Intracardiac catheter having an X-ray emitting probe

Abstract

A system (20) for tissue ablation includes a probe (22), an expandable capsule (50), a voltage discharge device (210), and a generator (49). The probe is configured to be inserted into a cavity of a patient's organ. The expandable capsule is attached to the distal end of the probe and is configured to expand within the cavity and be filled with a gas (250). The voltage discharge device is attached inside the expandable capsule and is configured to generate plasma by electrical excitation of the gas filling the expandable capsule, and the plasma emits X-rays (270) for ablating tissue within the cavity using the X-rays. The generator is wired to the voltage discharge device to apply an electrical signal for electrically exciting the plasma.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 390,324, filed Jul. 19, 2022, which is incorporated herein by reference.

[0002] (Field of the Invention) The present invention relates generally to medical devices, and more particularly, to methods and systems for ablating tissue using an in - body probe that generates X - rays.

Background Art

[0003] In - body probes that emit X - rays have been proposed in the patent literature. Typically, such probes include a small X - ray tube. For example, U.S. Patent No. 6,148,061 describes a small X - ray unit that includes a first electrical node, a second electrical node, and an insulating material that does not extend within a vacuum gap between the first electrical node and the second electrical node. By retreating the insulating material from the vacuum gap, the insulator is less likely to be electrically destroyed due to charge accumulation and / or accumulation of other materials on the surface of the insulator. In a preferred embodiment, the first node is an anode and the second node is a cathode. Alternatively, the first node may be a cathode and the second node may be an anode.

[0004] The present disclosure, together with the drawings, will be more fully understood from the following detailed description of embodiments of the present disclosure.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0006] Overview An X-ray radiotherapy catheter for ablating tissue may in principle be manufactured as a catheter including, for example, a small X-ray tube attached to the distal end of the catheter. Such a device has advantages over, for example, brachytherapy using radioactive elements. However, in practice, the availability of such catheters for ablation therapy is partly hampered by the availability of other radiotherapy methods and the very high complexity of the small devices that need to be attached to the distal end of the catheter.

[0007] The embodiments of the present disclosure described below provide X-ray radiotherapy techniques and radiotherapy catheters that are relatively easy to implement. In one example, an X-ray radiotherapy probe provided for insertion into a cavity of an organ of a patient's body includes an expandable capsule, such as an expandable balloon, attached to the distal end of the probe. The expandable capsule includes a high-voltage plasma discharge device that causes X-ray emission by electrical excitation of a noble gas filling the expandable capsule, and thus is configured to generate an X-ray emitting plasma that ablates the wall tissue of the cavity. An external high-voltage generator is wired to the discharge device to apply a high-voltage signal for electrically exciting the plasma.

[0008] In one embodiment, the discharge device includes two insulating wires that extend inside a capsule or balloon, the wires terminate at respective pairs of electrodes, and each electrode is powered by a respective wire. The capsule or balloon is filled with an inert noble gas (e.g., argon, neon, krypton, or xenon). In particular, the balloon can be inflated with an inert noble gas. In some embodiments, the expansion of the capsule may be assisted by an additional force provided, for example, by a self-expanding spline.

[0009] When a high voltage (e.g., 50 kV to 100 kV) is applied between the electrodes in an environment of a noble gas within the capsule / balloon, an arc discharge occurs between the electrodes. The arc discharge discharges a plasma that emits X-ray radiation during the process. For example, as will be described later, krypton plasma emits K-shell X-rays having energies in the range of about 13 to 16 keV. As further shown below, X-rays in the range of 13 to 16 keV have a penetration depth into tissue in the range of about 2 to 4 millimeters, which is an optimal depth range for clinical applications such as cardiac ablation (including tumor treatment, in addition to known applications for which such technology is suitable).

[0010] In some examples, to improve safety, the capsule / balloon is covered with an outer layer (e.g., a second balloon).

[0011] In the context of the present disclosure and the claims, the term "about" or "approximately" used with any numerical value or range indicates an appropriate dimensional tolerance that allows a component part or a set of components to function for its intended purpose as described herein.

[0012] Description of the system Figure 1 is a schematic diagram of a catheter-based position tracking and X-ray ablation system 20 according to an embodiment of the present disclosure. In the illustrated example, system 20 is used for X-ray ablation of the ostium 51 of the PV (shown in the inset 25) using a balloon 50 (an example of an expandable capsule 50 that can be used) disposed within the left atrium 57 of the heart 26. For this purpose, the balloon 50 is attached with an X-ray source (e.g., a voltage discharge device) as shown in FIG. 2 such that X-rays penetrate the tissue location of the target ostium 51 and ablate the tissue to a given extent (e.g., depth). To perform ablation, the physician 30 advances the balloon into the left atrium and then expands the balloon 50 (e.g., using a spline). The balloon expands (e.g., when the balloon exits the sheath 23, the balloon self-expands by a nitinol spline to return to a pre-formed shape).

[0013] Noble gases such as krypton may be introduced into the balloon 50 at a pressure lower than atmospheric pressure, e.g., a weak vacuum. For this purpose, as one of at least some possible options, the pump 43 on the console 24 of the system 20 sucks the balloon and then pumps the noble gas through a pipe 45 passing inside the catheter 22 (an example of an invasive probe 22 that can be used), and the catheter 22 is typically at a pressure below atmospheric pressure and is not involved in maintaining a fully expanded balloon.

[0014] The physician contacts, for example, the expanded balloon having krypton with the ostium 51 and then the X-ray source (seen in FIG. 2) within the balloon is excited to generate X-rays that emit krypton plasma.

[0015] As shown, balloon 50 is attached to the distal end of catheter 22 configured to perform cardiac procedures. System 20 includes console 24 that includes a high voltage generator 49 that uses a high voltage signal to generate krypton plasma within balloon 50. In some examples, a patient interface unit (PIU) 44 is connected to high voltage generator 49 that provides an electrical interface for the equipment included in system 10.

[0016] Console 24 further includes a processor 33 (typically a general purpose computer) that includes appropriate front end and interface circuitry for applying a high voltage signal via catheter 22 (to generate krypton plasma) and for controlling the other components of system 20 described herein. Console 24 further includes a user display 35 configured to receive graphic and / or text display items, such as map 27 of heart 26, from processor 33 and to display map 27.

[0017] In some examples, console 24 is used with additional catheters, such as an electroanatomical (EA) mapping catheter (not shown). For this purpose, console 34 includes a recording unit 38 configured to record in the event of a malfunction of the EA mapping system and / or a malfunction of pacing of a particular electrode. Patient interface unit (PIU) 44 may be configured to generate a signal indicative of position. PIU 44 may be configured to perform calculations and / or processing of the acquired electrocardiogram (ECG) signal.

[0018] In some examples, as shown in inset 25, prior to performing an X-ray ablation procedure, physician 30 inserts one or more catheters into the vasculature of patient 28 lying on table 29 and performs an EA mapping of the tissue of heart 26 that is problematic. Based on the EA mapping, physician 30 plans the X-ray ablation.

[0019] In this embodiment, physician 30 intends to perform an X-ray ablation procedure at an intended position on the surface of the left atrium 57 of the heart 26. Optionally, the physician uses the handle 32 to (i) insert the sheath 23 through the vasculature of the patient 28 into the right atrium 53 of the heart 26, (ii) puncture the septum 55 between the right atrium 53 and the left atrium 57 with the sheath to create a hole 54 (also referred to herein as a transseptal hole), (iii) insert the sheath 23 through the hole 54 to the intended location in the left atrium 57, (iv) advance the folded balloon within the sheath 23 to the intended location in the left atrium 57, (v) expand and inflate the balloon 50 outside the sheath 23, (vi) bring the balloon into contact with the target tissue and apply a high voltage signal to generate X-rays that ablate the tissue, thereby performing an X-ray ablation procedure. In another example, more direct access to the left atrium can be achieved through the aorta.

[0020] In some examples, the system 20 includes one or more patch electrodes 48, one of which is shown, and the patch electrodes 48 are attached to the skin of the patient 28 and electrically connected to the PIU 44 via the cable 21 to measure, for example, an ECG signal (the signal is not shown).

[0021] In some embodiments, the position of the balloon 50 within the vasculature of the patient 28 and the heart 26 is measured using the magnetic position sensor 66 of the magnetic position tracking system. In this embodiment, the console 24 and / or the PIU 44 includes a driver circuit 41 configured to drive a magnetic field generator 36 placed outside the patient 28 lying on the table 29, for example, under the torso of the patient. The position sensor is coupled to the distal end and is configured to generate a position signal in response to the sensed external magnetic field from the magnetic field generator 36. The position signal indicates the position of the distal end of the catheter 22 in the coordinate system of the position tracking system.

[0022] This location sensing method is implemented in various medical applications, for example, in the CARTO (trademark) system manufactured by Biosense Webster Inc. (Irvine, Calif.), and is described in detail in U.S. Patent Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, International Publication No. 96 / 05768, and U.S. Patent Application Publication Nos. 2002 / 0065455(A1), 2003 / 0120150(A1), and 2004 / 0068178(A1).

[0023] In some embodiments, processor 33 typically includes a general-purpose computer programmed in software to perform the functions described herein. The software can be downloaded to the computer in electronic form, for example, via a network, or alternatively or additionally, can be provided and / or stored on a non-transitory tangible medium such as magnetic memory, optical memory, or electronic memory.

[0024] This particular configuration of system 20 is shown by way of example to illustrate the particular problems addressed by embodiments of the present disclosure and to demonstrate the application of these embodiments in improving the performance of such a system. However, embodiments of the present disclosure are in no way limited to this particular type of exemplary system, and the principles described herein may be equally applicable to other types of medical systems. In particular, for example, a rigid wall capsule configured to expand when outside sheath 23, perhaps made modularly, may be used in place of the balloon.

[0025] Intracardiac catheter having an X-ray emitting probe FIG. 2 is a schematic side view of the X-ray ablation balloon 50 of the catheter 22 of the system 20 of FIG. 1 according to an embodiment of the present disclosure. As can be seen, the voltage discharge device 210 is included inside the balloon in the form of two insulating wires (215, 216) that extend inside the balloon and terminate at a respective pair of electrodes (225, 226) powered by the wires. The capsule or balloon is filled with an inert rare gas (250) (e.g., krypton) via a pipe 45 having an outlet 245 inside the balloon.

[0026] When a high voltage (e.g., 50 kV to 100 kV) is applied between the electrode 225 and the electrode 226 in an environment of the rare gas 250, an arc discharge occurs between the electrodes. The arc discharge discharges a plasma that emits X-ray radiation 270 during the process. As a result, when applied to PV isolation, the X-ray can penetrate the small hole 51 over the entire circumference of the small hole and ablate the tissue 251 to a depth 260 into the myocardium. The ablated tissue blocks the arrhythmogenic excitation that causes atrial fibrillation (AFib).

[0027] As seen in FIG. 1, in some examples, the position of the balloon 50 within the vasculature and heart 26 of the patient 28 is measured using a magnetic position sensor of a magnetic position tracking system that associates the balloon position with an electroanatomical map constructed by the system. Other ways to know when the balloon 50 is in the correct position to initiate X-ray ablation include using fluoroscopy, examining an intracardiac electrogram that indicates arrhythmogenic tissue, and electrically tracking the balloon position (e.g., using one or more electrodes disposed at the distal end).

[0028] FIG. 2 is simplified to clarify the presentation of the concept of the high voltage plasma discharge device included in the balloon. Accordingly, other elements that may be part of the balloon catheter (e.g., mechanical elements used to expand and fold the balloon) are omitted.

[0029] Furthermore, while the shape of the electrode is conceptual, the actual shape and geometric arrangement of the electrode can vary. For example, the electrodes can be arranged in a concentric circle shape with a central cathode and a ring anode to ionize the noble gas in a ring shape.

[0030] Selection of Noble Gas The penetration depth is defined as the depth at which the intensity of the X-ray radiation inside the material decreases to 1 / e (about 37%) of its original value at the surface (or more appropriately, just below the surface). The X-ray penetration depth in the range of 13 - 16 keV is in the range of more than 3 mm to more than 5 mm. In the case of muscle tissue, the penetration depth is slightly smaller by a few percent (based on the NIST attenuation table), i.e., in the range of about 3 - 5 mm.

[0031] Krypton K-shell X-ray emission lines (He-like and H-like) are generated at energies of about 13 - 16 keV and are more precisely listed in Table I below.

[0032] [Table 1]

[0033] Xenon X-ray emission lines are in the range of about 30 - 40 keV, which results in a tissue penetration length range of 3 - 4 cm. In the case of argon, the X-ray emission lines are in the range of about 6 - 8 keV, which results in a tissue penetration length range from a few micrometers to hundreds of micrometers.

[0034] Method of X-ray Ablation Using a Plasma Discharge Probe FIG. 3 is a flowchart schematically showing a method of performing X-ray ablation using the system 20 of FIG. 1 according to an embodiment of the present disclosure. This method starts from an X-ray ablation protocol selection step 302 where a physician 30 sets (e.g., selects and / or adjusts) an X-ray ablation protocol according to a clinical device. For example, the protocol indicates a duration based on the required depth of the tissue to be ablated input by the physician, or based on the type of arrhythmia and / or the location of the ablation site selected by the physician from a list, for example.

[0035] In a balloon catheter expansion step 304, the physician 30 advances the folded balloon into the heart cavity, then expands the balloon 50 (e.g., using the self-expanding spline described above), and fills the balloon with krypton gas at a pressure below atmospheric pressure.

[0036] Next, in a balloon catheter placement step 306, the physician 30 places the expanded balloon in contact with the intended tissue such as the small hole 51.

[0037] Finally, in an X-ray ablation step 308, the physician activates the system, applies a high-voltage signal according to the selected protocol to generate X-rays, and ablates the tissue.

Example

[0038] (Example 1) A system (20) for tissue ablation includes a probe (22), an expandable capsule (50), a voltage discharge device (210), and a generator (49). The probe is configured to be inserted into a cavity of a patient's organ. The expandable capsule is attached to the distal end of the probe and is configured to expand within the cavity and be filled with a gas (250). The voltage discharge device is attached inside the expandable capsule and is configured to generate plasma by electrical excitation of the gas filling the expandable capsule, and the plasma emits X-rays (270) for ablating tissue within the cavity using the X-rays. The generator is wired to the voltage discharge device to apply an electrical signal for electrically exciting the plasma.

[0039] (Example 2) The system according to Example 1, wherein the expandable capsule is an expandable balloon (50).

[0040] (Example 3) The system according to any one of Examples 1 and 2, wherein the voltage discharge device includes a pair of electrodes (225, 226).

[0041] (Example 4) The system according to any one of Examples 1 to 3, wherein the electrodes (225, 226) are arranged in a linear shape.

[0042] (Example 5) The system according to any one of Examples 1 to 4, wherein the electrodes are arranged in a concentric circle shape.

[0043] (Example 6) The system according to any one of Examples 1 to 5, wherein the gas (250) is krypton and the X-rays are generated from the K-shell transition lines of krypton plasma.

[0044] (Example 7) The system according to any one of Examples 1 to 5, wherein the gas (250) is xenon and the X-rays are generated from the K-shell transition lines of xenon plasma.

[0045] (Example 8) The system according to any one of Examples 1 to 5, wherein the gas (250) is argon and the X-rays are generated from the K-shell transition lines of argon plasma.

[0046] Although the examples described herein relate to cardiac ablation, the methods and systems described herein can also be used for other applications such as renal denervation.

[0047] It should be understood that the examples described above are given by way of example, and that the present disclosure is not limited to what is particularly illustrated and described above in this specification. Rather, the scope of the present disclosure includes both the various combinations and sub-combinations of the functions described above in this specification, as well as those modifications and variations thereof that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art. Documents incorporated by reference into this patent application should be considered an integral part of this application, provided that only the definitions in this specification are to be considered insofar as any terms are defined in those incorporated documents in a manner inconsistent with the definitions expressly or implicitly made in this specification.

[0048] 〔Embodiment〕 (1) A system for tissue ablation, the system comprising: a probe configured to be inserted into a cavity of a patient's organ; an expandable capsule attached to the distal end of the probe, configured to expand within the cavity and be filled with a gas; a voltage discharge device attached inside the expandable capsule and configured to generate plasma by electrical excitation of the gas filled in the expandable capsule, the plasma emitting X-rays and using the X-rays to ablate tissue within the cavity; a generator wired to the voltage discharge device for applying an electrical signal for electrically exciting the plasma. (2) The expandable capsule in the system according to Embodiment 1 is an expandable balloon. (3) The system according to Embodiment 1, wherein the voltage discharge device includes a pair of electrodes. (4) The system according to Embodiment 3, wherein the electrodes are arranged in a linear shape. (5) The system according to Embodiment 3, wherein the electrodes are arranged in a concentric circle shape.

[0049] (6) The system according to any one of Embodiments 1 to 5, wherein the gas is krypton and the X-ray is generated from the K-shell transition line of the krypton plasma. (7) The system according to any one of Embodiments 1 to 5, wherein the gas is xenon and the X-ray is generated from the K-shell transition line of the xenon plasma. (8) The system according to any one of Embodiments 1 to 5, wherein the gas is argon and the X-ray is generated from the K-shell transition line of the argon plasma. (9) The system according to any one of Embodiments 1 to 5, wherein the gas in the expandable capsule is filled to a pressure below atmospheric pressure. (10) A method of tissue ablation, the method comprising: inserting a probe into a cavity of a patient's organ, the probe including an expandable capsule attached to its distal end; filling the expandable capsule with gas; generating a plasma by electrically exciting the gas filled in the expandable capsule using a voltage discharge device attached inside the expandable capsule, the plasma emitting X-rays, and ablating the tissue in the cavity using the X-rays.

[0050] (11) The method according to Embodiment 10, wherein the expandable capsule is an expandable balloon. (12) The method according to Embodiment 10, wherein the voltage discharge device includes a pair of electrodes. (13) The method according to embodiment 12, wherein the electrodes are arranged in a linear shape. (14) The method according to embodiment 12, wherein the electrodes are arranged in a concentric circle shape. (15) The method according to any one of embodiments 10 to 14, wherein the gas is krypton and the X-rays are generated from the K-shell transition lines of the krypton plasma.

[0051] (16) The method according to any one of embodiments 10 to 14, wherein the gas is xenon and the X-rays are generated from the K-shell transition lines of the xenon plasma. (17) The method according to any one of embodiments 10 to 14, wherein the gas is argon and the X-rays are generated from the K-shell transition lines of the argon plasma. (18) The method according to any one of embodiments 10 to 14, wherein the gas in the expandable capsule is filled to a pressure less than atmospheric pressure.

Claims

1. A system for tissue ablation, the system comprising: a probe configured to be inserted into a cavity of a patient's organ; an expandable capsule attached to a distal end of the probe, configured to expand within the cavity and be filled with a gas; a voltage discharge device attached inside the expandable capsule and configured to generate plasma by electrical excitation of the gas filled in the expandable capsule, the plasma emitting X-rays and using the X-rays to ablate tissue within the cavity; a generator wired to the voltage discharge device to apply an electrical signal for electrically exciting the plasma.

2. The system according to claim 1, wherein the expandable capsule is an expandable balloon.

3. The system according to claim 1, wherein the voltage discharge device includes a pair of electrodes.

4. The system according to claim 3, wherein the electrodes are arranged in a linear shape.

5. The system according to claim 3, wherein the electrodes are arranged in a concentric circular shape.

6. The system according to any one of claims 1 to 5, wherein the gas is krypton and the X-rays are generated from the K-shell transition lines of the krypton plasma.

7. The system according to any one of claims 1 to 5, wherein the gas is xenon and the X-rays are generated from the K-shell transition lines of the xenon plasma.

8. The system according to any one of claims 1 to 5, wherein the gas is argon and the X-rays are generated from the K-shell transition lines of the argon plasma.

9. The system according to any one of claims 1 to 5, wherein the gas in the expandable capsule is filled to a pressure below atmospheric pressure.

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