JP7609435B2 - MRI compatible device - Google Patents

Description

This patent application claims priority to U.S. Patent Application No. 62/748,026, filed October 19, 2018. The above-referenced patent application is hereby incorporated by reference in its entirety for all purposes.

The present disclosure generally relates to an interventional device designed for active visualization via an implanted radio frequency (RF) antenna during an interventional magnetic resonance imaging procedure.

Interventional magnetic resonance imaging has great potential as an alternative to traditional X-ray fluoroscopy used during interventional procedures. However, visualization of interventional devices with MRI is more complicated compared to commercially available v-devices used for X-ray type procedures. The present disclosure is provided to solve these and other problems.

Advantages of the present disclosure will be described and become apparent from the following description. Further advantages of the present disclosure will be realized and attained by the methods and systems particularly pointed out in the written description, claims, and accompanying drawings.

When performing procedures such as percutaneous cardiovascular procedures, it is necessary to visualize the distal location and entire shaft of the device catheter to navigate within the vasculature and safely perform interventional procedures such as cardiac diagnostic or therapeutic catheterization, cardiac ablation, oncological procedures such as breast, lung, brain, or prostate biopsies, drug/contrast injections, and more.

There are two techniques for device visualization in MRI: passive visualization and active visualization. Passive visualization relies on the intrinsic susceptibility artifacts of metal components that cause signal voids in nuclear magnetic resonance imaging. Passive visualization devices often produce image artifacts that are poorly contrasted and larger than the actual device profile depending on the placement of the device relative to the main magnetic field. Active visualization devices incorporate a radio frequency receiving antenna. After RF excitation through the RF body coil of the MRI scanner, the excited hydrogen protons in the body transition back and emit RF waves. These RF waves can be received by the RF receiving antenna in close proximity to these metal protons. The SNR (signal to noise ratio) of the antenna is closely related to the tuning of the antenna to the Larmor frequency (resonance frequency) of the MRI scanner and also matches the impedance of the RF coil plug of the scanner. Typically, loop or coil antennas are used for visualization of the far end in interventional MRI (iMRI) and appear as a "bright spot" in real-time MRI guidance. Typically, monopole or bipole antennas are used for visualization of the entire shaft.

However, the received signal profile and the signal-to-noise ratio (SNR) of the received signal depend on the geometry of the RF receiving antenna and the conductive and insulating materials between the conductive layers. Conventional RF receiving antennas are manufactured using insulated or bare conductors in the form of wires, rods, sheets, twisted pairs, coaxial cables or tubes. Therefore, fine tuning the specific impedance values of each antenna component that affect the received signal profile is not practical.

The present disclosure provides embodiments that allow the impedance value of a particular portion of an antenna component to be controlled. The characteristic impedance of the entire antenna is inductive, but by modifying the profile of the antenna components, capacitive subsections can be created to tailor the profile of the signal received by the antenna. This can be achieved, for example, by making different portions of the antenna from subsections with wider/narrower and/or thicker/thin conductive material. Furthermore, the conductivity of the conductor itself can be selected to precisely control the profile of the received signal across the antenna. This can result in an improved MRI device with a signal profile that is smaller than the physical device itself, thereby preventing images of important body structures from being obscured.

Physicians typically require visualization of both the tip and shaft simultaneously. In certain applications, such as tumor biopsy, physicians need to know the total length of the inserted needle in real time. Thus, known active interventional MRI devices suffer from the deficiency of incorporating multiple RF receiving antenna components that increase the overall device profile and adversely affect mechanical performance.

Furthermore, active devices incorporating metallic components are exposed to the risk of RF-induced heating during MRI scans. Typically, when the electrical length of the metallic part is comparable to the Larmor frequency (i.e., a quarter wavelength of the scanner RF transmission system), the amount of heat can exceed the allowable range (2°C around the torso) according to international standards (ASTM 2182).

For visualization by the device, conventional active MRI devices have highly conductive antenna elements and transmission lines to transmit received RF signals to an MR scanner with minimal signal loss. However, these conductive structures may also be connected to RF transmission power during an MRI scan, causing RF induced currents to flow through the device. The blood vessels and tissues surrounding an active MRI device during an interventional procedure have high electrical resistance. When RF induced currents flow from the active device to the surrounding tissue (i.e., from the distal end of the active device, which has the highest current density along the device), resistive heating is then generated at the interface between the device and the tissue, causing a rapid temperature increase that is dangerous to the patient. The applicant has realized that the above problem can be solved by configuring the electrical characteristics of the device to match or nearly match the impedance of the surrounding body structures, since resistive heating can be reduced by reducing the impedance difference.

Therefore, one objective of the present disclosure is to provide a method for manufacturing an RF receiving antenna that can be used to build a device that can be used to visualize all desired locations on a device profile using one antenna design without changing the mechanical performance of the device, and to minimize RF inductive heating of the device body by seamlessly modifying the characteristic impedance of specific portions of the conductive structure.

To achieve these and other advantages in accordance with the objects of the present disclosure described herein, in one embodiment, the present disclosure provides a medical device having MRI compatible circuitry capable of determining its position unless the device projects a magnified profile in an iMRI procedure. An embodiment illustrating such a device includes a base surface, a first conductive layer disposed on the base surface, a first insulating layer disposed on at least a portion of the first conductive layer, and a second conductive layer disposed on at least a portion of the first insulating layer.

In some implementations, one or both of the first and second conductive layers may be formed from separate conductive materials. For example, the first and second conductive layers may be formed from alternating conductive materials having different impedances, such as by being composed of alternating conductive materials having different geometries, such as having different thicknesses and/or widths. For example, the separate conductive materials may be made from materials having the same bulk electrical properties, the same material, or from different materials. One or both of the first and second conductive layers may each be selectively formed to have an impedance that approximately matches a body structure adjacent to the medical device, for example, to prevent or minimize heating at the boundary around the body structure due to impedance mismatch.

In some implementations, the first conductive layer may form at least a portion of a first transmission line, and the second conductive layer may form at least a portion of a second transmission line.

Optionally, the alternating conductive materials each have a length less than about one-quarter of a wavelength of an applied RF signal corresponding to the MR scanner's background magnetic field _B0 , thereby reducing, minimizing or preventing standing wave heating effects in the conductive material. For example, the alternating conductive materials may be less than about one-quarter of a wavelength of the background magnetic field of the applied RF signal from 0.1 T to about 10 T in 0.1 T increments.

Optionally, one or both of the first conductive layer and the second conductive layer may be printed on the medical device. For example, the first conductive layer and the second conductive layer may be printed on the medical device using different materials and in configurations having different geometries. Optionally, the first conductive layer is printed on the medical device. Alternatively, at least one of the first conductive layer, the second conductive layer, and the first insulating layer may be formed using a technique other than printing. For example, at least one of the first conductive layer, the second conductive layer, and the first insulating layer may be formed at least in part by using one or more of chemical vapor deposition, plasma-enhanced chemical vapor deposition, chemical etching, and laser ablation, among others. Optionally, the first conductive layer and the second conductive layer may be formed by adhering a sheet-like planar conductor on the medical device. The first insulating layer may be formed at least in part by heat shrinking a polymer body around at least a portion of the medical device.

In some implementations, the base surface on which the first conductive layer is formed may be formed of an insulating material. Optionally, the device may include a layer of insulating material disposed over at least a portion of a surface of the base surface and under at least a portion of the first conductive layer. Optionally, the layer may further include a layer of insulating material disposed over the second conductive layer.

In some implementations, the device may further include at least one conductive winding disposed on the medical device that is electrically connected to at least one of the first conductive layer and the second conductive layer. Optionally, the first conductive layer may be electrically connected to the second conductive layer at locations where the first insulating layer is absent. In some implementations, the base surface may include an insulating sleeve configured to be placed over at least a portion of the device.

In some implementations, the medical device may be an interventional MRI (iMRI) medical device. For example, the iMRI device may be a cardiovascular medical device, such as a needle, catheter, device delivery catheter, guidewire, endoscope, flexible catheter, implant, shunt, stent, pacemaker, and pacemaker lead, among others. The iMRI device may be an orthopedic medical device, such as a spinal rod, pedicle screw, bone plate, pin, interbody fusion device, and the like. The iMRI device may be a diagnostic medical device, such as a biopsy needle, probe, dye introduction catheter, and the like. In some implementations, the iMRI device may be a laparoscopic surgical device, such as an endoscope, an electrosurgical dissector, an ultrasonic dissector, a surgical mesh, and the like. In some embodiments, the iMRI device may be a gynecological medical device, such as a uterine manipulator, a tissue dissector, a probe, an electrocautery device, and the like. Optionally, the iMRI device may be a therapeutic medical device, such as an implant, a neuromodulation device, a patch, and the like. In some embodiments, the iMRI device may be an absorbable medical device, such as an implant, an RFID tag, an edible pill, or the like.

In some implementations, an MRI marker and method for manufacturing the same is provided, which includes a conductive layer printed on a base surface.

In a further implementation, a method for manufacturing a device according to the present disclosure is provided.

The present disclosure also provides an implementation of a medical device having MRI-compatible circuitry. The medical device includes an elongated body formed at least in part by an extruded body, the elongated body including at least one transmission line. The at least one transmission line may be formed at least in part by a braided twisted pair of electrically insulated conductors.

Optionally, the medical device may include a plurality of transmission lines. Each transmission line may be at least partially formed by a braided twisted pair of conductors that are electrically insulated from one another. Optionally, the medical device may further include a needle connected to the extrusion body. At least one conductor of the braided twisted pair of conductors may include an insulating coating. In some implementations, the braided twisted pair of conductors may be disposed between two co-extruded layers of polymeric material. In another embodiment, the braided layer may be disposed between an inner shaft or inner tubular member and an outer annular member formed by a dipped layer of polymer or by a layer of shrink tubing that shrinks around the inner shaft or inner tubular member and the braided material. The present disclosure further provides a braided device and a method of manufacturing the device, comprising braiding at least one pair of conductors into a twisted pair arrangement to form at least a portion of the medical device.

It is understood that the foregoing general description and the following detailed description are examples and are intended to provide further explanation of the embodiments of the present disclosure. The accompanying drawings are incorporated in and constitute a part of this specification and are included to illustrate and provide a further understanding of the methods and systems of the present disclosure. The drawings, together with the description, serve to explain the principles of the present disclosure.

FIG. 1 shows an example of an MRI system. FIG. 2 illustrates a multi-layer structure of an RF antenna design printed directly onto a device surface in accordance with the present disclosure. FIG. 3 illustrates an example of an isometric rendering of an iMRI device in accordance with the present disclosure. FIG. 4 shows a first set of diagrams of a multiple head conductive and insulating ink printing system in accordance with the present disclosure. FIG. 5 shows a further view of an antenna printing system in accordance with the present disclosure. FIG. 6 shows an example of printing an RF receiving antenna on a catheter. FIG. 7 shows an example of a transmission line design that is impedance matched to its surroundings to minimize RF inductive heating. FIG. 8 illustrates an embodiment showing a braided layer formed on a polymeric liner that is placed over a mandrel. FIG. 9 illustrates an embodiment showing a braided layer formed on a polymeric liner that is placed over a mandrel.

Preferred embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The method and corresponding procedures of the present embodiment will be described together with a detailed description of the system.

The present disclosure provides embodiments of devices useful for interventional MRI (so-called iMRI) procedures. Applicant recognizes that there have been various attempts to make devices, such as surgical instruments and implants, more MRI compatible. However, such devices have had shortcomings.

For reference, Figure 1 shows an example of a nuclear magnetic resonance system comprising a plurality of primary magnetic coils 10 which generate a uniform, temporary, constant magnetic field _B0 along the longitudinal or Z axis of a central bore 12 of the device. In a preferred embodiment for superconducting, the primary magnetic coils are supported by a former 14 and received in an annular helium vessel or can 16. The vessel is filled with helium to maintain the primary magnetic coils at superconducting temperatures. The can is surrounded by a series of cold shields 18 supported in thermoses 20. Of course, annular resistive magnets, C-magnets, etc. may also be considered.

The global gradient coil assembly 30 includes x, y, and z coils mounted in the bore 12 to generate gradient magnetic fields Gx, Gy, and Gz. Preferably, the gradient coil assembly 30 is a self-shielded gradient coil including a primary x, y, and z coil assembly 32 encased in a dielectric mold and secondary x, y, and z coils supported in a bore defining the cylinder of the thermos flask 20. The global radio frequency coil 36 is mounted inside the gradient coil assembly 30. A global radio frequency shield 38, such as a copper mesh, may be attached to the global radio frequency coil 36 and the gradient coil assembly 30. If desired, an insertable radio frequency coil 40 may be removably mounted in a bore in a test volume defined around the isocenter of the magnet 10. In the embodiment of FIG. 2, the insertable radio frequency coil 40 is a head coil and a neck coil for imaging one or both of the patient's head and neck, but may be other limb coils such as a knee coil, a shoulder coil, a chest coil, a wrist coil, a posterior coil for imaging the spine, and the like.

1, an operator interface control station is provided that includes a human readable display such as a video monitor 52, and an operator input device such as a keyboard 54, mouse 56, trackball, light pen, etc. Also provided is a computer control and reconstruction module 58 that includes hardware and software for allowing the operator to select from a number of preprogrammed nuclear magnetic resonance sequences stored in a sequence control memory when RF pulses are to be used as part of an imaging study. A sequence controller 60 controls gradient amplifiers 62 connected to the gradient coil assembly for generating gradient magnetic fields Gx, Gy, Gz at appropriate times during a selected gradient sequence, and a digital transmitter 64 that drives a selected one of the global and insertable radio frequency coils to generate radio frequency field pulses _B1 at times as per the selected sequence when RF pulses are to be used in a study.

The MR signals received by the coil 40 are demodulated by a digital receiver 66 and stored in a data memory 68. Data from the data memory is reconstructed by a reconstruction or array processor 70 into a volumetric image representation that is stored in an image memory 72. If a phased array is used as the receive coil assembly, an image may be reconstructed from the coil signals. A video processor 74 under operator control converts selected portions of the volumetric image representation into slice images, projection images, perspective views, etc., as would be displayed on a video monitor in the prior art.

Further, in accordance with the present disclosure, there is provided a medical device having an MRI compatible circuit. An example of the device includes a base surface, a first conductive layer disposed on the base surface, a first insulating layer disposed on at least a portion of the first conductive layer, and a second conductive layer disposed on at least a portion of the first insulating layer.

Embodiments of the present disclosure include active interventional MRI devices, systems, and methods. In some embodiments, the devices include an antenna formed at least in part by printing conductive and/or insulating layers on a substrate. In particular, the present disclosure includes a multi-layer RF antenna assembly embedded in an interventional device, printed or otherwise formed, and an RF signal matching/detuning circuit, as described herein.

In example embodiments, the present disclosure provides RF receiving antenna designs (such as single antenna designs) that are printed directly onto the drive shaft or components to visualize the tip and shaft, eliminate traditional antenna components, and minimize RF induction heating under MRI without compromising mechanical performance. An active interventional MRI device with these integrated capabilities represents a breakthrough in the field of interventional MRI by ensuring safe clinical operation.

2 is an exploded view of an example MRI needle showing a base layer of bare needle 202 having a surface. A second insulating layer 204 is printed or deposited on the base layer. For example, layer 204 is formed by heat shrink tubing, printing insulating material on the surface of 202, dipping in a polymer, or the like. A first layer of conductive material is formed on layer 204 as an underlayer 206 of the transmission line by any method described herein. A second insulating layer 208 is then deposited on underlayer 206 using any suitable technique. A second layer of conductive material 210 is then formed using any suitable technique, comprising further transmission lines and one or more antenna coils, illustrated as loop coils. A final insulating layer 212 is then formed or heat shrunk on layer 212, for example.

All layers of the device shown in FIG. 2 may be formed using any suitable method, including, but not limited to, those described and/or referenced herein. For example, a combination of the methods described herein may be used to form one or more layers. In one embodiment, an insulating layer is formed using heat shrink, dipping, printing, etc., and the layer may be etched or cut to expose the conductors underneath, and then placed in electrical contact with the next conductive layer. Any suitable number of layers of conductive and insulating materials may be used to form any suitable circuit. Additionally, any layer may be fully or partially formed on the surface of the device. FIG. 3 shows the final assembly of the components shown in FIG. 2.

In an example embodiment, as shown in FIGS. 4-6, an RF antenna printing system is illustrated in the form of a 4-axis CNC system configured to print each layer of an RF antenna design onto a substrate, such as an interventional device shaft (e.g., 202 in FIG. 2). In the illustrated implementation, the interventional device shaft may be attached to a hollow shaft rotation axis (FIG. 4, Detail "B"), the printing head may be attached to one linear axis (e.g., Z axis), and the printing head may move in the other two axes (X and Y axes) to accomplish the printing operation by rotating the shaft about the rotation axis and adjusting the height of the workpiece and/or the printing head along the Z (vertical) axis.

A single channel RF antenna design may be formed from multiple layers using, for example, 3D design software. Certain portions of the antenna and/or transmission line may be marked to be printed with high impedance ink (i.e., approximately matching the complex impedance of the adjacent tissue or anatomical structure). This drawing may be converted to standard G-code using post-processing software, and special M-codes may be assigned to modify the complex impedance of the antenna parts and to modify the ink source to include an insulating layer between two adjacent conductive layers during printing of the RF antenna on the drive shaft. Instead of using a conventional transmission line (i.e., coaxial cable or twisted pair) with a homogenous profile over its entire length, the disclosed novel RF antenna, whether fully or partially formed by printing and/or other methods including deposition, foil, chemical etching, laser ablation, etc., allows for control of capacitive and inductive coupling effects along the antenna during MRI scanning, and also helps limit RF induction heating on the RF antenna without adding any bulky RF circuit elements such as RF traps, baluns, LC tanks, etc.

In the embodiment shown in Figures 2-7, the disclosed RF antenna printing system has a rotating print head housing multiple printing ink cartridges and nozzles that allow for controllably adjusting the properties of the conductive or insulating ink during printing of the antenna. The position of the rotating print head may be controlled through a stepper/servo motor. The nozzles may apply the ink to the surface of the shaft of the device by dispensing, spraying, or pressing, among other things.

In one embodiment, the RF antenna design printing system has a dispensing unit that incorporates both conductive and insulating ink nozzles, mounted on one axis (X, Y, Z, and A (rotary) axis) of a four-axis CNC controller. Based on the RF design data and the results of the simulation to perform, the digital RF antenna design may be split into multiple layers, and the digital design file may be converted into G-code (general purpose programming language for CNC machines), which is created by post-processing software so that the target RF antenna geometry is printed on the device shaft or part by the CNC unit. This is achieved by printing the antenna parts with the disclosed multi-head dispensing unit. The dispensing unit may have multiple nozzles for printing different conductive and insulating inks on the device surface based on the user-prepared design file. Thus, the system may mix two different inks to achieve suitable electrical and mechanical properties according to the design, for example.

A rotary switch mechanism may switch between printing conductive ink and insulating ink, for example by rotating the dispensing head. Conductive and insulating ink nozzles may be attached to the print head, and the preferred conductivity can be achieved by changing the active nozzles on the rotating head, and the preferred geometry (e.g., line, width, thickness, and arrangement) can be achieved by changing the print speed (faster axis movement results in thinner printed structures). By changing the geometry (e.g., line, width, thickness, and arrangement) of the antenna parts and the thickness of the insulating layers, high capacitive impedances can be achieved on small portions of the target, which can change the signal profile of the entire antenna without significantly changing the inductive characteristics of the overall antenna impedance. This flexibility allows users to design and manufacture RF receiving antennas on medical consent shafts or parts that are nearly identical to the envisioned antenna design, which was not practical with conventional RF antenna manufacturing methods.

In a further embodiment, the impedance values of the conductive elements of the RF receiving antenna can be adjusted during printing without changing the overall device profile of the active medical device, so that sections designed to amplify the induced magnetic field can be printed with low impedance inks, and certain sections of long transmission lines can be printed with wider lines insulated with a thin coating to improve capacitive coupling of the transmission line and its surrounding environment. This is achieved by seamlessly changing the characteristic impedance and geometry of each antenna component by alternating between different types of conductive inks, and by varying the speed of print head movement during manufacturing instead of using typical conductive transmission line materials (i.e., insulated wire, twisted pair, or micro-coax).

Layers of conductive material may be formed by printing mixed conductive inks at predetermined locations and/or by laminating different conductive inks directly on top of and/or alongside each other. Predetermined circuit paths may be formed on the paths of the layers, for example, by combining layers of conductive material at selected locations that are separated from other locations by insulating material and/or spatial separation along the surface of the substrate.

In another embodiment, RF resonant markers may be created to aid in locating one's spatial location under MRI. For example, such markers can be printed on the drive shaft or components by adjusting the width of the conductive structures and the thickness of the insulating material in adjacent layers to form the LC tank circuit. This can eliminate the long transmission lines required to transmit the received RF signal to the scanner for the active intervention device.

In yet another embodiment, the RF antenna can be printed on the drive shaft such that the electrical length of the entire RF antenna and its transmission line can be divided into subsections, each with a length equal to (or less than) a quarter wavelength of the Larmor frequency of hydrogen at a wavelength corresponding to the scanner's background magnetic field _B0 (e.g., 64 MHz at 1.5 Tesla) and with a complex impedance that corresponds to the adjacent tissue or anatomical structure (FIG. 7). This can be achieved by modifying the conductive ink at predetermined intervals so that each segment has an impedance that matches the anatomical structure around it. The induced current density is then homogenized along the shaft, preventing any "hot spots" from occurring along the drive shaft. This design also eliminates the need for bulky analog and electrical components that form RF traps or baluns along the transmission line, which can adversely affect both the overall active device profile and mechanical performance.

These disclosed embodiments allow for capacitive coupling between the radiated RF signal during MRI and specific placement of RF receiving antennas embedded in the interventional device. This feature provides better active MRI device shaft visualization using only one antenna. Also, the varying impedance characteristics along one metal part allows for control of the amount of RF induced heating across the active device, which is critical to patient safety during MRI scans. For example, as shown in the figures, an active MRI needle is provided with one or more RF receiving antennas printed on the needle shaft that can simultaneously provide both specific points along the shaft and the entire length.

It is understood that the conductive and insulating layers of the disclosed embodiments may be printed on the medical device using different materials and may be printed on the medical device in configurations having different geometries. Alternatively, one or more of the layers (or all of the layers) may be formed using techniques other than printing. For example, at least one of the conductive and insulating layers may be formed at least in part by using one or more of chemical vapor deposition, plasma-enhanced chemical vapor deposition, chemical etching, and laser ablation, among others. Optionally, one of the layers may be formed by adhering a sheet-like planar conductor onto the medical device. The first insulating layer may be formed at least in part by heat shrinking a polymer body around at least a portion of the medical device.

Although an MRI needle is specifically depicted in the drawings, it is understood that the disclosed techniques and systems may be used to form many different types of devices.

For example, an iMRI device may be formed. The device may be a cardiovascular medical device, such as a needle, a catheter, a device delivery catheter, a guidewire, an endoscope, a flexible catheter, an implant, a shunt, a stent, a pacemaker, and a pacemaker lead, among others.

The iMRI device may be an orthopedic medical device such as a spinal rod, pedicle screw, bone plate, pin, interbody fusion device, etc.

The iMRI device may be a diagnostic medical device such as a biopsy needle, probe, dye introduction catheter, etc.

In some implementations, the iMRI device may be a laparoscopic surgical device, such as an endoscope, an electrosurgical dissector, an ultrasonic dissector, a surgical mesh, or the like.

In some embodiments, the iMRI device may be a gynecological medical device, such as a uterine manipulator, tissue dissector, probe, electrocautery device, or the like.

Optionally, the iMRI device may be a therapeutic medical device such as an implant, neuromodulation device, patch, etc.

In some embodiments, the iMRI device may be an absorbable medical device, such as an implant, an RFID tag, an edible pill, or the like.

As described herein, in further implementations, one or more transmission lines are provided to the medical device in a process incorporating the braided conductor into the device. As described herein, generally, the RF transmission lines are useful for carrying RF signals detected by the device to a signal processor and/or computing device and minimizing signal attenuation.

An interventional device as described herein can be visualized under MRI by using active visualization or passive visualization techniques. With respect to active visualization techniques, the intravascular device may incorporate an RF receiving antenna embedded in the device body. After exciting the patient's region of interest (ROI) by the RF transmitting coil of the MR scanner, the patient's hydrogen protons in the ROI, the antenna in the medical device can pick up the weak RF signal emitted when the patient's excited protons return to a low energy state. After receiving the signal, the signal must be transmitted by the medical device to the MR scanner with minimal signal attenuation, so that the signal can be used for imaging or device tracking purposes, as needed, for example, by superimposing the image of the medical device or a portion thereof on an MRI image constructed from data received by other imaging coils around the ROI.

Depending on the required mechanical properties of the medical device (such as a transvascular catheter), such as torqueability, pushability, flexibility, etc., one or more of a variety of different braiding patterns, such as full load, half load, and diamond pattern on a variety of different braiding machines (such as a 16-head braiding machine, a 32-head braiding machine, etc.), may be used to construct the medical device. After finalizing the braiding head and pattern for suitable mechanical properties, the two braided fibers (and additional braided fibers, if necessary) may be replaced with insulated conductor wires (such as enameled copper wires) to form a twisted pair transmission line that is integrated into the braid layer, such as a layer of braided fibers located between two co-extruded polymer tubular layers. The opposing turns of each conductor wire forming the twisted pair may help to cancel out radial E-field components from each other, minimizing RF induction heating over long conductors under MRI. It may also minimize signal attenuation in the transmission line through the twisted pair transmission pair when transmitting received signals to the MR scanner.

Figure 8 shows an example of a hybrid braided layer formed on a PTFE liner placed on a mandrel. The two braided fibers in this example are replaced by, for example, enameled copper wires that form a twisted pair along the braided layer. The far end of the copper wire is cut off at a location that does not go to the far end of the device. The proximal end of the wire is also cut off. This allows the free ends of the transmission line to be located at the two ends of the solenoid loop coil antenna when the wire is placed across the braided layer. Figure 9 shows a full twisted pair integrated with the braided layer.

In this application, the advantages and features are described as representative examples of embodiments only, and are not exhaustive and/or exclusive. These are merely to aid in the understanding and teaching of the claimed principles. It is understood that these are not representative of all disclosed embodiments. Thus, some aspects of the disclosure are not described herein. Alternative embodiments are not described for a particular portion of the specification, and the absence of an alternative embodiment for a portion does not negate the alternative embodiment of that portion. It is understood that many embodiments not described incorporate the same principles of the present disclosure and other equivalents. Thus, it is understood that other embodiments may be utilized, and that functional, logical, structural, structural, and/or morphological changes may be made without departing from the scope and/or spirit of the present disclosure. Thus, throughout this disclosure, all examples and/or embodiments are treated as non-limiting. Furthermore, no inference should be drawn from the embodiments described herein to embodiments not described herein, except to reduce space and repetition. For example, it is understood that the logical and/or physical structure of any combination of any program components (groups of components), other components, and/or any present features described in the drawings and/or throughout are not limited to a fixed order of operation and/or arrangement, but rather, any order is an example, and all equivalent scope regardless of order is contemplated in this disclosure. Furthermore, such features are not limited to execution in that order, but rather, any number of threads, processes, services, servers, and/or the like that may be executed asynchronously, simultaneously, in parallel, together, synchronously, and/or otherwise is contemplated in this disclosure. Thus, some of these features may be inconsistent with one another in that they cannot exist simultaneously in one embodiment. Similarly, some features are applicable to one aspect of the disclosure and not applicable to others. Additionally, the disclosure includes embodiments other than those claimed herein. Applicant reserves all rights, such as the right to claim such embodiments, the right to file additional applications, the right to file continuation applications, the right to file continuation-in-part applications, the right to file divisional applications, and/or the like, to any currently unclaimed embodiments. Therefore, the advantages, embodiments, examples, functional, characteristic, logical, configurational, structural, morphological, and/or other aspects of the present disclosure should not be considered limitations on the present disclosure as defined by the claims or limitations on the scope of equivalents to the claims.

All statements herein that recite principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents. Moreover, such equivalents are intended to encompass both known equivalents and equivalents developed in the future, i.e., any elements developed that have the same function regardless of structure.

The circuits, methods, processes, and computer programs described herein represent conceptual embodiments of example circuits and software that implement the principles of the disclosed embodiments. Thus, the functionality of the various elements shown and described herein may be provided through the use of dedicated hardware and hardware capable of executing software in association with appropriate software as described herein.

In this disclosure, any element expressed as a method for performing a particular function encompasses any method for performing the function, including, for example, a) a combination of circuitry and associated hardware that performs that function, or b) software in any form, including firmware, microcode, or otherwise, as described herein, combined with appropriate circuitry for executing software to perform the function. Accordingly, applicants consider any method capable of providing those functions to be equivalent to those shown herein.

Similarly, it will be understood that the systems and process flows described herein are substantially represented in a computer-readable medium and, whether or not explicitly depicted, represent various processes executed by a computer or processor. Furthermore, the various processes may be understood as blocks of program code that perform such processes or functions, rather than representing only processes and/or other functions.

In particular, the disclosed method, system, computer program, and mobile device, as described above and shown in the drawings, provide an improved magnetic resonance imaging method, and a system and machine-readable program for carrying out the same. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed device, method, software program, and mobile device without departing from the spirit or scope of the present disclosure. Accordingly, the present disclosure includes modifications and variations within the scope of the subject matter of the present disclosure and their equivalents.

Claims (18)

1. An interventional magnetic resonance imaging (iMRI) medical device having a circuit configured for insertion into a living body, the device comprising:
the MRI medical device having a resonant frequency adapted and configured to match a resonant frequency of the MRI scanner and defining a first transmission line along the MRI medical device;
The first transmission line includes:
a first circuit segment having a first electrical impedance configured to match an electrical impedance of a first tissue type, the first circuit segment reducing current flow from the first circuit segment to the first tissue type;
a second circuit segment operably connected to the first circuit segment, the second circuit segment having a second electrical impedance different from the first electrical impedance;
and
the second electrical impedance is configured to match an electrical impedance of a second tissue type different from the first tissue type to reduce current flow from the second circuit segment to the second tissue type.
MRI medical equipment. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment have different geometries. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment have different thicknesses. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment have different widths. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment are made from the same material. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment are made from different materials. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment are formed from at least one conductive ink deposited on a substrate. The MRI medical device of claim 1, wherein the first circuit segment and the second circuit segment are formed from different conductive inks deposited on a substrate. 2. The MRI medical device of claim 1, wherein at least one of the first circuit segment and the second circuit segment has a length less than about one-quarter of a wavelength of an applied RF signal corresponding to a background magnetic field _B0 of an MR scanner. 10. The MRI medical device of claim 9, wherein at least one of the first circuit segment and the second circuit segment has a length less than about one-quarter of a wavelength of an applied RF signal corresponding to a background magnetic field _B0 of about 0.55 Tesla. 10. The MRI medical device of claim 9, wherein at least one of the first circuit segment and the second circuit segment each has a length less than about one-quarter of a wavelength of an applied RF signal corresponding to a background magnetic field _B0 of between about 1.5 Tesla and about 3.0 Tesla. The MRI medical device of claim 1, including an implant. The MRI medical device of claim 1, including a soft catheter. The MRI medical device of claim 1, including an endoscope. The MRI medical device of claim 1, including a guidewire. an active marker coil operatively connected to the first transmission line;
the active marker coil is configured to receive magnetic resonance signals from surrounding tissue and direct the magnetic resonance signals along the first transmission line to the MRI scanner to facilitate visualization of a physical position of the active marker coil relative to surrounding organs.
The MRI medical device of claim 1. The MRI medical device of claim 16, wherein the active marker coil comprises a solenoid coil. The MRI medical device of claim 17, wherein the active marker coil includes a saddle coil.