of Embodiments I io 46, wherein the core member is a continuous core member having a proximal end, a distal end, a term inal surface of the proximal end, and a terminal surface of the distal end, wherein a proximal end of the jacket covers the terminal surface of the proximal end of the core member and the distal end of the jacket covers the terminal surface of the distal end of the core member.

[0218] 48. The wire guide of Embodiment 47, wherein the continuous core member is a single wire having a proximal end terminal surface received against a proximal end wall of the jacket and a distal end terminal surface received against a distal end wall of the jacket,

[0219] 49. The wire guide of Embodiment 1, wherein:(he first and second passive MR1 markers are disposed along a distal-most segment of the core member that terminates in the distal end of the core member, the distal-most segment having a length of 10 cm: the first passive MR1 marker includes a first layer comprising a first passive MRI marker-forming material adhered to an outer surface of the distal most segment of the core member; the second passive MR! marker includes a second layer comprising a second passive MRI marker-forming material adhered to the outer surface of the distalmost segment of the core member; andthe wire guide also comprises a third passive MR! marker, wherein the third passive MRI marker includes a third layer comprising a third passive MRI marker-forming material adhered to the outer surface the distal-most segment of the core member; the polymeric jacket encapsulates foe core member, the first layer, the second layer and the third layer; and further wherein: the first passive MRI marker-forming material, the second passive MRI markerforming material, and the third passive MRI marker-forming material each have a magnetic susceptibility of at least 1 ; or the first passive MRI marker-forming material, the second passive MRI markerforming material, and the third passive MRI marker-forming material are each nickel, and the first layer, the second layer, and the third layer each have a volume of nickel of at least about 0.01 mm3, or in the range of 0.01 mm3to about 0.1 mnr, or in the range of about 0.015 nrmm3to about 0.075 min k or in the range of about 0.02 mm ' io about 0.05 mm*.

[0220] 50. The wire guide of Embodiment I or 49, wherein:(he first passive MRI marker, the second passive MRI marker, and the third passive MRI are configured to generate discrete visible image artifacts; and / or the first passive MRI marker, the second passive MRI marker, and the third passive MRI marker are each configured to generate a visible an artifact that has a maximum dimension that is in the range of 15 to about 100 times the greatest outer diameter of the polymeric jacket ; and / or the first passive MRI marker, the second passive MRI marker, and the third passive MRI marker are each configured to generate a visible an artifact that has a maximum dimension in the range of about 0.5 cm to about 3 cm, or about I cm to about 2 cm; and / or the second layer is positioned longitudinally between the first layer and the third layer and is spaced at least at least 1.5 cm, or in the range of 1 .5cm to 3cm, from each of the first layer and the third layer.

[0221] 51. A method for milking a polymer-encapsulated wire guide, comprising: providing a core member made of a first material; depositing al least one layer comprising a second material onto an outer surface of the core member, wherein the second material has a magnetic susceptibility greater than that of' the first material, and wherein the layer is configured to provide a passive MRI marker; and disposing a polymeric jacket over the core member and at least one layer.

[0222] 52. The method of Embodiment 51 , wherein said disposing comprises: advancing the core member longitudinally through an extrusion apparatus so as to extrude molten polymeric jacket material against and around the core member, and causing the molten polymeric jacket material to solidify; or heat shrinking a tube of heat-shrinkable polymeric jacket material over the core member.

[0223] 53. The method of Embodiment 51 or 52, wherein said first material is a metal, and wherein said depositing comprises plating.

[0224] 54. The method of any one of Embodiments 51 to 53, wherein said depositing at least one layer comprises depositing a plurality of discrete layers longitudinally spaced from one another along the core member.

[0225] 55. The method of Embodiment 54, wherein the layers are configured as passiveMRI markers.

[0226] 56. The method of Embodiment 55, also comprising applying a plurality of visible markings to an outer surface of polymeric jacket, with each visible marking at a location corresponding to a respective one of the passive MRI markers.

[0227] 57. The method of Embodiment 56, wherein the visible markings comprise a contrasting ink.

[0228] 58. The method of any one of Embodiments 51 to 57, wherein the at least one layer comprises nickel.

[0229] 59. The method of Embodiment 58, wherein the layer comprising nickel is a plated layer of nickel.

[0230] 60. The method of Embodiment 59, wherein the plated layer of nickel has a thickness not exceeding 0.04 mm.

[0231] 61. The method of any one of Embodiments 51 to 60, wherein the polymeric jacket material comprises a polyurethane polymer or a polytetrafhiorethylene polymer.

[0232] 62. The method of any one of Embodiments 51 to 61, wherein the polymeric jacket material comprises a particulate paramagnetic or ferromagnetic material.

[0233] 63. The method of any one of Embodiments 51 to 62, wherein the core member has a distal region of decreasing outer diameter, and wherein said depositing at least one layer comprises depositing a layer on the distal region of decreasing outer diameter.

[0234] 64. The method of any one of Embodiments 51 to 63, wherein said depositing at least one layer comprises depositing a plurality of discrete layers longitudinally spaced fromone another along the core member, and wherein each layer of the plurality' of discrete layers has substantially the same volume of the second material.

[0235] 65. The method of .Embodiment 64, wherein each layer of the plurality of layers is in the form of a circumferential band around the outer surface of the core wire.

[0236] 66. The method of Embodiment 64 or 65, wherein a first layer of the plurality of layers has a longitudinal length and / or a thickness that is at least .10% greater than that of a second layer of the plurality of layers.

[0237] 67. The method of Embodiment 66, wherein at least one of the first layer and the second layer is positioned around a constant diameter segment of the core wire and the other is positioned around a decreasing diameter segment of the core wire.

[0238] 68. The method of Embodiment 67, wherein the first layer and the second layer have substantially the same thickness, and wherein the longitudinal length of the first layer is at least 10% greater than the longitudinal length of the second layer.

[0239] 69. The method of Embodiment 68, wherein the first layer is positioned on the constant diameter segment and the constant diameter segment occurs distally of the decreasing diameter segment.

[0240] 70. The method of Embodiment 68, wherein the first layer is positioned on the decreasing diameter segment and the decreasing diameter segment occurs distally of the constant diameter segment.

[0241] 71. The method of any one of Embodiments 51 to 70, wherein said solidifying comprises cooling the molten polymeric jacket material and core wire by quenching in a liquid bath.

[0242] 72. The method of any one of Embodiments 51 to 71 , wherein said advancing comprises pulling on a segment of the core wire that has already passed by the extruder head.

[0243] 73. The method of any one of Embodiments 51 to 72, also comprising applying at least one visible marking to an outer surface of the polymeric jacket in a location corresponding to the layer.

[0244] 74. The method of Embodiment 73, wherein the visible marking comprises a contrasting ink.

[0245] 75. The method of any one of Embodiments 51 to 74, wherein the core member is a single supereiastic metal alloy wire.

[0246] 76. The method of Embodiment 75, wherein the superdasfic metal alloy is nitinol.

[0247] 77. The method of any one of Embodiments 51 to 76, wherein the plated layer of nickel has a volume of nickel of at least 0.01 mm3.

[0248] 78. The method of Embodiment 77, wherein the volume of nickel is in the range of 0.01 mm 0.01 mm3 to about 0.1 mm3.

[0249] 79. The method of Embodiment 77, wherein the volume of nickel is in the range of 0.015 mini to about 0.075 mm3.

[0250] 80. The method of Embodiment 77, wherein the volume of nickel is in the range of about 0.02 mm3 to about 0.05 mm3.

[0251] 81 . A polymer-encapsulated wire guide, comprising; a core member made of a superelastic nitinol alloy, the core member having a proximal end, a distal end, and a tapered distal segment having a decreasing outer diameter in a direction toward the distal end; a first layer comprising a first volume of first material adhered to an outer surface of the tapered distal segment, wherein the first material has a magnetic susceptibility greater than that of the superelastic nitinol, a second layer comprising a second volume of a second material adhered to an outer surface of the core member, the second layer longitudinally spaced from the first layer, wherein the second volume is substantially the same as the first volume, and wherein the second layer differs in at least one of thickness and surface area from the first layer; and a polymeric jacket encapsulating the first layer, the second layer, and the core member.

[0252] 82. The wire guide of Embodiment 81, wherein the first layer and the second layer are each a plated metal layer.

[0253] 83. The wire guide of Embodiment 82, wherein the first layer and the second layer are each an electroplated metal layer.

[0254] 84. The wire guide of any one of Embodiments 81 to 83, wherein the first and second layers are each in the form of a circumferential band around an outer surface of the core member.

[0255] 85. The wire guide of any one of Embodiments 81 to 84, wherein the first material is or comprises nickel.

[0256] 86, The wire guide of any one of Embodiments 81 to 85, wherein the polymeric jacket comprises a polyurethane polymer or a polytetrafluoroethylene polymer.

[0257] 87. The wire guide of any one of Embodiments 81 to 86, wherein the polymeric jacket comprises a particulate ferromagnetic or paramagnetic material.

[0258] 88. The wire guide of any one of Embodiments 81 to 87, wherein the second layer is positioned around a constant outer diameter segment of the core member.

[0259] 89. The wire guide of Embodiment 88, wherein the first layer and the second layer have substantially the same thickness, wherein the longitudinal length of the first layer is at least 10% greater than the longitudinal length of the second layer, and wherein the first layer is positioned distally of the second layer.

[0260] 90. The wire guide of Embodiment 88, wherein the first layer and the second layer have substantially the same thickness, wherein the longitudinal length of the second layer is at least 10% greater than the longi tudinal length of the first layer, and wherein the second layer is positioned distally of the first layer.

[0261] 91. The wire guide of Embodiment 90, wherein the second layer is positioned on the region of decreasing outer diameter.

[0262] 92. The wire guide of Embodi ment 90, wherein the second layer is positioned on a constant outer diameter region of the core wire that occurs distal of the decreasing diameter region.

[0263] 93. The wire guide of any one of Embodiments 81 to 92, also comprising visible markings on an outer surface of polymer jacket at locations corresponding to the first coating and the second coating, respectively.

[0264] 94. The wire guide of Embodimen t 93, wherein the visible markings comprise contrasting ink.

[0265] 95. A polymer-encapsulated wire guide, comprising; a core member made of a superelastic metal alloy, the core member having a proximal end and a distal end; a polymeric jacket encapsulating the core member;. wherein the wire guide has distal-most wire guide segment with a relaxed configuration in the absence of externally applied force, the distal-most wire guide segment having a longitudinal length of 10 cm; wherein the wire guide includes at least one layer comprising a first metallic material adhered to a distal segment of the core member within the distal-most wire guide segment, wherein the distal segment, of the core member has a diameter of less than about. 0.3 mm:wherein the distal segment of the core member, when the distal -most wire guide segment is forcibly and resiliently deformed from the relaxed configuration to a deformed configuration, is sized and configured to exert a resilient return force to urge resilient return of the distal-most wire guide segment to the relaxed configuration; wherein the one or more layers is / are sized and configured to plastically deform during movement of the distal-most wire guide segment from the relaxed configuration to the deformed configuration; and wherein the one or more layers is / are sized and configured so as to not plastically deform in response to said resilient return force, (hereby providing a selectively shape- settable character to the distal-most wire guide segment.

[0266] 96. The wire guide of Embodiment 95, wherein the at least one layer includes a layer having a longitudinal length of about 1 cm to about 3 cm.

[0267] 97. The wire guide of Embodiment 95 or 96, wherein the distal of (he core member has a diameter of less than about 0.2 mm.

[0268] 98. The wire guide of any one of Embodiments 95 to 97, wherein the one or more layers is / are plated metallic layers.

[0269] 99. The wire guide of Embodiment 98, wherein the one or more layers are plated nickel layers.

[0270] 100. The wire guide of any one of Embodiments 95 to 99, wherein the one or .more layers are each in the form of a circumferential band around an outer surface of the core member.

[0271] 101 .A method of imaging a portion of a body vessel of a patient using MRI, said method comprising: placing a portion of a patient within an MRI system having a scanner such that a portion of said body vessel is located within the scanner; grasping a wire guide comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the distal end of the wire guide into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system;operating the scanner of the MR1 system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel; obtaining a magnetic resonance image of the first portion of the body vessel; and

[0272] withdrawing the wire guide from the body vessel.

[0273] 102,The method of Embodiment 101, wherein the wire guide further comprises a marker formed of a metallic material.

[0274] 103. The method of Embodiment 102, wherein the core member has a first susceptibility and the marker has a second susceptibility that is different from the first susceptibility,

[0275] 104. The method of Embodiment 103, wherein the core member and the marker are formed of the same material.

[0276] 105. The method of Embodiment 103, wherein the core member and the marker are formed of different materials.

[0277] 106. The method of Embodiment 105, wherein the core member comprises a nickel-titanium ahoy and the marker comprises a stainless steel alloy.

[0278] 107. The method of Embodiment 103, wherein the core member has an outer surface; and the marker is disposed on the outer surface.

[0279] 108. The method of Embodiment 103, wherein the jacket has a thickness; and wherein the marker is disposed within the thickness of the jacket.

[0280] 109. The method of Embodiment 103, wherein the marker comprises a circumferential band disposed around the core member.

[0281] 1 10. The method of Embodiment 103, wherein the step of operating the scanner and the step of obtaining a magnetic resonance image are performed while the step of advancing the wire guide distal end through said body vessel is performed.

[0282] 1 11 . The method of Embodiment 110, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the step of ad vancing the wire guide distal end through said body vessel is performed.

[0283] 1 12. A method of performing interventional medical treatment under MRI. said method comprising : placing a portion of a patient within an M.RI system having a scanner such that a portion of said body vessel is located wi thin the scanner; grasping a wire guide having a wire guide proximal cud and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entirecore member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRS system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over the wire guide proximal end to dispose the wire guide proximal end within the lumen of the elon gate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within said body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; operating the scanner of the M'Rl system to scan the portion of the patient that Is positioned within the scanner and (hat includes the first portion of the body vessel; obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel .

[0284] 1 13.The method of Embodiment 1 12, wherein the wire guide further comprises a marker formed of a metallic material,

[0285] 1 14. The method of Embodiment 1 13, wherein the core member has a first susceptibility and the marker has a second susceptibility that is different from the first susceptibility,

[0286] 1 15, The method of Embodiment 113, wherein the core member and the marker are formed of the same material.

[0287] 116.The method of Embodiment 1 13, wherein the core member and the marker are formed of different materials,

[0288] 1 17,The method of Embodiment 116, wherein the core member comprises a nickel-tilanium alloy and the marker comprises a stainless steel alloy.

[0289] 118, The method of Embodiment 112, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times wink- the step of advancing the wire guide distal end through said body vessel is performed.

[0290] 1 19. The method of Embodiment 1 12. wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the step of advancing the medical device distal end through said body vessel is performed.

[0291] 120. The method of Embodiment 112, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the steps of advancing the wire guide device distal end through said body vessel, advancing the medical device distal end through said body vessel, and manipulating the medical device proximal end to produce a manipulation of the

[0292] 121 .An MRI compatible wire guide, comprising a continuous core member formed of a metallic material and having a first length; and a continuous jacket disposed over and fully encapsulating foe entire continuous core member, the continuous jacket formed of a dielectric material and having a second length that is greater than (he first length.

[0293] 122.The MRI compatible wire guide of Embodiment 121 , wherein foe wire guide further comprises a marker formed of a metallic material.

[0294] 123. The MRI compatible wire guide of Embodiment 122, wherein foe core member has a first susceptibility and the marker has a second susceptibility that is different from the first, susceptibility.

[0295] 124. The MRI compatible wire guide of Embodiment 123, wherein the core member and the marker are formed of the same material.

[0296] 125. The MRI compatible wire guide of Embodiment 123, wherein foe core member and the marker are formed of different materials.

[0297] 126. The MRI compatible wire guide of Embodiment 125, wherein foe core member comprises a nickel-titanium alloy and the marker comprises a stainless steel alloy.

[0298] 127. The MRI compatible wire guide of Embodiment 123. wherein the core member has an outer surface; and the marker is disposed on die outer surface.

[0299] 128. The MRI compatible wire guide of Embodiment 123, wherein the jacket has a thickness; and wherein the marker is disposed within the thickness of the jacket.

[0300] 129, The MRI compatible wire guide of Embodiment 123, wherein the marker comprises a c ircumferential band disposed around the core member.

[0301] 130.' The MRI compatible wire guide of Embodiment 121 , wherein the jacket has a first axial portion formed of a first dielectric material and a second axial portion formed of a second, different dielectric material.

[0302] 131 . The MRi compatible wire guide of Embodiment 130. wherein the first dielectric material comprises a first polymer and the second dielectric material comprises a second polymer.

[0303] 132. The MRI compatible wire guide of Embodiment 130, wherein the first dielectric material comprises a polymer and the second dielectric material comprises a nonpolymer.

[0304] 133.The MRI compatible wire guide of Embodiment 132, wherein the second dielectric material comprises a ceramic,

[0305] 134.The MRI compatible wire guide of Embodiment 130. wherein the jacket has a third axial portion formed of a third dielectric material: and wherein the second axial portion is disposed axially between the first axial portion and the third axial portion.

[0306] 135. The MRI compatible wire guide of Embodiment 134, wherein the first and third dielectric materials are the same dielectric material,

[0307] 136. The MRI compatible wire guide of Embodiment 135. wherein the first and third dielectric materials comprise a polymer.

[0308] 137. The MRI compatible wire guide of Embodiment 136, wherein the second dielectric material comprises a non-polymer.

[0309] 138. The MRI compatible wire guide of Embodiment 137, wherein the second dielectric material comprises a ceramic.

[0310] I 39. An MRI compatible wire guide, comprising a continuous core member formed of a metallic ma terial and having a first length; and a continuous jacket disposed over and fully encapsulating the entire continuous core member, the continuous jacket having a first axial portion formed of a first dielectric material, a second axial portion formed of a second, different dielectric material, and a second length that is greater than the first length,

[0311] 140. An MRI compatible wire guide, comprising a continuous core member formed of a metallic material and having a first length; and a continuous jacket having a jacket proximal end, a jacket distal end, a first axial portion extending from the jacket proximal end toward the jacket distal end and formed of anon-polymer dielectric, material, and a second axial portion extending from the jacket distal end toward the jacket proximal end and formed of a polymer dielectric material, the continuous jacket disposed over and fully encapsulating the entire continuous core member and having a second length that is greater than the first length: wherein the first axial portion extends along an axial length that is less than about20% of the second length.

[0312] 141. The wire guide of any one of Embodiments 121 to 140, wherein the continuous core member has a proximal end, a distal end, a terminal surface of the proximal end, and a terminal surface of the distal end, wherein a proximal end of the jacket covers (he terminal surface of the proximal end of the core member and the distal end of the jacket covers the terminal surface of the distal end of the core member.

[0313] 142. The wire guide of Embodiment 141 , wherein the continuous core member is a continuous length of wire having a proximal end terminal surface received against a proximal end wall of the jacket and a distal end terminal surface received against a distal end wall of the jacket.

[0314] Those with ordinary skill tn the art will appreciate that various modifications and alternatives for the described and illustrated examples can be developed in light of the overall teachings of the disclosure, and that the various elements and features of one example described and illustrated herein can be combined with various elements and features of another example without departing from the scope of the invention. Accordingly, the particular arrangement of elements and steps disclosed herein have been selected by the inventorfs) simply to describe and illustrate examples of the in vention and are not intended to limit the scope of the invention or its protec tion, which is to be given the full breadth of the appended claims and any and all equivalents thereof

Claims

What is claimed is:1 . An MR! compatible wire guide, comprising: a core member having a proximal end, a distal end, and a length between the proximal end and the distal end: a first passive MRI marker disposed along the length of the core member; a second passive .MRI marker disposed along the length of the core member and longitudinally spaced from the first passive MRI marker; and a polymeric j acket that encapsulates the core member.

2. The wire guide of claim 1 , wherein: the elongated core member has a proximal end, a distal region extending to the distal end, and a longitudinal axis, wherein the distal region includes a tapered core member segment having a decreasing outer diameter in a direction toward the distal end; at least the first passive MR! marker is disposed along the tapered core member segment and includes a first layer comprising a first passive MRI marker-forming material adhered to an outer surface of the tapered core member segment of the core mem ber;(he second passive MRI marker includes a second layer comprising a second passive MRI marker-forming material adhered to an outer s urface of the core member; and the polymeric jacket encapsulates the core member, the first layer and the second layer.

3. The wire guide of claim 2, wherein: the first layer is in the form of a circumferential band extending completely around the outer surface of the tapered core member segment; and the second layer is in the form of a circumferential band extending completely around the outer surface of the core member.

4. The wire guide of claim 2 or 3, wherein the second layer is adhered to an outer surface of the tapered core member segment of the core member.

5. The wire guide of claim 3, wherein the core member includes a first constant diameter core member segment distal of the tapered core member segment, and wherein the second layer is adhered to an outer surface of the first constant diameter core member segment,6. The wire guide of claim 4, also comprising: a third passive MRI marker including a third layer comprising a third passive MRI marker-forming material, the third layer adhered to an ou ter surface of the core member.

7. The wire guide of claim 6, wherein:the core member includes a first constant diameter core member segment distal of the tapered core member segment; and the third layer is adhered to an outer surface of the first constant diameter core member segment.

8. The wire guide of claim 7, also comprising: a fourth passive MRI marker including a fourth layer comprising a fourth passive MRI marker-forming material, the fourth layer adhered to an outer surface of the core member.

9. The wire guide of claim 8, wherein: the fourth layer is adhered to an outer surface of the first constant diameter core member segment.

10. The wire guide of any of claims 7 to 9, wherein: the third layer is in the form of a circumferential baud extending completely around the outer surface of the first constant diameter core member segment; and the fourth layer is in the form of a circumferential band extending completely around the outer surface of the first constant diameter core member segmen t, 1 1. The wire guide of claim 1, also comprising: a third passive MRI marker disposed along the length of (he core member and longitudinally spaced from the first and second passive MRI markers: and a fourth passive MR1 marker disposed along the length of the core member and longitudinally spaced from the first, second and third passive MRI markers; wherein the first and second passive MRI markers are disposed along a distal-most segment of the core member that terminates in the distal end of the core member, the distal- most segment having a length of 10 cm; wherein the first passive MRI marker is distal of the second passive MRI marker along the distal-most segment of the core member; wherein the third passive MRI marker is disposed along the core member proximal of the distal-most segment; wherein the fourth passive MRI marker is disposed along the core member proximal of the third passive MRI marker; wherein the first and second passive MRI markers am longitudinally spaced from one another a first longitudinal distance along {he length of the core member; wherein the third and fourth passive MRI markers are longitudinally spaced from one another a second longitudinal distance along the length of the core member; and wherein the second longitudinal distance is greater than the first longitudinal distance.

12. The wire guide of claim 1 I, also comprising: a filth passive MRI marker disposed along the length of the core member and longitudinally spaced from the first, second, third and fourth passive MRI markers along the length of the core member.

13. The wire guide of claim 12, wherein: the fifth passive MRI marker is disposed along the length of the core member proximal of tlie fourth passive MRI marker, the fourth and fifth passive MRI markers longitudinally spaced from one another a third longitudinal distance along the length of the corer member, wherein the third longitudinal distance is equal to the second longitudinal distance.

14. The wire guide of claim 12, wherein: the fifth passive MRI marker is disposed along the distal-most segment of the core member distal of the first passive MRI marker, the first and fifth passive MRI markers longitudinally spaced from one another a third longitudinal distance along the length of the core member, wherein the third longitudinal distance is equal to the first longitudinal distance, 15. The wire guide of claim 13, also comprising: a sixth passive MRI marker disposed along the distal-most segment of the core member distal of the first passive MRI marker, the first and sixth passive MRI markers longitudinally spaced from one another a fourth longitudinal distance along the length of the core member, wherein the fourth longitudinal distance is equal to the first longitudinal distance.

16. The wire guide of claim 15, also comprising: a seventh passive MRI marker disposed along the distal-most segment of the core member distal of the sixth passive MRI marker, the sixth and seventh passive MR.I markers longitudinally spaced from one ano ther a fifth longitudinal distance along the length of the core member, wherein the fifth longitudinal distance is equal to the first longitudinal distance.

17. The wire guide: of claim 1 1 , wherein the first, second, third and fourth passive MRI markers (i) each include a layer comprising a passive MRI marker Tonning material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket; or of any one of claims 12 to 14, wherein the first, second, third, fourth and fifth passiveMRI markers (i) each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (i I) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket; orof claim 15, wherein the first, second, third, fourth, fifth and sixth passive M.RI markers[1] each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (H) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket: or of claim 16, wherein the first, second, third, fourth, fifth, sixth and seventh passiveMRI markers (i) each include a layer comprising a passive MRI marker-forming material adhered to an outer surface of the core member, or (ii) each include a volume of a passive MRI marker-forming material disposed within a thickness of the polymeric jacket,18. The wire guide of any one of claims 11 to 16, wherein the first longitudinal distance is less than 3 cm,19. The wire guide of claim 18, wherein the first longitudinal distance is in the range of about 1 ,5 cm to about 2.5 cm.

20. The wire guide of any one of claims 1 .1 to 19, wherein the second longitudinal distance is at least about 8 cm, 21. The wire guide of claim 20, wherein the second longitudinal distance is in the range of about 8 cm to about 30 cm.

22. The wire guide of claim 21 , wherein the second longitudinal distance is in the range of about 10 cm to about 20 cm.

23. The wire guide of: any one of claims 1 to 22, wherein the first passive MRI marker and the second passiveMRI marker are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of claims 6 to 22, wherein the first, second and third passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of claims 8 to 22, wherein the first, second, third and fourth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of claims 12 to 22, wherein the first, second, third, fourth and fifth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in therange of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of claims .15 to 22, wherein the first, second, third, fourth, fifth and sixth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket; or any one of claims 16 to 22, wherein the first, second, third, fourth, fifth and sixth passive MRI markers are each configured to generate a visible artifact having a maximum dimension in the range of about 1.5 cm to about 3 cm and / or that is 15 to about 100 times a maximum outer diameter of the polymeric jacket.

24. The wire guide of any one of clai ms 2 to 23. wherein: the first passive MR1 marker includes a first layer comprising a first volume of a first passi ve MRI marker-forming material adhered to an outer surface of the core member; the second passive MRI marker includes a second layer comprising a second volume of a second passive MRI marker forming material adhered to an outer surface of the core member; the first passive MRI marker forming material and the second passive MRI marker forming material are the same; the first volume and the second volume are substantially the same; and the first layer differs at least 10% from the second layer in at least one of thickness and outer surface area,25. The wire guide of claim 24, wherein: the first layer is in the form of a first circumferential band that extends completely around the outer surface of the core member; and the second layer is in the form of a second circumferential band that extends completely around the outer surface of the core member.

26. The wire guide of claim 25, wherein: the first layer and the second layer have substantially the same thickness; and the first circumferential band has a longitudinal length along the core member that differs at least 10% from that of the second circumferential band.

27. The wire guide of claim 25, wherein: the first layer and the second layer differ substantially in thickness; andthe first circumferential band has a longitudinal length along the core member that is substantially the same as that of the second circumferential band.

28. The wire guide of any one of claims 1 to 27, wherein: the core member is a continuous length of wire made from a metal alloy and extending from the proximal end to the distal end of the core member.

29. The wire guide of claim 28, wherein the metal alloy is a superelastic nitinol alloy.

30. The wire guide of claim 28 or 29, wherein the first passive MR! marker comprises a first marker- forming material and the second passive M.RI marker comprises a second markerforming material, wherein the first marker-forming material and the second marker-forming material both have a magnetic susceptibility greater than that of the metal alloy.

31. The wire guide of claim 30, wherein the first marker-forming material and the second marker-forming material are each a metallic material.

32. The wire guide of claim 3 I, wherein the metallic material is a plated metallic material plated over the outer surface of the elongate member.

33. The wire guide of claim 31 or 32, wherein the metallic material has a magnetic susceptibility of at least about 70(X) ppm, or in the range of about 7000 ppm to about 1,000,000, or in the range of about 7000 ppm to about 100,000.

34. The wire guide of claim 31 or 32, wherein the metallic material is selected from nickel, alloys of nickel, iron, alloys of iron, cobalt, and alloys of cobalt.

35. The wire guide of claim 34, wherein the metallic material is nickel or an alloy containing nickel, molybdenum, and iron,36. The wire guide of claim 35, wherein the metallic material is nickel.

37. The wire guide of claim 36, wherein: the first passive MRf marker contains a first volume of nickel of at least about 0.01 mm5; and the second passive MR! marker each contains a second volume of nickel of at least about 0.01 mm- ; when present, the third passive MR1 marker contains a third volume of nickel of at least about 0.01 mm5; when present, the fourth passive MRI marker contains a fourth volume of nickel of at least about 0.01 mm?;when present, the fifth passive MRI marker contains a fifth volume of nickel of a t least about 0.01 msi3; when present, the sixth passive MRI marker contains a sixth volume of nickel of at least about 0.01 mm3; and when present, the seventh passive MRI marker contains a seventh volume of nickel of at least about 0.01 min3,38. The wire guide of claim 37, wherein the first volume, second volume, third volume, fourth volume, fifth volume, sixth volume and seventh volume are each in the range of about 0.01 mm5to about 0.1 mm\ or about 0,02 mtn3to about 0.075 mm3, or about 0.03 mm3to about 0.05 mm ’.

39. The wire guide of claim 37 or 38, wherein the first volume, second volume, third volume, fourth volume, fifth volume, sixth volume and seventh volume are each a plated volume of nickel plated onto the outer surface of the core member,40. The wire guide of any one of claims 1 io 39, wherein: the wire guide has distal-most wire guide segment with a relaxed configuration in the absence of ex ternally applied force, the distal-most wire guide segment having a length of 10 cm; at least the first passive MRI marker Is positioned in the distal-most wire guide segment and includes a layer of passive MRI marker-forming material adhered to an outer surface of the core member; the segment of the core member within the distal-most wire guide segment is sized and configured such that when the distal-most wire guide segment is forcibly and resiliently deformed from the relaxed configuration to a deformed configuration, the segment of the core member exerts a resilient return force that urges a resilient return of the distal-most wire guide segment to the relaxed configuration; any layer or layers of passive MRI marker forming material adhered to the outer surface of the distal-most segment of the core member is.'are sized and configured to plastically deform during movement of the distal-most segment of the core member from the preset relaxed configuration to the deformed configuration; and said any layer or layers of passive MRI marker forming material are sized and configured so as to again plastically deform in response to said resilient return force during resilient return of the distal-most wire guide segment to the set relaxed configuration.41 . The wire guide of claim 40, wherein the distal-most segment of the core member is free from any layer of passive MRI marker-forming material having a longitudinal length of greater than 2 mm, or greater than I mm.

42. The w ire guide of claim 40 or 41 , wherein the distal-most segment of the core member is free from any layer of passive MR! marker-forming material having a thickness greater than0.05 mm.

43. The wire guide of any one of claims 1 to 39, wherein: the wire guide has distal-most wire guide segment with a relaxed configuration in the absence of externally applied force, the distal -most wire guide segment having a longitudinal length of 10 cm; at least the first passi ve MRI marker is positioned in the distal-most wire guide segment and includes a layer of passive MRI marker-forming material adhered to an outer surface of the core member; the segment of the core member within the distal-most wire guide segment, when the distal-most wire S g-uide se Sg- ment is forcibl "yf and resilientlv J deformed from the set relaxed configuration to a deformed configuration, is sized and configured to exert a resilient return force to urge resilient return of the distal-most wire guide segment to the relaxed configuration; any layer or layers of passive MRI marker forming material adhered to the outer surface of the distal-most segment of the core member is / are sized and configured to plastically deform during movement of the distal-most wire guide segment from the relaxed configuration to the d e form ed co nfigurat i on; said any layer or layers of passive MRI marker forming material are sized and configured so as to not plastically deform in response to said resilient return force, thereby providing a selectively shape-settable character to the distal-most wire guide segment.

44. The wire guide of claim 40, wherein the distal-most segment of the core member has at least one layer of passive MRI marker-forming material having a longitudinal length of at least 7 mm.

45. The wire guide of any one of claims 1 to 44, wherein the distal-most segment of the core member has a maximum diameter of less than about 0.4mm. or less than about 0.3 mm, or less than about 0.2 mm.46, The wire guide of any one of cl aims 21 to 29, wherein a distal-most 50 cm segment of the core member includes a tapered portion having a decreasing outer diameter in a directiontoward the distal end of the core member, and the tapered portion has a longitudinal length of about 3 cm to about 40 cm.

47. The wire guide of any one of claims 1 to 46, wherein the core member is a continuous core member having a proximal end, a distal end, a terminal surface of the proximal end, and a terminal surface of the distal end, wherein a proximal end of the jacket covers the terminal surface of the proximal end of the core member and the distal end of the jacket covers the terminal surface of the distal end of the core member.

48. The wire guide of claim 47, wherein the continuous core member is a single wire having a proximal end terminal surface received against a proximal end wall of the jacket and a distal end terminal surface received against a distal end wall of the jacket.

49. The wire guide of claim I , wherein: the first and second passive MRJ markers are disposed along a distal-most segment of the core member that terminates in the distal end of the core member, the distal-most segment having a length of 10 cm; the first passive MRI marker includes a first layer comprising a first passive MRI marker-forming material adhered to an outer surface of the distal most segment of the core member; the second passive MRI marker includes a second layer comprising a second passiveMR.T marker-forming material adhered to the outer surface of the distalmost segment of the core member; and the wire guide also comprises a third passive MRI marker, wherein the third passiveMRI marker includes a third layer comprising a third passive MRI marker-forming material adhered to the outer surface the distal-most segment of the core member; the polymeric jacket encapsulates the core member, the first layer, the second layer and the third layer; and further wherein: the first passi ve MRI marker-forming material, the second passive MRI marker- formitrg material, and the third passive MRI marker-forming material each have a magnetic susceptibility of at least 1 ; or (he first passive MRI marker-forming material, the second passive MR! markerforming material, and the third passive MRI marker-forming material are each nickel, and the first layer, the second layer, and the third layer each have a volume of nickel of at least about0.01 mm5, or in the range of 0.01 mm3to about 0.1 mm3or in the range of about 0.015 nrni3to about 0.075 mm5, or in the range of about 0.02 mm5to about 0.05 mm5.

50. The wire guide of claim 1 or 49, wherein; the first passive MRI marker, the second passive MRI marker, and the third passive MR! are configured to generate discrete visible image artifacts; and / or the first passive MR! marker, the second passive MRI marker, and the third passive MRI marker are each configured to generate a visible an artifact that has a maximum dimension that is in the range of 15 to about 100 times the greatest outer diameter of the polymeric jacket; and or the first passive MRI marker, the second passive MRI marker, and the third passiveMRI marker are each configured to generate a visible an artifact that has a maximum dimension in the range of about 0.5 cm to about 3 cm, or about 1 cm to about 2 cm; and / or the second layer is positioned longitudinally between the first layer and the third layer and is spaced at least at least 1.5 cm, or in the range of 1.5cm to 3cm, from each of the first layer and the third layer.

51. A method for making a polymer-encapsulated wire guide, comprising; providing a core member made of a first material; depositing at least one layer comprising a second material onto an outer surface of the core member, wherein the second material has a magnetic susceptibility greater than that of the first material, and wherein the layer is configured to provide a passive MRI marker; and disposing a polymeric jacket over the core member and at least one layer,52. The method of claim 51 , wherein said disposing comprises: advancing the core member longitudinally through an extrusion apparatus so as to extrude molten polymeric jacket material against and around the core member, and causing the molten polymeric jacket material to solidify; or heat shrinking a tube of heat-shrinkable polymeric jacket material over the core member.

53. The method of claim 51 or 52, wherein said first material is a metal, and wherein said depositing comprises plating.

54. The method of any one of claims 51 to 53, wherein said depositing at least one layer comprises depositing a plurality of discrete layers longitudinally spaced from one another along the core member.

55. The method of claim 54, wherein the layers are configured as passive MRI markers.

56. The method of claim 55, also comprising applying a plurality of visible markings to an outer surface of polymeric jacket, with each visible marking at a location corresponding to a respective one of the passive MRI markers.

57. The method of claim 56, wherein the visible markings comprise a contrasting ink.

58. The method of any one of claims 51 to 57, wherein the at least one layer comprises nickel.

59. The method of claim 58, wherein the layer comprising nickel is a plated layer of nickel,60. The method of claim 59, wherein the plated layer of nickel has a thickness not exceeding 0.04 mm.

61. The method of any one of claims 51 to 60, wherein the polymeric jacket material comprises a polyurethane polymer or a polytetrafluorethylene polymer.

62. The method of any one of claims 51 to 61, wherein the polymeric jacket material comprises a particulate paramagnetic or ferromagnetic material.

63. The method of any one of claims 51 to 62, wherein the core member has a distal region of decreasing outer diameter, and wherein said depositing at least one layer comprises depositing a layer on the distal region of decreasing outer diameter,64. The method of any one of claims 51 to 63, wherein said depositing at least one layer comprises depositing a plurality of discrete layers longitudinally spaced from one another along the core member, and wherein each layer of the plurality of discrete layers has substantially the same volume of the second material.

65. The method of claim 64, wherein each layer of the plurality of layers is in the form of a circumferential band around the outer surface of the core wire.

66. The method of claim 64 or 65, wherein a first layer of the plurality of layers has a longitudinal length andrir a thickness that is at least .10% greater than that of a second layer of the plurality of layers.

67. The method of claim 66, wherein at least one of the first layer and the second layer is positioned around a constant diameter segment of the core wire and the other is positioned around a decreasing diameter segment of the core wire.

68. The method of claim 67, wherein the first layer and the second layer have substantially the same thickness, and wherein the longitudinal length of the first layer is at least 10% greater than the longitudinal length of the second layer,69. The method of claim 68, wherein the first layer is positioned on the constant diameter segment and the constant diameter segment occurs distally of the decreasing diameter segment.

70. The method of claim 68, wherein the first layer is positioned on the decreasing diameter segment and the decreasing diameter segment occurs distally of the constant diameter segment.

71. The method of any one of claims 51 to 70, wherein said solidifying comprises cooling the molten polymeric jacket material and core wire by quenching in a. liquid bath.

72. The method of any one of claims 51 to 71 , wherein said advancing comprises pulling on a segment of the core wire that has already passed by the extruder head.

73. The method of any one of claims 51 to 72, also comprising applying at least one visible marking to an outer surface of the polymeric jacket in a location corresponding to the layer.

74. The method of claim 73, wherein the visible marking comprises a contrasting ink.

75. The method of any one of claims 51 to 74, wherein the core member is a single superelastic metal alloy wire.

76. The method of claim 75, wherein the superelastic metal alloy is nitinol.

77. The method of any one of claims 51 to 76, wherein the plated layer of nickel has a vol ume of nickel of at least 0.01 mm3.

78. The method of claim 77, wherein the volume of nickel is in the range of 0.01 mm 0.01 mm3 to about 0.1 mm3.

79. The method of claim 77, wherein the volume of nickel is in the range of 0.015 mm3 to about 0.075 mm3.

80. The method of claim 77, wherein the volume of nickel is in the range of about 0.02 mm3 to about 0.05 mm3.

81. A polymer-encapsulated wire guide, comprising; a core member made of a superelastic nitinol alloy, the core member having a proximal end, a distal end, and a tapered distal segment having a decreasing outer diameter in a direction toward the distal end; a first layer comprising a first volume of first material adhered to an outer surface of the tapered distal segment, wherein the first material has a magnetic susceptibility greater than that of the superelastic nitinol, a second layer comprising a second volume of a second material adhered io an outer surface of the core member, the second layer longitudinally spaced from the first layer, wherein the second volume is substantially the same as the first volume, and wherein the second layer differs in at least one of thickness and surface area from the first layer; and a polymeric jacket encapsulating the first layer, the second layer, and the core member.

82. The wire guide of claim 81, wherein the first layer and the second layer are each a plated metal layer.

83. The wire guide of claim 82, wherein the first layer and the second layer are each an electroplated metal layer.

84. The wire guide of any one of claims 81 to 83, wherein the first and second layers are each in the form of a circumferential band around an outer surface of the core member,85. The wire guide of any one of claims 81 to 84, wherein the first material is or comprises nickel.

86. The wire guide of any one of claims 81 to 85, wherein the polymeric jacket comprises a polyurethane polymer or a polytetrafluoroethylene polymer,87. The wire guide of any one of claims 81 to 86, wherein the polymeric jacket comprises a particulate ferromagnetic or paramagnetic material.

88. The wire guide of any one of claims 81 to 87, wherein the second layer is positioned around a constant outer diameter segment of the core member, 89. The wire guide of claim 88, wherein the first layer and the second layer have substantially the same thickness, wherein (he longitudinal length of the first layer is at least 10% greater than the longitudinal length of the second layer, and wherein the first layer is positioned distally of the second layer.

90. The wire guide of claim 88, wherein the first layer and the second layer have substantially the same thickness, wherein the longitudinal length of the second layer is at least1030 greater than the longitudinal length of the first layer, and wherein the second layer is positioned distally of the first layer.

91. The wire guide of claim 90, wherein the second layer is positioned on the region of decreasing outer diameter, 92, The wire guide of claim 90, wherein the second layer is positioned on a constant outer diameter region of the core wire that occurs distal of the decreasing diameter region.

93. The wire guide of any one of claims 81 to 92, also comprising visible markings on an outer surface of polymer jacket at locations corresponding to the first coating and the second coating, respectively.

94. The wire guide of claim 93, wherein the visible markings comprise contrasting ink, 95, A polymer-encapsulated wire guide, comprising; a core member made of a superelastic metal alloy, the core member having a proximal end and a distal end;a polymeric, jacket encapsulating the core member;. wherein the wire guide has distal-most wire guide segment with a relaxed configuration in the absence of externally applied force, the distal-most wire guide segment having a longitudinal length of 10 cm; wherein the wire guide includes at least one layer comprising a first metallic material adhered to a distal segment: of the core member within the distal-most wire guide segment, wherein the distal segmen t of the core member has a diameter of less than about 0.3 nun; wherein the distal segment of the core member, when the distal-most wire guide segment is forcibly and resiliently deformed from the relaxed configuration to a deformed configuration, is sized and configured to exert a resilient return force to urge resilient return of the distal-most wire guide segment to the relaxed configuration; wherein the one or more layers is / are sized and configured to plastically deform during movement of the distal-most wire guide segment from the relaxed configuration to (he deformed configuration; and wherein the one or more layers is / are sized and configured so as to not plastically deform in response to said resilient return force, thereby providing a selectively shape-settable character to the distal-most wire guide segment.96, The wire guide of claim 95, wherein the at least one layer includes a layer having a longitudinal length of about 1 cm to about 3 cm.

97. The wire guide of claim 95 or 96, wherein the distal of the core member has a diameter of less than about 0.2 mm.

98. The wire guide of any one of claims 95 to 97, wherein the one or more layers is / are plated metallie layers.

99. The wire guide of claim 98, wherein the one or more layers are plated nickel layers.

100. The wire guide of any one of claims 95 to 99, wherein the one or more layers are each in the form of a circumferential band around an outer surface of the core member.

101. method of imaging a portion of a body vessel of a patient using MR1, said method comprising: placing a portion of a patient within an MRI system having a scanner such that a portion of said body vessel is located within the scanner; grasping a wire guide comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length;inserting the distal end of the wire guide into said body vessel: advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes die first portion of the body vessel; obtaining a magnetic resonance image of the first portion of the body vessel; and withdrawing the wire guide from the body vessel.

102. The method of claim 101 , wherein the wire guide further comprises a marker formed of a metallic material.

103. The method of claim 102, wherein the core member has a first susceptibility and the marker has a second susceptibility that is different from the first susceptibility.

104. The method of claim 103, wherein the core member and the marker are formed of the same material.

105. The method of claim 103, wherein the core member and the marker are formed of different materials.

106. The method of claim 105, wherein the core member comprises a nickel-ti tanium alloy and the marker comprises a stainless steel alloy.

107. The method of claim 103, wherein the core member has an outer surface: and the marker is disposed on the outer surface.

108. The method of claim 103, wherein the jacket has a thickness; and wherein the marker is disposed within the thickness of the jacket.

109. The method of claim 103, wherein the marker comprises a circumferential band disposed around the core member. 1 10. The method of claim 103, wherein the step of operating the scanner and the step of obtaining a magnetic resonance image are performed while the step of advancing the wire guide distal end through said body vessel is performed.1 11. The method of claim 1 10, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the step of advancing the wire guide distal end through said body vessel is performed.112, A method of performing interventional medical treatment under MRI, said method comprising:placing a portion of a patient within an MRI system having a scanner such that a portion of said body vessel is located within the scanner; grasping a wire guide having a wire guide proximal end and a wire guide distal end and comprising a continuous core member and a continuous jacket disposed over the entire core member, the core member formed of a metallic material and having a first length and the jacket having a second length that is greater than the first length; inserting the wire guide distal end into said body vessel; advancing the distal end of the wire guide through said body vessel until the distal end of the wire guide is disposed at a first position within a first portion of said body vessel that is located within the scanner of the MRI system; grasping a medical device having a medical device proximal end and a medical device distal end and comprising an elongate member defining a lumen; passing the medical device distal end over (he wire guide proximal end to dispose the wire guide proximal end within the lumen of the elongate member of the medical device; advancing the medical device distal end over the wire guide and into said body vessel until the medical device distal end reaches said point of treatment within said body vessel; manipulating the medical device proximal end to produce a manipulation of the medical device distal end at the point of treatment; operating the scanner of the MRI system to scan the portion of the patient that is positioned within the scanner and that includes the first portion of the body vessel; obtaining a magnetic resonance image of the first portion of the body vessel; withdrawing the medical device from the body vessel; and withdrawing the wire guide from the body vessel.

113. The method of claim 112, wherein the wire guide further comprises a marker formed of a metallic material.

114. The method of claim 1 13, wherein the core member has a first susceptibility and the marker lias a second susceptibility that is different from the first susceptibility.1 15. The method of claim 1 13, wherein the core member and the marker are formed of the same material. 1 16. The method of claim 113, wherein the core member and the marker are formed of different materials.

117. The method of claim 1 16, wherein the core member comprises a nickel-titanium alloy and the marker comprises a stainless steel alloy.

118. The method of claim 112, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the step of advancing the wire guide distal end through said body vessel is performed.1 19. The method of claim 112. wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the step of advancing the medical device distal end through said body vessel is performed.

120. The method of claim 112, wherein the steps of operating the scanner and obtaining a magnetic resonance image are performed multiple times while the steps of advancing the wire guide device distal end through said body vessel, advancing the medical device distal end through said body vessel, and manipulating the medical device proximal end to produce a manipulation of the121. An MR! compatible wire guide, comprising a continuous core member formed of a metallic material and having a first length; and a continuous jacket disposed over and fully encapsulating the entire continuous core member, the continuous jacket formed of a dielectric material and having a second length that is greater than the first length.

122. The MRI compatible wire guide of claim 121 , wherein the wire guide further comprises a marker formed of a metallic material.

123. The MRI compatible wire guide of claim 122, wherein the core member has a first susceptibility and the marker has a second susceptibility that is different from the first susceptibility.

124. The MRI compatible wire guide of claim 123, wherein the core member and the marker are formed of the same material.

125. The MRI compatible wire guide of claim 123, wherein the core member and the marker are formed of different materials.

126. The MRI compatible wire guide of claim 125, wherein the core member comprises a nickel-titanium alloy and the marker comprises a stainless steel alloy.

127. The MRI compatible wire guide of claim 123, wherein the core member has an outer surface; and the marker is disposed on the outer surface.128, The MRI compatible wire guide of claim 123, wherein the j acket has a thickness; and wherein the marker is disposed within the thickness of the jacket.

129. The MRI compatible wire guide of claim 123, wherein the marker comprises a circumferential band disposed around the core member.

130. The MRI compatible wire guide of claim 121, wherein the jacket has a first axial portion formed of a first dielectric material and a second axial portion formed of a second, different dielectric material.

131. The .MRI compatible wire guide of claim 130, wherein the first dielectric material comprises a first polymer and the second, dielectric material comprises a second polymer.

132. The MRI compatible wire guide of claim 130, wherein the first dielectric material comprises a polymer and the second dielectric material comprises a non-polymer.

133. The MRI compatible wire guide of claim 132, wherein the second dielectric material comprises a ceramic.

134. The MRI compatible wire guide of claim 130, wherein the jacket has a third axial portion formed of a third dielectric material; and wherein the second axial portion is disposed axially between the first axial portion and the third axial portion.

135. The MRI compatible wire guide of claim 134, wherein the first and third dielectric materials are the same dielectric ma terial.

136. The MRI compatible wire guide of claim 135, wherein the first and third dielectric, materials comprise a polymer.

137. The MRI compatible wire guide of claim 136, wherein the second dielectric material comprises a non-polymer,138. The MRI compatible wire guide of claim 137, wherein the second dielectric material comprises a ceramic.

139. An MRI compatible wire guide, comprising a continuous core member formed of a metallic material and having a first length; and a continuous jacket disposed over and fully encapsulating the entire continuous core member, the continuous jacket havin g a first axial portion formed of a first dielectric material, a second, axial portion formed of a second, different dielectric material, and a second length that is greater than the first length.

140. An MRI compatible wire guide, comprising a continuous core member formed of a metallic material and having a first length; and a continuous jacket having a jacket proximal end, a jacket distal end, a first axial portion extending from the jacket proximal end toward the jacket distal end and formed of a non-polymer dielectric material, and a second axial portion extending from the jacket distal end toward the jacket proximal end and formed of a polymer dielectric material, the continuous jacket disposed over and fully encapsulating the entire continuous core member and having a second length that is greater than the first length; wherein the first axial portion extends along an axial length that is less than about 20% of the second length.141 . The wire guide of any one of claims 121 to 140, wherein the continuous core member has a proximal end, a distal end, a terminal surface of the proximal end, and a terminal surface of the distal end, wherein a proximal end of the jacket covers the terminal surface of the proximal end of the core member and the distal end of the jacket covers the terminal surface of the distal end of the core member.

142. The wire guide of claim 141 , wherein the continuous core member is a continuous length of wire having a proximal end terminal surface received against a proximal end wall of the jacket and a distal end terminal surface received against a distal end. wall of the jacket.

Images