Active MRI intramyocardial injection catheter with a deflectable distal section

Abstract

A deflectable tip catheter that is safe and effective for use in a magnetic resonance imaging environment. The deflectable tip catheter is configured such that it includes a built-in antenna, such as a loopless antenna or a loop antenna. The built-in antenna permits the deflectable tip catheter to be actively tracked and/or visualized. Depending upon the specific configuration of the deflectable tip catheter, the catheter may be tracked and/or visualized as a single unit, it may be tracked and/or visualized separate and independent of other components or instruments associated with the catheter, such as pull wires, injection needles, surgical instruments, and the like. The catheters described herein include injection type catheters and/or guidance type catheters.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to catheters that have a deflectable portion. More particularly, the present invention relates to deflectable tip catheters that can be actively visualized and/or tracked in a magnetic resonance imaging (MRI) environment.

[0004] 2. Discussion of the Related Art

[0005] Occlusive coronary artery disease results in myocardial infarction and deleterious left ventricular remodeling. Occlusive coronary artery disease can be treated. Treatment includes coronary balloon angioplasty, coronary artery stenting and bypass graft surgery. However, due to the limited regenerative capacity of adult cardiomyocytes, ischemic events often result in irreversible cell injury and concurrent myocardial dysfunction, leading to congestive heart failure and death.

[0006] There is scientific evidence that delivering therapeutic agents, such as cells (e.g., stem cells), various genetic materials, growth factors, and the like, directly into the infracted myocardial tissue may help to restore healthy tissue and normal myocardial function. Conventional interventional cardiology procedures, including the aforementioned treatments, such as balloon angioplasty, typically involve the use of a balloon catheter to dilate the occluded artery and X-ray fluoroscopy to assist the attending cardiologist guide the catheter. X-ray fluoroscopy, however, does not distinguish healthy from infracted myocardial tissue, nor does it provide an anatomical image of the heart, where the ability to distinguish infracted tissue from healthy tissue within an anatomical image of the heart is of vital importance to the cardiologist who is attempting to precisely deliver therapeutic agents using any one of the above-identified conventional techniques.

[0007] There are electro-anatomical mapping systems capable of providing a functional map of the cardiac anatomy; however, these systems cannot provide real-time images of the heart. An example, is Biosense Webster's NOGA system, which is used in conjunction with X-ray fluoroscopy. The NOGA system employs a catheter comprising three coils and an endocardial potential measuring electrode located at the distal tip. During clinical use, three external magnets are placed at three different locations on the patient (e.g., under the patient's back and on the right and left side of the patient's chest). The cardiologist is then able to move the catheter around inside the left ventricle of the patient's heart, and in doing so, the NOGA system measures the electrical activity at endocardial surface, as well as the motion and the location of the distal tip of the catheter. The NOGA system uses these measurements to create a three dimensional, real-time, dynamic reconstruction of the ventricle, and assess the electrical and mechanical properties of the myocardium. The electrical potential and the motion of the ventricular wall are used, in turn, to differentiate healthy, viable and completely infracted tissue. The primary drawback of this system is that it does not provide an anatomical image of the entire heart. It is therefore difficult to know the cardiac anatomy in which the catheter tip is located, and whether the catheter tip is apposed against the septum or the lateral wall. In addition, this procedure associated with the NOGA system is lengthy and the quality of the ventricle image is highly dependent on operator skill. The NOGA system is used with

[0008] MRI is a diagnostic and imaging modality that is capable of providing a three-dimensional map, or image of the entire heart. furthermore, MRI offers this capability without the ionizing radiation associated with other imaging modalities, such as X-ray fluoroscopy. MRI also provides real-time images with excellent tissue contrast; thus, the attending cardiologist can quickly and efficiently see the entire heart and clearly differentiate healthy, viable and completely infracted tissue. Ideally, MRI should be available to cardiologists for use during intervention therapy to accurately track and precisely guide the catheter to regions of infracted myocardial tissue.

[0009] There are many types of injection catheters currently available; however, none are well suited for use in an MRI environment. For example, deflectable (i.e., steerable) tip catheters including multi-directional, bi-directional and uni-directional deflectable catheters are described in U.S. Pat. Nos. 5,487,757; 6,198,974; and 5,755,760, respectively. Injection catheters capable of delivering therapeutic agents to myocardial and other tissues are described, for example, in U.S. Pat. Nos. 5,980,516 and 6,004,295. Still further, deflectable injection type catheters are described for example, in U.S. Pat. Nos. 6,346,099 and 6,210,362.

[0010] The various catheter designs described in the above-identified patents are not, as stated, well suited for use in an MRI environment for both procedural reasons as well as patient safety reasons. For instance, these catheters have ferromagnetic components that pose a safety hazard to the patient in a magnetic field environment, as they can cause injury to the patient, as they may move in an undesired manner due to the magnetic field. The ferromagnetic components can also cause image distortions, thereby compromising the effectiveness of the procedure. Still further, such catheters contain long metallic components which can cause RF deposition in adjacent tissue and, in turn, tissue damage due to an extensive increase in temperature.

[0011] In addition, it would be difficult to track and/or visualize the location of the catheters described in the above-identified patents in an MRI environment. In general, there are two types of tracking in an MRI environment: active tracking and passive tracking. Active tracking is the preferred methodology. It involves incorporating a transmit and/or receive antenna into the catheter design. Because a high intensity signal is transmitted or received, active tracking provides precise location information. An example of a catheter that can be actively tracked in an MRI environment is described in U.S. Pat. No. 5,928,145. In this patent, the catheter employs a loopless antenna. Another example of a catheter that can be actively tracked in an MRI environment is described in U.S. Pat. No. 5,699,801. In this patent, the catheter does not have a deflectable tip, nor is it capable of delivering therapeutic agents to a target location, nor is it capable of deploying other surgical instruments such as forceps during a biopsy procedure.

[0012] It would be very desirable to provide attending cardiologists with a catheter design that he or she can easily steer. In addition, it would be desirable provide a catheter that can be effectively tracked and/or visualized in an MRI environment, a catheter that is safe and effective when used in an MRI environment, a catheter that can be used to effectively deliver therapeutic agents to a target location within the patient using an injection needle, and deploy other surgical instruments such as a laser, a suturing device, forceps, a cauterization tool, and the like.

SUMMARY OF THE INVENTION

[0013] Accordingly, the present invention is directed to a deflectable tip catheter that substantially obviates the deficiencies and disadvantages associated with the related art as set forth above. More specifically, the present invention is directed to a deflectable tip catheter that can be actively tracked in an MRI environment, without excessive RF deposition (i.e., local tissue heating) and the other safety and procedural drawbacks associated with the prior related art. The present invention is also directed to a deflectable tip catheter that can be effectively used to deliver therapeutics with an injection needle and deploy other surgical instruments during procedures, such as a biopsy procedure.

[0014] It should be noted that the following detailed description portrays the various exemplary embodiments of the present invention as being particularly useful in the field of cardiology. For example, the present invention is portrayed as being particularly useful for injecting and/or delivering therapeutics to cardiac tissue. However, it will be very clear to one skilled in the art that the present invention will be equally useful for other medical procedures, including biopsy procedures, as well as procedures that involve other anatomical systems such as the brain, liver and pancreas.

[0015] As such, one advantage of the present invention is to provide a deflectable tip catheter that can be easily and effectively visualized and tracked in an MRI environment.

[0016] Another advantage of the present invention is to provide a deflectable tip catheter that can be employed safely when used in an MRI environment.

[0017] Still another advantage of the present invention is to provide a deflectable tip catheter that is effective when used in an MRI environment and does not, among other things, distort the image, and does not cause local tissue damage due to excessive RF deposition along the length of the catheter.

[0018] Thus, in accordance with exemplary embodiments of the present invention, the aforementioned and other objectives are achieved with a deflectable tip catheter for use in an MRI environment. The deflectable tip catheter comprises a deflectable tip section and an RF antenna.

[0019] In accordance with exemplary embodiments of the present invention, the aforementioned and other objectives are also achieved with a bi-directional, deflectable tip guide catheter. The bi-directional, deflectable tip guide catheter includes a deflectable tip section, a first pull wire, and a second pull wire, where the first and second pull wires are configured to form a loop antenna.

[0020] In accordance with exemplary embodiments of the present invention, the aforementioned and other objectives are further achieved with a deflectable tip catheter that includes a deflectable tip section and an RF antenna. In addition, the catheter includes a plurality of distally located, non-magnetic, inductor loop coils.

[0021] In accordance with exemplary embodiments of the present invention, the aforementioned and other objectives are still further achieved with a MRI system. The MRI system comprises an MRI scanner, a deflectable tip catheter that is configured as an RF antenna, and an electrical connection between the deflectable tip catheter and the MRI scanner.

[0022] In accordance with exemplary embodiments of the present invention, the aforementioned and other objectives are also achieved through a magnetic resonance imaging method. The method involves generating a magnetic field around at least a portion of a patient and transmitting RF energy over a portion of the patient exposed to the magnetic field. In addition, the method involves receiving the RF energy using an RF antenna in a deflectable tip catheter located in the patient and generating a magnetic resonance image that includes a visualization of the deflectable tip catheter in the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, together with the detailed description below, set forth the various aspects and embodiment of the present invention, wherein:

[0024] FIG. 1 is a schematic diagram of a conventional, deflectable tip injection catheter 100;

[0025] FIG. 2 is a schematic diagram of an alternative deflectable tip section 200 associated with a conventional deflectable tip catheter;

[0026] FIG. 3 is a schematic diagram of an active MRI trackable, deflectable tip injection catheter, in accordance with a first exemplary embodiment of the present invention;

[0027] FIG. 4A is a schematic diagram of a catheter having a non-deflectable portion that includes multiple RF chokes, in accordance with an alternative embodiment;

[0028] FIG. 4B is a schematic diagram illustrating an alternative deflectable tip section for an injection catheter in accordance with an alternative embodiment;

[0029] FIG. 5A is a circuit diagram of a single RF output signal matching-tuning circuit that may be employed with a deflectable tip injection catheter, in accordance with exemplary embodiments of the present invention;

[0030] FIG. 5B is a circuit diagram of a multiple RF output signal matching-tuning circuit that may be employed with a deflectable tip injection catheter, in accordance with exemplary embodiments of the present invention;

[0031] FIG. 6 is a schematic diagram of an MRI trackable, deflectable tip injection catheter that has a pre-deflected (i.e., pre-shaped), distal deflectable tip section, in accordance with a second exemplary embodiment of the present invention;

[0032] FIG. 7 is a schematic diagram of an MRI trackable, deflectable tip injection catheter that includes an endiocardial potential measuring electrode, in accordance with a third exemplary embodiment of the present invention;

[0033] FIG. 8 is a circuit diagram of an interface circuit that may be used in conjunction with a deflectable tip injection catheter that has an endocardial potential measuring electrode;

[0034] FIGS. 9A and 9B are schematic diagrams of MRI trackable, deflectable tip injection catheters that include a side or lateral opening in the deflectable tip section, in accordance with a fourth exemplary embodiment of the present invention;

[0035] FIG. 10A is a schematic diagram of an MRI trackable, deflectable tip injection catheter, in accordance with a fifth exemplary embodiment of the present invention;

[0036] FIG. 10B is a schematic diagram of an interface circuit that might be used in conjunction with a deflectable tip injection catheter, in accordance with exemplary embodiments of the present invention;

[0037] FIG. 11 is a schematic diagram of a uni-directional, deflectable tip guide catheter, in accordance with a sixth exemplary embodiment of the present invention.;

[0038] FIG. 12 is a schematic diagram of a bi-directional, deflectable tip guide catheter 1200, in accordance with a seventh exemplary embodiment of the present invention;

[0039] FIG. 13 is a diagram of an injection needle that can be passively tracked in an MRI environment, for use with a deflectable tip injection catheter in accordance with exemplary embodiments of the present invention;

[0040] FIG. 14 is a diagram of an injection needle, configured as a loop antenna, capable of being actively tracked in an MRI environment, separately and independently from the catheter, in accordance with exemplary embodiments of the present invention;

[0041] FIG. 15 a diagram of an injection needle, configured as a loopless antenna, capable of being actively tracked in an MRI environment, separately and independently from the catheter, in accordance with exemplary embodiments of the present invention;

[0042] FIG. 16 a schematic diagram of a deflectable tip catheter, in accordance with a seventh exemplary embodiment of the present invention;

[0043] FIG. 17 is a schematic diagram of a deflectable tip catheter 1700, including three, non-magnetic inductor loop coils, in accordance with exemplary embodiments of the present invention; and

[0044] FIG. 18 is a schematic diagram of an M RI system, including a deflectable tip, MRI compatible catheter, in accordance with exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0045] FIG. 1 is a schematic diagram of a conventional injection catheter 100 with a deflectable tip. As shown, the catheter 100 comprises of a proximal portion that includes a non-deflectable section 105 and a handle 110. The catheter 100 also comprises a deflectable tip section 115. The deflection mechanism involves a pull wire 120 and an anchor wire 125, where the pull wire 120 and the anchor wire 125 are connected to each other at point A in the deflectable tip section 115, as shown. The pull wire 120 runs the length of the catheter through a lumen (not shown). The anchor wire 125 is fixed at point B where the distal end of the non-deflectable section 105 abuts the proximal end of the deflectable tip section 115. During clinical use, the attending physician (e.g., cardiologist) may actuate the deflectable tip section 115 by manipulating the deflection dial 130 on the handle 110. This action causes the pull wire 120 to move in the direction of the handle, relative to the anchor wire 125. As the anchor wire 125 is fixed, the movement of the pull wire 120 causes the deflectable tip section 115 to deflect as shown, for example, by arrow C. One skilled in the art will readily appreciate the fact that an injection needle 135 may run the length of the catheter, parallel or essentially parallel to the pull wire 120, through a second lumen (not shown), where the needle is typically made of metal, polymer or a combination of both. Again, the drawbacks associated with catheters, such as catheter 100, when employed in an MRI environment include image distortion, burns due to radiofrequency (RF) heat deposition, the inability to accurately track the position and/or location of the catheter during MRI scanning.

[0046] FIG. 2 is a schematic diagram of an alternative deflectable tip section 200 associated with a conventional deflectable catheter. As shown, the deflectable tip section 200 comprises a slotted, metallic hypotube 205. Examples of catheters comprising a slotted deflectable tip section can be found in U.S. Pat. Nos. 4,898,577 and 5,030,204. In FIG. 2, a pull wire 210 is connected to the distal end of the slotted tube at point A, as shown. Moving the pull wire 210 in a proximal direction causes the deflectable tip section 200 to deflect as indicated by arrow B. Again, it will be understood by one of ordinary skill in the art that the corresponding catheter may be used as a delivery device to advance a tool such as an injection needle (not shown) through lumen 215 of the catheter to carry out an injection and is described, for example in U.S. Pat. No. 6,102,887.

[0047] FIG. 3 is a schematic diagram of an active MRI tracking, injection catheter 300, with a deflectable tip, in accordance with a first exemplary embodiment of the present invention. More particularly, the catheter 300 is a single or uni-direction, deflectable tip MRI active injection catheter arranged as a loopless antenna with multiple cores. The catheter 300 has a proximal portion that includes a non-deflectable section 305 and a handle 310. The catheter 300 also has a distal, deflectable tip section 315. In addition, catheter 300 includes has a pull wire 320 and an anchor wire 325, where the pull wire 320 and the anchor wire 325 run through a polymeric tube 335, as shown, and where the anchor wire 325 is connected to the pull wire 320 at point A and is fixed at point B. In this exemplary embodiment, the anchor wire 325 is a flat wire, which limits the deflection of deflectable tip section 315 to the direction indicated by arrow C. However, it will be readily understood that the anchor wire 325 may be other than a flat wire, thereby allowing for deflection in more than the one direction indicated by arrow C. Together, the pull wire 320 and the anchor wire 325 make up a first core. It should be noted that the anchor wire 325 can be made of an elastic material and it may be oval, elliptical, flat, triangular, and the like, in its cross-section. The pull wire 320 too may take on other shapes in cross-section.

[0048] The catheter 300 includes a second core. In the exemplary embodiment illustrated in FIG. 3, the second core is a needle 330 which may be employed to deliver therapeutic agents, as set forth above, where the needle 330 runs through a needle tube 340. In a preferred embodiment, the needle 330 and the pull and anchor wires 320 and 325 run through separate tubes. Alternatively, the needle 330 and the pull and anchor wires 320 and 325 may run through a single tube in the distal, deflectable tip section 315. In another alternative to the first exemplary embodiment, an instrument other than or in addition to the needle 330 may be used, such as surgical forceps, where an additional instrument would preferably run through a separate corresponding tube, parallel or essentially parallel to the needle tube 340 and the polymeric tube 335.

[0049] The overall length of the catheter 300 might range from approximately 10 cm to approximately 200 cm, where the length of the distal, deflectable tip section 315 may range in length from 0.5 cm to 30 cm, though a length between 1 cm and 6 cm is more common. The proximal, non-deflectable portion 305 might have a length of approximately 10 cm to 199 cm. These lengths are intended to be illustrative and not limiting in any way as to the present invention. As one of skill in the art will appreciate, the length of any catheter in accordance with the various embodiments of the present invention can and will vary depending on the intended use and application for which the catheter is being employed.

[0050] As shown in FIG. 3, the needle 330 and the pull wire 320 are electrically connected, for example, at point D in the handle 310, where the pull wire 320 and the needle 330 together serve as the cores of a loopless antenna. The loopless catheter antenna is connected to an interface, decoupling circuit, also referred to as an interface circuit, such as the interface circuit illustrated in FIG. 5A or 5B, via a coaxial cable 345 and BNC connector 350. The interface circuit tunes the antenna to the appropriate frequency so the catheter 300 may be actively tracked within an MRI environment. The catheter antenna and the interface circuit is connected to the MRI scanner by a coaxial cable. The interface circuits in FIGS. 5A and 5B will be described in greater detail below.

[0051] The non-deflectable portion 305 of catheter 300 is covered by a braided polymeric tube 355, which acts as an RF shield for the loopless antenna. The braiding is preferably made from MRI compatible material, such as nitinol, tungsten, MP35N, copper, or other like materials. Alternatively, the non-deflectable portion 305 may be covered by a shield made from flexible MRI compatible hypotubing, where the hypotubing may be laser cut at different locations along its length, or heat-treated to modify the mechanical properties, so as to make the tubing flexible.

[0052] As stated, the proximal end of the catheter 300 includes a handle 310. The handle 310 houses, among other features, a deflection dial 312. The deflection dial 312 is part of the deflection mechanism. Manipulation of the deflection dial 312 causes the pull wire 320 to move relative to the anchor wire 325 which, in turn, causes the distal, deflectable tip section 315 to deflect under the constraint of anchor wire 325, for example, in the direction indicated by arrow C. The interface circuits 500 and 501 described in FIGS. 5A and 5B may be located in the handle of the deflectable tip catheter 300, in which case, the catheter will be directly connected to the MRI scanner.

[0053] FIG. 4A is a schematic diagram of a catheter 450 having a non-deflectable portion that includes the added safety feature of multiple RF chokes, in accordance with an alternative to the first exemplary embodiment illustrated in FIG. 1. This alternative embodiment may be particular useful in the event the non-reflectable portion of the catheter is excessively long, and there is added concern over heat build up along this portion of the catheter. As shown in FIG. 4A, the non-deflectable portion has primary shielding 451, secondary shielding 452, where the secondary shielding 452 has a length that is less than one-quarter wavelength (λ/4) and is connected to the primary shielding 451 at one end. At the other end, there may be a capacitor (not shown) located between the primary shielding 451 and the secondary shielding 452, or simply a stray capacitance resulting from the close proximity of the primary and secondary shielding, where there is a primary insulation layer 453 between the primary and secondary shielding 451 and 452. In addition, the secondary shielding 452 is, as shown, discontinuous. There is also a secondary insulation layer 456, located radially outside the secondary shielding 452. In a preferred embodiment, there is dual lumen tubing 457 running the length of the catheter 450, where a first one of the lumen is for pull wire 454, and the other lumen if for a surgical instrument, such as a needle 455.

[0054] It will be apparent that the needle 330 can extend beyond the distal deflectable tip 315, for example, in order to deliver or inject a therapeutic agent (e.g., cells, drugs, genetic material, other biological materials, and the like) into tissue during a clinical procedure. The mechanism for manipulating the needle 335 may include a spring mechanism (not shown) for ejecting the needle 330 tissue. The spring mechanism may be located in the distal, deflectable tip section 315 or in the handle 310. The mechanism for operating the needle 330 may also include a luer 360 which facilitates the attachment of a syringe (not shown) containing the therapeutic agent that is to be delivered to the tissue.

[0055] FIG. 4B is a schematic diagram illustrating an alternative distal, deflectable tip section 316 for injection catheter 300. As shown, the catheter 400 includes, in the distal, deflectable tip section 415, a pull wire 420 and an anchor wire 425. As was the case for the embodiment illustrated in FIG. 3, the anchor wire 425 is connected to the pull wire 420 at point A in the deflectable tip section 415 and fixed at a point B where the proximal end of the deflectable tip section 415 meets the distal end of the non-deflectable portion 405. The catheter 300 also includes an MRI compatible (i.e., non-magnetic), insulated metallic wire 465 connected to the pull wire 420 or the needle 430, where the metallic wire 465 is coiled backwards upon itself, as shown. The coiled wire 465 increases the MRI signal intensity associated with the distal tip of the catheter. Thus, the deflectable tip is more visible as compared to the rest of the catheter in the MR image, making it easier for the attending physician to locate and track the catheter 300.

[0056] FIG. 5A is a circuit diagram of an interface circuit 500 that may be employed if the needle 330 and the pull wire 320 are electrically connected or shorted at the proximal end in the handle section, as shown, for example, in FIG. 3. In a preferred embodiment, matching-tuning circuit 500 includes a balun 502, which prevents shield currents induced on the connecting coaxial cable (i.e., between the interface circuit and the scanner) from being transmitted to the catheter 300; decoupling circuitry 504, which decouples/detunes the catheter when the MRI scanner is transmitting RF energy, thus preventing excessive RF deposition along the length of the catheter 300; and matching-tuning circuitry 506, which tunes the loopless antenna associated with catheter 300 to the operating frequency of the MRI scanner (not shown), for example, 64 MHz at 1.5 Tesla.

[0057] If the needle 330 and the pull wire 320 are electrically connected, there is but one RF output signal associated with the loopless antenna, as shown by the single coaxial cable 345. Thus, the matching-tuning circuit 500 has but one electrical connection through the BNC connector 550, where the BNC connector 550, in FIG. 5A, connects with the BNC connector 350 in FIG. 3. The matching-tuning circuit 500 also has a BNC connector 570, which is electrically connected to the MRI scanner, via a coaxial cable (not shown). As there is but one RF output signal, the MRI scanner cannot separately and independently track the pull wire 320 (i.e., cannot separately and independently track the catheter, which serves as the first core of the loopless antenna) and the needle 330 (i.e., the second core of the loopless antenna).

[0058] FIG. 5B is a circuit diagram of an interface circuit 501 that may be employed if the needle 330 and the pull wire 320 are not electrically connected. As shown, matching-tuning circuit 501 has a decoupling and matching-tuning circuit A for the pull wire 320 and a separate decoupling and matching-tuning circuit B for the needle 330. In addition, the matching-tuning circuit 501 includes a BNC connector 551 with multiple insulated cores or a multi-pin connector, a BNC connector 571 and a BNC connector 572. BNC connector 551 contains three separate electrical conductors: one for the needle 330, one for the pull wire 320 and one that serves as a ground connection. BNC connector 571 is electrically connected to the MRI scanner via a coaxial cable (not shown), and the electrical conductor associated with the BNC connector 571 carries the output signal associated with the pull wire 320. Similarly, BNC connector 572 is electrically connected to the MRI scanner via a coaxial cable (not shown), and the electrical conductor associated with the BNC connector 572 carries the output signal associated with the needle 330. As there are two separate output signals, one for the needle 330 and one for the pull wire 320, the MRI scanner can separately and independently track the position and location of the needle 330 and the pull wire 320. As the pull wire 320 always remains inside the catheter 300, it will be understood that tracking the position and location of the pull wire 320 equates to tracking the position and location of the catheter 300.

[0059] FIG. 6 is a schematic diagram of an injection catheter 600 in accordance with a second exemplary embodiment of the present invention. As shown in FIG. 6, the distal, deflectable tip section 615 is pre-shaped into a relatively small radius, so the catheter 600 can more easily traverse through, for example, the aortic valve without causing damage. The catheter 600 is typically advanced into the left ventricle through the femoral artery and across the aortic arch through the aortic valve. Once in the left ventricle, the attending physician can manipulate the deflection dial 612 to deflect the tip of the catheter 600. To facilitate the retraction of the catheter 600 from the left ventricle, the attending physician may straighten the distal, deflectable tip section 615, as indicated by arrow A, by manipulating the deflection dial 612 appropriately.

[0060] FIG. 7 is a schematic diagram of an injection catheter 700 in accordance with a third exemplary embodiment of the present invention. In this embodiment, the catheter 700 includes an electrode 775 built into the distal end of the deflectable tip section 715. This electrode may be used to measure the electrical potential of adjacent tissue (e.g., endocardial tissue). Although the catheter 700, illustrated in FIG. 7, has but one electrode, it will be apparent to those skilled in the art that it would be feasible to employ more than a single electrode.

[0061] FIG. 8 is a circuit diagram of an exemplary matching-tuning circuit 800 that may be used in conjunction with injection catheter 700 illustrated in FIG. 7. As shown, matching-tuning circuit 800, like matching-tuning circuit 501 in FIG. 5B, has separate RF input leads for the pull wire 720 and the needle 730. In addition, there is separate decoupling and matching-tuning circuitry A and B for the pull wire 720 and the needle 730. Accordingly, the MRI scanner will be able to separately track the position and location of the catheter 700 (i.e., by tracking the position and location of the pull wire 720) and the needle 730. The matching-tuning circuit 800 also includes RF blocking circuitry 880. The RF blocking circuitry 880 filters out any RF components associated with the electrical potential output signal. Thus, the EP signal output will more accurately reflect the electrical potential of the tissue adjacent to the distal end of the deflectable tip section 715 of catheter 700.

[0062] In the embodiments described above, the needle, as stated previously, is preferably made of MRI compatible metal, e.g., nitinol, MP35N, titanium, tantalum, gold, platinum, various non-ferromagnetic alloys, and the like. In addition, the needle may be selectively heat-treated; for example, the distal end of the needle may be heat treated, such as the last 10 cm of the needle. By heat treating the distal end of the needle, the distal end of the needle can be adjusted for stiffness and made more flexible than the proximal portion of the needle. This makes it easier for the attending physician to advance the needle into adjacent tissue (e.g., myocardial tissue) particularly when the distal tip of the catheter is deflected. The needle may also be coated with a hydrophilic or hydrophobic coating on the inside and/or outside to enhance injection rates and reduce the shear stress experienced by cells being injected through the needle. Still further, the outer surface of the needle may be electroplated using a conducting metal, such as gold, silver, copper or the like, to enhance the RF and/or the electrical potential signal associated with the needle.

[0063] In the embodiments described above, the injection catheters employ but one needle. However, it will be evident that more than one needle may be employed, where each would serve as a separate core for the loopless antenna. The attending physician would, of course, have the ability to advance each needle individually, where each needle may contain a different therapeutic agent.

[0064] In each of the embodiments described above, the needle projects through the distal end of the deflectable tip section of the injection catheter. However, FIGS. 9A and 9B are schematic diagrams of an injection catheter 900 and an injection catheter 910, respectively, in accordance with a fourth exemplary embodiment of the present invention, wherein the injection needle 903 and the injection needle 913 project through a side or lateral opening in the deflectable tip section of the catheter, rather than an opening in the distal end of the deflectable tip section of the catheter. But for the side or lateral needle openings, injection catheter 900 and injection catheter 910 have the same, or substantially the same, configuration as injection catheter 300 and injection catheter 400, as illustrated in FIG. 3 and FIG. 4B, respectively. Alternatively, the injection catheter 900 and the injection catheter 910 may contain one or more needles and have multiple needle outlets through which the attending physician may advance a needle, including an opening in the distal end of the deflectable tip section 915, as well as one or more lateral openings. Similarly, needles may be concentrically places one inside the other and advanced by the attending physician in a telescopic fashion.

[0065] Side or lateral needle openings may be quite beneficial during certain procedures. For example, such a catheter as illustrated in FIG. 9A or 9B may be advanced into a coronary artery. The needle may then be advanced more easily through a side or lateral opening, in the deflectable tip section, through the arterial wall and into the adjacent myocardium to enable delivery of a therapeutic into the tissue. Such a catheter would also be useful in a vascular bypasss procedure.

[0066] There are many additional features associated with the catheter needle that may be incorporated into the various embodiments of the present invention. For example, the catheter may have a mechanism preferably located on or near the handle of the catheter for locking the needle in place, releasing the needle from a locked position and controlling the extent of needle insertion into adjacent tissue. For example, it may be useful to lock the needle in a retracted position to prevent the accidental injection of a therapeutic agent.

[0067] FIG. 10A is a schematic diagram of an injection catheter 1000, in accordance with a fifth exemplary embodiment of the present invention. In this embodiment, the needle 1030 and the pull wire 1020 serve as parallel wires of an elongated loop antenna, rather than a loopless antenna. The matching-tuning circuit for decoupling and tuning the loop antenna is shown as being located in the handle 1010 of the injection catheter 1000. However, the matching-tuning circuit could be externally located, like the previous embodiments described above.

[0068] FIG. 10B is a schematic diagram that more clearly depicts an interface circuit 1050 that might be used in conjunction with the injection catheter 1000. The circuit 1050 includes an electrical connector or lead for the pull wire 1020 and the needle 1030, a series capacitor 1021, a series capacitor 1031, a parallel capacitor 1032 and a PIN diode 1033. There may also be a series capacitor 1034 at the distal end of the inductor loop, or there may be stray capacitance induced by the close proximity of the two conductors and the dielectric there between. The parallel capacitor 1032 and the PIN diode 1033 serve as the decoupling circuitry. It will be understood, however, that other matching-tuning circuit configurations may be employed with the catheter 1000.

[0069] The exemplary embodiments described herein below, involve deflectable guide catheters. In general, the guide catheters covered by these embodiments comprise a proximal, non-deflectable shaft and a distal, deflectable tip section. The distal, deflectable tip section preferably includes an outer tubing and, within the outer tubing, thin walled hypotubing, made from a superelastic MRI compatible metal/alloy, such as nitinol, MP35N, and the like. The hypotubing is slotted (i.e., it has cut-outs) on at least one side, similar to that which is illustrated in FIG. 2. The diameter of the lumen associated with a guide catheter is relatively large, to accommodate the one or more medical instruments passing there through. The slotted hypotubing provides greater deflectability where the diameter of the distal, deflectable tip section is, as stated, relatively large.

[0070] In accordance with the guide catheters in the exemplary embodiments described below, the proximal, non-deflectable shaft portion is preferably covered by braided or non-braided polymeric tubing. If braided tubing is used, the material will be a MRI compatible metal, for example, nitinol, tungsten, titanium, tantalum, MP35N, or a non-metal, such as Kevlar. Moreover, these guide catheters may have an inner tubing running the length of the catheter, where the lumen of this inner tubing would accommodate the aforementioned medical instruments. The inner tubing will be made from a suitable, MRI compatible material that also facilitates the movement of the one or more medical instruments (e.g., teflon).

[0071] FIG. 11 is a schematic diagram of a uni-directional, deflectable tip guide catheter 1100, in accordance with a sixth exemplary embodiment of the present invention. As set forth above, the deflectable tip guide catheter 1100 includes a proximal, non-deflectable shaft 1105, a handle 1110, and a distal, deflectable tip section 1115. The non-deflectable shaft 1105 is covered by braided tubing 1106, where the braided tube 1106 is made from an MRI compatible material. The distal, deflectable tip section 1115 contains a slotted hypotube 1116. The distal, deflectable tip section 1115 is electrically isolated from the braid 1106 by an insulating strip 1107. In addition, the guide catheter 1100 includes a pull wire 1120. In the non-deflectable shaft 1105, the pullwire 1120 runs along the inside of the braided tubing 1106, within a wire tube 1130, thus creating an eccentric coaxial cable. In the distal, deflectable tip section 1115, the pull wire 1120 runs along the inner wall of the slotted hypertube 1116, and is attached thereto at point A, as shown. In this sixth exemplary embodiment, the braid 1106 and the pull wire 1120 together form a loopless antenna. An interface circuit, such as the one shown in FIG. 5A, may be used to decouple and tune the loopless antenna and to provide a single RF output signal for the MRI scanner, so the catheter 1100 can be actively tracked and/or visualized.

[0072] Further regarding the guide catheter 1100, the braid 1106 and the pull wire 1120 may, alternatively, be configured so as to form an elongated loop antenna, rather than a loopless antenna. In accordance with this alternative embodiment, the braid 1106 is electrically connected to the proximal end of the slotted hypotube 1116, whereas the insulated pull wire 1120 is connected to the distal end of the slotted hypotube 1116. Both the pull wire 1120 and the braid 1106 are connected to the core and the shielding of a coaxial cable at the proximal end of the catheter, for example, in the handle of the catheter, wherein an interface circuit, such as the matching-tuning circuit shown in FIG. 10B, is employed to decouple and tune the loop antenna, and to generate and forward an RF output signal to the MRI scanner so that the catheter 1100 can be actively tracked and/or visualized.

[0073] FIG. 12 is a schematic diagram of a bi-directional, deflectable tip guide catheter 1200, in accordance with a seventh exemplary embodiment of the present invention. The guide catheter 1200 is substantially similar to the guide catheter 1100, illustrated in FIG. 11, but for guide catheter 1200 has two pull wires 1220 and 1221, rather than one pull wire, where the pull wires 1220 and 1221 are attached to the inner wall of the slotted hypotube 1216 at points A and B, respectively, to facilitate bi-directional deflection. In addition, the two pull wires 1220 and 1221 are electrically configured to form a loop antenna. Although not shown in FIG. 12, an interface circuit, such as the matching-tuning circuit in the handle of catheter 1000, illustrated in FIG. 10, may be employed to decouple and tune the loop antenna, and to provide an RF output signal for the MRI scanner so the catheter 1200 can be actively tracked and/or visualized. It will be understood, however, that the two pull wires 1220 and 1221 could be configured, in the alternative, to form a loopless antenna.

[0074] The guide catheters 1100 and 1200, described above, can, of course, be modified such that they may be employed as injection catheters. This may be achieved, for example, by incorporating an injection needle into the guide catheter assembly, where the injection needle can be actively tracked and/or visualized by providing a corresponding, separate RF path between the needle and the MRI scanner via an interface circuit. Alternatively, the needle may also be passively tracked.

[0075] FIG. 13 is a diagram of an injection needle 1300 that can be passively tracked in an MRI environment. As shown, needle 1300 has a proximal, polymeric tube section 1301, a distal section 1302 and a leur 1303. The distal section 1302 is made of an MRI compatible metal, and it includes a beveled tip 1304. The leur 1303 is used to attach a syringe that may contain a therapeutic agent. The length of the needle 1300 will approximate {fraction (1/4)} wavelength (λ), for example, 10 cm for a 1.5 Tesla system). In addition, the needle 1300 may be insulated or uninsulated. Preferably, there would be some calibrated indicator on the handle, for example, that reflects the extent to which the needle 1300 is deployed in the patient tissue. The primary advantage realized by the use of needle 1300 is that the proximal polymeric section 1301 does not generate any significant heat, which might otherwise pose a safety hazard for the patient.

[0076] FIG. 14 is a diagram of an injection needle 1400 that is capable of being actively tracked, separately and independently from the guide catheter. As shown, the needle 1400 has a proximal section, where the proximal section is covered by an inner shielding layer 1401, and where the inner shielding 1401 is covered by an outer insulating layer 1402. The needle 1400 also has a distal tip portion with a beveled edge 1403. The distal tip portion is made from an MRI compatible metal, and it includes a polymeric insulating sheath. Together, the shielding layer 1401, the outer insulating layer 1402 and the polymeric insulating sheath prevent the needle 1400 from generating a significant amount of heat, which might otherwise pose a safety hazard for the patient. In addition, the needle 1400 has a built-in loopless antenna, which is connected to an interface circuit via one or more electrical leads 1404 through a BNC connector 1405. It is this built-in antenna that allows the needle 1400 to be actively tracked and/or visualized separate and independent of guide catheter in which the needle 1400 is contained. It should be noted that the needle may be coated with an insulating polymeric dielectric layer, e.g., polyimide, polyurethane lacquer, and the like, on the inside.

[0077] FIG. 15 is a diagram of an injection needle 1500 that is capable of being actively tracked, separately and independently from the guide catheter. It differs from the injection needle illustrated in FIG. 14 in that injection needle 1500 is configured as a loop antenna, rather than a loopless antenna.

[0078] It is of particular importance to be able to track and/or visualize the distal tip of the injection needle. Thus, the needles described above may include a thin metallic wire coiled around the distal tip. This will increase the intensity of the RF signal associated with the distal tip of the needle, thereby making the distal tip of the needle more visible under MRI.

[0079] The ability to identify and select the geometric plane in which the catheter lies during an MRI procedure is quite important, as it allows the attending physician to then more rapidly and precisely identify and prescribe image slices of interest that are associated with or intersect this plane. U.S. Pat. No. 6,687,530, which is incorporated herein by reference, proposes a methodology for tracking the location of individual coils located along the length of a catheter, in three dimensional space, using MRI, and acquiring an image in or associated with the geometric plane defined by the location of the coils. This technique then permits an attending physician to identify the geometric plane and, thereafter, select and visualize imaging slices relative to that geometric plane. A catheter in accordance with exemplary embodiments of the present invention will now be described for use with an MRI system that employs the capability provided by this or similar methodologies.

[0080] FIG. 16 is a diagram of a deflectable tip catheter 1600, that includes three individual inductor loop coils, in accordance with a seventh exemplary embodiment of the present invention, wherein the basic structure and design of the deflectable tip catheter 1600 may take the form of any one of the catheters described in the previous exemplary embodiments, with the addition of a guidewire lumen. The deflectable tip catheter 1600 has, in addition to those catheters described above, a guidewire 1601 which is made from a relatively stiff, MRI compatible material. Attached to or connected to the distal tip of the guidewire 1601 is an inductor loop coil 1602. The attending physician will advanced the guidewire 1601 into the left ventricle (LV), or other anatomical structure of interest, as shown in FIG. 16. The attending physician then advances the deflectable tip catheter 1600 over the guidewire 1601, where the guidewire 1601 runs through a guidewire lumen 1605. There are two additional inductor loop coils 1603 and 1604 located at the deflectable tip section of the catheter 1600. More specifically, coil 1603 is located at the fulcrum, or point of deflection, and coil 1604 is located at the distal tip of the catheter 1600.

[0081] Each of the three inductor loop coils 1602, 1603 and 1604 are electrically connected to a corresponding coaxial cable (not shown in FIG. 16) so that the MRI system using, for example, the aforementioned software, can identify the location of the three inductor loop coils 1602, 1603 and 1604 in three dimensional space within the anatomical structure of interest, track the geometric plane through the anatomical structure of interest defined by the location of the three coils 1602, 1603 and 1604, and generate an image slice relative to the geometric plane as specified by the attending physician. Once the attending physician has positioned the distal tip of deflectable catheter 1600 so that it is pointing towards the region of interest, the physician may advance the injection needle into, for example, the myocardial tissue to deliver a therapeutic agent.

[0082] FIG. 17 is a schematic diagram of a deflectable tip catheter 1700, including three, non-magnetic inductor loop coils, in accordance with an alternative to the seventh exemplary embodiment described above. As shown, the three inductor loop coils 1702, 1703 and 1704 are built into the distal, deflectable tip section 1715. Each of the inductor loop coils 1702, 1703 and 1704 are electrically connected to a corresponding coaxial cable, as shown, so that the MRI scanner, through, for example, software as described above, can individually identify the position and/or location of each coil in three dimensional space and, there from, acquire an image associated with the geometric plane defined by the position of the three coils. This information will assist the attending physician in guiding or steering the catheter 1700 into a desired location and/or position.

[0083] These individual loop coils could be coiled circumferentially around the diameter of the catheter, on the outside, or place inside the catheter tubing. In addition, the coils may be placed inside the distal tip, or other locations, and oriented in the x, y and z planes, i.e., orthogonal to one another. The aforementioned tracking methodology could be implemented to track the position and location of the coils.

[0084] FIG. 18 is a diagram of an MRI system 1800 in accordance with exemplary embodiments of the present invention. The MRI system 1800 of FIG. 18 includes a magnetic field generator 1801, for establishing a magnetic field on the patient, and an RF source 1802 for emitting RF signals to at least a portion of the patient disposed within the magnetic field. Of particular importance, the MRI system 1800 employs a deflectable tip, MRI compatible catheter 1803, in accordance with the present invention, such as any of the deflectable tip catheters described herein above. In addition, the MRI system 1800 includes an interface circuit 1804. The specific antenna interface circuit that is employed will, of course, depend on the deflectable tip, MRI compatible catheter 1803 that is employed, as set forth above. The RF signals received by the antenna in the deflectable tip, MRI compatible catheter 1803 and the antenna interface circuit 1804 are then amplified by the pre-amplifier 1805, and converted from analog to digital by the A/D converter 1806. The digital signals are then provided to the processor 1807, which employs hardware and/or software, as discussed above) to generate MRI information relating to the patient, as well as the position and location of the deflectable tip, MRI compatible catheter 1803 and, in accordance with certain embodiments described above, the position and location of any surgical instrument or instruments contained in the catheter 1803 (e.g., the position and location of an injection needle). The MRI information is then displayed in the form of a MR image on display 1808, so that the attending physician can visualize and more effectively steer the catheter 1803 to or within the anatomical structure of interest.

[0085] It will be apparent to those skilled in the art that various modifications and variations of the exemplary embodiments described above can be made without departing from the spirit or scope of the present invention. Thus, it is intended that the present invention cover these modifications and variations provided they come within the scope of the appended claims and the equivalents thereof.

Claims

1. A deflectable tip catheter for use in an MRI environment comprising: a deflectable tip section; and an RF antenna.

2. The deflectable tip catheter of claim 1 further comprising: a pull wire; and a surgical instrument, wherein said pull wire and said surgical instrument are made of a non-magnetic material and configured to form said antenna.

3. The deflectable tip catheter of claim 2, wherein said antenna is a loop antenna.

4. The deflectable tip catheter of claim 2, wherein said antenna is a loopless antenna.

5. The deflectable tip catheter of claim 4, wherein said loopless antenna has multiple cores insulated from one another, and wherein the cores move with respect to each other.

6. The deflectable tip catheter of claim 5, wherein said pull wire serves as a first core of the loopless antenna and said surgical instrument serves as a second core for the loopless antenna.

7. The deflectable tip catheter of claim 2 further comprising: an interface circuit including at least one RF output.

8. The deflectable tip catheter of claim 7, wherein the interface circuit includes: a first RF output corresponding to the surgical instrument; and a second RF output corresponding to the pull wire.

9. The deflectable tip catheter of claim 2, wherein said deflectable tip section comprises: at least one opening for said surgical instrument.

10. The deflectable tip catheter of claim 9, wherein the at least one opening for said surgical instrument is located in the distal end of the deflectable tip section.

11. The deflectable tip catheter of claim 9, where the at least one opening for said surgical instrument is located laterally in the deflectable tip section.

12. The deflectable tip catheter of claim 2, wherein said surgical instrument is an injection needle.

13. The deflectable tip catheter of claim 2, wherein said surgical instrument is a forceps.

14. The deflectable tip catheter of claim 2, wherein said deflectable tip section comprises: a non-magnetic conductor coil electrically connected to said pull wire.

15. The deflectable tip catheter of claim 1, wherein said RF antenna is a loopless antenna comprising multiple cores that move relative to each other.

16. The deflectable tip catheter of claim 15, where at least one core provides means for delivering therapeutics.

17. The deflectable tip catheter of claim 15, where at least one core provides means for measuring an electrical potential.

18. The deflectable tip catheter of claim 15, where at least one core provides means for steering the deflectable tip catheter.

19. The deflectable tip catheter of claim 1 further comprising: a handle; and a shielded, non-deflectable section located between said handle and said deflectable tip section, wherein said deflectable tip section is pre-deflected.

20. The deflectable tip catheter of claim 19, wherein the RF antenna is a loopless antenna including multiple cores insulated from one another, and wherein the shielded, non-deflectable section comprises a plurality of non-magnetic RF chokes connected to the shielding.

21. The deflectable tip catheter of claim 20, wherein the RF chokes are substantially one-quarter wavelength (λ/4).

22. The deflectable tip catheter of claim 1, wherein said catheter is a deflectable tip guide catheter, and wherein said deflectable tip section comprises a slotted hypotube.

23. The deflectable tip catheter of claim 1, wherein said deflectable tip section comprises: an electrode for sensing the electrical potential of adjacent tissue.

24. The deflectable tip catheter of claim 1 further comprising: an interface circuit that includes at least one RF output, RF blocking circuitry and an electrical potential output connected to the RF blocking circuitry.

25. A bi-directional, deflectable tip guide catheter comprising: a deflectable tip section; a first pull wire; and a second pull wire, wherein said first and said second pull wires are configured to form a loop antenna.

26. The guide catheter of claim 25 further comprising: a handle; and a shielded, non-deflectable shaft portion located between the deflectable tip section and the handle.

27. The guide catheter of claim 25 further comprising: a lumen axially located along the length of the guide catheter, wherein the lumen is adapted to accommodate at least one surgical instrument.

28. The guide catheter of claim 27, wherein the surgical instrument is an injection needle.

29. The guide catheter of claim 28, wherein the injection needle comprises: a proximal, polymeric section; and a distal tip section that includes a beveled edge.

30. The guide catheter of claim 28, wherein the injection needle comprises: an insulated, shielded proximal section; and a polymeric, insulated tip section, that includes a beveled edge, and wherein the injection needle is configured as a loopless antenna.

31. The guide catheter of claim 28, wherein the injection needle comprises: an insulated wire, and wherein the injection needle is configured as a loop antenna.

32. A deflectable tip catheter comprising: a deflectable tip section; an antenna; and a plurality of distally located, non-magnetic, inductor loop coils.

33. The deflectable tip catheter of claim 32 further comprising: a guidewire; and a guidewire lumen running axially along the length of the catheter, wherein said catheter is moveable over said guidewire.

34. The deflectable tip catheter of claim 33, wherein at least one non-magenetic, inductor loop coil is located on the guidewire.

35. The deflectable tip catheter of claim 33, wherein at least two non-magnetic, inductor loop coils are located in the deflectable tip section of the catheter.

36. The deflectable tip catheter of claim 32 comprising at least three non-magnetic, inductor loop coils. III-B.

37. An MRI system comprising: an MRI scanner; a deflectable tip catheter that is configured as an RF antenna; and an electrical connection between said deflectable tip catheter and said MRI scanner.

38. The MRI system of claim 37, wherein said electrical connection comprises: an interface circuit.

39. The MRI system of claim 38, wherein the interface circuit is located in a handle portion of the deflectable tip catheter.

40. The MRI system of claim 38, wherein said antenna is configured as a loopless antenna.

41. The MRI system of claim 38, wherein said antenna is configured as a loop antenna.

42. The MRI system of claim 37 further comprising: means for processing RF signals received from said antenna.

43. The MRI system of claim 42 further comprising: means for tracking the deflectable tip catheter inside a patient based on the processed RF signals received from the antenna.

44. The MRI system of claim 42 further comprising: means for visualizing the deflectable tip catheter inside the patient based on the processed RF signals received from the antenna.

45. The MRI system of claim 42, wherein said deflectable tip catheter comprises a plurality of inductor loop coils, and wherein the processing means comprises: means for determining a location within the patient for each of the inductor loop coils; means for identifying an image slice, in three dimensional space, as a function of the location of the inductor loop coils.

46. The MRI system of claim 42, wherein said catheter contains an injection needle, and wherein said MRI system further comprises: an electrical connection between the needle and the MRI scanner, separate and independent of said electrical connection between said deflectable tip catheter and said MRI scanner.

47. The MRI system of claim 46, wherein the processing means comprises: means for tracking said deflectable tip catheter based on the RF signal received from the antenna; and means for tracking the needle, separate and independent of said deflectable tip catheter based on signals received by said MRI scanner over the electrical connection between the needle and the MRI scanner.

48. A magnetic resonance imaging method comprising the steps of: generating a magnetic field around at least a portion of a patient; transmitting RF energy over a portion of the patient exposed to the magnetic field; receiving the RF energy using an RF antenna in a deflectable tip catheter located in the patient; and generating a magnetic resonance image that includes a visualization of the deflectable tip catheter in the patient.

49. The method of claim 48 further comprising the step of: steering the deflectable tip catheter to a location of interest in the patient using the image that includes the visualization of the deflectable tip catheter.

50. The method of claim 49, wherein the deflectable tip catheter is an injection catheter that contains an injection needle, said method further comprising the step of: injecting a therapeutic into the patient using the injection needle.