Trackable, identifiable interventional MRI devices and systems

Abstract

Interventional medical devices and systems useful in a medical procedure guided under magnetic resonance imaging (MRS) are described. The interventional systems include a passive MRI marking system that includes discrete passive MRI markers on at least first and second medical devices. The passive MRI marking system can generate unique patterns of MRI image artifacts that facilitate observation and / or tracking of the medical devices of the interventional system.

Description

[0001] TRACKABLE, IDENTIFIABLE INTERVENTIONAL MRI DEVICES AND SYSTEMS

[0002] REFERENCE TO RELATED APPLICATION

[0003] This application claims the benefit of priority of United States Provisional Patent

[0004] Application No. 63 / 708,328 filed October 17, 2024 and entitled Trackable, Identifiable

[0005] Interventional MRI Devices and Systems, which his hereby incorporated herein by reference in its entirety.

[0006] BACKGROUND

[0007] The present invention relates generally to the field of interventional medical procedures and more particularly to elongate devices, such as introducer sheaths, wire guides, needles, and catheters, utilized in interventional medical procedures.

[0008] Elongate devices, for example, wire guides, sheaths, catheters and needles, are commonly utilized together in a wide variety of interventional medical procedures.

[0009] Oftentimes, it is beneficial that the individual devices of the device combinations, and their relative positions, be identifiable and discernable relative to one another in medical imaging.

[0010] Interventional medical procedures have historically been conducted largely with X- ray guidance. Sometimes, radiopaque markers or marked lengths are included on catheters and wire guides that can be seen in images during X-ray guidance. However,

[0011] X-ray-guided procedures expose the patient to significant ionizing radiation.

[0012] Needs exist, therefore, for improved and / or alternative medical devices and systems that can be effectively visually tracked and discerned during procedures guided by other imaging modalities, such as in MRI-guided procedures. Aspects of the present disclosure are addressed to these needs. SUMMARY

[0013] In certain aspects, the present disclosure relates to interventional medical systems useful in a medical procedure guided under magnetic resonance imaging (MRI). The interventional systems include a passive MRI marking system that includes discrete passive

[0014] MRI markers on at least first and second medical devices. The passive MRI marking system can generate unique patterns of MRI image artifacts that facilitate observation and / or tracking of the medical devices of the interventional system.

[0015] In still further aspects herein, provided are magnetic resonance imagining methods, MRI systems, and devices for controlling MRI systems, that include steps or that are configured to automate or facilitate operations using a computer processor (e.g. of a computer), and that may involve medical devices, interventional systems, kits, and / or other embodiments disclosed herein.

[0016] Additional aspects of the present disclosure relate to methods for making, and methods for using, interventional medical devices and systems as described herein.

[0017] Still further aspects of the present disclosure, and features and advantages of aspects of the present disclosure, will be apparent to those skilled in the art from the descriptions herein.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the drawings wherein like reference numerals represent like parts:

[0020] FIG. 1 depicts one embodiment of an interventional system including multiple devices and a passive MRI marker system, with generated visible artifacts graphically depicted.

[0021] FIG. 2 depicts another embodiment of an interventional system including multiple devices and a passive MRI marker system, with generated visible artifacts graphically depicted.

[0022] FIG. 3 depicts another embodiment of an interventional system including multiple devices and a passive MRI marker system, with generated visible artifacts graphically depicted.

[0023] FIG. 4 depicts another embodiment of an interventional system including multiple devices and a passive MRI marker system, with generated visible artifacts graphically depicted.

[0024] FIG. 5 depicts an embodiment of an interventional system useful for providing transjugular intrahepatic access and including a passive MRI marker system.

[0025] FIG. 6 depicts one embodiment of a long needle and catheter combination useful in the interventional system of FIG. 5.

[0026] FIG. 7 depicts another embodiment of a long needle and catheter combination useful in the interventional system of FIG. 5. FIG. 8 depicts one embodiment of a stent delivery system bearing passive MRI markers.

[0027] FIG. 9 depicts the stent delivery system of FIG. 8 after operation to release a stent.

[0028] FIG. 10 depicts one embodiment of a catheter and wire guide combination useful for accessing a pulmonary artery and including a passive MRI marking system.

[0029] FIG. 11 depicts one embodiment of a vascular filter delivery system including a passive MRI marking system.

[0030] FIGs. 12 to 21 depict various structures for providing a passive MRI marker(s) on medical devices of interventional systems herein.

[0031] FIGs. 22A to 22F depict an interventional system useful for providing access to an artery of a kidney and having a passive MRI marking system, at various stages of a procedure.

[0032] FIG. 23 is a schematic illustration of an MRI system in accordance with embodiments herein.

[0033] FIGs. 24A to 24F are representative MRI images showing markers of a passive MRI marking system of the interventional system depicted in FIGs. 22A to 22F, corresponding to the various stages of the procedure.

[0034] DETAILED DESCRIPTION

[0035] Reference will now be made to embodiments, some of which are illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications in the described embodiments and any further applications of the principles as described herein are contemplated as would normally occur to one skilled in the art to which this disclosure relates.

[0036] As disclosed above, aspects of the present disclosure relate to interventional medical devices and systems that are useful in MRI-guided procedures, such as catheters, wire guides, sheaths, needles or dilators, and to systems including them, and to methods for making and using the devices and systems. In preferred forms, the interventional medical devices and systems are configured for percutaneous insertion into a vessel of the patient to conduct an endoluminal procedure, such as an intravascular procedure.

[0037] 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 with the intended use of an item that includes the members in their attached form.

[0038] As used herein, the term "plug" refers to a member having a size and configuration suitable for disposition within a hole, passageway, recess, or void in another member.

[0039] The term does not require any particular size or configuration, and the size and configuration of a particular plug will depend on the size and configuration of the hole, passageway, recess, or void into which the plug is intended to be disposed.

[0040] As used herein, the term "circumference" refers to an external, or internal, enclosing boundary of a body, element, or feature and does not impart any structural configuration on the body, element, or feature. As used herein, the term "passive discrete MRI marker" refers to an amount of a first material positioned relative to a second material such that the first material generates a discrete visible artifact that is distinguishable from the second material under MRI. In embodiments herein the second material is typically represented by a material forming an elongate member, such as a shaft that is solid in cross section or that defines a single lumen or multiple lumens, and having a magnetic susceptibility that is less than the magnetic susceptibility of the first material.

[0041] As used herein, the term "passive," in relation to an MRI marker, refers to a marker that is either unpowered or powered exclusively by the electromagnetic field of a MR scanner.

[0042] 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

[0043] (2013) and using a primary field strength of 0.55T and the following parameters:

[0044] Gradient echo sequence

[0045] Time to Echo (TE) [ms] 15

[0046] Repetition Time (TR) [ms] 317

[0047] Flip angle [°] 30

[0048] Matrix size 256 x 256

[0049] Slice thickness [mm] 10mm

[0050] Pixel bandwidth [Hz / px] 120

[0051] Field of View (FOV) [mm x mm] 400 x 400

[0052] 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

[0053] ("ppm"), and persons skilled in the pertinent art will understand that the reference to

[0054] "ppm" is equivalent to a reference to

[0055] FIG. 1 provides a schematic view depicting one embodiment of an interventional system 20 including multiple devices and a passive MRI marking system. In some forms, such a passive marking system as described herein is provided by a set of discrete passive MRI markers including one or more discrete passive MRI markers located on a distal region of each of the multiple devices of the system, for example located on a distalmost 20 cm segment, or a distalmost 10 cm segment, or a distalmost 7cm segment, of each of the multiple devices of the system. In addition or alternatively, the set of discrete passive MRI markers of the passive MRI marking system can include one or multiple discrete passive markers on a distal region of a first medical device that are positionable distal of a distal end of a second medical device also bearing one or multiple discrete passive MRI markers of the set; and, in such a system also including a third medical device bearing one or multiple discrete passive MRI markers of the set. wherein the one or multiple discrete passive MRI markers of the set that are on the second medical device are positionable distal of a distal end of the third medical device.

[0056] As will be understood, the devices of the interventional system 20 can be used coaxially with one another.

[0057] Interventional system 20 includes at least a first medical device 22 that is longitudinally movable relative to a second medical device 24. In preferred forms, second medical device 24 defines a longitudinal lumen 34 therethrough and first medical device 22 is slidably receivable in longitudinal lumen 34. First medical device 22 has a distal end 28 and second medical device 24 has a distal end 30. First medical device 22 and second medical device 24 are configured such that a distal longitudinal segment of the first medical device is positionable distally beyond the distal end 30 of the second medical device 24, for example as shown. Interventional system 20 includes a passive MRI marking system. For these purposes, first medical device 22 and second medical device 24 each include at least one discrete passive MRI marker of the passive MRI marking system. In some beneficial forms, first medical device 22 and second medical device 24 each include at least two such discrete passive MRI markers. In the passive MRI marking system of the interventional system 20, the discrete passive MRI marker(s) of the second medical device 24 are each configured to generate an MRI image artifact having a maximum dimension that differs from that of, and more preferably that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), an

[0058] MRI image artifact generated by the discrete passive MRI marker(s) of the first medical device 22. In some forms, the discrete passive MRI marker(s) of the second medical device 24 included in the passive MRI marking system of interventional system 20 are each configured to generate an MRI image artifact having a maximum dimension that is about 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, an MRI image artifact generated by the discrete passive MRI marker(s) of the first medical device 22 included in the passive MRI marking system. In addition or alternatively, in embodiments in which one of or each of devices 22 and 24 includes two or more discrete passive MRI markers of the passive MRI marking system, the discrete passive MRI markers of a given device can be configured to generate MRI image artifacts that have the same maximum dimension as one another.

[0059] In the passive MRI marking system of the specific illustrated interventional system

[0060] 20, the first medical device 22 includes a first discrete passive MRI marker 38 configured to generate a first MRI image artifact 38A, a second discrete passive MRI marker 40 configured to generate a second MRI image artifact 40A, and a third discrete passive

[0061] MRI marker 42 configured to generate a third MRI image artifact 42A. Marker 38 is positioned to demark the distal end 28 of the first medical device 22, for example being positioned at or within about 2mm of the distal end 28. MRI image artifacts 38A, 40A and 42A each have the same maximum dimension, which can for example be in the range of 5 mm to 25 mm, or 10 mm to 20 mm. Second medical device 24 includes a first discrete passive MRI marker 44 of the marking system configured to generate a first MRI image artifact 44A and a second discrete passive MRI marker 46 of the marking system configured to generate a second MRI image artifact 46A. Marker 44 is positioned to demark the distal end 30 of the second medical device 24, for example be positioned at or within about 5 mm of, or at or within about 3 mm of, the distal end 30. In this regard, in this instance and in other instances described herein in which a discrete passive MRI marker demarks a distal end of a device, in certain forms, such discrete passive MRI marker can be configured to generate an MRI image artifact the distalmost edge of which longitudinally aligns with the distal end of the device. MRI image artifacts 44A and 46A each have the same maximum dimension, which can for example be in the range of 7 mm to 38 mm, or in the range of 13 mm to 30 mm and / or at least about 25% greater than or at least about 50% greater than that of the maximum dimension of MRI image artifacts generated by the discrete passive MRI marker(s) of the first medical device 22, for example image artifacts 38A, 40A and 42A.

[0062] Interventional system 20 can also include a third medical device 26 that is longitudinally movable relative to the second medical device 24 and the first medical device 22. In preferred forms, third medical device 26 defines a longitudinal lumen 36 therethrough and second medical device 24 is slidably receivable in longitudinal lumen

[0063] 36 (including with first medical device 22 extending through lumen 34 of second medical device 24). Third medical device 26 has a distal end 32. Third medical device 26 and second medical device 24 are configured such that a distal longitudinal segment of the second medical device is positionable distally beyond the distal end 32 of the third medical device 26, for example as shown.

[0064] As disclosed above, interventional system 20 includes a passive MRI marking system.

[0065] For these purposes, third medical device 26 includes at least one discrete passive MRI marker of the marking system. In some forms, third medical device 26 includes at least two discrete passive MRI markers, and in other forms, third medical device 26 includes only one discrete passive MRI marker, of the marking system. In the marking system of the interventional system 20, the discrete passive MRI marker(s) of the third medical device 26 are each configured to generate an MRI image artifact having a maximum dimension that differs from that of, and more preferably that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), an

[0066] MRI image artifact generated by the discrete passive MRI marker(s) of the marking system provided on second medical device 24. In some forms, the discrete passive MRI marker(s) of the third medical device 26 included in the marking system are each configured to generate an MRI image artifact having a maximum dimension that is about

[0067] 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, an MRI image artifact generated by the discrete passive MRI marker(s) of the second medical device 24 included in the marking system, for example MRI image artifacts 44A and 46A. In addition or alternatively, in embodiments in which one of or each of devices

[0068] 22, 24 and 26 includes two or more discrete passive MRI markers of the marking system, the discrete passive MRI markers of a given device can be configured to generate MRI image artifacts that have the same maximum dimension as one another.

[0069] In the specific illustrated system 20, the third medical device 26 includes a first discrete passive MRI marker 48 of the marking system configured to generate a first MRI image artifact 48A. Marker 48 is positioned to demark the distal end 32 of the third medical device 26, for example being positioned at or within about 5 mm of, or at or within about 3 mm of, the distal end 32. MRI image artifact 48A can have a maximum dimension in the range of 9 mm to 58 mm or of 16 mm to 45 mm, and / or that is at least about 25% greater than, or at least about 50% greater than, that of the maximum dimension of MRI image artifacts generated by the discrete passive MRI marker(s) of the marking system on second medical device 24, for example image artifacts 44A and 46A.

[0070] Additionally or alternatively, in embodiments in which medical device 26 includes two or more discrete passive MRI markers of the marking system, such markers can each be configured to generate an MRI image artifact having a maximum dimension as specified above for artifact 48A and / or having the same maximum dimension.

[0071] Referring now to FIG. 2, shown is another embodiment of an interventional system

[0072] 20A including a passive MRI marker system. Unless stated otherwise, the components of interventional system 20A are the same as those of interventional system 20 discussed above, and are similarly numbered in FIGs. 1 and 2. In the passive MRI marking system of the interventional system 20A, the discrete passive MRI marker(s) of the first medical device 22 are each configured to generate an MRI image artifact having a maximum dimension that differs from that of, and more preferably that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), an MRI image artifact generated by the discrete passive MRI marker(s) of the second medical device 24. In some forms, the discrete passive MRI marker(s) of the marking system provided on first medical device 22 are each configured to generate an

[0073] MRI image artifact having a maximum dimension that is about 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, an MRI image artifact generated by the discrete passive MRI marker(s) of the marking system on the second medical device 24. In addition or alternatively, in embodiments in which one of or each of devices 22 and 24 includes two or more discrete passive MRI markers of the marking system, the discrete passive MRI markers of a given device can be configured to generate MRI image artifacts that have the same maximum dimension as one another.

[0074] In the marking system of the specific illustrated interventional system 20A, the first medical device 22 includes a first discrete passive MRI marker 38 configured to generate a first MRI image artifact 38A, and a second discrete passive MRI marker 42 configured to generate a second MRI image artifact 42A. Marker 38 is positioned to demark the distal end 28 of the first medical device 22, for example being positioned at or within about 5 mm of the distal end 28, or at or within about 3 mm of distal end 28. MRI image artifacts 38A and 42A desirably each have the same maximum dimension, which can for example be in the range of 9 mm to 58 mm or of 16 mm to 45 mm. Second medical device 24 includes a first discrete passive MRI marker 44 of the marking system configured to generate a first MRI image artifact 44A and a second discrete passive MRI marker 46 of the marking system configured to generate a second MRI image artifact

[0075] 46A. Marker 44 is positioned to demark the distal end 30 of the second medical device

[0076] 24, for example be positioned at or within about 2mm of the distal end 30. MRI image artifacts 44A and 46A each have the same maximum dimension, which can for example be in the range of 5 mm to 25 mm or in the range of 10 to 20 mm; and / or the maximum dimension of MRI image artifacts generated by the discrete passive MRI marker(s) of the marking system on the first medical device 22, for example image artifacts 38A, 40A and

[0077] 42A, can be at least about 25% greater than or at least about 50% greater than that of the MRI image artifacts generated by the discrete passive MRI marker(s) of the marking system on second medical device 24, for example MRI image artifacts 44A and 46A.

[0078] Similar to interventional system 20 discussed above, interventional system 20A can also include a third medical device 26 that is longitudinally movable relative to the second medical device 24 and the first medical device 22. Third medical device 26 includes at least one discrete passive MRI marker of the marking system. In some forms, third medical device 26 includes at least two discrete passive MRI markers of the marking system, and in other forms, third medical device 26 includes only one discrete passive MRI marker of the marking system. In the passive MRI marking system of the interventional system 20A, the discrete passive MRI marker(s) of the second medical device 24 are each configured to generate an MRI image artifact having a maximum dimension that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), an MRI image artifact generated by the discrete passive MRI marker(s) of the third medical device 26. In some forms, the discrete passive MRI marker(s) of the marking system on the second medical device 24 are each configured to generate an MRI image artifact having a maximum dimension that is about

[0079] 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, an MRI image artifact generated by the discrete passive MRI marker(s) of the marking system on the third medical device 26, for example MRI image artifact 48A. In addition or alternatively, in embodiments in which one of or each of devices 22, 24 and

[0080] 26 includes two or more discrete passive MRI markers of the marking system, the discrete passive MRI markers of a given device can be configured to generate MRI image artifacts that have the same maximum dimension as one another.

[0081] In the specific illustrated system 20A, the third medical device 26 includes a first discrete passive MRI marker 48 of the marking system configured to generate a first MRI image artifact 48A. Marker 48 is positioned to demark the distal end 32 of the third medical device 26, for example being positioned at or within about 2mm of the distal end 32. MRI image artifact 48A can have a maximum dimension, and the maximum dimension of the MRI image artifact generated by the discrete passive MRI marker(s) of the marking system on the second medical device 24 (for example MRI image artifacts

[0082] 44A and 46A) can be at least about 25% greater than, or at least about 50% greater than, that of the maximum dimension of MRI image artifact 48A. Additionally or alternatively, the maximum dimension of the MRI image artifact 48A can be in the range of 5 mm to 25 mm or in the range of 10 mm to 20 mm. Still further additionally or alternatively, in embodiments in which medical device 26 includes two or more discrete passive MRI markers of the marking system, such markers can each be configured to generate an MRI image artifact having a maximum dimension as specified above for artifact 48A and / or having the same maximum dimension.

[0083] Preferred interventional systems 20 and 20A include discrete passive MRI marking systems in which the maximum dimension of the MRI image artifacts generated by discrete passive MRI markers on the respective included devices are progressively larger

[0084] (system 20), or progressively smaller (system 20A), as one considers the devices of the system from the smallest diameter device (most inwardly-received in a coaxial arrangement) to the largest diameter device (most outwardly-received in a coaxial arrangement). Such passive MRI marking patterns can enable beneficial visual or automated (e.g. using a computer processor and image analysis software) detection of markers on each respective device and discernment of the position of one device relative to the other device(s) during relative movement and / or while stationary.

[0085] Referring now to FIG. 3, shown is another embodiment of an interventional system

[0086] 20B including a passive MRI marker system. Unless stated otherwise, the components of interventional system 20B are the same as those of interventional system 20 discussed above, and are similarly numbered in FIGs. 1 and 3. In the passive MRI marking system of the interventional system 20B, the first medical device 22 has a first discrete passive MRI marker 38 positioned to demark the distal end 28, and at least a second discrete passive MRI marker spaced from and longitudinally proximal of the first discrete passive MRI marker 38, and in some forms a plurality of additional discrete passive MRI markers spaced from and longitudinally proximal of the first discrete passive MRI marker 38 (e.g. at least first and second discrete passive MRI markers longitudinally spaced from one another, such as markers 40 and 42). The first discrete passive MRI marker 38 is configured to generate an MRI image artifact having a maximum dimension that differs from that of, and preferably that is greater than that of

[0087] (e.g. at least about 25% greater than that of, or at least about 50% greater than that of),

[0088] (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on the first medical device 22 or (ii) an MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on the first medical device 22, when such a plurality is present. In some forms, the discrete passive

[0089] MRI marker 38 of the first medical device 22 is configured to generate an MRI image artifact having a maximum dimension that is about 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on first medical device

[0090] 22 or (ii) an MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on the first medical device 22. In addition or alternatively, in embodiments in which device 22 includes a plurality of additional discrete passive MRI markers of the marking system spaced proximally from the discrete passive MRI marker 38, the additional discrete passive MRI markers can each be configured to generate an MRI image artifact that has the same maximum dimension.

[0091] In the passive MRI marking system of the interventional system 20B, the second medical device 24 has a first discrete passive MRI marker 44 positioned to demark the distal end 30, and at least a second discrete passive MRI marker (e.g. discrete passive

[0092] MRI marker 46) spaced from and longitudinally proximal of the first discrete passive MRI marker 44, and in some forms a plurality of additional discrete passive MRI markers spaced from and longitudinally proximal of the first discrete passive MRI marker 44. The first discrete passive MRI marker 44 is configured to generate an MRI image artifact having a maximum dimension that differs from that of, and preferably that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on the second medical device 24 (e.g. marker 46) or (ii) an

[0093] MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on the second medical device 24, when such a plurality is present.

[0094] In some forms, the discrete passive MRI marker 44 of the second medical device 24 is configured to generate an MRI image artifact having a maximum dimension that is about

[0095] 25% to about 400% greater than that of, or about 50% to about 300% greater than that of, (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on second medical device 24 or (ii) an MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on second medical device 24, when such a plurality is present. In addition or alternatively, in embodiments in which the marking system of interventional system 20B includes a plurality of additional discrete passive MRI markers spaced proximally from the discrete passive MRI marker 44 on device 24, the additional discrete passive MRI markers can each be configured to generate an MRI image artifact that has the same maximum dimension.

[0096] In the specific illustrated system 20B, the first medical device 22 includes a first discrete passive MRI marker 38 configured to generate a first MRI image artifact 38A, a second discrete passive MRI marker 40 configured to generate a second MRI image artifact 40A, and a third discrete passive MRI marker 42 configured to generate a third

[0097] MRI image artifact 42A. MRI image artifacts 40A and 42A can have the same maximum dimension, which can for example be in the range of 5 mm to 25 mm or in the range of

[0098] 10 mm to 20 mm. MRI artifact 38A can have a maximum dimension that is greater than those of artifacts 40A and 42A as disclosed above, which can be in the range of 7 mm to

[0099] 38 mm or in the range of 13 mm to 30 in some forms. Second medical device 24 includes a first discrete passive MRI marker 44 configured to generate a first MRI image artifact 44A and a second discrete passive MRI marker 46 configured to generate a second MRI image artifact 46A. MRI image artifact 46A can have a maximum dimension in the range of 5 mm to 25 mm or in the range of 10 mm to 20 mm, and / or that is the same as that of artifacts 40A and 42A. MRI image artifact 44A has a maximum dimension that is greater than that of artifact 46A as disclosed above, and in some forms that is the same as that of MRI image artifact 38A.

[0100] Similar to interventional system 20 discussed above, interventional system 20B can also include a third medical device 26 that is longitudinally movable relative to the second medical device 24 and the first medical device 22. Third medical device 26 includes at least one discrete passive MRI marker of the passive MRI marking system. In some forms, third medical device 26 includes at least two discrete passive MRI markers of the marking system, and in other forms, third medical device 26 includes only one discrete passive MRI marker of the marking system. In embodiments in which the medical device 26 includes at least two discrete passive markers of the marking system, the third medical device 26 has a first discrete passive MRI marker 48 positioned to demark the distal end 32, and at least a second discrete passive MRI marker (e.g. discrete passive MRI marker 50) spaced from and longitudinally proximal of the first discrete passive MRI marker 48, and in some forms a plurality of additional discrete passive MRI markers spaced from and longitudinally proximal of the first discrete passive MRI marker 48. The first discrete passive MRI marker 48 is configured to generate an MRI image artifact having a maximum dimension that differs from that of, and preferably that is greater than that of (e.g. at least about 25% greater than that of, or at least about 50% greater than that of), (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on the third medical device

[0101] 26 (e.g. marker 50) or (ii) an MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on the third medical device 26, when such a plurality is present. In some forms, the discrete passive MRI marker 48 of the third medical device 26 is configured to generate an MRI image artifact having a maximum dimension that is about 25% to about 400% greater than that of, or about

[0102] 50% to about 300% greater than that of, (i) an MRI image artifact generated by the second discrete passive MRI marker of the marking system on third medical device 26 or

[0103] (ii) an MRI image artifact of each of the plurality of additional discrete passive MRI markers of the marking system on third medical device 26, when such a plurality is present. In addition or alternatively, in embodiments in which the marking system of interventional system 20B includes a plurality of additional discrete passive MRI markers spaced proximally from the discrete passive MRI marker 48 on device 26, the additional discrete passive MRI markers can each be configured to generate an MRI image artifact that has the same maximum dimension.

[0104] In the specific illustrated system 20B, the third medical device 26 includes a first discrete passive MRI marker 48 configured to generate a first MRI image artifact 48A and a second discrete passive MRI marker 50 configured to generate a second MRI image artifact 50A. Marker 48 is positioned to demark the distal end 32 of the third medical device 26, for example being positioned at or within about 2mm of the distal end 32. MRI image artifact 48A can have a maximum dimension that is greater than that of MRI image artifact 50A, for example where artifact 48A has a maximum dimension that is at least about 25% greater than, or at least about 50% greater than, that of the maximum dimension of MRI image artifact 50A. Additionally or alternatively, the maximum dimension of the MRI image artifact 48A can be in the range of 7 mm to

[0105] 38 mm or in the range of 13 mm to 30 mm, and / or the maximum dimension of the MRI image artifact 50A can be in the range of about 5 mm to 25 mm or in the range of 10 mm to 20 mm. Still further additionally or alternatively, in embodiments in which medical device 26 includes a plurality of discrete passive MRI markers additional to discrete passive MRI marker 48, such additional markers can each be configured to generate an MRI image artifact having the same maximum dimension. MRI image artifact 50A can have a maximum dimension that is the same as that of artifact 46A and / or that is the same as artifacts 40A and 42A. In some forms, MRI image artifact 48A of interventional system 20B has a maximum dimension that is the same as that of MRI image artifact 44A and / or the same as that of MRI image artifact 38A. In addition or alternatively, MRI image artifact 48A of system 20B can have a maximum dimension that is greater than that of MRI image artifact 46A and / or that is greater than that of MRI image artifacts 40A and 42A.

[0106] While the third medical device 26 of interventional system 20B as specifically illustrated in FIG. 3 includes discrete passive MRI markers 48 and 50, in other forms the interventional system can exclude discrete passive MRI marker 50, such that discrete passive MRI marker 48 is the only discrete passive MRI marker of the marking system provided by third device 26. Such interventional systems can otherwise have features that are the same as those disclosed above for system 20B.

[0107] Preferred interventional systems such as system 20B discussed above include discrete passive MRI marking systems in which the distal ends of the multiple devices of the system are demarked by discrete passive MRI markers that generate MRI image artifacts having a maximum dimension that is greater than that of other passive MRI markers on the respective device and preferably of other non-end-demarking passive

[0108] MRI markers of the marking system. Such passive MRI marking patterns can enable beneficial visual or automated (e.g. using a computer processor and image analysis software) detection of markers on each respective device and discernment of the position of one device relative to the other device(s) during relative movement and / or while stationary.

[0109] Referring now to FIG. 4, shown is another embodiment of an interventional system

[0110] 20C including a passive MRI marker system. Unless stated otherwise, the components of interventional system 20C are the same as those of interventional system 20 discussed above, and are similarly numbered in FIGs. 1 and 4. In the passive MRI marking system of the interventional system 20C, the first medical device 22 includes a plurality of discrete passive MRI markers that are spaced from one another longitudinally by a first distance (measured between the longitudinal center points of adjacent markers), and the second medical device 24 includes a plurality of discrete passive MRI markers that are spaced from one another longitudinally by a second distance (again, measured between the longitudinal center points of adjacent markers), where the second distance differs from the first distance. In preferred forms, the second distance will differ from the first distance by at least about 25%, or at least about

[0111] 50%, and in some forms by about 25% to about 200% or by about 50% to about 200%. In the marking system, the discrete passive MRI markers of the first medical device

[0112] 22 are each configured to generate an MRI image artifact having a maximum dimension and the discrete passive MRI markers of the second medical device 24 are each configured to generate an MRI image artifact having a maximum dimension. The maximum dimension of the artifacts generated by such discrete passive MRI markers of the first medical device 22 can be the same as, or different from, that of the artifacts generated by such discrete passive MRI markers of the second medical device 24. In addition or alternatively, each of the discrete passive MRI markers of the marking system that is on the first medical device 22 can be configured to generate an MRI image artifact with a maximum dimension that is the same as, or that differs from, other such passive MRI marker(s) on the first medical device 22; and / or, each of the discrete passive MRI markers of the marking system that is on the second medical device 24 can be configured to generate an MRI image artifact with a maximum dimension that is the same as, or that differs from, other such passive MRI marker(s) on the second medical device 24.

[0113] In the marking system of the specific illustrated interventional system 20C, the first medical device 22 includes a first discrete passive MRI marker 38 configured to generate a first MRI image artifact 38A, a second discrete passive MRI marker 40 configured to generate a second MRI image artifact 40A, and a third discrete passive MRI marker 42 configured to generate a third MRI image artifact 42A. Marker 38 is positioned to demark the distal end 28 of the first medical device 22, for example being positioned at or within about 2mm of the distal end 28. Markers 38, 40, and 42 are equidistantly spaced from one another a first distance. Such first distance can, for example, be in the range of about 0.5 cm to about 5 cm or in the range of about 1 cm to 3 cm. MRI image artifacts 38A, 40A and 42A of the specific illustrated system each have the same maximum dimension, which can for example be in the range of 5 mm to 25 mm or in the range of 10 mm to 20 mm. Second medical device 24 includes a first discrete passive

[0114] MRI marker 44 of the marking system configured to generate a first MRI image artifact

[0115] 44A and a second discrete passive MRI marker 46 of the marking system configured to generate a second MRI image artifact 46A. Marker 44 is positioned to demark the distal end 30 of the second medical device 24, for example be positioned at or within about

[0116] 2mm of the distal end 30. Markers 44 and 46 are spaced from one another a second distance. The second distance will be different from (e.g. greater than) the first distance noted above and can, for example, be in the range of about 0.5 cm to about 5 cm or in the range of about 1 cm to about 3 cm. MRI image artifacts 44A and 46A each have the same maximum dimension, which can for example be in the range of 5 mm to 25 mm or in the range of 10 mm to 20 mm. In some preferred forms, the plurality of discrete passive markers of at least one of the first medical device 22 and the second medical device 24 will include at least three discrete passive MRI markers of the system, where the markers of such plurality are beneficially equidistantly spaced from one another. In addition or alternatively, the plurality of discrete passive MRI markers of the first medical device 22 can include a different number of discrete passive MRI markers than the plurality of discrete passive MRI markers of the second medical device 24.

[0117] In some embodiments, one of the first medical device 22 and the second medical device 24 will include two discrete passive MRI markers of the marking system, and the other will include three or more discrete passive MRI markers, for example three to seven, passive MRI markers, of the marking system. In other embodiments, one of the first medical device 22 and the second medical device 24 will include three discrete passive MRI markers of the marking system, and the other will include four or more discrete passive MRI markers, for example four to seven, passive MRI markers, of the marking system. In still other embodiments, one of the first medical device 22 and the second medical device 24 will include four discrete passive MRI markers of the marking system, and the other will include five or more discrete passive MRI markers, for example five to ten, passive MRI markers, of the marking system. In these and other embodiments herein in which the first medical device 22 and / or the second medical device 24 includes three or more discrete passive MRI markers of the marking system, such markers on a given device are equidistantly spaced from one another in certain advantageous forms. Similar to interventional system 20 discussed above, interventional system 20C can also include a third medical device 26 that is longitudinally movable relative to the second medical device 24 and the first medical device 22. Third medical device 26 includes at least one discrete passive MRI marker of the marking system, and in some forms only one discrete passive MRI marker of the marking system, for example demarking the distal end 32. In the passive MRI marking system of the interventional system 20C, the discrete passive MRI marker(s) of the third medical device 26 are each configured to generate an MRI image artifact having a maximum dimension. The maximum dimension of the artifacts generated by such discrete passive MRI markers of the third medical device 26 can be the same as, or different from, that of the artifacts generated by such discrete passive MRI markers of the second medical device 24 and / or the first medical device 22. In addition or alternatively, when multiple discrete passive

[0118] MRI markers of the marking system are present on the third medical device 26, each such discrete passive MRI marker can be configured to generate an MRI image artifact with a maximum dimension that is the same as, or that differs from, other such passive

[0119] MRI marker(s) on the third medical device 26.

[0120] In the specific illustrated interventional system 20C, the third medical device 26 includes a discrete passive MRI marker 48 of the marking system configured to generate a first MRI image artifact 48A. Marker 48 is positioned to demark the distal end 32 of the third medical device 26, for example being positioned at or within about 2mm of the distal end 32. In certain embodiments, MRI image artifact 48A can have a maximum dimension that is at least about 25% greater than, or at least about 50% greater than, that of the MRI image artifact generated by the discrete passive MRI marker(s) of the marking system on the second medical device 24 (for example MRI image artifacts 44A and 46A). Additionally or alternatively, the maximum dimension of the MRI image artifact 48A can be in the range of 7 mm to 58 mm or in the range of 13 mm to 45 mm.

[0121] Interventional system 20C includes a discrete passive MRI marking system in which the longitudinal spacing between discrete passive MRI markers on the first device 22 differs from that on the second device 24. As well, where third device 26 includes multiple discrete passive MRI markers of the marking system, the spacing between such markers can differ from that of the discrete passive MRI markers on the second device

[0122] 24 and / or on the first device 22. In some forms, the spacing between discrete passive

[0123] MRI markers on the respective included devices can be progressively greater or progressively smaller as one considers the devices of the system from the smallest diameter device (most inwardly-received in a coaxial arrangement) to the largest diameter device (most outwardly-received in a coaxial arrangement) and / or the spacing between discrete passive MRI markers on the respective included devices of the system is selected such that no adjacent pair of the discrete passive MRI markers on a given one of the devices longitudinally aligns with an adjacent pair of the discrete passive MRI markers on any other one of the devices as the devices are moved longitudinally with respect to one another. Such passive MRI marking patterns can enable beneficial visual or automated (e.g. using a computer processor and image analysis software) detection of markers on each respective device and discernment of the position of one device relative to the other device(s) during relative movement and / or while stationary.

[0124] Further, these marker spacing arrangements can be included in marking systems of interventional systems where the discrete passive MRI markers also generate differing sized MRI image artifacts, for example in interventional systems 20, 20A, and 20B shown in FIGs. 1, 2 and 3 and discussed above, and the combination of marker spacing patterns and marker size patterns can further benefit visual or automated device recognition and tracking of devices of the interventional system.

[0125] Exemplary embodiments of interventional systems 20, 20A, 20B and 20C are provided wherein:

[0126] Systems including at least two medical devices:

[0127] (a) The first medical device is a wire guide, and the second medical device is a catheter (which in some forms may be a microcatheter);

[0128] (b) the first medical device is a wire guide, and the second medical device is a needle; (c) the first medical device is a catheter (e.g. a microcatheter), and the second medical device is a catheter;

[0129] (d) the first medical device is a needle, and the second medical device is a catheter;

[0130] (e) the first medical device is a catheter, and the second medical device is a sheath;

[0131] (f) the first medical device is a dilator, and the second medical device is a sheath;

[0132] (g) the first medical device is a sheath, and the second medical device is a sheath;

[0133] (h) the first medical device is a needle, and the second medical device is a dilator;

[0134] (i) the first medical device is a wire guide, and the second medical device is a medical implant (e.g. stent or vascular filter or embolic coil) delivery system; or

[0135] (j) the first medical device is a medical implant (e.g. stent or vascular filter or embolic coil) delivery system, and the second medical device is a sheath.

[0136] Systems including at least three medical devices:

[0137] (a) the first medical device is a wire guide, the second medical device is a catheter, and the third medical device is an introducer sheath;

[0138] (b) the first medical device is a wire guide, the second medical device is a needle; and the third medical device is a catheter;

[0139] (c) the first medical device is a wire guide, the second medical device is a catheter

[0140] (e.g. microcatheter), and the third medical device is a catheter; the first medical device is a catheter (e.g. microcatheter), the second medical device is a catheter, and the third medical device is an introducer sheath; and

[0141] (d) the first medical device is a needle, the second medical device is a catheter, and the third medical device is an introducer sheath; or

[0142] (e) the first medical device is a wire guide, the second medical device is a catheter, needle, dilator or medical implant (e.g. stent or vascular filter or embolic coil) delivery system, and the third medical device is an introducer sheath.

[0143] Discussions below pertain to various interventional systems and devices useful for therapeutic and / or diagnostic procedures conducted on a patient while utilizing MRI guidance. It will be understood that in addition to the specific marking systems discussed below for the interventional systems, in alternative forms the interventional systems can incorporate the marking system described above in conjunction with any of FIGs. 1 to 4 on at least two, or at least three, of the medical devices of the interventional system.

[0144] Referring now to FIG. 5, shown is an interventional system 60 configured for use in providing transjugular intrahepatic access under MRI guidance. Such access can, for example, be used in a transjugular intrahepatic portosystemic shunt (TIPS) procedure.

[0145] Interventional system 60 includes a catheter / needle system 62, an introducer sheath / dilator system 64, a hepatic access catheter 66, a dilation catheter 68, a first wire guide 70 which may have a curved or angled distal tip region (e.g. configured for selective vessel navigation), and a second wire guide 72 which can be stiffer than the first wire guide 70 and may have a straight distal tip region. Catheter needle system 62 includes a needle 74 slidably receivable through a lumen of a catheter 76, and introducer / dilator system 64 includes a dilator 78 slidably receivable through a lumen of an introducer sheath 80.

[0146] Catheter 76 includes a first discrete passive MRI marker 82 demarking its distal end and a second discrete passive MRI marker 84 spaced proximally from the first marker

[0147] 82. Needle 74 also includes discrete passive MRI markers as discussed below. Dilator 78 includes a discrete passive MRI marker 86 demarking its distal end. Sheath 80 includes a discrete passive MRI marker 88 demarking its distal end. Hepatic access catheter 66 includes a first discrete passive MRI marker 90 demarking its distal end and a second discrete passive MRI marker 92 spaced proximally from marker 90. Dilation catheter 68 includes a first discrete passive MRI marker 94 demarking its distal end and a second discrete passive marker 96 spaced proximally from marker 94. Wire guide 70 includes a first discrete passive MRI marker 98 demarking its distal end, a second discrete passive

[0148] MRI marker 100 spaced proximally from marker 98, a third discrete passive MRI marker

[0149] 102 spaced proximally from marker 100, and a fourth discrete passive MRI marker 104 spaced proximally from marker 102. Wire guide 72 includes a first discrete passive MRI marker 106 demarking its distal end, a second discrete passive MRI marker 108 spaced proximally from marker 106, a third discrete passive MRI marker 110 spaced proximally from marker 108, and a fourth discrete passive MRI marker 112 spaced proximally from marker 110.

[0150] FIG. 6 shows one embodiment of the catheter / needle system 62 with the catheter

[0151] 76 and the needle 74 separated. In this embodiment, needle 74 includes a single discrete passive MRI marker 114 demarking its distal end. As shown, needle 74 has a curved distal end region. Needle 74 also includes a direction indicator member 116 that provides visual indication of the direction of the curve of the curved distal end region of the needle 74. In the illustrative embodiment shown, the indicator member 116 is in the form of a plate having an asymmetrical shape. FIGs. 6A and 6B show MRI images of this embodiment of catheter / needle system 62 in a phantom material with the distal end of the needle 74 extended beyond the distal end opening of the catheter 76. For use under MRI, needle 74 can be constructed from materials that are non- ferromagnetic. In preferred aspects, the needle will have a needle shaft formed from a material that has a magnetic susceptibility not exceeding about 3000 ppm, or not exceeding about 2000 ppm, or not exceeding about 1000 ppm, and in some aspects in the range of about 1 ppm to about 3000 ppm or about 1 ppm to about 2000 ppm, or about 1 ppm to about 1000 ppm. Certain preferred materials for forming the needle shaft include, as examples, titanium, tungsten, nickel-titanium alloys such as superelastic nickel-titanium alloys (e.g. nitinol), nickel-cobalt alloys such as superalloys containing nickel, cobalt, chromium and molybdenum (e.g. MP35N), and austenitic nickel-chromium based superalloys (such as Inconel 625 or another Inconel alloy available from Special Metals Corporation). As specific examples, the cannula of needle

[0152] 74 can be made of nitinol (a nickel-titanium alloy) or Inconel (a nickel chromium alloy).

[0153] The indicator 116 and the Luer fitting shown proximal of it can be made of brass (e.g. chrome or nickel plated) or any other suitable material, for example any of those specified above for the needle shaft.

[0154] FIG. 7 shows another embodiment of the catheter / needle system 62 with the catheter 76 and the needle 74 separated. In this embodiment, needle 74 includes a first discrete passive MRI marker 118A demarking its distal end, a second discrete passive MRI marker 118B spaced proximally from marker 118A, a third discrete passive MRI marker 118C spaced proximally from marker 118B, and a fourth discrete passive MRI marker 118D spaced proximally from marker 118C. FIGs. 7 A and 7B show MRI images of this embodiment of catheter / needle system 62 in a phantom material with the distal end of the needle 74 extended beyond the distal end opening of the catheter 76.

[0155] In an illustrative method, the interventional system 60 can be used under MRI guidance to establish transjugular intrahepatic access in the following manner, where the MRI guidance can include visualization and / or automated tracking of the medical devices of the system using MRI image artifacts generated by the discrete passive MRI markers on the devices. After establishing percutaneous access to the jugular vein of a patient, the wire guide 72 is percutaneously introduced and its distal end is advanced through the jugular vein and into the inferior vena cava. The hepatic access catheter 66 is advanced over the wire guide 72 and used to catheterize the right hepatic vein or another adequate hepatic vein branch. The distal end of the wire guide 72 is left in a distal position and the hepatic access catheter 66 is removed. The sheath / dilator system 64 is advanced over the wire guide 72 into the hepatic vein. FIG. 5A provides representative MRI image slices at this stage of a procedure conducted in an in vivo nonclinical model. The wire guide 72 and the dilator 78 are then removed from the sheath 80. The catheter / needle system 64 is advanced through the lumen of the sheath

[0156] 80 while maintaining the distal end of the needle 74 within the lumen of the catheter

[0157] 76, and the distal end of the catheter 76 is positioned in the hepatic vein. The catheter / needle system 64 is oriented inferiorly and rotated anteriorly (during which the indicator 116 remains outside the patient and visually indicates the direction of the curve of the curved distal region of the needle 74). The distal end of the catheter / needle system 62, here provided by the distal end of the catheter 76, is wedged against the hepatic vein wall, after which the needle 74 is forced forward through the hepatic parenchyma and toward the portal system of the liver to penetrate a branch of the portal venous system. FIG. 5B provides representative MRI image slices of the in vivo nonclinical model procedure showing these stages of portal system access.

[0158] A syringe filled with contrast medium (e.g. an MRI contrast medium) is connected to the proximal port of the needle 74, and suction is applied to the lumen of the needle 74 while the needle 74 is withdrawn until blood is seen in the syringe barrel. A volume of contrast medium is injected from the syringe through the needle, which can be visualized under MRI to confirm that the distal end of the needle 74 is in the portal venous system. The catheter 76 is then advanced over the needle 74 to position the distal end of the catheter 76 in the portal venous system, and the wire guide 70 is then passed through the lumen of the needle and into the portal venous system, and the wire guide 70 is navigated distally to position its distal end in the main portal vein. FIG. 5C provides representative MRI image slices of the in vivo nonclinical model procedure showing this stage. In some procedures, the needle 74 and catheter 76 are then removed, and a therapy can be delivered by advancing one or more devices over the wire guide 70. In certain forms, a dilating catheter 76 can be advanced over the wire guide 70 through the parenchymal tract and into the main portal vein, after which an interventional diagnostic or therapeutic procedure can be performed using the access thus provided, for example a TIPS procedure in which a tubular shunt is placed across the parenchymal tract created in order to shunt blood flow from the portal venous system to the hepatic venous system.

[0159] FIGs. 8 and 9 depict one embodiment of a stent delivery system 120 including a passive MRI marking system. FIG. 8 shows the system 120 with the stent in an undeployed (loaded) condition. FIG. 9 shows the system 120 with the stent in the deployed condition. Delivery system 120 includes a handle 122 and a cannula 126 extending within the handle 122. Cannula 126 has a hub 124 at its proximal end.

[0160] System 120 also includes an outer sheath 128 distal of and connected to the handle 122 and an inner catheter 130 within outer sheath 128 and having a distal end 132. Inner catheter 130 is connected to cannula 126. System 120 further includes a safety lock

[0161] 134 that prevents longitudinal movement of the handle 122 and outer sheath 128 relative to the cannula 126 and inner catheter 130 until altered to an unlocked condition. In the illustrated embodiment, the safety lock 134 is a tab that is removed to provide the unlocked condition. System 120 also includes a flush port 136. Flush port

[0162] 136 fluidly communicates with an annular spaced between the inner catheter 130 and the outer sheath 128 that houses a stent 138, and can be used to flush the annular space and stent 138 with a flushing liquid such as saline. Inner catheter 130 can have a reduced diameter in the region housing the stent 138 which provides shoulder 140 proximal of the loaded stent 138 and shoulder 142 distal of the loaded stent 138.

[0163] Delivery system 120 includes a passive MRI marking system. The marking system includes a first discrete passive MRI marker 144 on the inner catheter 130, and a first discrete passive MRI marker 146 on the outer sheath 128 and demarking a distal end of the sheath 128. In preferred forms, the markers 144 and 146 are configured to generate respective MRI image artifacts that overlap one another when the system 120 is in the locked and undeployed condition (FIG. 8), but that become longitudinally spaced from one another during movement of the outer sheath 128 relative to the inner catheter

[0164] 130 during deployment of the stent 138. This relative movement and positioning of the respective MRI image artifacts can aid in confirming that stent deployment has begun.

[0165] The passive marking system of delivery system 120 also desirably includes a second discrete passive MRI marker 148 on the inner catheter 130 positioned longitudinally at or proximal of the proximal end of the stent 138, for example to demark the shoulder

[0166] 140, when the system is in the locked and undeployed condition. The MRI image artifact generated by marker 148 can be useful in identifying the location at which the proximal end of the stent 138 will be deployed. In preferred forms, markers 148 and

[0167] 146 are configured to generate respective MRI image artifacts, wherein during movement of the outer sheath 128 relative to the inner catheter 130 to deploy the stent

[0168] 138, the MRI image artifact generated by marker 146 moves at least into longitudinal overlap with the MRI image artifact generated by marker 148, and in some forms moves proximally past the MRI image artifact generated by marker 148 (see e.g. FIG. 9 in which safety lock 134 has been altered to its unlocked condition and handle 122 has been pulled proximally over the cannula 126 and against the hub 124 to deploy the stent

[0169] 138). This relative movement and positioning of the respective MRI image artifacts can aid in confirming that stent deployment has been completed. FIG. 8A provides an MRI image slice of delivery system 120 in position in an in vivo nonclinical model and in a safety-locked condition where the stent is undeployed as illustrated in FIG. 8. Shown are the MRI image artifacts generated by the first discrete passive MRI marker 144 on the inner catheter 130 ("Distal System Marker") and the first discrete passive MRI marker 146 on the outer sheath 128 ("Distal Sheath Marker") in an overlapped condition, and the MRI image artifact generated by the second discrete passive MRI marker 148 on the inner catheter 130 ("Proximal System Marker") longitudinally aligned with the proximal end of the stent 138 ("Loaded Stent"). FIG. 9A provides an MRI image slice of delivery system 120 in position in an in vivo nonclinical model and in a condition where the stent has been deployed as illustrated in FIG. 9.

[0170] Shown are the MRI image artifacts generated by the first discrete passive MRI marker

[0171] 144 on the inner catheter 130 ("Distal System Marker"), the first discrete passive MRI marker 146 on the outer sheath 128 ("Distal Sheath Marker"), and the second discrete passive MRI marker 148 on the inner catheter 130 ("Proximal System Marker"). As shown, the MRI image artifact generated by the discrete passive MRI marker 146 on the outer sheath is no longer overlapped with that generated by the discrete passive MRI marker 144 on the inner catheter 130, but rather has moved to a position proximal of the MRI image artifact generated by the discrete passive MRI marker 148 on the inner catheter 130.

[0172] In some preferred forms, the passive MRI marking system of delivery system 120 also includes a third discrete passive MRI marker 150 on the inner catheter 130 and demarking the distal end thereof. Also, in a further stent delivery system embodiment, the system 120 can be combined with a wire guide slidably receivable through a wire guide lumen provided through the cannula 126 and inner catheter 130, where the wire guide has a plurality of discrete passive MRI markers in a distal region thereof, for example such as shown and discussed for wire guide 70 and / or wire guide 72 discussed above. In such systems, the wire guide can represent the first medical device and the system 120 can represent the second medical device of interventional systems 20, 20A,

[0173] 20B and 20C, and the characteristic discrete passive marker patterning of such interventional systems can be incorporated in the stent delivery system. FIG. 10 depicts another illustrative embodiment of an interventional system 160 including a catheter 162 and a wire guide 164, and having a passive MRI marking system thereon. Interventional system 160 is useful in procedures conducted under MRI guidance, and can be useful in accessing the pulmonary artery of a patient by percutaneously navigating through the right side of the heart. Catheter 162 includes a first discrete passive MRI marker 166 and a second discrete passive MRI marker 168 of the marking system. First discrete passive MRI marker 166 demarks the distal end of catheter 162 and second discrete passive MRI marker 168 is spaced proximally from marker 166 longitudinally along the catheter 162. In preferred forms, the markers 166 and 168 are configured to generate MRI image artifacts that do not overlap one another when the catheter is in its extended, relaxed configuration (as shown in FIG. 10).

[0174] Wire guide 164 includes a first, second, third and fourth discrete passive MRI markers 170, 172, 174 and 176, respectively, of the marking system. First discrete passive MRI marker 170 demarks the distal end of the wire guide 164, second discrete passive MRI marker 172 is spaced proximally from marker 170, third discrete passive

[0175] MRI marker 174 is spaced proximally from marker 172, and fourth discrete passive MRI marker 176 is spaced proximally from marker 174, longitudinally along the wire guide

[0176] 164. In preferred forms, the markers 170, 172, 174 and 176 are configured to generate

[0177] MRI image artifacts that do not overlap one another when the wire guide is in its extended, relaxed configuration (as shown in FIG. 10).

[0178] The catheter 162 includes a distal catheter segment 178 and a proximal catheter segment 180 attached to and immediately proximal of the distal catheter segment 178.

[0179] Distal catheter segment 178 has a catheter wall that is free of any embedded reinforcing member, preferably wherein the catheter wall is formed from a polymeric material such as a dielectric polymeric material. Catheter can include a bonded joint 182 joining the distal catheter segment 178 to the proximal catheter segment 180. Proximal catheter segment 180 incudes a reinforcing member embedded in its catheter wall, for example a wire coil and / or a wire braid. In the specific illustrative embodiment, proximal catheter segment 180 includes a wire braid 184 embedded in its catheter wall. Embedded wire braid 184 or any other reinforcing member can be formed for example from a metal or metal alloy, a glass material, or a polymeric material, and can enhance the column strength and / or enhance the torque response of the catheter 162 (i.e. the amount of torque transmitted through the catheter 162). In certain forms herein, the reinforcing member is formed from a material that has a magnetic susceptibility not exceeding about 3000 ppm, or not exceeding about 2000 ppm, or not exceeding about 1000 ppm, and in some aspects in the range of about 1 ppm to about 3000 ppm or about 1 ppm to about 2000 ppm, or about 1 ppm to about 1000 ppm. Certain preferred materials for forming the reinforcing member include, as examples, titanium, tungsten, nickeltitanium alloys such as superelastic nickel-titanium alloys (e.g. nitinol), nickel-cobalt alloys such as superalloys containing nickel, cobalt, chromium and molybdenum (e.g.

[0180] MP35N), and austenitic nickel-chromium based superalloys (such as Inconel 625 or another Inconel alloy available from Special Metals Corporation).

[0181] The reinforcing member can be embedded in the catheter wall by any suitable technique or structural arrangement, including as an example being positioned between inner and outer layers of the catheter wall. Distal catheter segment 178 can for example be a 5 cm to 20 cm length of flexible polymeric material, which can optionally be softer and more flexible and / or have a durometer lower than a polymeric material of the proximal catheter segment 180. The flexible polymeric material of distal shaft portion 34 can comprise a thermoplastic elastomer material. The thermoplastic elastomer material can comprise a polyether block amide. Alternative thermoplastic elastomer materials that may be used include polyester elastomers, polyurethanes, and polyamide elastomers.

[0182] In certain forms, the catheter wall of the distal catheter segment 178 contains a particulate radiopaque agent to render the segment 178 visible under X-ray imaging, whereas the catheter wall of the proximal catheter segment 180 does not contain a particulate radiopaque agent that renders segment 180 visible under X-ray imaging.

[0183] Such devices may be useful in both MRI guided and X-ray guided interventional procedures. The particulate radiopaque agent is preferably a particulate metal or metal alloy having a magnetic susceptibility of less than about 500 ppm. In some specific forms, the particulate radiopaque agent may be a bismuth compound or a barium compound, for example bismuth oxychloride, bismuth subcarbonate, bismuth trioxide, or barium sulfate.

[0184] As disclosed above, the interventional system 160 can be useful in accessing the pulmonary artery by percutaneous navigation through the right heart of a patient under real time MRI guidance. The passive marking system of the interventional system 160 is used to visually monitor and guide the procedure. In an illustrative procedure, after establishing percutaneous access through the femoral vein, the system 160 is navigated through the inferior vena cava into the right atrium, through the tricuspid valve into the right ventricle (see e.g. FIGs. 10A and 10B), through the right ventricular outflow tract and across the pulmonary valve into the pulmonary artery (see e.g. FIGs. 10C and 10D).

[0185] If desired, the system can then be navigated into the right pulmonary artery branch (see e.g. FIG. 10F and 10G) or the left pulmonary artery branch (see e.g. FIGs. 10H and 101).

[0186] In these steps the distal region of the wire guide 164 typically leads, and its distal curved region can be used to facilitate selective navigation in the desired path. As well, the curved distal region of the catheter 162 can be used to direct the orientation of the distal region of the wire guide 164 and / or at times can be used to lead the system 160 during navigation. In an alternative illustrative procedure, after establishing percutaneous access through the jugular vein or subclavian vein, the system 160 is navigated through the superior vena cava and into the right atrium, after which the navigation path is the same as that discussed above for the femoral vein access procedure.

[0187] FIG. 11 depicts another embodiment of an interventional system 190 including a passive MRI marking system. System 190 can be used to insert a vascular filter, such as an inferior vena cava filter, in a patient under real time MRI guidance. System 190 includes a pre-dilator 192, a filter introducer / protection sheath assembly 194 having a protection sheath hub 196 connected to a protection sheath 197, and a handle 198 connected to a filter delivery core 199 which in turn is connected to a self-expanding filter 200. In particular, the delivery core includes a release wire having a distal release hook that is connected to a hook of the filter 200. The self-expanding vascular filter 200 is contained in the protection sheath 197 in a compressed condition. These or other known filter retention / release systems may be utilized in embodiments herein. The vascular filter 200 includes a plurality of legs that expand outwardly to contact the vascular wall when the filter 200 is deployed.

[0188] System 190 also includes a coaxial introducer system 202 including an introducer dilator 204 having a shaft 206 defining a longitudinal lumen and including multiple (e.g.

[0189] 8) sideports and a proximal hub 208, an introducer sheath 210 having a shaft 212 defining a lumen and a sheath hub 214 connected to the shaft 212 and including a hemostatic valve, and a three-way stopcock 216 fluidly communicating with the sheath hub 214 and the lumen of the shaft 212.

[0190] The interventional system 190 includes a passive MRI marking system. For this purpose, the shaft 212 of the introducer sheath 210 includes a first discrete passive MRI marker 218 demarking the distal end of the shaft 212, and the shaft 206 of the introducer dilator 204 includes a first discrete passive MRI marker 220 and a second discrete passive MRI marker 222 spaced longitudinally proximal of the marker 220. The markers 220 and 222 are spaced longitudinally from one another a distance that is the same as or approximately the same as (e.g. within about 15% of, or within about 10% of) the length of the filter 200 in its expanded condition. As shown, the first discrete passive MRI marker 220 can be spaced proximally of the distal end of the dilator shaft

[0191] 206 so as not to demark the distal end thereof. Instead, when the dilator 204 is in a dilating configuration relative to the sheath 210 with the tapered distal end region of the dilator 204 extending distally of the distal end of the sheath, the first discrete passive MRI marker 220 on the dilator 204 is longitudinally positioned at or proximate to the distal end of the introducer sheath 210. As disclosed above, the interventional system 190 can be useful in percutaneously deploying a vascular filter, such as an inferior vena cava filter, under real time MRI guidance. The passive marking system of the interventional system 190 is used to visually monitor and guide stages of the procedure. In an illustrative procedure, after establishing percutaneous access through the jugular vein, performing preliminary diagnostics, and placing a wire guide in the inferior vena cava, the puncture site can be dilated (if necessary) with the pre-dilator 192, which in some forms can have a discrete passive MRI marker of the demarking system that demarks its distal end. After removal of the pre-dilator 192 (if used), the coaxial introducer system 202 is advanced over the wire guide until the distal end of the shaft 212 sheath is positioned approximately 5 cm caudal to the lowest renal vein. The wire guide can then be removed. The MRI image artifacts generated by the discrete passive MRI markers 220 and 222 can be visualized in an MRI image and / or automatically detected to approximate the position that will be occupied by the filter 200 when deployed and expanded. The introducer dilator 204 is then removed from the introducer sheath 210. In illustrated embodiment, this requires turning the introducer dilator hub 208 relative to the introducer sheath hub 214 to disconnect them prior to withdrawing the introducer dilator 204 from the introducer sheath 210. The filter introducer / protection sheath assembly 194 is then advanced through the hemostatic valve of the hub 214 and advanced into the shaft 212. The introducer sheath hub 214 is then connected to the protection sheath hub 196. In this illustrated embodiment, this is accomplished by rotating the hub 214 relative to the hub

[0192] 196. At this stage, the distal end of the vascular filter 200 will be positioned at the discrete passive MRI marker 218 of the shaft 212 of the introducer sheath 210, and the hook of the filter should be caudal to the renal veins. FIG. 11A provides MRI image slides showing the image artifact generated by marker 218. As also shown, the vascular filter 200, which in the disclosed embodiment is made of a paramagnetic cobalt chromium alloy with platinum markers at the ends of some of its legs), also provides

[0193] MRI image artifacts that can be visualized. The introducer sheath 210 and protection sheath 197 are then withdrawn until the protection sheath hub 196 and the handle 198 are in contact with one another. At this point the filter is expanded, still connected to the filter introducer / protection sheath assembly 194. To release the filter 200, a release button on the handle 198 is operated (e.g. pushed) to withdraw the release wire and disconnect its hook from that of the filter 200, deploying the filter 200 (see e.g. FIG.

[0194] 11B).

[0195] Also, in a further vascular filter delivery system embodiment, the system 190 can be combined with a wire guide that has a plurality of discrete passive MRI markers in a distal region thereof, for example such as shown and discussed for wire guide 70 and / or wire guide 72 discussed above. This wire guide can be the wire guide placed in the inferior vena cava as discussed in the filter delivery procedure above. In such systems, the wire guide can represent the first medical device, the introducer dilator 204 can represent the second medical device, and optionally the introducer sheath 210 can represent the third medical device, of interventional systems 20, 20A, 20B and 20C, and the characteristic discrete passive marker patterning of such interventional systems can be incorporated in the filter delivery interventional system.

[0196] With reference now to FIGs. 22A through 22F, shown are medical devices of interventional systems useful for providing access to an artery, for example a lower pole segmental artery, of a kidney of a patient, at various stages of a procedure. FIGs. 24A to

[0197] 24F are representative MRI images showing image artifacts generated by markers of a passive MRI marking system of the interventional system depicted in FIGs. 22A to 22F, corresponding to the various stages of the procedure (and presented alongside their companion figure of FIGs. 22A to 22F). For these purposes, a first wire guide 224 (for example having a diameter of 0.035") has discrete passive MRI markers 225, 226, 227 and 228 positioned and longitudinally spaced from one another in the distal region thereof, and a first catheter 229 has discrete passive MRI markers 230 and 231 positioned and longitudinally spaced from one another in the distal region thereof having a preset curve shape. A second wire guide 232 having an outer diameter smaller than that of the first wire guide, for example having an outer diameter of 0.018", has discrete passive MRI markers 233, 234 and 235 positioned and longitudinally spaced from one another in the distal region thereof. A second catheter 236 having an outer diameter smaller than that of the first catheter and passable through the lumen of the first catheter, has discrete passive MRI markers 237 and 238 thereon. In use, the first wire guide 224 can be navigated into the region of an arterial branch leading into the kidney (see e.g. FIGs. 22A and 24A), after which the first catheter 229 can be passed over the first wire guide into the region of the arterial branch (see e.g. FIGs. 22B and

[0198] 24B). The first wire guide 224 can then be removed to release the preset curve of the distal region of the first catheter 229 to direct its distal end toward and potentially into the arterial branch. The second wire guide 232 and the second catheter 236 are then passed through the lumen of the first catheter 224, into the arterial branch, and into an artery of the kidney such as a lower pole segmental artery (see e.g. FIGs. 22D and 24D, and FIGs. 22E and 24E). The second wire guide 232 can then be removed (see e.g. FIGs.

[0199] 22F and 24F), after which a therapeutic or diagnostic procedure can be applied to the artery of the kidney. In one example, an embolic coil delivery system, which can include one or multiple discrete passive MRI markers thereon, can be passed through the lumen of the second catheter and used to introduce an embolic coil into the artery so as to embolize the artery.

[0200] Reference will now be made to FIGs. 12 to 21 to describe various beneficial embodiments for discrete passive MRI markers incorporated in medical devices herein.

[0201] While the discussions refer specifically to discrete passive MRI marker "M", it will be understood that any or all of the discrete passive MRI markers included in a device or system herein can have the discussed features. For example, all of the discrete passive

[0202] MRI markers of a passive MRI marking system can have the same configuration, e.g. selected from one of those disclosed below, or all of the discrete passive MRI markers on a given medical device of an interventional system can have the same configuration, e.g. selected from one of those disclosed below. In other forms, the passive MRI marking system can have discrete passive MRI markers that have configurations that differ from one another, e.g. different ones selected from those disclosed below, or discrete passive MRI markers on a given medical device of an interventional system can have discrete passive MRI markers that have configurations that differ from one another. These and other variations will be understood from the descriptions herein.

[0203] In particular, FIGs. 12 to 16 depict various marker structures that can be incorporated in a lumen-defining portion (e.g. shaft) of a medical device, for example a sheath, catheter. needle, or other medical device described herein, and FIGs. 17 to 21 depict various marker structures that can be incorporated in a medical device portion (e.g. shaft) that includes a solid core surrounded by an outer layer, for example in some forms of a wire guide described herein.

[0204] Marker Structures for Lumen-Defining Medical Device Shafts

[0205] FIGs. 12A, 13A, 14A, 15A and 16A are top views of a longitudinal portion of a shaft of the medical device including a discrete passive MRI marker. FIGs. 12B, 13B, 14B, 15B and 16B are cross-sectional views taken in a plane perpendicular to the longitudinal axis of the shaft shown in FIGS. 12A to 16A, respectively, and through the discrete passive

[0206] MRI marker M.

[0207] Shown in FIGs. 12A and 12B are views depicting one illustrative structure for passive

[0208] MRI marker "M". In this form, the marker M is a plug 250 embedded within the polymeric material of the wall of the catheter shaft 12. Plug 250 includes a material having a magnetic susceptibility suitable for generating the visible artifact under MRI as discussed herein (herein sometimes called a "passive MRI marker-forming material"). It has been found that relatively small amounts of suitable materials can be used for these markers. 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 the range of about 7000 ppm to about

[0209] 100,000. In some forms, the marker-forming material will have a volume not exceeding

[0210] 5 mm3, or not exceeding 3 mm3, or not exceeding 1 mm3, or not exceeding 0.1 mm3; in each of these aspects, the volume may be at least 0.00005 mm3, or at least about

[0211] 0.0001 mm3. 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 mm3, for example in the range of 0.00001 mm3to

[0212] 0.1 mm3, or in the range of 0.00005 mm3to 0.02 mm3, can be used in forming the passive MRI marker. Particular materials that may be used are discussed hereinbelow.

[0213] 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 artifact of a given size. These aspects can be selected and controlled 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.

[0214] The ability to utilize relatively small volumes of passive MRI marker-forming material and yet generate beneficially sized visible artifacts is advantageous, as it enables the incorporation of a marker while minimizing disturbance of the physical performance properties of the medical device shaft, which are often carefully engineered with polymeric or other materials that are relatively soft and flexible. In the illustrated embodiment, the plug 250 is positioned fully within the tubular wall of the lumendefining shaft S, having a first volume VI of the polymeric or other material from which the catheter shaft is formed occurring radially outward of the plug 250 and extending to the outer surface of the shaft S, and a second volume V2 of such polymeric or other material occurring radially inward of the plug 250 and extending to the surface of the lumen L. Such an arrangement can for example be accomplished by a preparative method embodiment herein that includes inserting the plug 250 into an opening in the wall of the shaft S extending from its outer surface and only partly through its thickness, and causing molten volumes of the material (e.g. polymeric material) from which the shaft S is made to fill the opening and form a new outer surface portion of the shaft S over the plug 250. For these purposes, the polymeric or other material can be heated before, during and / or after insertion of the plug 250, for example ultrasonically or otherwise, to cause it to melt, flow and fill the opening and surround the plug 250, and then cooled (e.g. passively or actively) to solidify. Plug 250 can be mounted to the heated tip of a probe, for example with an ultrasonically heated tip, for insertion into the wall of shaft S. The probe can heat the plug 250 and the polymeric or other material during the insertion and can also heat the polymeric or other material after deposit of the plug 250 in the shaft wall and during its withdrawal from the material. This can aid in causing the polymeric or other material to flow and surround the plug and fill in the first volume VI of polymeric material overtop the plug. Such a technique can aid in achieving a self-healing of the polymeric or other material in forming a new outer surface of the shaft S over the plug 250.

[0215] Shown in FIGs. 13A and 13B are views depicting another illustrative structure for passive MRI marker M. In this form, the marker M is a plug 260 embedded within the wall of the lumen-defining shaft S. A solid fill material 262, different from the polymeric or other material from which the wall of shaft S is formed, occurs radially outward of plug 260 and provides an overlying surface SF of the fill material that in some forms can be substantially flush with the adjacent surfaces of the lumen-defining shaft S. Fill material 262 may, for example, be an adhesive, such as a polymeric adhesive. Plug 260, like plug 250 discussed above, includes a material having a magnetic susceptibility suitable for generating the visible artifact under MRI as discussed herein.

[0216] FIGs. 14A and 14B provide views depicting another illustrative structure for passive

[0217] MRI marker M. In this form, the marker M is a plug 270 within the wall of the lumendefining shaft S. Plug 270 is formed of a particulate material 272 having a magnetic susceptibility suitable for generating the visible artifact under MRI as discussed herein, dispersed within a matrix material 274, such as a polymeric matrix material (which may be the same as or different from a polymeric material forming the shaft S) and / or adhesive matrix material. Plug 270 provides a surface 276 that can be flush with adjacent surfaces of the shaft S. This arrangement for marker M form can be created by filling an opening created in the wall of catheter shaft S with a flowable material including the particulate material 272 and a precursor to the matrix material 274, for example an adhesive, and curing the precursor material to form the matrix material 274.

[0218] FIGs. 15A and 15B provide views depicting another illustrative structure for passive

[0219] MRI marker M. In this form, the marker M is a band 280 of the MRI marker-forming material extending around the circumference of the shaft S and providing an outer band surface 282 over the shaft S. Band 280 can include a matrix material 284 in which particles 286 of the MRI marker-forming material are dispersed. Band 280 can in some aspects be formed by curing a flowable material applied to the shaft S including a precursor to the matrix material 284 and the particles 286, for example where the flowable material is in the nature of a MRI marker-forming ink that may also include a colorant selected to provide contrast between the band 280 and adjacent surfaces of the shaft S. In other forms, the band 280 can be or include a metal plated, for example electroplated or applied by electroless plating, onto the outer surface of the shaft S.

[0220] This can be particularly beneficial when the shaft S is formed of a metal, for example in the case where the subject medical device is a needle (e.g. as discussed in certain interventional system embodiments herein). Plated nickel is particularly preferred for these purposes. The plated or other band 280 preferably has a thickness not exceeding about 0.1 mm, and typically being in the range of about 0.01 mm to about 0.05 mm, or about 0.01 mm to about 0.03 mm, or about 0.01 to about 0.02 mm.

[0221] FIGs. 16A and 16B provide views depicting another illustrative structure for passive

[0222] MRI marker M. In this form, the marker M is a band 290 of the MRI marker-forming material captured between an inner tubular shaft layer LI and an outer tubular shaft layer L2 that are attached (e.g. bonded) to one another to form catheter shaft S. The respective polymeric or other materials forming layers LI and L2 can be the same as or different from each other, and can in some aspects be selected from any of the polymeric materials disclosed herein. In making this depicted arrangement for marker

[0223] M, in some forms, the band 290 can be provided by applying a flowable material such as that discussed above for band 280 to the outer surface of tubular shaft layer LI, and then attaching the shaft layers LI and L2 to one another to form shaft S. In other forms, the band 290 can be a solid film or ring positioned over the outer surface of tubular shaft layer LI and after which the shaft layers LI and L2 are attached to one another to form shaft S.

[0224] While some of the discussions above refer to MRI-marker-forming material occurring in a band extending circumferentially around a shaft or other layer, it will be understood that in other embodiments the discussed MRI marker-forming material could be or occur in a layer that does not extend completely around the circumference of the shaft or other layer. These and other variations are contemplated within the scope of the present disclosure.

[0225] Marker Structures For Medical Device Shafts With A Solid Core and Outer Laver

[0226] FIGs. 17 to 21 will be described below in connection with a wire guide having a core member "CM" surrounded by an outer layer "OL". Preferably in the case of a wire guide, the outer layer OL is a polymeric jacket that completely encapsulates the core member of the wire guide. It will be understood, however, that the depicted and described structures can also be present in the shafts of medical devices other than wire guides having a core member that is solid in cross section surrounded by an outer material layer.

[0227] FIGs. 17A, ISA, 19A, 20A and 21A show top views of a longitudinal portion of the shaft S of the wire guide WG including a discrete passive MRI marker M. FIGs. 17B, 18B,

[0228] 19B, 20B and 21B are cross-sectional views taken in a plane perpendicular to the longitudinal axis of the shaft shown in FIGs. 17A to 21A, respectively, and through the discrete passive MRI marker M.

[0229] Shown in FIGs. 17A and 17B are views depicting one illustrative structure for a discrete passive MRI marker M. The marker M is a plug 320 embedded within the polymeric material of the outer layer OL. Plug 320 includes an MRI marker-forming material as discussed herein. It has been found that relatively small amounts of suitable materials can be used for these markers. In the illustrated embodiment, the plug 320 is positioned fully within the tubular wall of the outer layer OL, having a first volume 322 of the polymeric or other material from which the outer layer OL is formed occurring radially outward of the plug 320 and extending to the outer surface of the outer layer

[0230] OL, and a second volume 324 of such polymeric or other material occurring radially inward of the plug 320 and extending to the surface of the core member CM. Such an arrangement can for example be accomplished by a preparative method embodiment herein that includes inserting the plug 320 into an opening in the wall of the outer layer OL extending from its outer surface and only partly through its thickness, and causing molten volumes of the polymeric or other material from which the outer layer OL is made to fill the opening and form a new outer surface portion of the outer layer OL over the plug 320. For these purposes, the polymeric or other material can be heated before, during and / or after insertion of the plug 320, for example ultrasonically or otherwise, to cause it to melt, flow and fill the opening and surround the plug 320, and then cooled

[0231] (e.g. passively or actively) to solidify. Plug 320 can be mounted to the heated tip of a probe, for example with an ultrasonically heated tip, for insertion into the wall of outer layer OL. The probe can heat the plug 320 and the polymeric material during the insertion and can also heat the polymeric material after deposit of the plug 320 in the outer layer OL wall and during its withdrawal from the polymeric material. This can aid in causing the polymeric or other material to flow and surround the plug 320 and fill in the first volume 322 of polymeric or other material overtop the plug 320. Such a technique can aid in achieving a self-healing of the polymeric or other material in forming a new outer surface of the outer layer OL over the plug 320. The plug 320 is embedded in the outer layer OL, and the outer layer OL surrounds the core member CM.

[0232] While in the illustrated embodiment the plug 320 is positioned only partly through the wall thickness of the outer layer OL, in other forms the plug 320 can be inserted completely through the wall thickness of the outer layer OL and contact the core member CM, and the volume 322 of polymeric or other material can nonetheless extend between the plug 320 and the outer surface of the outer layer OL.

[0233] Shown in FIGs. ISA and 18B are views depicting another illustrative structure for a discrete passive MRI marker M. In this form, the marker M is a plug 330 embedded within the wall of the outer layer OL. A solid fill material 332, different from the polymeric or other material from which the wall of outer layer OL is formed, occurs radially outward of plug 330 and provides an overlying surface 334 of the fill material that in some forms can be substantially flush with the adjacent surfaces of the outer layer OL. Fill material 332 may, for example, be an adhesive, such as a polymeric adhesive. Plug 330, like plug 320 discussed above, includes an MRI marker-forming material as discussed herein. FIGs. 19A and 19B provide views depicting another illustrative structure for a discrete passive MRI marker M. In this form, the marker M is a band 340 of the MRI marker-forming material captured between the outer surface of the core member CM and the inner surface of the outer layer OL. The band 340 preferably has a thickness not exceeding about 0.1 mm, and typically being in the range of about 0.01 mm to about

[0234] 0.05 mm, or about 0.01 mm to about 0.03 mm, or about 0.01 to about 0.02 mm. In some forms, the band 340 of MRI marker-forming material is adherent at least to the outer surface of the core member CM. In some forms, the band 340 can include a matrix material in which particles of the MRI marker-forming material are dispersed. In making such an arrangement for marker M, in some forms, the band 340 can be formed by curing a flowable material applied to the outer surface of the core member CM. The flowable material includes a precursor to the matrix material and the particles, and upon curing solidifies to form the band 340. The outer layer OL can then be applied over the core member CM. In other forms, the band 340 can include a metal plated, for example electroplated or applied by electroless plating onto the outer surface of the core member CM, e.g. prior to applying the outer layer OL to the core member CM.

[0235] Plated nickel is particularly preferred for these purposes. In still other forms, the band

[0236] 340 can be formed from a solid layer material, for example a metal foil such as a nickel foil, placed over and potentially adhered (e.g. with an adhesive) to the outer surface of the core member CM prior to applying the outer layer OL to the core member CM.

[0237] FIGs. 20A and 20B provide views depicting another illustrative structure for a discrete passive MRI marker M. In this form, the marker M is a band 350 of the MRI marker-forming material extending around the outer circumference of the outer layer

[0238] OL and providing an outer band surface 352 over the outer layer OL. Band 350 can include a matrix material 354 in which particles 356 of the MRI marker-forming material are dispersed. Band 360 can in some aspects be formed by curing a flowable material applied to the shaft including a precursor to the matrix material 354, for example an adhesive, and the particles 356, for example where the flowable material is in the nature of a MRI marker-forming ink that may also include a colorant selected to provide contrast between the band 350 and adjacent surfaces of the outer layer OL.

[0239] FIGs. 21A and 21B provide views depicting another illustrative structure for a discrete passive MRI marker M. In this form, the marker M is a plug 360 within the wall of the outer layer OL. Plug 360 is formed of a particulate MRI marker-forming material

[0240] 362 dispersed within a matrix material 364, such as a polymeric matrix material (which may be the same as or different from a polymeric material forming the outer layer OL).

[0241] Plug 360 provides a surface 366 that can be flush with adjacent surfaces of the outer layer OL. This arrangement for marker M form can be created by filling an opening created in the wall of outer layer OL with a flowable material including the particulate material 362 and a precursor to the matrix material 364, e.g. an adhesive, and curing the precursor material to form the matrix material 364.

[0242] While some of the discussions above refer to MRI-marker-forming material occurring in a band extending circumferentially around the core member CM or the outer layer

[0243] OL, it will be understood that in other embodiments the discussed MRI marker-forming material could be or occur in a layer that does not extend completely around the circumference of the core member CM or the outer layer OL. These and other variations are contemplated within the scope of the present disclosure.

[0244] As disclosed above, in some embodiments herein, the interventional system includes a wire guide having one or multiple discrete passive MRI markers. The wire guide can include a core member and a jacket disposed on the core member. The core member in some preferred forms is a continuous elongate member having a proximal end and a distal end. The core member can have a generally circular outer profile in cross section.

[0245] The core member is preferably fully encapsulated by the jacket, such that no portion of the core member is exposed to the external environment surrounding the wire guide.

[0246] The jacket can have a generally circular outer profile in cross section. The core member of the wire guide can be formed of any suitable material, and in typical forms comprises a metallic material, such as a metal alloy. Examples of metallic materials considered suitable for forming the core member include, but are not limited to, superelastic metal alloys, including nickel-titanium alloys such as Nitinol, Superelastic Nitinol SE508 straight with black oxide, matte finished Nitinol, polished Nitinol, nickel chromium, nickel cobalt, titanium, tungsten, nickel oxide, cobalt chromium nickel molybdenum alloys, such as the alloy available under the trade name Elgiloy from Elgiloy Specialty Metals (Elgin, IL), combinations of those described herein, and any other metallic materials considered suitable for a particular embodiment. In preferred forms, the core member of the wire guide is a continuous length of wire. The core member can have any suitable longitudinal 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. The jacket of the wire guide can be formed of one or more dielectric materials, and will typically be formed of a dielectric polymeric material. Examples of suitable dielectric polymeric materials include, but are not limited to, heat-formable polymeric materials, such as polyamide materials, including Nylon 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. Fluoropolymers, such as polytetrafluoroethylene, polyurethanes, and other polymeric materials can also be used.

[0247] Additional materials can be applied to the jacket if desired. For example, a lubricious material can be applied as a topcoat on the jacket.

[0248] Advantageously, the markers discussed above in conjunction with FIGs. 12 to 21, or other markers herein, can occur within a relatively small region of the shaft S or other device portion upon which they are positioned. For example, such markers can occur within a longitudinal length not exceeding 10 mm, or not exceeding 5 mm, and typically in the range of 0.2 to 5 mm; and / or, in the case of plug-form markers or some non- circumferential layer markers, can have a width perpendicular to the axis of the shaft S that does not exceed about 90%, or about 80%, or about 70%, of the corresponding width of the shaft S, or that is in the range of about 10% to about 100%, or about 10% to about 70%, of the corresponding width of the shaft S. Markers that include plugs as discussed above are particularly beneficial in applying a marker within such recited widths as well as such recited longitudinal lengths. Passive MRI markers provided in such limited regions can facilitate avoidance or minimization of any impact of the marker(s) on physical performance properties of the shaft S, for example bending or resilient properties, by the passive MRI marker-forming material, any other materials

[0249] (e.g. adhesives) associated therewith, or any disruption of the polymeric or other material forming the shaft during incorporation of the passive MRI marker-forming material.

[0250] Particular passive MRI marker-forming materials that can be used 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. In certain advantageous forms, 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 shaft S or another elongate member of a medical device herein. Such continuous volume-forms of passive

[0251] MRI markers herein can facilitate minimizing the volume of material needed to be added to and / or to replace a volume of the material forming the shaft S or other medical device elongate member herein, 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.

[0252] The size, such as maximum dimension, of a visible artifact generated by a discrete passive MRI marker herein can be controlled in any suitable fashion. Varying the volume of and / or the composition of the discrete passive MRI marker-forming material of respective discrete passive MRI markers can be used for these purposes. For example, in some forms, a discrete passive MRI marker that generates a larger size (e.g. greater maximum dimension) artifact than another can include a greater volume of the same MRI marker-forming material. In other forms, a discrete passive MRI marker that generates a larger size artifact than another can include a different passive MRI marker- forming material than the other. In such forms, the larger artifact-generating discrete passive MRI marker can have the same volume or a lesser volume of a passive MRI marker-forming material having a higher magnetic susceptibility than that of the other passive MRI marker; or, a greater volume of a passive MRI marker-forming material that has a lower magnetic susceptibility than that of the other discrete passive MRI marker.

[0253] It will be understood that these passive MRI marker configurations apply to the discrete passive MRI markers of all devices herein.

[0254] Preferred passive MRI marking systems on interventional systems herein are configured to generate a pattern of MRI image artifacts that can be used to beneficially identify, track and / or discern between the multiple different devices included in the systems. The patterns can include differing MRI image artifact sizes and / or differing longitudinal spacing between passive discrete MRI markers on the multiple different devices. The MRI system used in an MRI guided interventional procedure using the interventional systems can be configured to detect such positional and / or artifact size patterns, or movements thereof, using a computer processor, for example having been trained using artificial intelligence (Al) to recognize such patterns, and to execute a function controlled by the computer processor based on that detection. For example, the MRI system can provide a signal, such as an audible signal through a speaker or a visible graphic on an electronic display such as the display showing the MRI image(s). with the graphic potentially provided as an overlay of the MRI image(s). Such a graphic overlay may, for example, estimate a shape and / or size of a region of one or more of the included medical devices, and / or provide a graphic overlay indicating the distal-most position of the system and / or of one of or each of the medical devices of the interventional system. A user input device such as a keyboard of the system may be used as a control to display or not display the graphic, as desired.

[0255] The interventional systems, interventional devices, or passive MRI marking systems disclosed herein can be used in conjunction with and / or be a component of an MRI system, for example to carry out or provide a system configured to carry out a procedure on a patient under MRI guidance, that can include steps or operations as described herein. In this regard, FIG. 23 provides a schematic representation of an example MRI system 710 in accordance with certain aspects of the present disclosure.

[0256] The MRI system 710 includes the magnetic resonance scanner (data acquisition unit)

[0257] 712 with an examination space or patient tunnel 714 in which a patient can be positioned on a driven bed 713.

[0258] The magnetic resonance scanner 712 is typically equipped with a basic or primary field magnet system 718, a gradient system 720, as well as an RF transmission antenna system 722. and an RF reception antenna system 724, e.g. a surface coil which may include one or more loop antennas. In certain embodiments, a medical device as disclosed herein can be closely associated with (e.g. placed under or through an opening in) the surface coil. In the shown exemplary embodiment, the RF transmission antenna system 722 is a whole-body coil permanently installed in the magnetic resonance scanner 712. However, the whole-body coil can also be used as an RF reception antenna system.

[0259] The basic field magnet system 718 typically generates a basic or primary magnetic field in the longitudinal direction of the patient, i.e. along the longitudinal axis of the magnetic resonance scanner 712 that proceeds in the z-direction. The gradient system

[0260] 720 typically includes individually-controllable gradient coils to selectively switch

[0261] (activate) gradients in the x-direction, y-direction, or z-direction independently of one another.

[0262] The MRI system 710 as shown is a whole-body system with a patient tunnel 714 into which a patient can be completely introduced. However, in principle the embodiments as described herein may also be used with other MRI systems, for example with a laterally open, C-shaped housing, as well as in smaller magnetic resonance scanners in which only one body part can be positioned.

[0263] The MRI system 710 has a central control device 726 that is used to control the MRI system 710. Control device 726 typically includes at least one computer processor 728, and potentially multiple computer processors, and at least one electronic memory storage device 730, and potentially multiple such memory storage devices. As is known, the control device can include other circuitry components as well. This central control device 726 is configured to control a series of radio-frequency pulses (RF pulses) and gradient pulses depending on a selected pulse sequence or, respectively, a series of multiple pulse sequence to acquire magnetic resonance images of slices of the scanned region. For example, such a series of pulse sequence can be predetermined. Different control protocols for different scan sessions are typically stored in memory 730 and can be selected by an operator and potentially modified as needed or desired.

[0264] Operation of the central control device 726 can take place via a terminal 732, which includes a user input device 734 and an electronic display 736 for such a purpose, through which the entire MRI system 710 can thus also be operated by a user. MR images can also be displayed at the display 736, and scan sessions can be planned and started by means of the input device 734 potentially in combination with the electronic display 736. Moreover, suitable control protocols may be selected (and possibly modified) with a suitable series of pulse sequences. Additionally, in typical forms, the

[0265] MRI system 710 will also include another electronic display or displays (additional to display 736) positioned in the vicinity of the scanner, e.g. for viewing by a clinician or other health care working performing a procedure on a patient as guided by the MRI system.

[0266] In certain embodiments herein, the control unit 726 can be configured to facilitate the performance of methods and / or method steps according to the present disclosure, including for example those discussed in conjunction with the Figs 5, 5A-5C, 8, 8A, 9, 9A,

[0267] 10, 10A-10I, 11, 11A-B, and 22A-F. Such configuration of the control unit 726 may be implemented as hardware (e.g. computer processors), software, or a combination of both hardware and software (e.g. a non-transitory computer-readable medium with executable instructions stored thereon). It will be understood that the control unit 726 may include additional or alternate components as well. The manner by which suitable raw data are acquired by radiation of RF pulses, the generation of gradient fields, and MR images are reconstructed from the raw data, may be performed in any suitable manner, such as using known techniques, and thus need not be explained in detail herein.

[0268] In accordance with some forms, an MRI scan of the medical device can be acquired when the medical device is moved into the scannable region. Based on this acquired scan data, one or multiple attributes of the medical device may be determined. The attributes are in some aspects herein determined directly from the scan data. In other aspects, an identifying feature on the medical device, for example recognizable by the

[0269] MRI system due to the presence of an MRI visible material therein and / or due to the presence of a pattern of MRI markers, such as passive MRI artifact markers, can provide an identification of the medical device by which the MRI system, using a computer processor, can look up attributes of the medical device stored in electronic memory, for example in a lookup table stored in the memory. In addition or alternatively, a user can input an identifier (e.g. make / model number) of the medical device to the system via a user input device and a computer processor can use the identifier to look up attributes of the medical device stored in electronic memory of the MRI system. In some forms, the MRI system can determine MRI scanning parameters, such as sequence parameters, for real-time tracking and / or imaging of the medical device, based on the determined attributes of the instrument. For example, the scanning parameters may be stored in electronic memory and correlated to the attribute(s) of the medical device, and a computer processor may look up the scanning parameters based on the instrument attribute(s) either detected by the MRI system using scan data or input by a user. In certain embodiments, the determined scanning parameters, and / or other scanning parameters that are inputted, are implemented for real-time tracking, typically including real-time imaging, of the medical device during the procedure. For example, the scanning parameters may be stored in electronic memory and in some forms correlated to the attribute(s) of the medical device, and a computer processor may look up the scanning parameters based on the instrument attribute(s) either detected by the MRI system using scan data or input by a user. In certain embodiments, the determined scanning parameters are implemented for real-time tracking, typically including real- time imaging, of the medical device during the procedure.

[0270] It will be understood that the MRI systems discussed in conjunction with FIG. 23 hereinabove can be configured to facilitated performance of one or more steps of the methods detailed herein using one or more computer processors thereof, unless those steps are expressly discussed as limited to manual steps conducted by a user. In this regard, the corresponding components discussed in respect of the MRI systems of FIG.

[0271] 23 can be employed in the implementation of these methods or routines (e.g. electronic memory components, computer processor(s), user input device(s), electronic displays, etc. As well, it will be understood that any scan acquisition steps can generate data that is processed into an image, or multiple images, displayed on an electronic display device and visible to the user. Also, it will be understood that although the above discussions refer to steps or processes conducted by an "MRI system" configured to do so, corresponding embodiments herein relate to controller devices for controlling an MRI system (e.g. central control device 726 and / or terminal 732 of FIG. 23) that do not necessarily include an MRI scanner but are configured to control an MRI scanner (e.g. scanner 712 of FIG. 23). It will further be understood that other MRI scans of the region of interest may be available to the user either acquired in the same procedure or in some cases acquired in a previous procedure, for example a previous diagnostic procedure. These and other variations will be apparent to those skilled in the art from the descriptions herein.

[0272] LISTING OF CERTAIN DISCLOSED EMBODIMENTS

[0273] The following enumerated clauses provide an illustrative, non-limiting listing of some embodiments that are disclosed herein. It will be understood that individual features or combinations of features (e.g. 1, 2, 3 or 4 features) as described in the Detailed

[0274] Description above can be combined with the features of the enumerated Embodiments below to provide additional embodiments herein. Embodiment 1. An interventional system for a magnetic resonance imaging (MRI) guided procedure on a patient at a primary magnetic field strength, comprising: a first elongate medical device configured for percutaneous insertion into a vessel of the patient; a second elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the first elongate medical device is slidably positionable through a lumen of the second elongate medical device; and a passive MRI marking system on the interventional system; wherein the passive MRI marking system includes: a first discrete passive MRI marker on the first elongate medical device configured to generate a first medical device-positioned image artifact under the MRI having a maximum dimension, and a first discrete passive MRI marker on the second elongate medical device configured to generate a second medical device-positioned image artifact under the MRI having a maximum dimension, wherein the maximum dimension of the second medical device-positioned artifact is different from the maximum dimension of the first medical device-positioned artifact; and / or first and second discrete passive MRI markers on and longitudinally spaced from one another a first distance along the first elongate medical device, and first and second discrete passive MRI markers on and longitudinally spaced from one another a second distance along the second medical device, wherein the second distance is different from the first distance; and / or a first total number of discrete passive MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number; and / or a first discrete passive MRI marker on and demarking a distal end of the first elongate medical device and configured to generate a first medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the first elongate medical device, and a first discrete passive MRI marker on and demarking a distal end of the second elongate medical device and configured to generate a second medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the second medical device.

[0275] Embodiment 2. The interventional system of Embodiment 1, wherein the first elongate medical device is a wire guide.

[0276] Embodiment 3. The interventional system of Embodiment 2, wherein the wire guide comprises a core member and a polymeric jacket encapsulating the core member.

[0277] Embodiment 4. The interventional system of Embodiment 3, wherein the core member is a single, continuous length of wire.

[0278] Embodiment 5. The interventional system of Embodiment 4, wherein the wire is formed of a superelastic metal alloy.

[0279] Embodiment 6. The interventional system of Embodiment 5, wherein the superelastic metal alloy is nitinoL

[0280] Embodiment 7. The interventional system of any one of Embodiments 3 to 6, wherein the polymeric jacket is formed of a polyamide polymer.

[0281] Embodiment 8. The interventional system of any one of Embodiments 3 to 7, wherein the first passive MRI marker on the wire guide comprises a passive MRI markerforming material between the polymeric jacket and the core member.

[0282] Embodiment 9. The interventional system of Embodiment 8, wherein the passive

[0283] MRI marker-forming material is a metal layer plated onto an outer surface of the core member, optionally wherein the metal layer is a nickel layer.

[0284] Embodiment 10. The interventional system of any one of Embodiments 3 to 7, wherein the first discrete passive MRI marker on the first elongate medical device comprises a passive MRI marker-forming material embedded in a wall of the polymeric jacket.

[0285] Embodiment 11. The interventional system of Embodiment 1 or 2, wherein the second elongate medical device is a catheter or sheath.

[0286] Embodiment 12. The interventional system of any one of Embodiments 1 to 11, wherein the passive MRI marking system is provided by discrete passive MRI markers positioned on a distalmost 20cm long segment of each of the first elongate medical device and the second elongate medical device.

[0287] Embodiment 13. The interventional system of any one of Embodiments 1 to 12, wherein the second medical device is a catheter or sheath, and wherein the first passive

[0288] MRI marker on the second medical device comprises a passive MRI marker-forming material embedded in a wall of the catheter or sheath.

[0289] Embodiment 14. The interventional system of Embodiment 13, wherein the wall includes a first volume of a polymeric material forming the wall positioned radially inward of the passive MRI marker-forming material and between the passive MRI marker forming material and a lumen surface defined by the first volume of polymeric material.

[0290] Embodiment 15. The interventional system of Embodiment 14, wherein the polymeric material comprises a thermoplastic elastomer material.

[0291] Embodiment 16. The interventional system of any one of Embodiments 1 to 15, wherein the first discrete passive MRI markers on the first elongate medical device and the second elongate medical device each include (i) an MRI marker-forming material having a volume not exceeding 5 mm3, or not exceeding 3 mm3, or not exceeding 1 mm3, or not exceeding 0.1 mm3, wherein in each of these aspects, the volume may be at least 0.00005 mm3, or at least about 0.0001 mm3; or (ii) an MRI marker-forming material having a magnetic susceptibility of at least about 1 and having a volume not exceeding 0.1 mm3, or in the range of 0.00001 mm3 to 0.1 mm3, or in the range of

[0292] 0.00005 mm3 to 0.02 mm3.

[0293] Embodiment 17. The interventional system of any one of Embodiments 1 to 16, wherein the first discrete passive MRI markers on the first elongate medical device and the second elongate medical device each include an MRI-marking forming material having a magnetic susceptibility of at least about 500 ppm, or at least about 2000 ppm, or in the range of about 500 ppm to about 1000, or in the range of about 7000 ppm to about 1000.

[0294] Embodiment 18. The interventional system of any one of Embodiments 1 to 17, wherein: the first passive MRI markers on the first and second elongate medical devices each include an MRI marker-forming material selected from nickel, nickel alloys, cobalt, cobalt alloys, iron, and iron alloys.

[0295] Embodiment 19. The interventional system of any one of Embodiments 1 to 18, also comprising: a third elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the second elongate medical device is slidably positionable through a lumen of the third elongate medical device, and wherein the passive MRI marking system includes a first discrete passive MRI marker on the third elongate medical device.

[0296] Embodiment 20. The interventional system of Embodiment 19, wherein the first discrete passive MRI marker on the third elongate medical device demarks a distal end of the third elongate medical device. Embodiment 21. The interventional system of Embodiment 19 or 20, wherein the first elongate medical device is a wire guide, the second elongate medical device is a catheter, and the third elongate medical device is an introducer sheath.

[0297] Embodiment 22. The interventional system of any preceding Embodiment, wherein the passive MRI marking system includes a first discrete passive MRI marker on the first elongate medical device configured to generate a first medical device-positioned image artifact under the MRI having a maximum dimension, and a first discrete passive MRI marker on the second elongate medical device configured to generate a second medical device-positioned image artifact under the MRI having a maximum dimension, wherein the maximum dimension of the second medical device-positioned artifact is different from the maximum dimension of the first medical device-positioned artifact.

[0298] Embodiment 23. The interventional system of any preceding Embodiment, wherein the passive MRI marking system incudes first and second discrete passive MRI markers on and longitudinally spaced from one another a first distance along the first elongate medical device, and first and second discrete passive MRI markers on and longitudinally spaced from one another a second distance along the second medical device, wherein the second distance is different from the first distance.

[0299] Embodiment 24. The interventional system of any preceding Embodiment, wherein the passive MRI marking system includes a first total number of discrete passive MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number.

[0300] Embodiment 25. The interventional system of any preceding Embodiment, wherein the passive MRI marking system includes a first discrete passive MRI marker on and demarking a distal end of the first elongate medical device and configured to generate a first medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the first elongate medical device, and a first discrete passive MRI marker on and demarking a distal end of the second elongate medical device and configured to generate a second medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the second medical device.

[0301] Embodiment 26. The interventional system of any preceding Embodiment, wherein the passive MRI marking system includes at least three discrete passive MRI markers on the first elongate medical device and at least two discrete passive MRI marker on the second medical device.

[0302] Embodiment 27. An interventional system for a magnetic resonance imaging (MRI) guided procedure on a patient at a primary magnetic field strength, comprising: a first elongate medical device configured for percutaneous insertion into a vessel of the patient; a second elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the first elongate medical device is slidably positionable through a lumen of the second elongate medical device; and a passive MRI marking system on the interventional system; wherein the passive MRI marking system includes: a first discrete passive MRI marker on the first elongate medical device and configured to generate a first medical device-positioned artifact under the MRI having a maximum dimension; a first discrete passive MRI marker on the second elongate medical device and configured to generate a second medical device-positioned artifact under the MRI having a maximum dimension; and wherein the maximum dimension of the second medical device-positioned artifact differs from the maximum dimension of the first medical device-positioned artifact. Embodiment 28. The interventional system of Embodiment 27, wherein the maximum dimension of the first medical device-positioned artifact is greater than the maximum dimension of the second medical device-positioned artifact.

[0303] Embodiment 29. The interventional system of Embodiment 28, wherein: the passive MRI marking system includes a plurality of discrete passive MRI markers on the first elongate medical device and configured to generate respective first medical device-positioned artifacts under the MRI each having a maximum dimension, and a plurality of discrete passive MRI markers on the second elongate medical device and configured to generate respective second medical device-positioned artifacts under the

[0304] MRI each having a maximum dimension; and the maximum dimension of each of the first medical device-positioned artifacts is greater than the maximum dimension of each of the second medical device-positioned artifacts.

[0305] Embodiment 30. The interventional system of Embodiment 27, wherein the maximum dimension of the first medical device-positioned artifact is less than the maximum dimension of the second medical device-positioned artifact.

[0306] Embodiment 31. The interventional system of Embodiment 30, wherein: the passive MRI marking system includes a plurality of discrete passive MRI markers on the first elongate medical device and configured to generate respective first medical device-positioned artifacts under the MRI each having a maximum dimension, and a plurality of discrete passive MRI markers on the second elongate medical device and configured to generate respective second medical device-positioned artifacts under the

[0307] MRI each having a maximum dimension; and the maximum dimension of each of the first medical device-positioned artifacts is less than the maximum dimension of each of the second medical device-positioned artifacts. Embodiment 32. The interventional system of any one of Embodiments 28 to 31, wherein the maximum dimension of each of the first medical device-positioned artifacts is the same.

[0308] Embodiment 33. The interventional system of any one of Embodiments 28 to 32, wherein the maximum dimension of each of the second medical device-positioned artifacts is the same.

[0309] Embodiment 34. The interventional system of any one of Embodiments 27 to 31, wherein the passive MRI marking system is provided by discrete passive MRI markers on the distalmost 20 cm of, or on the distalmost 10cm of, each of the first elongate medical device and second elongate medical device.

[0310] Embodiment 35. The interventional system of any one of Embodiments 27 to 32, wherein the passive MRI marking system includes at least three discrete passive MRI markers on the first elongate medical device and at least two discrete passive MRI markers on the second elongate medical device.

[0311] Embodiment 36. The interventional system of any one of Embodiments 27 to 25, wherein the passive MRI marking system includes a first total number of discrete passive

[0312] MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number and / or wherein the discrete passive

[0313] MRI markers on the first elongate medical device are longitudinally spaced from one another a distance that is different from that of the discrete passive MRI markers on the second elongate medical device.

[0314] Embodiment 37. The interventional system of any one of Embodiments 27 to 36, wherein the first elongate medical device is a wire guide. Embodiment 38. The interventional system of Embodiment 37, wherein the wire guide comprises a core member and a polymeric jacket encapsulating the core member.

[0315] Embodiment 39. The interventional system of Embodiment 38, wherein the core member is a single, continuous length of wire.

[0316] Embodiment 40. The interventional system of Embodiment 39, wherein the wire is formed of a superelastic metal alloy.

[0317] Embodiment 41. The interventional system of Embodiment 40, wherein the superelastic metal alloy is nitinol.

[0318] Embodiment 42. The interventional system of any one of Embodiments 38 to 41, wherein the polymeric jacket is formed of a polyamide polymer.

[0319] Embodiment 43. The interventional system of any one of Embodiments 38 to 42, wherein the discrete passive MRI marker(s) on the wire guide each comprise a passive

[0320] MRI marker-forming material between the polymeric jacket and the core member.

[0321] Embodiment 44. The interventional system of Embodiment 43, wherein the passive

[0322] MRI marker-forming material is a metal layer plated onto an outer surface of the core member, optionally wherein the metal layer is a nickel layer.

[0323] Embodiment 45. The interventional system of any one of Embodiments 38 to 42, wherein the first passive MRI marker and the second passive MRI marker each comprise a passive MRI marker-forming material embedded in a wall of the polymeric jacket.

[0324] Embodiment 46. The interventional system of any one of Embodiments 27 to 45, wherein each discrete passive MRI marker of the passive MRI marking system includes an MRI-marking forming material having a magnetic susceptibility of at least about 500 ppm, or at least about 2000 ppm, or in the range of about 500 ppm to about 1000, or in the range of about 7000 ppm to about 1000.

[0325] Embodiment 47. The interventional system of any one of Embodiments 27 to 26, wherein each discrete passive MRI marker of the passive MRI marking system includes an MRI marker-forming material selected from nickel, nickel alloys, cobalt, cobalt alloys, iron, and iron alloys.

[0326] Embodiment 48. The interventional system of any one of Embodiments 27 to 47, wherein the first elongate medical device is a wire guide and the second elongate medical device is a catheter or sheath.

[0327] Embodiment 49. The interventional system of any one of Embodiments 27 to 47, wherein the first elongate medical device is a wire guide, the second elongate medical device is a catheter, and the system also includes a third elongate medical device configured for percutaneous insertion into the vessel, wherein the third medical device is an introducer sheath and the passive MRI marking system further includes a first discrete passive MRI marker on the introducer sheath.

[0328] Embodiment 50. The interventional system of Embodiment 49, wherein the first discrete passive marker on the introducer sheath demarks a distal end of the introducer sheath.

[0329] Embodiment 51. A stent delivery system, comprising: an outer sheath defining a lumen extending to a distal end opening at a distal end of the outer sheath; an inner catheter member received through the outer sheath, the inner catheter member defining a stent-carrying region and a distal region positioned distal of the stent-carrying region, the distal region having a proximal end received against a distal end of the outer sheath, the outer sheath and the inner catheter member being configured for longitudinal movement relative to one another to deploy a stent from the stent-carrying region; a stent received over the stent carrying region in a compressed condition and located in an annular space between an outer surface of the stent-carrying region of the inner catheter member and an inner surface defining a portion of the lumen of the outer sheath; a first discrete passive MRI marker on the outer sheath, the first discrete passive MRI marker demarking the distal end of the outer sheath and configured to generate a first image artifact under MRI; a first discrete passive MRI marker on the inner catheter member and demarking a distal end of the stent-carrying region and configured to generate a second image artifact under MRI; and wherein the second image artifact overlaps the first image artifact while the proximal end of the distal region is received against the distal end of the outer sheath but is longitudinally spaceable from the first image artifact during said longitudinal movement.

[0330] Embodiment 52. The stent delivery system of Embodiment 51, wherein the inner catheter member also includes a second discrete passive MRI marker thereon, the second discrete passive MRI marker demarking a proximal end of the stent-carrying region.

[0331] Embodiment 53. The stent delivery system of Embodiment 52, wherein the inner catheter member also includes a third passive MRI marker thereon, the third passive

[0332] MRI marker demarking a distal end of the distal region of the inner catheter member.

[0333] Embodiment 54. An interventional system useful in a procedure for magnetic resonance imaging(MRI)-guided transjugular intrahepatic access, comprising: an introducer sheath defining a sheath lumen and including a sheath-positioned discrete passive MRI marker demarking a distal tip of the sheath; a catheter defining a catheter lumen, the catheter positionable through the sheath lumen and including first and second catheter-positioned passive MRI markers, optionally wherein the first and second catheter-positioned passive MRI markers are positioned on a distalmost 5 cm long segment of the catheter; and a needle including a needle shaft defining a needle lumen, the needle positionable through the catheter lumen to extend a distal end of the needle distally beyond a distal end of the catheter, and the needle including a first needle-positioned passive MRI marker, optionally wherein the first needle-positioned passive MRI marker is positioned on a distalmost 2 cm segment of the needle and / or demarks the distal end of the needle.

[0334] Embodiment 55. The interventional system of Embodiment 54, wherein the needle has a curved distal region defining a curve extending to the distal end of the needle.

[0335] Embodiment 56. The interventional system of Embodiment 55, wherein the needle further comprises a directional indicator configured to indicate a direction of the curve.

[0336] Embodiment 57. The interventional system of any one of Embodiments 54 to 56, wherein the needle comprises a needle shaft formed from a metal having a magnetic susceptibility not exceeding 3000 ppm.

[0337] Embodiment 58. The interventional system of any one of Embodiments 54 to 57, wherein the needle comprises a needle shaft formed from a metal selected from a nickel-titanium alloy and a nickel-chromium alloy.

[0338] Embodiment 59. The interventional system of any one of Embodiments 54 to 58, also comprising a wire guide having at least one discrete passive MRI marker thereon.

[0339] Embodiment 60. The interventional system of Embodiment 59, wherein the wire guide has the features of the wire guide defined in any one of Embodiments 2 to 10. Embodiment 61. The interventional system of any one of Embodiments 54 to 60, also comprising a dilator positionable through the sheath lumen and including a dilator- positioned discrete passive MRI marker demarking a distal tip of the dilator.

[0340] Embodiment 62. The interventional system of any one of Embodiments 54 to 61, wherein the first discrete passive MRI marker on the needle demarks the distal end of the needle, and wherein the needle further includes a second passive discrete MRI marker proximal of and longitudinally spaced from the first discrete passive MRI marker on the needle.

[0341] Embodiment 63. The interventional system of Embodiment 62, wherein the needle further includes a third passive discrete MRI marker proximal of and longitudinally spaced from the second discrete passive MRI marker on the needle.

[0342] Embodiment 64. The interventional system of Embodiment 63, wherein the needle further includes a fourth passive discrete MRI marker proximal of and longitudinally spaced from the third discrete passive MRI marker on the needle.

[0343] Embodiment 65. The interventional system of any one of Embodiments 54 to 64, wherein the first discrete passive MRI marker on the needle, and, when present, the second, third and / or fourth passive MRI markers on the needle, are each a metal layer plated onto an outer surface of the needle shaft, optionally wherein the metal layer is a nickel layer.

[0344] Embodiment 66. An interventional system useful for providing magnetic resonance imaging(MRI)-guided access to a pulmonary artery of a patient, comprising: a catheter defining a catheter lumen, the catheter including first and second catheter-positioned passive MRI markers, the first and second catheter-positioned passive MRI markers occurring in a distalmost 5 cm segment of the catheter, the distalmost 5 cm segment of the catheter having a preformed curve configuration; and a wire guide positionable through the catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second wire guide-positioned passive MRI markers occurring in a distalmost 5 cm segment of the wire guide.

[0345] Embodiment 67. The interventional system of Embodiment 66, wherein the catheter is sized and configured for percutaneous introduction and navigation from a jugular vein access point or a subclavian vein access point, through the superior vena cava, through the right atrium, through the tricuspid valve, through the right ventricle, through the pulmonary valve, and into the pulmonary artery.

[0346] Embodiment 68. The interventional system of Embodiment 66, wherein the catheter configured for percutaneous introduction and navigation from a femoral vein access point, through the inferior vena cava, through the right atrium, through the tricuspid valve, through the right ventricle, through the pulmonary valve, and into the pulmonary artery.

[0347] Embodiment 69. The interventional system of any one of Embodiments 66 to 68, wherein the catheter has a distal catheter segment and a proximal catheter segment attached to and proximal of the distal catheter segment, wherein the proximal catheter segment has a catheter wall reinforced with a reinforcing member embedded therein and the distal catheter segment has a catheter wall that is free from any reinforcing member embedded therein.

[0348] Embodiment 70. The interventional system of Embodiment 69, wherein the catheter wall of the proximal catheter segment is reinforced with a reinforcing member in the form of a wire braid or a wire coil embedded therein.

[0349] Embodiment 71. The interventional system of any one of Embodiments 66 to 70, wherein the distal catheter segment has a length of about 5 cm to about 20 cm. Embodiment 72. The interventional system of any one of Embodiments 66 to 71, wherein the distalmost 5 cm segment of the wire guide has a preformed curve configuration.

[0350] Embodiment 73. The interventional system of any one of Embodiments 66 to 72, wherein the wire guide has the features of the wire guide defined in any one of

[0351] Embodiments 2 to 10.

[0352] Embodiment 74. The interventional system of any one of Embodiments 66 to 73, also comprising an introducer sheath including a first discrete passive MRI marker thereon.

[0353] Embodiment 75. The interventional system of Embodiment 74, wherein the first discrete passive MRI marker on the introducer sheath demarks a distal end of the introducer sheath.

[0354] Embodiment 76. An interventional system useful in a procedure for providing magnetic resonance imaging(MRI)-guided delivery of a vascular filter, comprising: an introducer sheath including a shaft defining a sheath lumen and having a distal end; a dilator slidably positionable through the sheath lumen to a dilating configuration in which a tapered distal end region of the dilator is positioned distal of the distal end of the introducer sheath; and a filter delivery member carrying a vascular filter, the filter delivery member slidably positionable through the sheath lumen to position an end of the vascular filter at the distal end of the introducer sheath; and wherein the introducer sheath includes a discrete passive MRI marker demarking the distal end of the sheath.

[0355] Embodiment 77. The interventional system of Embodiment 76, wherein the dilator includes a first discrete passive MRI marker thereon and a second passive MRI marker thereon spaced proximally and longitudinally from the first discrete passive MRI marker a distance.

[0356] Embodiment 78. The interventional system of Embodiment 77, wherein said distance approximates a length of the vascular filter in an expanded condition.

[0357] Embodiment 79. The interventional system of Embodiment 77 or 78, wherein when the dilator is in said dilating configuration the first discrete passive MRI marker on the dilator is longitudinally positioned at or proximate to the distal end of the introducer sheath.

[0358] Embodiment 80. The interventional system of any one of Embodiments 76 to 79, also including a wire guide having a first discrete passive MRI marker thereon.

[0359] Embodiment 81. The interventional system of Embodiment 80, wherein the wire guide has the features of the wire guide defined in any one of Embodiments 2 to 10.

[0360] Embodiment 82. An interventional system useful for providing magnetic resonance imaging(MRI)-guided access to an artery of a kidney of a patient, comprising: a first catheter defining a first catheter lumen, the first catheter including first and second first catheter-positioned passive MRI markers, the first and second catheter- positioned passive MRI markers occurring in a distalmost 5 cm segment of the first catheter, the distalmost 5 cm segment of the catheter having a preformed curve configuration; a first wire guide positionable through the first catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second first wire guide-positioned passive MRI markers occurring in a distalmost 5 cm segment of the first wire guide; a second catheter defining a second catheter lumen, the second catheter including first and second catheter-positioned passive MRI markers, the first and second catheter- positioned passive MRI markers occurring in a distalmost 5 cm segment of the second catheter, the second catheter positionable through the lumen of the first catheter; and a second wire guide positionable through the second catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second wire guide-positioned passive MRI markers occurring in a distalmost 5 cm segment of the second wire guide.

[0361] Embodiment 83. The interventional system of Embodiment 82, wherein the first wire guide and / or the second wire guide has / have the features of the wire guide defined in any one of Embodiments 2 to 10.

[0362] Embodiment 84. A method, comprising: generating an MRI image of an interventional system according to any one of

[0363] Embodiments 1 to 83.

[0364] Embodiment 85. The method of Embodiment 84, wherein said generating comprises generating real time MRI images.

[0365] Embodiment 86. A method according to Embodiment 84 or 85, which is a method for conducting an interventional procedure on a patient.

[0366] Embodiment 87. A method for conducting a procedure under MR imaging in a patient, comprising: acquiring MR imaging data of a region of patient tissue with an interventional system according to any one of claims 1-50 or 54-83, or a stent delivery system according to any one of claims 51-53 ; and based at least in part on the MR imaging data, conducting at least one of, at least two of, or all three of, the following steps, using a computer processor:

[0367] (a) determining the presence of a medical device;

[0368] (b) determining one or more characteristics of a medical device; (c) determining one or more imaging sequence parameters to be used in the MR imaging of the patient; and optionally implementing the one or more imaging sequence parameters; and

[0369] (c) tracking a position of a medical device.

[0370] Embodiment 88. A system for conducting a procedure under MR imaging in a patient, comprising: a magnetic resonance imaging (MRI) system configured to acquire MRI data of a patient tissue region; and wherein the MRI system is configured to perform, based at least in part on the MRI data, at least one of, at least two of, or all three of, the following operations, using a computer processor:

[0371] (a) determining the presence of a medical device;

[0372] (b) determining one or more characteristics of a medical device;

[0373] (c) determining one or more imagining sequence parameters to be used in the MR imaging of the patient; and optionally implementing the one or more imaging sequence parameters; and

[0374] (d) tracking a position of a medical device.

[0375] Embodiment 89. The system of Embodiment 88, also comprising the medical device; optionally, wherein the medical device is: the first elongate medical device or the second elongate medical device of an interventional system according to any one of Embodiments 1 to 50; or, as and to the extent recited therein, a sheath, catheter, needle, dilator, wire guide, or filter delivery member of a system according to any one of Embodiments 51 to 83.

[0376] Embodiment 90. A method according to Embodiment 87 wherein said conducting comprises conducting at least step (a), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct operation (a). Embodiment 91. A method according to Embodiment 87 wherein said conducting comprises conducting at least step (b), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct operation (b).

[0377] Embodiment 92. A method according to Embodiment 87 wherein said conducting comprises conducting at least step (c), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct operation (c).

[0378] Embodiment 93. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (a) and (b), or a system according to Embodiment 88 or

[0379] 89 wherein the MRI system is configured to conduct at least operations (a) and (b).

[0380] Embodiment 94. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (a) and (c), or a system according to Embodiment 88 or

[0381] 89 wherein the MRI system is configured to conduct at least operations (a) and (c).

[0382] Embodiment 95. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (b) and (c), or a system according to Embodiment 88 or

[0383] 89 wherein the MRI system is configured to conduct at least operations (b) and (c).

[0384] Embodiment 96. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (a) and (d), or a system according to Embodiment 88 or

[0385] 89 wherein the MRI system is configured to conduct at least operations (a) and (d).

[0386] Embodiment 97. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (b) and (d), or a system according to Embodiment 88 or

[0387] 89 wherein the MRI system is configured to conduct at least operations (b) and (d).

[0388] Embodiment 98. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (c) and (d), or a system according to Embodiment 88 or

[0389] 89 wherein the MRI system is configured to conduct at least operations (c) and (d). Embodiment 99. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (a), (b) and (c), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct at least operations (a), (b) and (c).

[0390] Embodiment 100. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (a), (c) and (d ), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct at least operations (a), (c) and (d).

[0391] Embodiment 101. A method according to Embodiment 87 wherein said conducting comprises conducting at least steps (b), (c) and (d), or a system according to Embodiment 88 or 89 wherein the MRI system is configured to conduct at least operations (b), (c) and (d).

[0392] Embodiment 102. A system for conducting a procedure under magnetic resonance imaging in a patient, comprising: a magnetic resonance imaging (MRI) system configured to acquire MRI data of a patient tissue region; and a system according to any one of Embodiments 1 to 83.

[0393] While embodiments of the disclosure have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only some embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosures herein are desired to be protected.

[0394] The uses of the terms "a" and "an" and "the" and similar references herein

[0395] (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language

[0396] (e.g., "such as") provided herein, is intended merely to better illuminate embodiments of the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the products or methods defined by the claims.

[0397] All references cited herein are indicative of the level of skill in the art and are hereby incorporated by reference in their entirety.

Claims

CLAIMS1. An interventional system for a magnetic resonance imaging (MRI) guided procedure on a patient at a primary magnetic field strength, comprising: a first elongate medical device configured for percutaneous insertion into a vessel of the patient; a second elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the first elongate medical device is slidably positionable through a lumen of the second elongate medical device; and a passive MRI marking system on the interventional system; wherein the passive MRI marking system includes:(a) a first discrete passive MRI marker on the first elongate medical device configured to generate a first medical device-positioned image artifact under theMRI having a maximum dimension, and a first discrete passive MRI marker on the second elongate medical device configured to generate a second medical device- positioned image artifact under the MRI having a maximum dimension, wherein the maximum dimension of the second medical device-positioned artifact is different from the maximum dimension of the first medical device-positioned artifact; and / or(b) first and second discrete passive MRI markers on and longitudinally spaced from one another a first distance along the first elongate medical device, and first and second discrete passive MRI markers on and longitudinally spaced from one another a second distance along the second medical device, wherein the second distance is different from the first distance; and / or(c) a first total number of discrete passive MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number; and / or(d) a first discrete passive MRI marker on and demarking a distal end of the first elongate medical device and configured to generate a first medical device- positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the first elongatemedical device, and a first discrete passive MRI marker on and demarking a distal end of the second elongate medical device and configured to generate a second medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the second medical device.

2. The interventional system of claim 1, wherein the first elongate medical device is a wire guide.

3. The interventional system of claim 2, wherein the wire guide comprises a core member and a polymeric jacket encapsulating the core member.

4. The interventional system of claim 3, wherein the core member is a single, continuous length of wire.

5. The interventional system of claim 4, wherein the wire is formed of a superelastic metal alloy.

6. The interventional system of claim 5, wherein the superelastic metal alloy is nitinol.

7. The interventional system of any one of claims 3 to 6, wherein the polymeric jacket is formed of a polyamide polymer.

8. The interventional system of any one of claims 3 to 7, wherein the first passive MRI marker on the wire guide comprises a passive MRI marker-forming material between the polymeric jacket and the core member.

9. The interventional system of claim 8, wherein the passive MRI marker-forming material is a metal layer plated onto an outer surface of the core member, optionally wherein the metal layer is a nickel layer.

10. The interventional system of any one of claims 3 to 7, wherein the first discrete passive MRI marker on the first elongate medical device comprises a passive MRI marker- forming material embedded in a wall of the polymeric jacket.

11. The interventional system of claim 1 or 2, wherein the second elongate medical device is a catheter or sheath.

12. The interventional system of any one of claims 1 to 11, wherein the passive MRI marking system is provided by discrete passive MRI markers positioned on a distalmost20cm long segment of each of the first elongate medical device and the second elongate medical device.

13. The interventional system of any one of claims 1 to 12, wherein the second medical device is a catheter or sheath, and wherein the first passive MRI marker on the second medical device comprises a passive MRI marker-forming material embedded in a wall of the catheter or sheath.

14. The interventional system of claim 13, wherein the wall includes a first volume of a polymeric material forming the wall positioned radially inward of the passive MRI markerforming material and between the passive MRI marker forming material and a lumen surface defined by the first volume of polymeric material.

15. The interventional system of claim 14, wherein the polymeric material comprises a thermoplastic elastomer material.

16. The interventional system of any one of claims 1 to 15, wherein the first discrete passive MRI markers on the first elongate medical device and the second elongate medical device each include (i) an MRI marker-forming material having a volume not exceeding 5 mm3, or not exceeding 3 mm3, or not exceeding 1 mm3, or not exceeding 0.1 mm3, wherein in each of these aspects, the volume may be at least 0.00005 mm3, or at least about 0.0001 mm3; or (ii) an MRI marker-forming material having a magnetic susceptibility of at leastabout 1 and having a volume not exceeding 0.1 mm3, or in the range of 0.00001 mm3to 0.1 mm3, or in the range of 0.00005 mm3to 0.02 mm3.

17. The interventional system of any one of claims 1 to 16, wherein the first discrete passive MRI markers on the first elongate medical device and the second elongate medical device each include an MRI-marking forming material having a magnetic susceptibility of at least about 500 ppm, or at least about 2000 ppm, or in the range of about 500 ppm to about 1000, or in the range of about 7000 ppm to about 1000.

18. The interventional system of any one of claims 1 to 17, wherein: the first passive MRI markers on the first and second elongate medical devices each include an MRI marker-forming material selected from nickel, nickel alloys, cobalt, cobalt alloys, iron, and iron alloys.

19. The interventional system of any one of claims 1 to 18, also comprising: a third elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the second elongate medical device is slidably positionable through a lumen of the third elongate medical device, and wherein the passive MRI marking system includes a first discrete passive MRI marker on the third elongate medical device.

20. The interventional system of claim 19, wherein the first discrete passive MRI marker on the third elongate medical device demarks a distal end of the third elongate medical device.

21. The interventional system of claim 19 or 20, wherein the first elongate medical device is a wire guide, the second elongate medical device is a catheter, and the third elongate medical device is an introducer sheath.

22. The interventional system of any preceding claim, wherein the passive MRI marking system includes a first discrete passive MRI marker on the first elongate medical device configured to generate a first medical device-positioned image artifact under the MRIhaving a maximum dimension, and a first discrete passive MRI marker on the second elongate medical device configured to generate a second medical device-positioned image artifact under the MRI having a maximum dimension, wherein the maximum dimension of the second medical device-positioned artifact is different from the maximum dimension of the first medical device-positioned artifact.

23. The interventional system of any preceding claim, wherein the passive MRI marking system incudes first and second discrete passive MRI markers on and longitudinally spaced from one another a first distance along the first elongate medical device, and first and second discrete passive MRI markers on and longitudinally spaced from one another a second distance along the second medical device, wherein the second distance is different from the first distance.

24. The interventional system of any preceding claim, wherein the passive MRI marking system includes a first total number of discrete passive MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number.

25. The interventional system of any preceding claim, wherein the passive MRI marking system includes a first discrete passive MRI marker on and demarking a distal end of the first elongate medical device and configured to generate a first medical device-positioned artifact under the MRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the first elongate medical device, and a first discrete passive MRI marker on and demarking a distal end of the second elongate medical device and configured to generate a second medical device-positioned artifact under theMRI having a maximum dimension that is greater than that of at least one additional discrete passive MRI marker on the second medical device.

26. The interventional system of any preceding claim, wherein the passive MRI marking system includes at least three discrete passive MRI markers on the first elongate medical device and at least two discrete passive MRI marker on the second medical device.

27. An interventional system for a magnetic resonance imaging (MRI) guided procedure on a patient at a primary magnetic field strength, comprising: a first elongate medical device configured for percutaneous insertion into a vessel of the patient; a second elongate medical device configured for percutaneous insertion into the vessel of the patient, wherein the first elongate medical device is slidably positionable through a lumen of the second elongate medical device; and a passive MRI marking system on the interventional system; wherein the passive MRI marking system includes: a first discrete passive MRI marker on the first elongate medical device and configured to generate a first medical device-positioned artifact under the MRI having a maximum dimension; a first discrete passive MRI marker on the second elongate medical device and configured to generate a second medical device-positioned artifact under the MRI having a maximum dimension; and wherein the maximum dimension of the second medical device-positioned artifact differs from the maximum dimension of the first medical device-positioned artifact.

28. The interventional system of claim 27, wherein the maximum dimension of the first medical device-positioned artifact is greater than the maximum dimension of the second medical device-positioned artifact.

29. The interventional system of claim 28, wherein: the passive MRI marking system includes a plurality of discrete passive MRI markers on the first elongate medical device and configured to generate respective first medical device- positioned artifacts under the MRI each having a maximum dimension, and a plurality of discrete passive MRI markers on the second elongate medical device and configured togenerate respective second medical device-positioned artifacts under the MRI each having a maximum dimension; and the maximum dimension of each of the first medical device-positioned artifacts is greater than the maximum dimension of each of the second medical device-positioned artifacts.

30. The interventional system of claim 27, wherein the maximum dimension of the first medical device-positioned artifact is less than the maximum dimension of the second medical device-positioned artifact.

31. The interventional system of claim 30, wherein: the passive MRI marking system includes a plurality of discrete passive MRI markers on the first elongate medical device and configured to generate respective first medical devicepositioned artifacts under the MRI each having a maximum dimension, and a plurality of discrete passive MRI markers on the second elongate medical device and configured to generate respective second medical device-positioned artifacts under the MRI each having a maximum dimension; and the maximum dimension of each of the first medical device-positioned artifacts is less than the maximum dimension of each of the second medical device-positioned artifacts.

32. The interventional system of any one of claims 28 to 31, wherein the maximum dimension of each of the first medical device-positioned artifacts is the same.

33. The interventional system of any one of claims 28 to 32, wherein the maximum dimension of each of the second medical device-positioned artifacts is the same.

34. The interventional system of any one of claims 27 to 31, wherein the passive MRI marking system is provided by discrete passive MRI markers on the distalmost 20 cm of, or on the distalmost 10cm of, each of the first elongate medical device and second elongate medical device.

35. The interventional system of any one of claims 27 to 32, wherein the passive MRI marking system includes at least three discrete passive MRI markers on the first elongate medical device and at least two discrete passive MRI markers on the second elongate medical device.

36. The interventional system of any one of claims 27 to 25, wherein the passive MRI marking system includes a first total number of discrete passive MRI markers on the first elongate medical device and a second total number of discrete passive MRI marker on the second elongate medical device, wherein the first total number is different from the second total number and / or wherein the discrete passive MRI markers on the first elongate medical device are longitudinally spaced from one another a distance that is different from that of the discrete passive MRI markers on the second elongate medical device.

37. The interventional system of any one of claims 27 to 36, wherein the first elongate medical device is a wire guide.

38. The interventional system of claim 37, wherein the wire guide comprises a core member and a polymeric jacket encapsulating the core member.

39. The interventional system of claim 38, wherein the core member is a single. continuous length of wire.

40. The interventional system of claim 39, wherein the wire is formed of a superelastic metal alloy.

41. The interventional system of claim 40, wherein the superelastic metal alloy is nitinol.

42. The interventional system of any one of claims 38 to 41, wherein the polymeric jacket is formed of a polyamide polymer.

43. The interventional system of any one of claims 38 to 42, wherein the discrete passive MRI marker(s) on the wire guide each comprise a passive MRI marker-forming material between the polymeric jacket and the core member.

44. The interventional system of claim 43, wherein the passive MRI marker-forming material is a metal layer plated onto an outer surface of the core member, optionally wherein the metal layer is a nickel layer.

45. The interventional system of any one of claims 38 to 42, wherein the first passiveMRI marker and the second passive MRI marker each comprise a passive MRI markerforming material embedded in a wall of the polymeric jacket.

46. The interventional system of any one of claims 27 to 45, wherein each discrete passive MRI marker of the passive MRI marking system includes an MRI-marking forming material having a magnetic susceptibility of at least about 500 ppm, or at least about 2000 ppm, or in the range of about 500 ppm to about 1000, or in the range of about 7000 ppm to about 1000.

47. The interventional system of any one of claims 27 to 26, wherein each discrete passive MRI marker of the passive MRI marking system includes an MRI marker-forming material selected from nickel, nickel alloys, cobalt, cobalt alloys, iron, and iron alloys.

48. The interventional system of any one of claims 27 to 47, wherein the first elongate medical device is a wire guide and the second elongate medical device is a catheter or sheath.

49. The interventional system of any one of claims 27 to 47, wherein the first elongate medical device is a wire guide, the second elongate medical device is a catheter, and the system also includes a third elongate medical device configured for percutaneous insertion into the vessel, wherein the third medical device is an introducer sheath and the passiveMRI marking system further includes a first discrete passive MRI marker on the introducer sheath.

50. The interventional system of claim 49, wherein the first discrete passive marker on the introducer sheath demarks a distal end of the introducer sheath.

51. A stent delivery system, comprising: an outer sheath defining a lumen extending to a distal end opening at a distal end of the outer sheath; an inner catheter member received through the outer sheath, the inner catheter member defining a stent-carrying region and a distal region positioned distal of the stentcarrying region, the distal region having a proximal end received against a distal end of the outer sheath, the outer sheath and the inner catheter member being configured for longitudinal movement relative to one another to deploy a stent from the stent-carrying region; a stent received over the stent carrying region in a compressed condition and located in an annular space between an outer surface of the stent-carrying region of the inner catheter member and an inner surface defining a portion of the lumen of the outer sheath; a first discrete passive MRI marker on the outer sheath, the first discrete passive MRI marker demarking the distal end of the outer sheath and configured to generate a first image artifact under MRI; a first discrete passive MRI marker on the inner catheter member and demarking a distal end of the stent-carrying region and configured to generate a second image artifact underMRI; and wherein the second image artifact overlaps the first image artifact while the proximal end of the distal region is received against the distal end of the outer sheath but is longitudinally spaceable from the first image artifact during said longitudinal movement.

52. The stent delivery system of claim 51, wherein the inner catheter member also includes a second discrete passive MRI marker thereon, the second discrete passive MRI marker demarking a proximal end of the stent-carrying region.

53. The stent delivery system of claim 52, wherein the inner catheter member also includes a third passive MRI marker thereon, the third passive MRI marker demarking a distal end of the distal region of the inner catheter member.

54. An interventional system useful in a procedure for magnetic resonance imaging(MRI)-guided transjugular intrahepatic access, comprising: an introducer sheath defining a sheath lumen and including a sheath-positioned discrete passive MRI marker demarking a distal tip of the sheath; a catheter defining a catheter lumen, the catheter positionable through the sheath lumen and including first and second catheter-positioned passive MRI markers, optionally wherein the first and second catheter-positioned passive MRI markers are positioned on a distalmost 5 cm long segment of the catheter; and a needle including a needle shaft defining a needle lumen, the needle positionable through the catheter lumen to extend a distal end of the needle distally beyond a distal end of the catheter, and the needle including a first needle-positioned passive MRI marker, optionally wherein the first needle-positioned passive MRI marker is positioned on a distalmost 2 cm segment of the needle and / or demarks the distal end of the needle.

55. The interventional system of claim 54, wherein the needle has a curved distal region defining a curve extending to the distal end of the needle.

56. The interventional system of claim 55, wherein the needle further comprises a directional indicator configured to indicate a direction of the curve.

57. The interventional system of any one of claims 54 to 56, wherein the needle comprises a needle shaft formed from a metal having a magnetic susceptibility not exceeding 3000 ppm.

58. The interventional system of any one of claims 54 to 57, wherein the needle comprises a needle shaft formed from a metal selected from a nickel-titanium alloy and a nickel-chromium alloy.

59. The interventional system of any one of claims 54 to 58, also comprising a wire guide having at least one discrete passive MRI marker thereon.

60. The interventional system of claim 59, wherein the wire guide has the features of the wire guide defined in any one of claims 2 to 10.

61. The interventional system of any one of claims 54 to 60, also comprising a dilator positionable through the sheath lumen and including a dilator-positioned discrete passiveMRI marker demarking a distal tip of the dilator.

62. The interventional system of any one of claims 54 to 61, wherein the first discrete passive MRI marker on the needle demarks the distal end of the needle, and wherein the needle further includes a second passive discrete MRI marker proximal of and longitudinally spaced from the first discrete passive MRI marker on the needle.

63. The interventional system of claim 62, wherein the needle further includes a third passive discrete MRI marker proximal of and longitudinally spaced from the second discrete passive MRI marker on the needle.

64. The interventional system of claim 63, wherein the needle further includes a fourth passive discrete MRI marker proximal of and longitudinally spaced from the third discrete passive MRI marker on the needle.

65. The interventional system of any one of claims 54 to 64, wherein the first discrete passive MRI marker on the needle, and, when present, the second, third and / or fourth passive MRI markers on the needle, are each a metal layer plated onto an outer surface of the needle shaft, optionally wherein the metal layer is a nickel layer.

66. An interventional system useful for providing magnetic resonance imaging(MRI)- guided access to a pulmonary artery of a patient, comprising: a catheter defining a catheter lumen, the catheter including first and second catheter- positioned passive MRI markers, the first and second catheter-positioned passive MRI markers occurring in a distalmost 5 cm segment of the catheter, the distalmost 5 cm segment of the catheter having a preformed curve configuration; and a wire guide positionable through the catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second wire guide-positioned passive MRI markers occurring in a distalmost 5 cm segment of the wire guide.

67. The interventional system of claim 66, wherein the catheter is sized and configured for percutaneous introduction and navigation from a jugular vein access point or a subclavian vein access point, through the superior vena cava, through the right atrium, through the tricuspid valve, through the right ventricle, through the pulmonary valve, and into the pulmonary artery.

68. The interventional system of claim 66, wherein the catheter configured for percutaneous introduction and navigation from a femoral vein access point, through the inferior vena cava, through the right atrium, through the tricuspid valve, through the right ventricle, through the pulmonary valve, and into the pulmonary artery.

69. The interventional system of any one of claims 66 to 68, wherein the catheter has a distal catheter segment and a proximal catheter segment attached to and proximal of the distal catheter segment, wherein the proximal catheter segment has a catheter wall reinforced with a reinforcing member embedded therein and the distal catheter segment has a catheter wall that is free from any reinforcing member embedded therein.

70. The interventional system of claim 69, wherein the catheter wall of the proximal catheter segment is reinforced with a reinforcing member in the form of a wire braid or a wire coil embedded therein.

71. The interventional system of any one of claims 66 to 70, wherein the distal catheter segment has a length of about 5 cm to about 20 cm.

72. The interventional system of any one of claims 66 to 71, wherein the distalmost 5 cm segment of the wire guide has a preformed curve configuration.

73. The interventional system of any one of claims 66 to 72, wherein the wire guide has the features of the wire guide defined in any one of claims 2 to 10.

74. The interventional system of any one of claims 66 to 73, also comprising an introducer sheath including a first discrete passive MRI marker thereon.

75. The interventional system of claim 74, wherein the first discrete passive MRI marker on the introducer sheath demarks a distal end of the introducer sheath.

76. An interventional system useful in a procedure for providing magnetic resonance imaging(MRI)-guided delivery of a vascular filter, comprising: an introducer sheath including a shaft defining a sheath lumen and having a distal end; a dilator slidably positionable through the sheath lumen to a dilating configuration in which a tapered distal end region of the dilator is positioned distal of the distal end of the introducer sheath; and a filter delivery member carrying a vascular filter, the filter delivery member slidably positionable through the sheath lumen to position an end of the vascular filter at the distal end of the introducer sheath; and wherein the introducer sheath includes a discrete passive MRI marker demarking the distal end of the sheath.

77. The interventional system of claim 76, wherein the dilator includes a first discrete passive MRI marker thereon and a second passive MRI marker thereon spaced proximally and longitudinally from the first discrete passive MRI marker a distance.

78. The interventional system of claim 77, wherein said distance approximates a length of the vascular filter in an expanded condition.

79. The interventional system of claim 77 or 78, wherein when the dilator is in said dilating configuration the first discrete passive MRI marker on the dilator is longitudinally positioned at or proximate to the distal end of the introducer sheath.

80. The interventional system of any one of claims 76 to 79, also including a wire guide having a first discrete passive MRI marker thereon.

81. The interventional system of claim 80, wherein the wire guide has the features of the wire guide defined in any one of claims 2 to 10.

82. An interventional system useful for providing magnetic resonance imaging(MRI)- guided access to an artery of a kidney of a patient, comprising: a first catheter defining a first catheter lumen, the first catheter including first and second first catheter-positioned passive MRI markers, the first and second catheter- positioned passive MRI markers occurring in a distalmost 5 cm segment of the first catheter, the distalmost 5 cm segment of the catheter having a preformed curve configuration; a first wire guide positionable through the first catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second first wire guidepositioned passive MRI markers occurring in a distalmost 5 cm segment of the first wire guide; a second catheter defining a second catheter lumen, the second catheter including first and second catheter-positioned passive MRI markers, the first and second catheter- positioned passive MRI markers occurring in a distalmost 5 cm segment of the second catheter, the second catheter positionable through the lumen of the first catheter; anda second wire guide positionable through the second catheter lumen and including first and second wire guide-positioned passive MRI markers, the first and second wire guide- positioned passive MRI markers occurring in a distalmost 5 cm segment of the second wire guide.

83. The interventional system of claim 82, wherein the first wire guide and / or the second wire guide has / have the features of the wire guide defined in any one of claims 2 to10.

84. A method, comprising: generating an MRI image of an interventional system according to any one of claims 1 to83.

85. The method of claim 84, wherein said generating comprises generating real timeMRI images.

86. A method according to claim 84 or 85, which is a method for conducting an interventional procedure on a patient.

87. A method for conducting a procedure under MR imaging in a patient, comprising: acquiring MR imaging data of a region of patient tissue with an interventional system according to any one of claims 1-50 or 54-83, or a stent delivery system according to any one of claims 51-53 ; and based at least in part on the MR imaging data, conducting at least one of, at least two of, or all three of, the following steps, using a computer processor:(a) determining the presence of a medical device;(b) determining one or more characteristics of a medical device; and(c) determining one or more imaging sequence parameters to be used in the MR imaging of the patient; and optionally implementing the one or more imaging sequence parameters.

88. A system for conducting a procedure under MR imaging in a patient, comprising: a magnetic resonance imaging (MRI) system configured to acquire MRI data of a patient tissue region; and wherein the MRI system is configured to perform, based at least in part on the MRI data, at least one of, at least two of, or all three of, the following operations, using a computer processor:(a) determining the presence of a medical device;(b) determining one or more characteristics of a medical device; and(c) determining one or more imagining sequence parameters to be used in the MR imaging of the patient; and optionally implementing the one or more imaging sequence parameters89. The system of claim 88, also comprising the medical device; optionally, wherein the medical device is: the first elongate medical device or the second elongate medical device of an interventional system according to any one of claims 1 to 50; or, as and to the extent recited therein, a sheath, catheter, needle, dilator, wire guide, or filter delivery member of a system according to any one of claims 51 to 83.

90. A method according to claim 87 wherein said conducting comprises conducting at least step (a), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct operation (a).

91. A method according to claim 87 wherein said conducting comprises conducting at least step (b), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct operation (b).

92. A method according to claim 87 wherein said conducting comprises conducting at least step (c), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct operation (c).

93. A method according to claim 87 wherein said conducting comprises conducting at least steps (a) and (b), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct at least operations (a) and (b).

94. A method according to claim 87 wherein said conducting comprises conducting at least steps (a) and (c), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct at least operations (a) and (c).

95. A method according to claim 87 wherein said conducting comprises conducting at least steps (b) and (c), or a system according to claim 88 or 89 wherein the MRI system is configured to conduct at least operations (b) and (c).

96. A method according to Claim 87 wherein said conducting comprises conducting at least steps (a) and (d), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (a) and (d).

97. A method according to Claim 87 wherein said conducting comprises conducting at least steps (b) and (d), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (b) and (d).

98. A method according to Claim 87 wherein said conducting comprises conducting at least steps (c) and (d), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (c) and (d).

99. A method according to Claim 87 wherein said conducting comprises conducting at least steps (a), (b) and (c), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (a), (b) and (c).

100. A method according to Claim 87 wherein said conducting comprises conducting at least steps (a), (c) and (d), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (a), (c) and (d).

101. A method according to Claim 87 wherein said conducting comprises conducting at least steps (b), (c) and (d), or a system according to Claim 88 or 89 wherein the MRI system is configured to conduct at least operations (b), (c) and (d).

102. A system for conducting a procedure under magnetic resonance imaging in a patient, comprising: a magnetic resonance imaging (MRI) system configured to acquire MRI data of a patient tissue region; and a system according to any one of claims 1 to 83.

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