Acoustic refraction for ultrasound blood flow sensor of intravascular guidewire

Abstract

An apparatus includes an intravascular guidewire configured to be positioned within a blood vessel of a patient. The intravascular guidewire includes a distal tip, a longitudinal axis, and an intravascular sensor positioned proximal of the distal tip and oriented at a first angle with respect to the longitudinal axis of the guidewire, where the intravascular sensor is configured to obtain intravascular data while the intravascular guidewire is positioned within the blood vessel. The intravascular guidewire also includes a window material at least partially surrounding the intravascular sensor and having a first impedance less than an impedance of blood in the blood vessel.

Description

ACOUSTIC REFRACTION FOR ULTRASOUND BLOOD FLOW SENSOR OF INTRAVASCULAR GUIDEWIRETECHNICAL FIELD

[0001] The subject matter described herein relates to intraluminal sensing devices. For example, intravascular catheters or guidewires can include low-acoustic-impedance acoustic windows to steer ultrasound energy from an ultrasound blood flow sensor that is positioned proximal of a distal tip in a direction more forward (e.g., distal) and parallel to blood flow.BACKGROUND

[0002] Intraluminal physiology sensing devices may be introduced into a body lumen of a patient, and may for example include physiological sensors at a distal end of a catheter or guidewire. Small-diameter medical devices such as intraluminal (e.g., intravascular) catheters and guidewires may incorporate sensors (e.g., pressure, temperature, flow, or imaging sensors) whose power and communications occur through metal wires or filars, flat metal ribbons, or conductive ink traces.

[0003] The current design and implantation of Doppler flow-sensing guidewires and catheters may require the ultrasound sensor to be placed at the distal tip of the guidewire so that the sensor is the center axis of the body lumen (e.g., a blood vessel) in which it is positioned. This allows the sensor to see the flow of blood instead of the vessel wall.However, this can require a large, mechanically stiff sensor housing to be placed distal to the shaped portion of the guidewire.

[0004] The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded as subject matter by which the scope of the disclosure is to be bound.SUMMARY

[0005] Disclosed are intravascular flow-sensing guidewires with improved robustness and maneuverability. By angling the blood flow sensor and carefully selecting matching layer materials to refractively steer ultrasound signals in a desired direction (more along the direction of blood flow within the blood vessel), the acoustically refracted flow sensor of the present disclosure permits the flow sensor to be placed proximal to the tip and coil of a guidewire. This more proximal position allows the guidewire to be maneuvered more easily through the body lumen and to be more robust against handling. The acoustically refracted flow sensor disclosed herein has particular, but not exclusive, utility for intraluminal medical catheters and guidewires.

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the acoustically refracted flow sensor, as defined in the claims, is provided in the following written description of various aspects of the disclosure and illustrated in the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Illustrative aspects of the present disclosure will be described with reference to the accompanying drawings, of which:

[0008] Figure 1 is a diagrammatic side view of an intravascular sensing system that includes an intravascular device comprising conductive members and conductive ribbons, according to aspects of the present disclosure.

[0009] Figure 2 is a diagrammatic side view of another type of intravascular device, according to aspects of the present disclosure.

[0010] Figure 3 is a diagrammatic cross-sectional view of an example sensor assembly 251, which may for example be included in the intravascular device of Figure 1 or Figure 2, according to aspects of the present disclosure.

[0011] Figure 4 is a schematic view of an intravascular device during measurement of a flow velocity inside a blood vessel with blood vessel walls, according to aspects of the present disclosure.

[0012] Figure 5 is a diagrammatic cross-sectional view of an intraluminal (e.g., intravascular) sensing device that includes a flexible elongate member, and a flow sensor located proximal of the tip coil, according to aspects of the present disclosure.

[0013] Figure 6 is a side cross-sectional view of a flow sensor mount, according to aspects of the present disclosure.

[0014] Figure 7 is a side cross-sectional view of the flow sensor mount of Figure 6, according to aspects of the present disclosure.

[0015] Figure 8 is a side cross-sectional view of a flow sensor housing, according to aspects of the present disclosure.

[0016] Figure 9 is a side cross-sectional view of the sensor mount of Figures 6 and 7 positioned inside the sensor housing 280 of Figure 8, according to aspects of the present disclosure.

[0017] Figure 10 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel, according to aspects of the present disclosure.

[0018] Figure 11 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel, according to aspects of the present disclosure.

[0019] Figure 12 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel, according to aspects of the present disclosure.

[0020] Figure 13 is a side cross-sectional view an alternative aspect wherein the sensor is mounted directly in the sensor housing without a sensor mount, according to aspects of the present disclosure.

[0021] Figure 14 is a schematic diagram of a processor circuit, according to aspects of the present disclosure.

[0022] Figure 15 is a perspective view of the sensor mount body of an example sensor mount, according to aspects of the present disclosure.

[0023] Figure 16 is a perspective view of the sensor mount body of Figure 15, with a flow sensor attached, according to aspects of the present disclosure.

[0024] Figure 17 is a perspective view of the sensor mount body and flow sensor of Figure 16, with a low-acoustic-impedance acoustic window material mounted over the sensor, according to aspects of the present disclosure.

[0025] Figure 18 is a perspective view of the sensor mount body, flow sensor, and low- acoustic-impedance acoustic window material of Figure 17, with an additional layer of a second low-acoustic-impedance material coated over the first low-acoustic-impedance acoustic window material, according to aspects of the present disclosure.

[0026] Figure 19 is a perspective view of an example sensor housing, according to aspects of the present disclosure.

[0027] Figure 20 is a perspective view of an assembled example sensor mount assembly, according to aspects of the present disclosure.

[0028] Figure 21 is a side view of an assembled example sensor mount assembly, according to aspects of the present disclosure.

[0029] Figure 22 is a top view of an assembled example sensor mount assembly, according to aspects of the present disclosure.

[0030] Figure 23 is a side cross-sectional view, along cut line 23-23 of Figure 22, of an assembled example sensor mount assembly, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0031] Disclosed are intraluminal flow-sensing devices (e.g., intravascular catheters or guidewires) with improved robustness and maneuverability. By angling the sensor and carefully selecting matching layer materials to refractively steer ultrasound signals in a desired direction, the acoustically refracted flow sensor of the present disclosure permits the flow sensor to be placed proximal to the tip and coil of a guidewire, in a housing and / or mount similar to those currently used for pressure sensors. This more proximal position allows the guidewire to be maneuvered more easily through the body lumen, as the tip can be an atraumatic tip that does not include a stiff, bulky sensor housing, sensor, or acoustic matching layer, and the flexible coil can be located immediately proximal of the atraumatic tip.

[0032] The current generation of flow guidewires have large (e.g., ~1.5 - 2.0 mm long) sensor housings located at the distal tip. The sensor housing plays a large role in the mechanical handleability of the guidewire. The present disclosure locates the sensor housing further back, and thus allow maneuverability and robustness to handling that are comparable to a pressure-sensing guidewire and thus represent a substantial improvement over existing flow-sensing guidewires.

[0033] The acoustically refracted flow sensor of the present disclosure uses an angled ultrasound sensor and carefully selected matching layer materials so that the signal is refracted away from the vessel wall and toward the longitudinal axis of the lumen. When the acoustic impedance of the matching layer is less than the acoustic impedance of blood, the acoustic signal is refracted upon contact with the blood. This allows the sensor to be facing out from an acoustic window, at an angle toward the vessel wall, while directing the acoustic signal in a direction more aligned with the longitudinal axis of the body lumen.

[0034] The present disclosure aids substantially in intraluminal flow measurement, by improving both the robustness and the maneuverability of the intraluminal measurement device. Implemented on a catheter or guidewire in communication with a processing system, the acoustically refracted flow sensor disclosed herein provides practical improvement in the ability to measure flow in a body lumen (e.g., a blood vessel) without compromising the robustness or maneuverability of the device. This improved sensor architecture transforms a catheter or guidewire with a large, stiff tip housing into one that has a flexible distal tip coil immediately proximal of an atraumatic tip, without the normally routine need to place the flow sensor at the tip of the device. This unconventional approach improves the functioningof the intraluminal measurement system, by allowing flow measurements to be taken by a device with robustness and maneuverability similar to those of a pressure-sensing guidewire (e.g., a guidewire with a sensor placed proximal of the flexible tip coil).

[0035] These descriptions are provided for exemplary purposes only, and should not be considered to limit the scope of the acoustically refracted flow sensor. Certain features may be added, removed, or modified without departing from the spirit of the claimed subject matter.

[0036] In that regard, aspects of the present disclosure may relate to U.S. Provisional Application No. 63 / 414,017, filed October 7, 2022, and titled “Spacer For Sensor In Intraluminal Sensing Device”, and U.S. Provisional Application No. 63 / 328,355, filed April 7, 2022, and titled “Multi-Component Housing For Sensor In Intraluminal Device”, each of which is incorporated by reference as though fully set forth herein.

[0037] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the aspects illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one aspect may be combined with the features, components, and / or steps described with respect to other aspects of the present disclosure. Further, while the aspects of the present disclosure may be described with respect to a blood vessel, it will be understood that the devices, systems, and methods described herein may be configured for use in any suitable anatomical structure or body lumen including a blood vessel, blood vessel lumen, an esophagus, eustachian tube, urethra, fallopian tube, intestine, colon, and / or any other suitable anatomical structure or body lumen. In other aspects, the devices, systems, and methods described herein may be used to examine any number of anatomical locations and tissue types, including without limitation, organs including the liver, heart, kidneys, gall bladder, pancreas, lungs; ducts; intestines; nervous system structures including the brain, dural sac, spinal cord and peripheral nerves; the urinary tract; as well as valves within the blood vessels, chambers or other parts of the heart, and / or other systems of the body. In addition to natural structures, the device 102 may be used to examine man-made structures such as, but without limitation,heart valves, stents, shunts, filters and other devices. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0038] Figure 1 is a diagrammatic side view of an intraluminal (e.g., intravascular) sensing system 100 that includes an intravascular device 102 comprising conductive members 230 (e.g., a multi-filar electrical conductor bundle) and conductive ribbons 260, according to aspects of the present disclosure. The intravascular device 102 can be an intravascular guidewire sized and shaped for positioning within a vessel of a patient. The intravascular device 102 includes a distal tip 108 and an electronic component 112. For example, the electronic component 112 can be a pressure sensor and / or flow sensor configured to measure a pressure of blood flow within the vessel of the patient, or another type of sensor including but not limited to a temperature or imaging sensor, or combination sensor measuring more than one property. For example, the flow data obtained by a flow sensor can be used to calculate physiological variables such as coronary flow reserve (CFR). The intravascular device 102 includes a flexible elongate member 106. The electronic component 112 is disposed at a distal portion 107 of the flexible elongate member 106. The electronic component 112 can be mounted at the distal portion 107 within a housing 280 in some aspects. A flexible tip coil 290 extends distally from the housing 280 at the distal portion 107 of the flexible elongate member 106. A connection portion 114 located at a proximal end of the flexible elongate member 106 includes conductive portions 132, 134. In some aspects, the conductive portions 132, 134 can be conductive ink that is printed and / or deposited around the connection portion 114 of the flexible elongate member 106, and may or may not include a resistive ink for impedance matching with other components or materials. In some aspects, the conductive portions 132, 134 are conductive, metallic bands or rings that are positioned around the flexible elongate member. A locking area is formed by a collar or locking section 118 and knob or retention section 120 are disposed at the proximal portion 109 of the flexible elongate member 106.

[0039] The intravascular device 102 in Figure 1 includes core wire comprising a distal core 210 and a proximal core 220. The distal core 210 and the proximal core 220 are metallic components forming part of the body of the intravascular device 102. For example, the distal core 210 and the proximal core 220 may be flexible metallic rods that provide structure for the flexible elongate member 106. The distal core 210 and / or the proximal core 220 can be made of a metal or metal alloy. For example, the distal core 210 and / or the proximal core 220 can be made of stainless steel, Nitinol, nickel-cobalt-chromium-molybdenum alloy (e.g., MP35N), and / or other suitable materials. In some aspects, the distal core 210 and theproximal core 220 are made of the same material. In other aspects, the distal core 210 and the proximal core 220 are made of different materials. The diameter of the distal core 210 and the proximal core 220 can vary along their respective lengths. A joint between the distal core 210 and proximal core 220 is surrounded and contained by a hypotube 215. The electronic component 112 can in some cases be positioned at a distal end of the distal core 210.

[0040] In some aspects, the intravascular device 102 comprises a distal subassembly and a proximal subassembly that are electrically and mechanically joined together, which creates an electrical communication between the electronic component 112 and the conductive portions 132, 134. For example, flow data obtained by the electronic component 112 (in this example, electronic component 112 is a flow sensor) can be transmitted to the conductive portions 132, 134. In an exemplary aspect, the flow sensor 112 is a single ultrasound transducer element such as a crystal of piezoelectric lead zirconate titanate (PZT) material with activating electrodes to either apply an electric field to compress the material or to receive an electric field given off by the material as it is compressed by an external force. The transducer element emits ultrasound signals and receives echoes. The transducer element generates electrical signals representative of the echoes. The signal carrying filars carry this electrical signal from the sensor at the distal portion to the connector at the proximal portion. The processing system 306 processes the electrical signals to extract the flow velocity of the fluid.

[0041] Control signals from a processing system 306 (e.g., a processor circuit of the processing system 306) in communication with the intravascular device 102 can be transmitted to the electronic component 112 via a connector 314 that attached to the conductive portions 132, 134. The distal subassembly can include the distal core 210. The distal subassembly can also include the electronic component 112, the conductive members 230, and / or one or more layers of insulative polymer / plastic 240 surrounding the conductive members 230 and the core 210. For example, the polymer / plastic layer(s) can insulate and protect the conductive members of the multi-filar cable or conductor bundle 230. The proximal subassembly can include the proximal core 220. The proximal subassembly can also include one or more polymer layers 250 (hereinafter polymer layer 250) surrounding the proximal core 220 and / or conductive ribbons 260 embedded within the one or more insulative and / or protective polymer layer 250. In some aspects, the proximal subassembly and the distal subassembly are separately manufactured. During the assembly process for the intravascular device 102, the proximal subassembly and the distal subassembly can be electrically and mechanically joined together. As used herein, flexible elongate member canrefer to one or more components along the entire length of the intravascular device 102, one or more components of the proximal subassembly (e.g., including the proximal core 220, etc.), and / or one or more components the distal subassembly 410 (e.g., including the distal core 210, etc.). Accordingly, flexible elongate member may refer to the combined proximal and distal subassemblies described above. The joint between the proximal core 220 and distal core 210 is surrounded by the hypotube 215.

[0042] In various aspects, the intravascular device 102 can include one, two, three, or more core wires extending along its length. For example, a single core wire can extend substantially along the entire length of the flexible elongate member 106. In such aspects, a locking section 118 and a section 120 can be integrally formed at the proximal portion of the single core wire. The electronic component 112 can be secured at the distal portion of the single core wire. In other aspects, such as the aspect illustrated in Figure 1, the locking section 118 and the section 120 can be integrally formed at the proximal portion of the proximal core 220. The electronic component 112 can be secured at the distal portion of the distal core 210. The intravascular device 102 includes one or more conductive members 230 (e.g., a multi-filar conductor bundle or cable) in communication with the electronic component 112. For example, the conductive members 230 can be one or more electrical wires that are directly in communication with the electronic component 112. In some instances, the conductive members 230 are electrically and mechanically coupled to the electronic component 112 by, e.g., soldering. In some instances, the conductor bundle 230 comprises two or three electrical wires (e.g., a bifilar cable or a trifilar cable). An individual electrical wire can include a bare metallic conductor surrounded by one or more insulating layers. The conductive members 230 can extend along the length of the distal core 210. For example, at least a portion of the conductive members 230 can be spirally wrapped around the distal core 210, minimizing or eliminating whipping of the distal core within tortuous anatomy.

[0043] Depending on the implementation, the intravascular device 102 can include one or more conductive ribbons 260 at the proximal portion of the flexible elongate member 106. The conductive ribbons 260 may be embedded within polymer layer 250. The conductive ribbons 260 are directly in communication with the conductive portions 132 and / or 134. In some instances, a multi-filar conductor bundle 230 is electrically and mechanically coupled to the electronic component 112 by, e.g., soldering. In some instances, the conductive portions 132 and / or 134 comprise conductive ink (e.g., metallic nano-ink, such as copper,silver, gold, or aluminum nano-ink) that is deposited or printed directed over the conductive ribbons 260.

[0044] As described herein, electrical communication between the conductive members 230 and the conductive ribbons 260 can be established at the connection portion 114 of the flexible elongate member 106. By establishing electrical communication between the conductor bundle 230 and the conductive ribbons 260, the conductive portions 132, 134 can be in electrical communication with the electronic component 112.

[0045] In some aspects represented by Figure 1, the intravascular device 102 includes a locking section 118 and a retention section 120. To form locking section 118, a machining process is used to remove polymer layer 250 and conductive ribbons 260 in locking section 118 and to shape proximal core 220 in locking section 118 to the desired shape. As shown in Figure 1, locking section 118 includes a reduced diameter while retention section 120 has a diameter substantially similar to that of proximal core 220 in the connection portion 114. In some instances, because the machining process removes conductive ribbons in locking section 118, proximal ends of the conductive ribbons 260 would be exposed to moisture and / or liquids, such as blood, saline solutions, disinfectants, and / or enzyme cleaner solutions, an insulation layer 158 is formed over the proximal end portion of the connection portion 114 to insulate the exposed conductive ribbons 260.

[0046] In some aspects, a connector 314 provides electrical connectivity between the conductive portions 132, 134 and a patient interface monitor 304. The Patient Interface Monitor 304 may in some cases connect to a console or processing system 306, which includes or is in communication with a display 308.

[0047] The system 100 may be deployed in a catheterization laboratory having a control room. The processing system 306 may be located in the control room. Optionally, the processing system 306 may be located elsewhere, such as in the catheterization laboratory itself. The catheterization laboratory may include a sterile field while its associated control room may or may not be sterile depending on the procedure to be performed and / or on the health care facility. In some aspects, device 102 may be controlled from a remote location such as the control room, such that an operator is not required to be in close proximity to the patient.

[0048] The intraluminal device 102, PIM 304, and display 308 may be communicatively coupled directly or indirectly to the processing system 306. These elements may be communicatively coupled to the medical processing system 306 via a wired connection such as a standard copper multi-filar conductor bundle 230. The processing system 306 may becommunicatively coupled to one or more data networks, e.g., a TCP / IP-based local area network (LAN). In other aspects, different protocols may be utilized such as Synchronous Optical Networking (SONET). In some cases, the processing system 306 may be communicatively coupled to a wide area network (WAN).

[0049] The PIM 304 transfers the received signals to the processing system 306 where the information is processed and displayed (e.g., as physiology data in graphical, symbolic, or alphanumeric form) on the display 308. The console or processing system 306 can include a processor and a memory. The processing system 306 may be operable to facilitate the features of the intravascular sensing system 100 described herein. For example, the processor can execute computer readable instructions stored on the non-transitory tangible computer readable medium.

[0050] The PIM 304 facilitates communication of signals between the processing system 306 and the intraluminal device 102. The PIM 304 can be communicatively positioned between the processing system 306 and the intraluminal device 102. In some aspects, the PIM 304 performs preliminary processing of data prior to relaying the data to the processing system 306. In examples of such aspects, the PIM 304 performs amplification, filtering, and / or aggregating of the data. In an aspect, the PIM 304 also supplies high- and low-voltage DC power to support operation of the intraluminal device 102 via the conductive members 230.

[0051] A multi-filar cable or transmission line bundle 230 can include a plurality of conductors, including one, two, three, four, five, six, seven, or more conductors. In the example shown in Figure 1, the multi -filar conductor bundle 230 includes two straight portions 232 and 236, where the multi-filar conductor bundle 230 lies parallel to a longitudinal axis of the flexible elongate member 106, and a spiral portion 234, where the multi-filar conductor bundle 230 is wrapped around the exterior of the flexible elongate member 106 and then overcoated with an insulative and / or protective polymer 240. Communication, if any, along the multi-filar conductor bundle 230 may be through numerous methods or protocols, including serial, parallel, and otherwise, wherein one or more filars of the bundle 230 carry signals. One or more filars of the multi-filar conductor bundle 230 may also carry direct current (DC) power, alternating current (AC) power, or serve as a ground connection.

[0052] The display or monitor 308 may be a display device such as a computer monitor or other type of screen. The display or monitor 308 may be used to display selectable prompts, instructions, and visualizations of imaging data to a user. In some aspects, thedisplay 308 may be used to provide a procedure-specific workflow to a user to complete an intraluminal procedure.

[0053] It is noted that in some aspects, the proximal and / or distal core wire do not carry electrical signals, and in some aspects, proximal and / or distal core wire do not carry data signals (control signals, pressure signals, flow / echo signals). For example, the core wire could provide electrical ground, or could be electrically isolated from the other components.

[0054] Before continuing, it should be noted that the examples described above are provided for purposes of illustration, and are not intended to be limiting. Other devices and / or device configurations may be utilized to carry out the operations described herein.

[0055] Figure 2 is a side view of another type of intravascular device 102, according to aspects of the present disclosure. The intravascular device 102 can be an intravascular guidewire sized and shaped for positioning within a vessel of a patient. The intravascular device 102 can include an electronic component 112. For example, the electronic component 112 can be a pressure sensor configured to measure a pressure of blood flow within the vessel of the patient, or another type of sensor. Pressure data obtained by a pressure sensor may for example be used to calculate a physiological pressure ratio (e.g., FFR, iFR, Pd / Pa, or any other suitable pressure ratio). However, the device 102 may be used in any suitable anatomical structure or body lumen including a blood vessel, blood vessel lumen, an esophagus, eustachian tube, urethra, fallopian tube, intestine, colon, and / or any other suitable anatomical structure or body lumen.

[0056] The intravascular device 102 includes a flexible elongate member 106, such as a guidewire. The electronic component 112 is disposed at the distal portion 107 of the flexible elongate member 106. The electronic component 112 can be mounted at the distal portion 107 within a housing 280 in some aspects. A flexible tip coil 290 extends between the housing 280 and the distal end 108 (e.g., a solder ball). The flexible tip coil 290 and / or the distal end 108 can define the distal end (e.g., the distal-most end) of the intravascular device 102. The flexible tip coil 290 can be spiral wrapping / winding of a metal, metal alloy, and / or polymer. The flexible tip coil 290 can be any suitable any suitable length, such as 1 cm, 2 cm, 3 cm, and / or other values both larger and smaller. The connection portion 114 is disposed at the proximal portion of the flexible elongate member 106. The connection portion includes the conductive portions 132, 134, 136. In some aspects, the conductive portions 132, 134, 136 can be conductive ink that is printed and / or deposited around the flexible elongate member. In some aspects, the conductive portions 132, 134, 136 are conductive, metallic rings or bands that are positioned around the flexible elongate member.The locking section 118 and retention section 120 are disposed at the proximal portion of the flexible elongate member 106.

[0057] In some aspects, the intravascular device 102 comprises a distal subassembly 410 and a proximal subassembly 400 that are electrically and mechanically coupled, which provides for electrical communication between the electronic component 112 and the conductive portions 132, 134, 136. For example, pressure data obtained by the electronic component 112 (in this example, electronic component 112 is a pressure sensor) can be transmitted to the conductive portions 132, 134, 136. Control signals from a processing system in communication with the intravascular device 102 can be transmitted to the electronic component 112 via the conductive portions 132, 134, 136. The distal subassembly 410 can include the distal core 210. The distal subassembly 410 can also include the electronic component 112, the conductive members 230, and / or one or more layers of polymer / plastic 240 surrounding the conductive members 230 and the core 210. For example, the polymer / plastic layer(s) can protect the conductive members 230. The proximal subassembly 400 can include the proximal core 220. The proximal subassembly 400 can also include one or more polymer layers 250 surrounding the proximal core 220 and / or conductive ribbons 260 embedded within the one or more polymer layers 250. In some aspects, the proximal subassembly 400 and the distal subassembly 410 can be separately manufactured. During the assembly process for the intravascular device 102, the proximal subassembly 400 and the distal subassembly 410 can be electrically and mechanically joined together, and the joint can be enclosed in a hypotube 215. As used herein, flexible elongate member can refer to one or more components along the entire length of the intravascular device 102, one or more components of the proximal subassembly 400 (e.g., including the proximal core 220, etc.), and / or one or more components the distal subassembly 410 (e.g., including the distal core 210, etc.).

[0058] In various aspects, the intravascular device 102 can include one, two, three, or more core wires extending along its length. For example, a single core wire can extend substantially along the entire length of the flexible elongate member 106. In such aspects, a locking section 118 and a retention section 120 can be integrally formed at the proximal portion of the single core wire. The electronic component 112 can be secured at the distal portion of the single core wire. In other aspects, such as the aspect illustrated in Figure 2, the locking section 118 and the retention section 120 can be integrally formed at the proximal portion of the proximal core 220. The electronic component 112 can be secured at the distal portion of the distal core 210. The intravascular device 102 includes one or more conductivemembers 230 in communication with the electronic component 112. For example, the conductive members 230 can be one or more electrical wires that are directly in communication with the electronic component 112.

[0059] The intravascular device 102 includes one or more conductive ribbons 260 at the proximal portion of the flexible elongate member 106. The conductive ribbons 260 are embedded within polymer layer(s) 250. The conductive ribbons 260 are directly in communication with the conductive portions 132, 134, and / or 136. In some instances, the conductive members 230 are electrically and mechanically coupled to the electronic component 112 by, e.g., soldering, welding, terminals, clamps, conductive adhesive, or other appropriate methods. In some instances, the conductive portions 132, 134, and / or 136 comprise conductive ink (e.g., metallic nano-ink, such as silver or gold nano-ink) and / or resistive ink that is deposited or printed directed over the conductive ribbons 260. In an example, the resistive ink conducts electricity, but has a higher resistance or impedance than the conductive ink.

[0060] As described herein, electrical communication between the conductive members 230 and the conductive ribbons 260 can be established at the connection region 265 of the flexible elongate member 106. By establishing electrical communication between the conductive members 230 and the conductive ribbons 260, the conductive portions 132, 134, 136 can be in electrically communication with the electronic component 112.

[0061] In some instances, the machining process that forms locking section 118 may remove of the conductive ribbons 260, proximal ends of the conductive ribbons 260 would be exposed to moisture and / or liquids, such as blood, saline solutions, disinfectants, and / or enzyme cleaner solutions. In these cases, an insulation layer 158 can be formed over the proximal end portion of the connection portion 114 to insulate the exposed conductive ribbons 260.

[0062] Figure 3 is a diagrammatic cross-sectional view of an example sensor assembly 251, which may for example be included in the intravascular device 102 of Figure 1 or Figure 2, according to aspects of the present disclosure. More specifically, Figure 3 illustrates a sensor assembly 251 that includes a sensing component 112, a housing 280, and an acoustic matching layer 252. As indicated by the positions of the sensing component 112 and the housing 280 illustrated in Figure 1, the sensor assembly 251 may be included in a distal portion of the intravascular device 102 such that the surface 272 of the sensing component 112 faces distally.

[0063] As illustrated in Figure 3, the sensing component 112 is positioned within the housing 280 and includes a proximal surface 270, an opposite, distal surface 272, and a side surface 274. In some aspects, one or more of the proximal surface 270, the distal surface 272, or the side surface 274 may be coated in an insulating layer 276. The insulating layer 276 may be formed from parylene, which may be deposited on the one or more surfaces, for example. The insulating layer 276 may additionally or alternatively be formed from any other suitable insulating material. In some aspects, the insulating layer 276 may prevent a short (e.g., an electrical failure), which may otherwise be caused by contact between a conductive portion of the sensing component 112 and the housing 280, which may be formed with a metal. As used herein, references to the distal surface 272 encompass the insulating layer 276 in aspects where a distal end of the sensing component 112 is covered by the insulating layer 276, references to the proximal surface 270 encompass the insulating layer in aspects where a proximal end of the sensing component 112 is covered by the insulating layer 276, and references to the side surface 274 encompass the insulating layer in aspects where the side of the sensing component 112 is covered by the insulating layer 276 unless indicated otherwise.

[0064] In some aspects, the sensing component 112 may include a transducer element, such as an ultrasound transducer element on the distal surface 272 such that the transducer element faces distally and may be used by the sensing component 112 to obtain sensor data corresponding to a structure distal of the sensing component 112. The sensing component 112 may additionally or alternatively include a transducer element on the proximal surface 270 such that the transducer faces proximally and may be used to obtain sensor data corresponding to a structure proximal of the sensing component. A transducer element may additionally or alternatively be positioned on a side surface 274 (e.g., on a perimeter or circumference) of the sensing component 112 in some aspects. In some aspects, a transducer and its associated electrodes and electrical connection points may form the entire sensing component 112, such that all surfaces of the sensing component 112 comprise the transducer.

[0065] As further illustrated, the sensing component 112 is coupled to the multi -filar conductor bundle 230, and at least a portion (e.g., a distal portion) of the multi-filar conductor bundle 230 are extends through the housing 280. In some aspects, the multi-filar conductor bundle 230 and the sensing component 112 may be physically (e.g., mechanically) coupled. Further, one or more filars (e.g., conductive members) of the multi-filar conductor bundle 230 may electrically couple to (e.g., be in electrical communication) with the sensing component 112. In particular, one or more filars of the multi -filar conductor bundle 230 maycouple to an element, such as a transducer (e.g., an ultrasound transducer), of the sensing component 112 and may provide power, control signals, an electrical ground or signal return, and / or the like to the element. As described above, such an element may be positioned on the distal surface 272 of the sensor. In that regard, in some aspects, one or more filars of the multi-filar conductor bundle 230 may extend through a cutout or hole in the sensing component 112 (e.g., in at least the proximal surface 270) to establish electrical communication with an element on the distal surface 272 of the sensor. Filars may additionally or alternatively wrap around the side surface 274 to establish electrical communication with the element on the distal surface 272. Moreover, in some aspects, filars of the multi-filar conductor bundle 230 may terminate at and / or electrically couple to the proximal surface 270 (e.g., to an element on the proximal surface 270) of the sensing component 112. Further, in some aspects, a subset of the filars of the multi-filar conductor bundle 230 may extend to the distal surface 272 and / or electrically couple to an element at the distal surface 272, while a different subset of the filars may electrically couple to an element at the proximal surface 270, for example.

[0066] In some aspects, the multi -filar conductor bundle 230 may be coated in the insulating layer 276. In some aspects, for example, the multi-filar conductor bundle 230 and the sensing component 112 may be coupled together in a sub-assembly before being positioned in the housing 280. In such aspects, the insulating layer 276 may be applied (e.g., coated and / or deposited) onto the entire sub-assembly, resulting in an insulating layer 276 on both the sensing component 112 and the multi -filar conductor bundle 230.

[0067] In some aspects, the acoustic matching layer 252 may be positioned on (e.g., over) the distal surface 272 of the sensing component 112. In particular, the acoustic matching layer 252 may be disposed directly on the sensing component 112, or the acoustic matching layer 252 may be disposed on the insulating layer 276 coating the sensing component 112. Further, the acoustic matching layer 252 may be disposed on a transducer element (e.g., an ultrasound transducer element) positioned on the sensing component (e.g., the distal surface 272) and / or at least a portion of a conductive filar of the multi-filar conductor bundle 230 that is in communication with the transducer element, such as a filar extending through a hole or along a side of the sensing component 112. To that end, the acoustic matching layer 252 may contact and / or at least partially surround the portion of the conductive filar and / or the transducer element. Moreover, the acoustic matching layer 252 may provide acoustic matching to the sensing component 112 (e.g., to an ultrasound transducer of the sensing component 112). For instance, the acoustic matching layer 252 may minimize acousticimpedance mismatch between the ultrasound transducer and a sensed medium, such as a fluid and / or a lumen that the intravascular device 102 is positioned within. In that regard, the acoustic matching layer 252 may be formed from any suitable material, such as a polymer or an adhesive, to provide acoustic matching with the sensing component 112. The portion of the acoustic matching layer 252 positioned on the distal surface 272 may include and / or be formed from the same material as a portion of the acoustic matching layer positioned on the side surface 274 and / or the proximal surface 270. Further, the acoustic matching layer 252 may be applied to the sensing component 112 before or after the sensing component 112 is positioned within the housing 280 during assembly of the sensor assembly 251. In this regard, the portion of the acoustic matching layer 252 positioned on the distal surface 272 and the portion of the acoustic matching layer positioned on the side surface 274 and / or the proximal surface 270 may be included in the sensor assembly 251 in the same or different steps. Further, in addition to the one or more materials the acoustic matching layer 252 is formed from, the acoustic matching layer 252 may provide acoustic matching with the sensing component 112 via one or more dimensions of the acoustic matching layer 252.

[0068] In some aspects, the sensor assembly 251 may include an atraumatic tip, such as the distal tip 108 illustrated in Figure 1. In some aspects, the distal tip 108 may include the same material as the acoustic matching layer 252. In some aspects, the distal tip may include a different material than the acoustic matching layer 252. Additionally or alternatively the distal tip 108 may be formed from one or more layers of materials. The layers may include different materials and / or different configurations (e.g., shape and / or profile, thickness, and / or the like). Further, the distal tip 108 may be arranged to cover the distal surface 272 of the sensing component 112. In some aspects, the distal tip 108 may also cover a distal end 272 of the housing 280. Moreover, while the distal tip 108 is illustrated as having a domed shape, aspects are not limited thereto. In this regard, the distal tip 108 may include a flattened profile or any suitable shape. In some aspects, the entire sensing component 112 may be positioned within (e.g., surrounded by the continuous surface of) the housing 280.

[0069] In some aspects, the multi-filar conductor cable 230 may be replaced with coated conductive traces, as described below.

[0070] Figure 4 is a schematic view of an intravascular device 102 (e.g., a flow-sensing guidewire 350) during measurement of a flow velocity 380 inside a blood vessel 320 with blood vessel walls 340, according to aspects of the present disclosure. In the example shown in Figure 4, the sensor 112 (e.g., an ultrasound transducer 360) at the tip of the flexibleelongate member is shown to emit ultrasound waves 370 that are backscattered as reflections 375 by flowing cells 390 in the blood and sensed by the transducer 360.

[0071] In the example shown in Figure 4, because the blood cells 390 are flowing away from the sensor 112, the backscattered reflections 375 have a longer wavelength and lower frequency than the ultrasound waves 370, due to the Doppler effect. If the blood cells 390 were flowing toward the sensor 112, then the backscattered reflections 375 would have a shorter wavelength and higher frequency than the ultrasound waves 370.

[0072] Figure 5 is a diagrammatic cross-sectional view of an intraluminal (e.g., intravascular) sensing device 102 that includes a flexible elongate member 106, and a flow sensor 112 located proximal of the tip coil 290, according to aspects of the present disclosure. The flow sensor 112 may be at least partially contained within a flow sensor housing 280. A coil 290 is disposed distal of the flow sensor housing 280, and an atraumatic tip 108 is disposed at the distal end of the coil 290. The flow sensor housing 280 may at least partially enclose a flow sensor mount 412, to which the flow sensor 112 is attached. At a proximal end of the flexible elongate member 106 is a connection portion 114 comprising a plurality of conductive portions 432, such as conductive bands. In an example, the flow sensor 112 may be operated by two conductor paths, such as two conductive wires or filars, or one conductive wire or filar plus a conductive core wire. Thus, two conductive bands 432 may be electrically connected to the flow sensor 112.

[0073] In an example, the flow sensor 112 may be an intravascular blood flow sensor, and may comprise a single ultrasound transducer element. In an example, intravascular blood flow data obtained by the flow sensor 112 can be or include blood flow velocity (e.g., magnitude and direction of blood flow), blood flow volume, and / or blood temperature data. In some instances, the blood flow data is not intravascular image data (e.g., not an IVUS or OCT image), although in other instances, the blood flow data may be or include an image. In some aspects, the sensor mount and / or the sensor housing are not rotated by a motor-driven drive shaft or a drive cable (as in a rotational intravascular imaging device).

[0074] The flow sensor 112 is also surrounded at least partially by a low-acoustic- impedance material 510. The low-acoustic impedance material causes ultrasound waves to refract (e.g., bend) away from the vessel wall and toward the longitudinal axis of the vessel, as described in detail below.

[0075] Figure 6 is a side cross-sectional view of a flow sensor mount 412, according to aspects of the present disclosure. The sensor mount 412 includes a sensor mount body 610 (which may for example be fabricated from a metallic, dielectric, or polymer material), asensor cavity 620, a filar lumen 630, a core wire recess 640, and a shaping ribbon attachment point 650. The sensor cavity 620 includes an angled wall 660 (e.g., situated at an angle of 30 degrees, 45 degrees, 60 degrees, etc.), onto which the sensor will be mounted. The angled wall 660 permits ultrasound energy emitted by the sensor, as well as echoes received by the sensor, to be partially aligned with the longitudinal axis of the blood vessel or other body lumen. In some cases, the angled wall 660 may be replaced with a stepped wall (e.g., staircase-shaped), especially in cases where manufacturing processes do not allow for a continuously smooth angled surface.

[0076] Figure 7 is a side cross-sectional view of the flow sensor mount 412 of Figure 6, according to aspects of the present disclosure. Visible are the body 610, sensor cavity 620, filar lumen 630, core wire recess 640, shaping ribbon attachment point 650, and angled wall 660. In the example shown in Figure 7, a flow sensor 112 and acoustic backing material 710 have been attached (e.g., with an adhesive) to the angled wall 660. The flow sensor 112 is operated by two wires or filars 720, which pass through the filar lumen 630.

[0077] Figure 8 is a side cross-sectional view of a flow sensor housing 280, according to aspects of the present disclosure. The flow sensor housing 280 may for example be a tube 800 that includes a sidewall 810, where the sidewall 810 defines a sensor mount lumen 820, with a sensor aperture 830 defined by a cutout (e.g., a rectangular laser cutout) of the sidewall 810 of the tube 810. The sensor mount 412 of Figures 6 and 7 can be fitted inside the sensor housing 280, as shown below.

[0078] Figure 9 is a side cross-sectional view of the sensor mount 412 of Figures 6 and 7 positioned inside the sensor housing 280 of Figure 8, according to aspects of the present disclosure. Visible are the sensor 112, sensor mount body 610, sensor cavity 620, filar lumen 630, shaping ribbon attachment point 650, angled wall 660, acoustic backing material 710, wires or filars 720, housing sidewall 810, and sensor aperture 830. Within the housing 280, the core wire recess 640 now defines a core wire lumen 940, as well as an open space 920 that may for example be filled with adhesive. In the example shown in Figure 9, both the sensor cavity 620 of the sensor mount 412 and the sensor aperture 830 of the sensor housing 280 have been filled with a low-acoustic-impedance material or acoustic window material 910.

[0079] A traditional flow sensor may be covered by an acoustic matching layer, with an acoustic impedance Z (e.g., 15 MegaRayls or MRayl) that falls roughly halfway between the high acoustic index of the sensor itself (e.g., 30 MRayl) and the acoustic index of blood (e.g., 1.7 MRayl). By contrast, the low-acoustic-impedance material 910 (e.g., a polymer such asethyl vinyl acetate, low-density polyethylene, porous polymethyl methacylate, or softer materials such as silicone or a silicone-based adhesive) has an acoustic impedance lower than that of blood. This causes an index mismatch where the material contacts the blood, which in turn causes sound waves to refract (e.g., bend) at the interface, as described below.

[0080] It is noted that one or more adhesives may be used between the sensor 112 and the backing material 710, between the backing material 710 and the sensor mount body 610 or angled surface 660, within the filar lumen 630, between the shaping ribbon attachment point 650 and the shaping ribbon 1010 (see Figure 10), between the sensor mount body 610 and the distal core wire 210, coil 290, polymer layer 240, and / or sensor housing 280 (see Figure 10), or other components as necessitated by the design. In some aspects, the low-acoustic- impedance material 910 may be or include an adhesive.

[0081] Figure 10 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel 1000, according to aspects of the present disclosure. The intraluminal device includes the sensor mount 412 positioned inside the sensor housing 280. Visible are the sensor 112, acoustic backing material 710, wires or filars 720, and low- acoustic-impedance material 910. Also visible in Figure 10 are the distal core wire 210, polymer j acker 240, coil 290, and shaping ribbon 1010.

[0082] The blood vessel 1000 includes a vessel wall 1020 defining a vessel lumen filled with blood 1030. The vessel lumen 1025 has a longitudinal axis 1040. Generally speaking, the blood 1030 in the lumen 1025 travels along the direction of the longitudinal axis 1040 (e.g., towards the intraluminal device or away from the intraluminal device). Thus, in order to take Doppler measurements of the blood velocity, it is desirable to emit ultrasound waves (and receive ultrasound echoes) that are traveling substantially in the direction of the longitudinal axis 1040 (e.g., more longitudinal than transverse, less than 45 degrees relative to longitudinal axis 1040).

[0083] The sensor 112 emits ultrasound waves whose centerline 1050 is substantially perpendicular to the surface of the sensor 112. Thus, if the sensor is mounted at (for example) a 45 -degree angle, then the centerline 1050 will form an angle ai with the vertical of approximately 45 degrees. Vertical can refer to a radial axis of the guidewire that exits through the sensor aperture 830. The sensor or transducer 112 has an acoustic impedance / transducer, which may for example be around 30 MRayls for a PZT transducer, and emits orthogonally into the low-acoustic-impedance material 910, which may have an acoustic impedance Zi of less than 1.7 MRayls. For example, depending on the composition of thelow-acoustic-impedance material 910, Zi may have a value of approximately 0.0004 MRayls (for air), approximately 0.9 MRayls (for alcohol), approximately 1.0 MRayls (for Siltrust RTV-112 polymer), approximately 1.2 MRayls (for Siltrust RTV- 11 polymer), approximately 1.3 MRayls (e.g., for fat or a fat-like material), approximately 1.5 MRayls (for water), approximately 1.6 MRayls (for certain grades of polyurethane), or other values both larger and smaller. It is noted that in some cases, porous and / or low-durometer versions of materials may have smaller acoustic impedance than their solid or high-durometer counterparts.

[0084] Because of the orthogonality of the ultrasound waves leaving the sensor 112, the ultrasound waves do not substantially refract at the interface between the sensor 112 and the low-acoustic-impedance material 910. However, the blood 1030 has an acoustic impedance Zbiood of approximately 1.7 MRayls, which is larger than Zi. Because the centerline 1050 strikes the blood 1030 at a non-orthogonal angle ai, the refraction mismatch between Zi and Zbiood causes the ultrasound waves to refract (e.g., bend), such that the refracted ultrasound wave centerline 1060 forms an angle Pi with the vertical, where Pi is larger a than ai and thus closer to the direction of the longitudinal axis 1040 of the blood vessel 1000 and blood vessel lumen 1025. In an example, Pi may also form an acute or oblique angle (e.g., a nonzero angle less than 90 degrees, such as less than 45 degrees) with respect to the longitudinal axis 1070 of the core wire 210. Thus, the acoustically refracted flow sensor of the present disclosure has enabled a flow sensor 112 located proximal of the coil 290 to capture Doppler flow information in a direction substantially parallel to the direction of flow. For example, relative to the longitudinal axis 1040, angle Pi can be between 1 degree and 45 degrees, between 1 degree and 30 degrees, between 1 degree and 15 degrees, including values such as 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, and / or other values both larger and smaller.. The angle Pi can serve as an input to the processing system 306 (see Figure 1) in interpreting Doppler ultrasound echoes to determine blood flow velocity along the longitudinal axis 1040. In addition to the longitudinal axis 1040 of the blood vessel 1000, the longitudinal axis 1070 of the core wire 210 is also visible in Figure 10. In many cases, the longitudinal axis 1070 of the core wire represents a longitudinal axis for the entire intraluminal device 102, and may be considered parallel or approximately parallel to the longitudinal axis 1040 of the blood vessel 1000. Thus, for example if angle Pi is 20 degrees with respect to the longitudinal axis 1040, then it may be considered to be 20 degrees with respect to the longitudinal axis 1070 as well.

[0085] In the example shown in Figure 10, the angles ai and Pi are labeled relative to the radial axis 1080. In general, the angles ai and Pi can be described with respect to the longitudinal axis 1040, the longitudinal axis 1070 and / or the radial axis 1080. The longitudinal axes 1040, 1070 and the radial axis 1080 are perpendicular to one another. When the angles ai and Pi are described with respect to the longitudinal axis 1070, the angle Pi is smaller than the angle ai. When the angles ai and Pi and are described with respect to the radial axis 1080, the angle Pi is larger than the angle ai.

[0086] It is noted that because transducer » Zi, there may be substantial reflection losses at the interface between the sensor 112 and the low-acoustic-impedance material 910. Such reflection losses may, in some cases, be compensated for by increasing the transmit power of the sensor or transducer 112, or may be reduced through the addition of an impedance matching layer, as described below in Figure 12.

[0087] In general, aspects of the present disclosure are illustrated with the flow sensor is angled in a more forward and / or distal direction and the acoustic energy being transmitted by the flow sensor in a generally more forward and / or distal direction (and acoustic reflections are received from a more backward and / or proximal direction). In some aspects, the sensor mount can be configured in a mirror image of or flipped from what is shown in Fig. 10. In such aspects, the flow sensor is angled in a more backward and / or proximal direction and the acoustic energy being transmitted by the flow sensor in a generally more backward and / or proximal direction (and acoustic reflections are received from a more forward and / or distal direction).

[0088] Figure 11 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel 1000, according to aspects of the present disclosure. In the example shown in Figure 11, the low-acoustic-impedance material 910, with acoustic impedance Zi, has been overlaid with a second low-acoustic-impedance material or acoustic window material 1110, with acoustic impedance Z2, where Zi < Z2 < Zbiood « transducer. With this arrangement, the centerline 1050 of the acoustic waves emitted (and echoes received) by the sensor or transducer 112 forms an angle 0.2 with the vertical, but refracts (e.g., bends) at the interface between material 910 and material 1110, due to the refraction mismatch between Zi and Z2. Thus, the first refracted centerline 1060 forms an angle P2 with the vertical. The first refracted centerline 1060 then refracts again on contact with the blood 1030, such that a second refracted centerline 1160 forms an angle 72 with the vertical, where a.2 < P2 < 72. Thus, the acoustically refracted flow sensor of the present disclosure hasenabled a flow sensor 112 located proximal of the coil 290 to capture Doppler flow information in a direction even more parallel to the direction of blood flow.

[0089] Figure 12 is a side cross-sectional view a distal portion of an intraluminal device 102 positioned inside a blood vessel 1000, according to aspects of the present disclosure. In the example shown in Figure 12, to limit reflection losses at the interface between the sensor or transducer 112 and the low-acoustic-impedance material 910, an impedance matching layer 1210 has been added on top of the sensor or transducer 112. The impedance matching layer 1210 may for example have an acoustic impedance Z3 that falls midway between the high acoustic impedance / transducer of the sensor or transducer 112 and the low acoustic impedance Z1 of the low-acoustic-impedance material. In an example, the impedance matching layer may be made of a glass or glass-like material, microparticle-doped quartz, or polymer with an acoustic impedance of around 16 MRayls. As will be appreciated by a person of ordinary skill in the art, depending on the implementation, the impedance matching layer 1210 may include multiple sub-layers, each with its own acoustic impedance, in order to step down gradually from the high impedance transducer to the low impedance Zi.

[0090] Figure 13 is a side cross-sectional view an alternative aspect wherein the sensor 112 is mounted directly in the sensor housing 280 without a sensor mount, according to aspects of the present disclosure. Visible are the sensor housing 280, housing tube sidewall 810, sensor 112, backing material 710, wires or filars 720, sensor mount lumen 820, and low- acoustic-impedance material 910. In the example shown in Figure 13, the sensor 112 is attached to the sidewall 810 by an adhesive 1310, and is supported at the appropriate angle (e.g., 45 degrees from vertical) by the adhesive 1310 and / or the wires or filars 720. This arrangement requires fewer components than the aspects shown in Figures 9-12, and so may be advantageous under some circumstances.

[0091] Figure 14 is a schematic diagram of a processor circuit 1450, according to aspects of the present disclosure. The processor circuit 1450 may be implemented in the intravascular sensing system 100 (e.g., the processing system 306) or other devices or workstations (e.g., third-party workstations, network routers, etc.), or on a cloud processor or other remote processing unit, as necessary to implement the method. As shown, the processor circuit 1450 may include a processor 1460, a memory 1464, and a communication module 1468. These elements may be in direct or indirect communication with each other, for example via one or more buses.

[0092] The processor 1460 may include a central processing unit (CPU), a digital signal processor (DSP), an ASIC, a controller, or any combination of general-purpose computingdevices, reduced instruction set computing (RISC) devices, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other related logic devices, including mechanical and quantum computers. The processor 1460 may also comprise another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 1460 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0093] The memory 1464 may include a cache memory (e.g., a cache memory of the processor 1460), random access memory (RAM), magnetoresistive RAM (MRAM), readonly memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an aspect, the memory 1464 includes a non-transitory computer-readable medium. The memory 1464 may store instructions 1466. The instructions 1466 may include instructions that, when executed by the processor 1460, cause the processor 1460 to perform the operations described herein. Instructions 1466 may also be referred to as code. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

[0094] The communication module 1468 can include any electronic circuitry and / or logic circuitry to facilitate direct or indirect communication of data between the processor circuit 1450, and other processors or devices. In that regard, the communication module 1468 can be an input / output (I / O) device. In some instances, the communication module 1468 facilitates direct or indirect communication between various elements of the processor circuit 1450 and / or the intravascular measurement system 100. The communication module 1468 may communicate within the processor circuit 1450 through numerous methods or protocols. Serial communication protocols may include but are not limited to United States Serial Protocol Interface (US SPI), Inter-Integrated Circuit (I2C), Recommended Standard 232 (RS- 232), RS-485, Controller Area Network (CAN), Ethernet, Aeronautical Radio, Incorporated 429 (ARINC 429), MODBUS, Military Standard 1553 (MIL-STD-1553), or any other suitable method or protocol. Parallel protocols include but are not limited to IndustryStandard Architecture (ISA), Advanced Technology Attachment (ATA), Small Computer System Interface (SCSI), Peripheral Component Interconnect (PCI), Institute of Electrical and Electronics Engineers 488 (IEEE-488), IEEE-1284, and other suitable protocols. Where appropriate, serial and parallel communications may be bridged by a Universal Asynchronous Receiver Transmitter (UART), Universal Synchronous Receiver Transmitter (USART), or other appropriate subsystem.

[0095] External communication (including but not limited to software updates, firmware updates, preset sharing between the processor and central server, or readings from the intraluminal device) may be accomplished using any suitable wireless or wired communication technology, such as a cable interface such as a universal serial bus (USB), micro USB, Lightning, or FireWire interface, Bluetooth, Wi-Fi, ZigBee, Li-Fi, or cellular data connections such as 2G / GSM (global system for mobiles) , 3G / UMTS (universal mobile telecommunications system), 4G, long term evolution (LTE), WiMax, or 5G. For example, a Bluetooth Low Energy (BLE) radio can be used to establish connectivity with a cloud service, for transmission of data, and for receipt of software patches. The controller may be configured to communicate with a remote server, or a local device such as a laptop, tablet, or handheld device, or may include a display capable of showing status variables and other information. Information may also be transferred on physical media such as a USB flash drive or memory stick.

[0096] Figure 15 is a perspective view of the sensor mount body 610 of an example sensor mount 412, according to aspects of the present disclosure. The body 610 has a proximal portion 1510 terminating in a proximal end, and a distal portion 1520 terminating in a distal end. The distal portion 1520 includes the angled wall 660. In some aspects, the sensor mount body 610 may include one or more lumens or cutouts partially or fully through the sensor mount body 610 for carrying electrical wires, as shown for example in Figure 7, and / or to accommodate the distal core wire 210, as shown for example in Figure 10. For example, the distal core wire 210 can extend distally past the sensor mount body 610. In other aspects, a proximal end 1510 of the body 610 may attach to the distal end of the distal core wire 210.

[0097] Figure 16 is a perspective view of the sensor mount body 610 of Figure 15, with a flow sensor 112 (e.g., an ultrasound transducer element) coupled thereto, according to aspects of the present disclosure. A back surface the flow sensor 112 is positioned on, attached to, and / or otherwise coupled to the angled wall 660 on the distal portion of the sensor mount body 610. In some aspects, the flow sensor 112 may be mounted over a lumen within thesensor mount body 610, to accommodate electrical wires that operate the flow sensor, as shown for example in Figure 7.

[0098] Figure 17 is a perspective view of the sensor mount body 610 and flow sensor 112 of Figure 16, with a low-acoustic-impedance acoustic window material 910 positioned over a front surface of the sensor 112, according to aspects of the present disclosure. The acoustic window material 910 can partially and / or completely cover the front surface of the sensor 112, the side surfaces of the sensor 112, and / or the back surface of the sensor 112. When ultrasound waves are emitted from the front surface of the flow sensor 112, the low- acoustic-impedance material 910 can bend the waves in a more longitudinal (e.g., distal) direction, as shown for example in Figure 10. Depending on the implementation, the flow sensor 112 may be of different dimensions than shown in Figure 17.

[0099] Figure 18 is a perspective view of the sensor mount body 610, flow sensor 112, and low-acoustic-impedance acoustic window material 910 of Figure 17, with an additional layer of a second low-acoustic-impedance material 1110 coated over the first low-acoustic- impedance acoustic window material 910, according to aspects of the present disclosure. In some aspects, the second low-acoustic-impedance material 1110 can bend ultrasound waves emitted by the flow sensor 112 in an even more longitudinal (e.g., distal) direction, as shown for example in Figure 11.

[0100] Figure 19 is a perspective view of an example sensor housing 280, according to aspects of the present disclosure. The sensor housing 280 includes a sensor aperture 830 and a sensor mount lumen 820 to accommodate the sensor mount, sensor, and low-acoustic- impedance materials shown in Figure 18, as shown below.

[0101] Figure 20 is a perspective view of an assembled example sensor mount assembly 2000, according to aspects of the present disclosure. The sensor mount assembly 2000 includes the sensor housing 280, sensor mount body 610, sensor 112, first low-acoustic- impedance material 910, and second low-acoustic-impedance material 1110. In some aspects, the example sensor mount assembly 2000 may be the same as, similar to, or analogous to the structure shown in Figure 11.

[0102] It is understood that the structure shown in Figures 15-20 are exemplary and not necessarily representative of a particular manufacturing step or process. The order of manufacturing steps can vary. For example, it is possible to put the mount body 610 with the sensor 112 (as shown in Figure 16) inside a housing (as shown in Figure 19) through a proximal or distal opening of the lumen 820, and then one or multiple acoustic impedance materials can be added inside the housing (e.g., through the sensor aperture 830).Alternatively, the mount body 610 with the sensor 112 (as shown in Figure 16) can be coated with the low-acoustic-impedance material 910, all of which is then put inside the housing through a proximal or distal opening of the lumen 820. Then the second acoustic impedance material 1110 can be added on top of the first acoustic impedance material 910 (e.g., through the sensor aperture 830). Still other steps, processes, and methods are possible, and fall within the scope of the present disclosure.

[0103] Figure 21 is a side view of an assembled example sensor mount assembly 2000, according to aspects of the present disclosure. Visible are the sensor housing 280, sensor mount body 610, and second low-acoustic-impedance material 1110. In the example shown in Figure 21, the outer profile of material 1110 is aligned with the outer profile of the housing 280 to form a smooth, continuous surface. In other aspects, the surface of material 1110 may not necessarily align with the surface of the housing 280. In some aspects, the example sensor mount assembly 2000 may be the same as, similar to, or analogous to the structure shown in Figure 11.

[0104] Figure 22 is a top view of an assembled example sensor mount assembly 2000, according to aspects of the present disclosure. Visible are the sensor housing 280, sensor mount body 610, sensor 112, and second low-acoustic-impedance material 1110. In some aspects, the example sensor mount assembly 2000 may be the same as, similar to, or analogous to the structure shown in Figure 11.

[0105] Figure 23 is a side cross-sectional view, along cut line 23-23 of Figure 22, of an assembled example sensor mount assembly 2000, according to aspects of the present disclosure. Visible are the sensor housing 280, sensor mount body 610, sensor 112, first low- acoustic-impedance material 910, and second low-acoustic-impedance material 1110. The sensor 112 is positioned on the angled wall 660 at the distal portion 1520 of the mount body 610, such that it can send acoustic waves and receive acoustic echoes through the sensor aperture 830. The proximal portion 1510 of the sensor mount body 610 projects proximal of a proximal portion 2310 of the sensor housing 280. In the example shown in Figure 23, the outer profile of material 1110 is aligned with the outer profile of the housing 280 to form a smooth, continuous surface. In other aspects, the surface of material 1110 may not necessarily align with the surface of the housing 280. In some aspects, the example sensor mount assembly 2000 may be the same as, similar to, or analogous to the structure shown in Figure 11.

[0106] Accordingly, it can be seen that the acoustically refracted flow sensor of the present disclosure advantageously permits a flow sensor located proximal of the guidewire tip(and in some cases, proximal of the tip coil), looking outward at an angle through a radial aperture, to emit and receive Doppler ultrasound signals in a direction substantially parallel to the longitudinal axis of a blood vessel. It is understood that the acoustically refracted flow sensor may employ different materials, sizes, geometries, angles, mounts, housings, or other components than those described herein, while performing the same or a similar function. The principles and technologies described herein can be applied to intraluminal guidewires bot body lumens other than blood vessels, as well as to intraluminal catheters.

[0107] One general aspect includes an apparatus which includes an intravascular guidewire configured to be positioned within a blood vessel of a patient, where the intravascular guidewire may include: a distal tip; a longitudinal axis; an intravascular sensor positioned proximal of the distal tip and oriented at a first angle with respect to the longitudinal axis of the guidewire, where the intravascular sensor is configured to obtain intravascular data while the intravascular guidewire is positioned within the blood vessel; and a window material at least partially surrounding the intravascular sensor that may include a first impedance less than an impedance of blood in the blood vessel. Other aspects include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0108] Implementations may include one or more of the following features. In some aspects, the intravascular sensor may include an intravascular blood flow sensor. In some aspects, the intravascular blood flow sensor may include an ultrasound transducer, where the window material may include a first acoustic material, where the first impedance may include a first acoustic impedance, where the impedance of blood may include an acoustic impedance of blood. In some aspects, the first acoustic material forms an outer surface of a portion of the intravascular guidewire such that the first acoustic material is configured to be in contact with the blood. In some aspects, the ultrasound transducer is configured to emit ultrasound energy, where the first acoustic material may include an interface at the blood, where the ultrasound energy is refracted at the interface, such that the ultrasound energy is transmitted from the intravascular guidewire at a second, smaller angle with respect to the longitudinal axis. Ultrasound echoes returning along the second, smaller angle are refracted at the interface, such that the ultrasound echoes are received at the intravascular flow sensor along the first angle. In some aspects, the second, smaller angle is between 1 degree and 45 degrees relative to the longitudinal axis. In some aspects, the second, smaller angle is closer than the first angle to a direction of blood flow within the blood vessel. In some aspects, the second acoustic material may include a second acoustic impedance in between the first acousticimpedance and the acoustic impedance of the blood. In some aspects, the third acoustic material may include a third acoustic impedance in between the first acoustic impedance and an acoustic impedance of the intravascular sensor. In some aspects, the intravascular guidewire further may include an acoustic backing material positioned behind the intravascular sensor. In some aspects, the intravascular guidewire further may include a sensor housing at a distal portion of the guidewire, where the intravascular sensor and the first acoustic material are positioned inside the sensor housing. In some aspects, the intravascular guidewire further may include a sensor mount positioned inside the sensor housing, where the intravascular sensor is mounted on the sensor mount at the first angle. In some aspects, the intravascular guidewire further may include a flexible tip coil terminating at the distal tip, where the intravascular sensor is positioned proximal of the flexible tip coil.

[0109] One general aspect includes an apparatus which includes an intravascular guidewire configured to be positioned within a blood vessel of a patient, where the intravascular guidewire may include: a longitudinal axis; a distal tip coil; a sensor housing proximal of the distal tip coil; an intravascular flow sensor positioned within the sensor housing and configured to obtain intravascular flow data while the intravascular guidewire is positioned within the blood vessel, where the intravascular flow sensor is oriented at an oblique first angle with respect to the longitudinal axis, where the intravascular flow sensor may include an ultrasound transducer that does not obtain an intravascular image of the blood vessel; and an acoustic material at least partially surrounding the intravascular flow sensor that may include an acoustic impedance less than an acoustic impedance of blood in the blood vessel, where ultrasound energy emitted by the ultrasound transducer through the acoustic material is refracted at an interface between the acoustic material and the blood to a smaller second angle with respect to the longitudinal axis.

[0110] One general aspect includes an apparatus which includes an intravascular guidewire configured to be positioned within a blood vessel of a patient. The intravascular guidewire comprises a distal tip coil and an intravascular flow sensor positioned proximal of the distal tip coil. The intravascular flow sensor is configured to obtain intravascular flow data while the intravascular guidewire is positioned within the blood vessel. The intravascular flow sensor comprises an ultrasound transducer that does not obtain an intravascular image of the blood vessel.

[0111] Implementations may include one or more of the following features. The intravascular flow sensor is a single ultrasound transducer element. The intravascular guidewire further comprising a sensor housing proximal of the distal tip coil. Theintravascular flow sensor positioned within the sensor housing. The intravascular guidewire further comprises a sensor mount positioned inside the sensor housing. The intravascular flow sensor is mounted on the sensor mount at an oblique angle.

[0112] The logical operations making up the aspects of the technology described herein are referred to variously as operations, steps, objects, elements, components, or modules. Furthermore, it should be understood that these may be arranged or performed in any order, unless explicitly claimed otherwise or a specific order is inherently necessitated by the claim language. It should further be understood that the described technology may be employed in single-use and multi-use electrical and electronic devices for medical or nonmedical use.

[0113] All directional references e.g., upper, lower, inner, outer, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, proximal, and distal are only used for identification purposes to aid the reader’s understanding of the claimed subject matter, and do not create limitations, particularly as to the position, orientation, or use of the acoustically refracted flow sensor . Connection references, e.g., attached, coupled, connected, and joined are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily imply that two elements are directly connected and in fixed relation to each other. The term “or” shall be interpreted to mean “and / or” rather than “exclusive or.” The word "comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Unless otherwise noted in the claims, stated values shall be interpreted as illustrative only and shall not be taken to be limiting.

[0114] The above specification, examples and data provide a complete description of the structure and use of exemplary aspects of the acoustically refracted flow sensor as defined in the claims. Although various aspects of the claimed subject matter have been described above with a certain degree of particularity, or with reference to one or more individual aspects, those skilled in the art could make numerous alterations to the disclosed aspects without departing from the spirit or scope of the claimed subject matter.

[0115] Still other aspects are contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular aspects and not limiting. Changes in detail or structure may be made without departing from the basic elements of the subject matter as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. An apparatus, comprising: an intravascular guidewire configured to be positioned within a blood vessel of a patient, wherein the intravascular guidewire comprises: a distal tip; a longitudinal axis; an intravascular sensor positioned proximal of the distal tip and oriented at a first angle with respect to the longitudinal axis of the guidewire, wherein the intravascular sensor is configured to obtain intravascular data while the intravascular guidewire is positioned within the blood vessel; and a window material at least partially surrounding the intravascular sensor and comprising a first impedance less than an impedance of blood in the blood vessel.

2. The apparatus of claim 1, wherein the intravascular sensor comprises an intravascular blood flow sensor.

3. The apparatus of claim 2, wherein the intravascular blood flow sensor comprises an ultrasound transducer, wherein the window material comprises a first acoustic material, wherein the first impedance comprises a first acoustic impedance, wherein the impedance of blood comprises an acoustic impedance of blood.

4. The apparatus of claim 3, wherein the first acoustic material forms an outer surface of a portion of the intravascular guidewire such that the first acoustic material is configured to be in contact with the blood.

5. The apparatus of claim 4, wherein the ultrasound transducer is configured to emit ultrasound energy, wherein the first acoustic material comprises an interface at the blood,wherein the ultrasound energy is refracted at the interface, such that the ultrasound energy is transmitted from the intravascular guidewire at a second, smaller angle with respect to the longitudinal axis .

6. The apparatus of claim 5, wherein ultrasound echoes returning along the second, smaller angle are refracted at the interface, such that the ultrasound echoes are received at the intravascular flow sensor along the first angle.

7. The apparatus of claim 5, wherein the second, smaller angle is between 1 degree and 45 degrees relative to the longitudinal axis.

8. The apparatus of claim 5, wherein the second, smaller angle is closer than the first angle to a direction of blood flow within the blood vessel.

9. The apparatus of claim 3, further comprising a second acoustic material positioned between the first acoustic material and the blood, wherein the second acoustic material comprises a second acoustic impedance in between the first acoustic impedance and the acoustic impedance of the blood.

10. The apparatus of claim 3, further comprising a third acoustic material positioned between the intravascular sensor and the first acoustic material, wherein the third acoustic material comprises a third acoustic impedance in between the first acoustic impedance and an acoustic impedance of the intravascular sensor.

11. The apparatus of claim 3, wherein the intravascular guidewire further comprises an acoustic backing material positioned behind the intravascular sensor.

12. The apparatus of claim 2, wherein the intravascular guidewire further comprises a sensor housing at a distal portion of the guidewire, wherein the intravascular sensor and the first acoustic material are positioned inside the sensor housing.

13. The apparatus of claim 12, wherein the intravascular guidewire further comprises a sensor mount positioned inside the sensor housing, wherein the intravascular sensor is mounted on the sensor mount at the first angle.

14. The apparatus of claim 1, wherein the intravascular guidewire further comprises a flexible tip coil terminating at the distal tip, wherein the intravascular sensor is positioned proximal of the flexible tip coil.

15. An apparatus, comprising: an intravascular guidewire configured to be positioned within a blood vessel of a patient, wherein the intravascular guidewire comprises: a longitudinal axis; a distal tip coil; a sensor housing proximal of the distal tip coil; an intravascular flow sensor positioned within the sensor housing and configured to obtain intravascular flow data while the intravascular guidewire is positioned within the blood vessel, wherein the intravascular flow sensor is oriented at an oblique first angle with respect to the longitudinal axis, wherein the intravascular flow sensor comprises an ultrasound transducer that does not obtain an intravascular image of the blood vessel; and an acoustic material at least partially surrounding the intravascular flow sensor and comprising an acoustic impedance less than an acoustic impedance of blood in the blood vessel, wherein ultrasound energy emitted by the ultrasound transducer through the acoustic material is refracted at an interface between the acoustic material and the blood to a smaller second angle with respect to the longitudinal axis.

16. An apparatus, comprising: an intravascular guidewire configured to be positioned within a blood vessel of a patient, wherein the intravascular guidewire comprises: a distal tip coil; andan intravascular flow sensor positioned proximal of the distal tip coil and configured to obtain intravascular flow data while the intravascular guidewire is positioned within the blood vessel, wherein the intravascular flow sensor comprises an ultrasound transducer that does not obtain an intravascular image of the blood vessel.

17. The apparatus of claim 1, wherein the intravascular flow sensor is a single ultrasound transducer element.

18. The apparatus of claim 1, wherein the intravascular guidewire further comprising a sensor housing proximal of the distal tip coil; and wherein the intravascular flow sensor positioned within the sensor housing.

19. The apparatus of claim 18, wherein the intravascular guidewire further comprises a sensor mount positioned inside the sensor housing, wherein the intravascular flow sensor is mounted on the sensor mount at an oblique angle.

Images