Power supply device and ablation system

Abstract

A power supply device 8 for performing ablation using an irreversible electroporation method includes: a power supply unit 26 that is electrically connected to a catheter 4 having a plurality of electrodes and a counter electrode plate 6 and applies a voltage to the plurality of electrodes and the counter electrode plate 6; and a control unit 28 that controls the power supply unit 26 so as to execute, in combination, a monopolar mode application for applying a voltage between the electrode and the counter electrode plate 6 and a bipolar mode application for applying a voltage between the electrodes.

Description

Power Supply and Ablation System

[0001] The present disclosure relates to a power supply and an ablation system.

[0002] Patent Document 1 discloses an ablation system including an ablation catheter and a pulse waveform generator that delivers voltage pulses to the ablation catheter.

[0003] Special table 2019-500170 publication

[0004] As a result of extensive research, the present inventors have come up with a novel technique for catheter ablation.

[0005] The present disclosure has been made in light of these circumstances, and its purpose is to provide a novel technique related to catheter ablation.

[0006] One aspect of the present disclosure is a power supply device for performing ablation using irreversible electroporation, which includes a power supply unit electrically connected to a catheter having multiple electrodes and a return electrode plate, and which applies voltages to the multiple electrodes and the return electrode plate, and a control unit which controls the power supply unit to perform a combination of monopolar application, which applies a voltage between the electrodes and the return electrode plate, and bipolar application, which applies a voltage between the electrodes.

[0007] Another aspect of the present disclosure is an ablation system for performing ablation using irreversible electroporation, comprising a catheter having multiple electrodes, a return electrode, and the power supply device of the above aspect.

[0008] Any combination of the above components, and conversion of the expression of the present disclosure into a method, device, system, etc., are also valid aspects of the present disclosure.

[0009] According to the present disclosure, a novel technique for catheter ablation can be provided.

[0010] 1 is a schematic diagram of an ablation system according to an embodiment; FIG. 2 is a perspective view of an electrode assembly; FIG. 3(A) and FIG. 3(B) are schematic diagrams for explaining a first application mode; FIG. 4(A) and FIG. 4(B) are schematic diagrams for explaining a second application mode; and FIG. 5(A) and FIG. 5(B) are schematic diagrams for explaining switching control of application methods according to the state of the spline.

[0011] The present disclosure will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the present disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the present disclosure. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not represent any order or importance, but are intended to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted from each drawing.

[0012] FIG. 1 is a schematic diagram of an ablation system 1 according to an embodiment. In FIG. 1, some of the components of the ablation system 1 are depicted as functional blocks. At least some of these functional blocks can be realized as a hardware configuration using elements and circuits such as a computer CPU and memory, and as a software configuration using a computer program or the like. Those skilled in the art will understand that these functional blocks can be realized in various ways by combining hardware and software.

[0013] The ablation system 1 performs ablation on an affected area 2 of a patient. The affected area 2 may be, for example, an organ experiencing arrhythmia. The ablation system 1 may also be used to ablate other affected areas 2. The ablation system 1 includes a catheter 4, a return electrode 6, and a power supply 8.

[0014] The catheter 4, as an example, includes a shaft 10, an electrode assembly 12, and a handle 14. The shaft 10 is formed of a flexible tubular body, and at least the distal end is inserted into the patient's body. The shaft 10 is made of a known flexible material, including resins such as polyolefin, polytetrafluoroethylene, polyether block amide, and polyamide. The shaft 10 has a multi-lumen structure, for example, having multiple lumens. Various thin wires (not shown), such as lead wires and operating wires, as well as an inner tube 22 (see FIG. 2), which will be described later, are inserted into the lumens.

[0015] An electrode assembly 12 is provided on the distal end side of the shaft 10. Fig. 2 is a perspective view of the electrode assembly 12. The electrode assembly 12 has a plurality of splines 16 and a plurality of electrodes 18. Note that Fig. 1 illustrates the splines 16 in a folded state, while Fig. 2 illustrates the splines 16 in an expanded state.

[0016] Each spline 16 is a linear body extending in the axial direction of the shaft 10 and is made of the same flexible material as the shaft 10. The electrode assembly 12 shown in Figure 2 has, as an example, a first spline 16a, a second spline 16b, a third spline 16c, a fourth spline 16d, a fifth spline 16e, and a sixth spline 16f, but the number of splines 16 is not limited to six and may be any number as long as there is a plurality of splines. In the present disclosure, when there is no need to distinguish the first spline 16a to the sixth spline 16f from one another, they may be simply referred to as "splines 16."

[0017] The splines 16 are arranged at intervals around the axis of the shaft 10. The distal end of each spline 16 is connected to a distal tip 20. The proximal end of each spline 16 is inserted into the shaft 10 from the distal end and fixed to the shaft 10. The distal end of an inner tube 22 is connected to the distal tip 20. The inner tube 22 is passed through the lumen of the shaft 10, and its proximal end is connected to the handle 14. The inner tube 22 can be advanced and retreated toward the distal end and proximal end of the shaft 10 by operating the handle 14.

[0018] The splines 16 can be switched between a folded state and an unfolded state. When the inner tube 22 is retracted toward the base end of the shaft 10 with the splines 16 in the folded state, in other words, when the splines 16 are extended linearly, the distal tip 20 is displaced toward the base end of the shaft 10. This causes the splines 16 to curve and bulge outward, resulting in the unfolded state. When the splines 16 are unfolded, the electrode assembly 12 assumes a basket shape. When the inner tube 22 is pushed toward the distal end of the shaft 10 with the splines 16 unfolded, the distal tip 20 is displaced away from the base end of the shaft 10. This causes the splines 16 to fold. The term "basket shape" comes from the fact that the shape of the splines 16 in the unfolded state resembles the curved pattern on the surface of a basketball.

[0019] Each spline 16 is provided with a plurality of electrodes 18. The electrodes 18 are arranged at predetermined intervals along the length of the spline 16. Each electrode 18 is ring-shaped and made of a highly conductive metal, such as platinum, gold, silver, copper, aluminum, or stainless steel, or an alloy thereof. The electrode assembly 12 shown in FIG. 2 has, as an example, a first electrode 18a, a second electrode 18b, a third electrode 18c, and a fourth electrode 18d on each spline 16. However, the number of electrodes 18 is not limited to four, as long as there is at least one. In the present disclosure, when it is not necessary to distinguish the first electrode 18a to the fourth electrode 18d from one another, they may be simply referred to as "electrodes 18."

[0020] The distal end of a lead wire (not shown) is connected to each electrode 18. The lead wire is passed through the lumen of the shaft 10, and the proximal end is connected to a connector (not shown) of the handle 14 shown in FIG. 1. The power supply unit 8 is electrically connected to each lead wire via the connector of the handle 14. Thus, each electrode 18 is electrically connected to the power supply unit 8 via the lead wire and the connector. As will be described in detail later, power for ablation is supplied to the multiple electrodes 18 by the power supply unit 8.

[0021] Returning to FIG. 1 , the handle 14 is provided on the proximal end side of the shaft 10, and is disposed outside the body when the catheter 4 is in use and is grasped or operated by the operator. The handle 14 has a main body portion grasped by the operator and an operating portion for advancing and retracting the inner tube 22. By operating the operating portion, the inner tube 22 can be displaced toward the proximal end relative to the shaft 10. This causes the electrode assembly 12, which is in a collapsed state, to unfold in a direction intersecting the axis of the shaft 10. Furthermore, by operating the operating portion, the inner tube 22 can be displaced toward the distal end relative to the shaft 10. This causes the electrode assembly 12, which is in an expanded state, to unfold. A connector is provided on the main body portion. The catheter 4 may have an irrigation mechanism that sprays irrigation fluid, such as saline, from the distal end side during ablation.

[0022] The return electrode 6 is attached to the patient's body surface during ablation. The return electrode 6 is electrically connected to a power supply 8. As will be described in detail later, power for ablation is supplied to the return electrode 6 by the power supply 8.

[0023] The power supply device 8 includes an input unit 24, a power supply unit 26, a control unit 28, and a display unit 30. The input unit 24 is configured with, for example, a dial, a button, a touch panel, etc., and is operated by the operator of the ablation system 1. The operator can input various setting values ​​and signals instructing operations to the power supply device 8 via the input unit 24. Note that the various setting values ​​may be set in advance, such as at the time of product shipment, and stored in the power supply device 8. Signals indicating the setting values, etc., are sent from the input unit 24 to the control unit 28.

[0024] The power supply unit 26 applies an ablation voltage V to the plurality of electrodes 18 and the return electrode plate 6 in accordance with a control signal CTL sent from the control unit 28. ｏｕｔ The power supply unit 26 is configured with a predetermined power supply circuit such as a switching regulator. The control unit 28 controls the operation of the entire power supply device 8 and executes predetermined arithmetic processing. The control unit 28 is configured with a microcomputer, for example. The control unit 28 controls the application of voltage Vout to the electrode 18 and the return electrode 6 by sending a control signal CTL to the power supply unit 26. The display unit 30 displays various types of information to the outside. The display unit 30 is configured with a liquid crystal display, a CRT display, an organic EL display, etc.

[0025] Next, the content of the control executed by the control unit 28 will be described. The ablation system 1 and power supply device 8 of this embodiment perform ablation on the affected area 2 using irreversible electroporation (IRE). Because IRE is non-thermal, it is possible to suppress damage to tissues and nerves located around the affected area 2. For example, when performing pulmonary vein dissection to treat atrial fibrillation, it is possible to suppress damage to the esophagus and phrenic nerve around the affected area, and to suppress the occurrence of complications such as esophageal fistula and phrenic nerve paralysis.

[0026] IRE involves pulsed electric field ablation (PFA). PFA is an ablation technique that kills cells by applying a pulsed electric field between each electrode 18 and the return electrode 6, or between the electrodes 18, to form a lesion in the affected area 2. Electric fields tend to be reflected at tissue boundaries. This can prevent damage to adjacent tissues when the affected area is cauterized.

[0027] After the electrode assembly 12 is inserted into the patient's body via a blood vessel or the like and positioned at the affected area 2, the control unit 28 controls the power supply unit 26 to apply voltages to the electrodes 18 and the return electrode 6 according to the rules described below. That is, the control unit 28 controls the power supply unit 26 to perform a combination of monopolar application (also referred to as unipolar application) and bipolar application. In monopolar application, a voltage is applied between the electrode 18 and the return electrode 6. In bipolar application, a voltage is applied between the electrodes 18. Therefore, monopolar application can more easily form a region deep in the tissue than bipolar application. On the other hand, bipolar application can more easily form a region over a wide area in the surface direction of the tissue (i.e., the direction in which the surface extends) than monopolar application. As an example, the control unit 28 can execute at least a first application mode and a second application mode.

[0028] 3A and 3B are schematic diagrams illustrating the first application mode. In the first application mode, the control unit 28 controls the power supply unit 26 to apply a predetermined monopolar voltage and then a predetermined bipolar voltage. A combination of the monopolar and bipolar voltages is considered to be one set, and the control unit 28 applies one or more sets of voltages in one ablation treatment.

[0029] 3A, in the monopolar application of the first application mode, each spline 16 is sequentially selected as a target for voltage application, and a voltage is applied between the first electrode 18a to the third electrode 18c on the target spline 16 and the return electrode 6. In other words, voltages are simultaneously applied to the first electrode 18a to the third electrode 18c. In the present disclosure, "simultaneously applied" means that the states in which voltages are applied to the electrodes 18 overlap at least temporarily.

[0030] As an example, first, a voltage is applied between the first electrode 18a to the third electrode 18c of the first spline 16a and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the second spline 16b and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the third spline 16c and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fourth spline 16d and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fifth spline 16e and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the sixth spline 16f and the return electrode 6. This completes the monopolar voltage application.

[0031] 3B, in the subsequent bipolar voltage application, a voltage is applied between the electrode 18 provided on a given spline 16 and the electrode 18 provided on the spline 16 adjacent to that spline 16. In this embodiment, a voltage is applied between the first electrodes 18a of a pair of adjacent splines 16, then a voltage is applied between the second electrodes 18b, and then a voltage is applied between the third electrodes 18c. Thereafter, a similar voltage application is performed for another pair of splines 16.

[0032] As an example, first, a voltage is applied between the first electrode 18a of the first spline 16a and the first electrode 18a of the second spline 16b. Next, a voltage is applied between the second electrode 18b of the first spline 16a and the second electrode 18b of the second spline 16b. Subsequently, a voltage is applied between the third electrode 18c of the first spline 16a and the third electrode 18c of the second spline 16b.

[0033] When the voltage application to the pair of the first spline 16a and the second spline 16b is completed, a similar voltage application is performed to the pair of the second spline 16b and the third spline 16c. Subsequently, a similar voltage application is performed to the pair of the third spline 16c and the fourth spline 16d. Subsequently, a similar voltage application is performed to the pair of the fourth spline 16d and the fifth spline 16e. Subsequently, a similar voltage application is performed to the pair of the fifth spline 16e and the sixth spline 16f. Subsequently, a similar voltage application is performed to the pair of the sixth spline 16f and the first spline 16a. This completes the bipolar voltage application.

[0034] 4A and 4B are schematic diagrams illustrating the second application mode. In the second application mode, the control unit 28 controls the power supply unit 26 to apply a predetermined monopolar voltage and then a predetermined bipolar voltage. A combination of the monopolar and bipolar voltages is considered to be one set, and the control unit 28 applies one or more sets of voltages in one ablation treatment.

[0035] 4A, in the monopolar application of the second application mode, similarly to the first application mode, each spline 16 is sequentially selected as a target for voltage application, and a voltage is applied between the first electrode 18a to the third electrode 18c on the target spline 16 and the return electrode 6. In other words, a voltage is simultaneously applied to the first electrode 18a to the third electrode 18c.

[0036] As an example, first, a voltage is applied between the first electrode 18a to the third electrode 18c of the first spline 16a and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the second spline 16b and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the third spline 16c and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fourth spline 16d and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fifth spline 16e and the return electrode 6. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the sixth spline 16f and the return electrode 6. This completes the monopolar voltage application.

[0037] As shown in FIG. 4B , in the subsequent bipolar voltage application, a voltage is applied between the electrode 18 provided on a given spline 16 and the electrode 18 provided on the spline 16 adjacent to that spline 16. In this embodiment, a voltage is applied between the first electrodes 18 a to the third electrodes 18 c in a pair of adjacent splines 16. That is, a voltage is simultaneously applied to the first electrodes 18 a to the third electrodes 18 c. Thereafter, a similar voltage application is performed on another pair of splines 16. This shortens the time required to complete the bipolar voltage application compared to the case in which a voltage is sequentially applied to the first electrodes 18 a to the third electrodes 18 c, as in the bipolar voltage application in the first voltage application mode.

[0038] As an example, first, a voltage is applied between the first electrode 18a to the third electrode 18c of the first spline 16a and the first electrode 18a to the third electrode 18c of the second spline 16b. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the second spline 16b and the first electrode 18a to the third electrode 18c of the third spline 16c. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the third spline 16c and the first electrode 18a to the third electrode 18c of the fourth spline 16d. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fourth spline 16d and the first electrode 18a to the third electrode 18c of the fifth spline 16e. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the fifth spline 16e and the first electrode 18a to the third electrode 18c of the sixth spline 16f. Next, a voltage is applied between the first electrode 18a to the third electrode 18c of the sixth spline 16f and the first electrode 18a to the third electrode 18c of the first spline 16a. This completes the bipolar voltage application.

[0039] In this embodiment, the fourth electrode 18d on each spline 16 is excluded from the targets to which a voltage is applied. The fourth electrode 18d is provided for potential measurement or as a spare in case the ablation range is wide. In other words, not all of the electrodes 18 of the catheter 4 are necessarily targets to which an ablation voltage is applied. The fourth electrode 18d can also be omitted.

[0040] In this embodiment, the power supply unit 26 applies voltage to each electrode 18 and the return electrode 6 to generate biphasic pulses (bipolar pulses). Accordingly, a positive voltage phase pulse and a negative voltage phase pulse are applied to each electrode 18 and the return electrode 6, and the polarity of each electrode 18 and the return electrode 6 alternates. The voltage amplitude Am is, for example, 1000 V or more and 4000 V or less. The pulse width Δp is, for example, 0.1 μs or more and 100 μs or less.

[0041] In monopolar application in each application mode, the region that can be formed by monopolar application can be enlarged by switching the target of voltage application on a spline-by-spline basis, rather than simultaneously applying voltage to all of the electrodes 18 that are the target of voltage application and are provided on the catheter 4. This is thought to be because, when voltage is applied to all of the electrodes 18 that are the target of voltage application at the same time, the current flows in a dispersed manner, reducing the current density, but when voltage is applied to each spline 16 in sequence, the current concentrates and the current density increases.

[0042] Furthermore, with the above-described monopolar voltage application, regions tend to be formed on the straight lines connecting each spline 16 and the return electrode 6, and regions are less likely to be formed between adjacent splines 16. Therefore, gaps may occur in the regions. In contrast, by applying a voltage between adjacent splines 16 using bipolar voltage application, regions can be formed between adjacent splines 16 as well, and the gaps between the regions can be filled. Therefore, by combining monopolar voltage application and bipolar voltage application, uniform regions can be easily formed over a wide area.

[0043] Furthermore, the target to which the voltage is applied is switched in units of splines between the monopolar application of each application mode and the bipolar application of the second application mode. This makes it easier to simplify the power supply circuit for switching the target to which the voltage is applied. This also makes it easier to reduce the size of the power supply device 8. It also makes it easier to add more electrodes 18.

[0044] The manner of voltage application in the monopolar and bipolar application modes of each application mode can be set as appropriate based on the designer's empirical knowledge or experiments or simulations performed by the designer. For example, the order of splines 16 to which voltage is applied in the monopolar application mode of each application mode is not limited to the above. Furthermore, some splines 16 may be excluded from the targets of power supply. Furthermore, the combination of electrodes to which voltage is simultaneously applied does not have to be for each spline, but may be a combination of any two or more electrodes 18, or may be all electrodes 18 to which voltage is to be applied. Furthermore, voltage may be applied sequentially to each electrode 18. The order of power supply to each electrode 18 can be set as appropriate.

[0045] Furthermore, in the monopolar application of each application mode, the splines 16 may be divided into a plurality of groups, the number of which is less than the number of splines 16, and the target to which the voltage is applied may be switched on a group-by-group basis. For example, the first spline 16a, the third spline 16c, and the fifth spline 16e may be classified as a first group, and the second spline 16b, the fourth spline 16d, and the sixth spline 16f may be classified as a second group. Then, a voltage is applied between the return electrode 6 and one or more electrodes 18 on the splines 16 belonging to the first group, and then a voltage is applied between the return electrode 6 and one or more electrodes 18 on the splines 16 belonging to the second group. Note that there may be a group to which only one spline 16 belongs, or the same spline 16 may be assigned to two or more different groups.

[0046] In the bipolar application of each application mode, the number and combination of electrodes to which voltage is simultaneously applied, the order in which voltage is applied, and the like are not limited to those described above. For example, the electrodes 18 on each spline 16 may be divided into multiple groups, and the voltage application target may be switched between groups. As an example, the first electrodes 18a and the second electrodes 18b on each spline 16 may be classified as a first group, and the second electrodes 18b and the third electrodes 18c on each spline 16 may be classified as a second group. Then, a voltage may be applied between the first groups of adjacent splines 16, and then a voltage may be applied between the second groups. Note that there may be a group to which only one electrode 18 belongs, or the same electrode 18 may be assigned to two or more different groups.

[0047] Furthermore, in bipolar application in each application mode, a voltage may be applied between two electrodes 18 on the same spline 16. However, when performing bipolar application to fill gaps in regions that may occur with monopolar application, it is preferable to apply a voltage between electrodes 18 on different splines 16 that tend to be spaced apart from each other. Furthermore, a voltage may be applied not between electrodes 18 on adjacent splines 16, but between electrodes 18 on two adjacent splines 16 that are separated by one or more splines 16. However, in order to more reliably fill gaps in regions that may occur with monopolar application, it is preferable to apply a voltage between electrodes 18 on adjacent splines 16.

[0048] Furthermore, in both monopolar and bipolar application modes, the target of application may be switched after a single voltage application, or after multiple consecutive voltage applications to the same target. Continuously applying voltage to the same electrode 18 reduces the number of times the target of application must be switched compared to switching the target of application after each voltage application. This simplifies the control performed by the control unit 28. In this disclosure, "applying voltage multiple times consecutively" refers to applying biphasic pulses to the same electrode 18 multiple times without application to another electrode 18 in between. The fact that voltage is being applied multiple times consecutively to each electrode 18 can be confirmed, for example, by connecting an oscilloscope to each electrode 18.

[0049] In each application mode, a monopolar application may be performed after a bipolar application. In each application mode, the number of monopolar applications and bipolar applications included in one set is not limited to one each. For example, one set may be composed of one or more consecutive monopolar applications and one or more consecutive bipolar applications. Furthermore, multiple sets with different contents may be combined in one ablation treatment.

[0050] In the first application mode described above, voltage is applied sequentially to the first electrode 18a through the third electrode 18c in bipolar application. Meanwhile, in the second application mode, voltage is applied simultaneously to the first electrode 18a through the third electrode 18c in bipolar application. Therefore, the execution time of bipolar application differs between the first application mode and the second application mode. Therefore, the ratio of execution time of monopolar application to execution time of bipolar application in one ablation treatment differs between ablation performed in the first application mode and ablation performed in the second application mode.

[0051] In other words, the control unit 28 of this embodiment can execute multiple application modes that differ in the ratio of the execution time of monopolar application to the execution time of bipolar application in one ablation treatment. By being able to select and execute multiple application modes in this way, it is possible to perform ablation that is appropriate for the affected area 2. Therefore, the usability of the ablation system 1 can be improved. The control unit 28 may also be able to execute an nth application mode (n is a natural number of 3 or greater) in which the voltage application mode in at least one of the monopolar application and the bipolar application, in other words, the execution time ratio, differs from that of the first application mode and the second application mode.

[0052] The control unit 28 may also switch the application method depending on the degree of curvature of each spline 16. Figures 5(A) and 5(B) are schematic diagrams for explaining the control of switching the application method depending on the state of the spline 16. Note that Figures 5(A) and 5(B) show an electrode assembly 12 having eight splines 16 as an example.

[0053] That is, the control unit 28 controls the power supply unit 26 to apply monopolar voltage when each spline 16 is in a first deployed state in which it is curved to a predetermined degree, as shown in FIG. 5A. The control unit 28 also controls the power supply unit 26 to apply bipolar voltage when each spline 16 is in a second deployed state in which it is curved more sharply than in the first deployed state, as shown in FIG. 5B. Each spline 16 is curved more gently in the first deployed state than in the second deployed state, and more sharply in the second deployed state than in the first deployed state. The second deployed state means that each spline 16 has a portion with a greater curvature than in the first deployed state. In other words, the curvature of the portion with the greatest curvature in the second deployed state is greater than the curvature of the portion with the greatest curvature in the first deployed state.

[0054] When the splines 16 are in the first deployed state, the electrodes 18 can be positioned over a wide area. Therefore, by applying a monopolar voltage when the splines 16 are in the first deployed state, a region can be formed over a wide area. Furthermore, when the splines 16 transition from the first deployed state to the second deployed state, which is more curved, they tend to displace around the axis of the shaft 10. This allows the spacing between the electrodes 18 to which voltage is applied to be narrowed. Therefore, by applying a bipolar voltage when the splines 16 are in the second deployed state, the gaps in the region can be more reliably filled. The degree of curvature of each spline 16 in the first deployed state and the second deployed state, in other words, the amount of retraction of the inner tube 22, can be appropriately set based on the designer's empirical knowledge or experiments, simulations, or the like.

[0055] Furthermore, the configurations of the catheter 4 and the power supply device 8 can be modified as appropriate. For example, the distal end of the shaft 10 of the catheter 4 may be bendable in one direction or in multiple directions by operating the handle 14. The control of the power supply unit 26 by the control unit 28 may be realized by hardware (circuitry) or software (program). When realized by software, the software is composed of a group of programs for causing a computer to execute each function. Each program may be pre-installed in the computer, or may be installed into the computer from a network or a recording medium.

[0056] Furthermore, the shapes and numbers of the splines 16 and the electrodes 18 are not limited. Alternatively, the catheter 4 may not have splines 16 at the tip of the shaft 10, and the electrodes 18 may be disposed on the shaft 10. Alternatively, the electrodes 18 may be disposed on a balloon provided on the tip side of the shaft 10. Furthermore, the power supply unit 26 may apply a voltage to each electrode 18 to generate a monophasic pulse.

[0057] Whether monopolar or bipolar application is to be performed may be determined based on the results of impedance measurement using the electrode 18 to which the ablation voltage is to be applied. Hereinafter, the electrode 18 to which the ablation voltage is to be applied will be referred to as the target electrode 18x, as appropriate. That is, when the electrode assembly 12 is inserted into the patient's body via a blood vessel or the like, targets that the electrode 18 comes into contact with include biological tissue such as the affected area 2 and blood. Furthermore, when saline for irrigation is sprayed from the tip of the catheter 4, the targets that the electrode 18 comes into contact with also include the saline.

[0058] Biological tissue has significantly lower conductivity than blood or physiological saline. Therefore, the impedance Z generated when a voltage is applied between the return electrode 6 and the target electrode 18x is relatively high when the target electrode 18x is in contact with biological tissue, and is relatively low when the target electrode 18x is not in contact with biological tissue. Therefore, by measuring the impedance Z, it is possible to determine whether the target electrode 18x is in contact with biological tissue.

[0059] Therefore, the control unit 28 transmits a control signal CTL to the power supply unit 26 to control the power supply unit 26 to apply a voltage for impedance measurement between the target electrode 18x and the return electrode 6. The control unit 28 then acquires information, including the voltage value and current value obtained by applying the voltage, via the power supply unit 26. This allows the control unit 28 to measure the impedance Z between the target electrode 18x and the return electrode 6. The control unit 28 then controls the power supply unit 26 to perform bipolar voltage application using the target electrode 18x when the difference ΔZ between the measured impedance Z and a predetermined reference impedance Z0 is equal to or greater than a predetermined threshold value Zth. Furthermore, the control unit 28 controls the power supply unit 26 to perform monopolar voltage application using the target electrode 18x when the difference ΔZ is less than the threshold value Zth.

[0060] The reference impedance Z0 is an impedance that serves as a reference point, i.e., a zero point, when determining whether the target electrode 18x is in contact with biological tissue. As an example, the reference impedance Z0 can be measured by applying an impedance measurement voltage between the target electrode 18x and the other electrodes 18 after the electrode assembly 12 is inserted into the patient's body and ensuring that the two electrodes 18 are not in contact with biological tissue. Alternatively, two reference electrodes dedicated to measuring the reference impedance Z0 may be provided in the electrode assembly 12 at positions that are guaranteed not to contact biological tissue, and the reference impedance Z0 may be measured using these two reference electrodes. The reference impedance Z0 is measured in advance inside the patient's body and stored in the control unit 28. The threshold value Zth can be set as appropriate based on the designer's empirical knowledge or experiments or simulations, and is set in advance and stored in the control unit 28.

[0061] When the difference Δ is equal to or greater than the threshold value Zth, it can be determined that the target electrode 18x is in contact with the biological tissue. When the target electrode 18x is in contact with the biological tissue, a bipolar application can generate an electric field in the biological tissue more reliably than when the target electrode 18x is not in contact. Therefore, when the difference Δ is equal to or greater than the threshold value Zth, the control unit 28 controls the power supply unit 26 to perform bipolar application using the target electrode 18x. Note that when performing this bipolar application, contact determination based on the impedance Z is also performed on the electrode 18 that is the counterpart of the target electrode 18x, so that bipolar application can be performed using only the electrode 18 that is guaranteed to be in contact with the biological tissue.

[0062] On the other hand, when the difference Δ is less than the threshold value Zth, it can be determined that the target electrode 18x is not in contact with the biological tissue. In bipolar application when the target electrode 18x is not in contact with the biological tissue, a large amount of current flows into the blood or physiological saline, making it difficult to generate an electric field in the biological tissue. Therefore, when the difference Δ is equal to or greater than the threshold value Zth, the control unit 28 controls the power supply unit 26 to perform monopolar application using the target electrode 18x. Monopolar application can generate an electric field in the biological tissue more reliably than bipolar application, even when the target electrode 18x is not in contact with the biological tissue.

[0063] Furthermore, the impedance Z generated when a voltage is applied between the target electrode 18x and the other electrode 18 in contact with biological tissue is relatively high when the target electrode 18x is in contact with biological tissue, and is relatively low when the target electrode 18x is not in contact with biological tissue. Therefore, the control unit 28 may control the power supply unit 26 to apply a voltage for impedance measurement between the target electrode 18x and the other electrode 18. In this case, it is preferable that the other electrode 18 that is the counterpart of the target electrode 18x is in guaranteed contact with biological tissue. This allows for more accurate determination of whether the target electrode 18x is in contact with biological tissue.

[0064] Alternatively, the other electrode 18 may also be an electrode used for bipolar voltage application, i.e., a target electrode 18x. In this case, if the difference Δ between the impedance Z between the two target electrodes 18x and the reference impedance Z0 is equal to or greater than the threshold value Zth, it can be determined that both target electrodes 18x are in contact with biological tissue. Therefore, the control unit 28 controls the power supply unit 26 to perform bipolar voltage application using these target electrodes 18x. On the other hand, if the difference Δ is less than the threshold value Zth, it can be determined that at least one target electrode 18x is not in contact with biological tissue. In this case, for example, the control unit 28 controls the power supply unit 26 to perform monopolar voltage application for both target electrodes 18x.

[0065] Furthermore, whether to perform monopolar or bipolar voltage application may be determined based on the pressure P applied to the target electrode 18x. That is, when the pressure P applied to the target electrode 18x is equal to or greater than a predetermined threshold value Pth, it can be determined that the target electrode 18x is in contact with biological tissue. Therefore, when the pressure P is equal to or greater than the threshold value Pth, the control unit 28 controls the power supply unit 26 to perform bipolar voltage application using the target electrode 18x. Note that when performing this bipolar voltage application, contact determination based on the pressure P is also performed on the electrode 18 that is the counterpart of the target electrode 18x, so that bipolar voltage application can be performed using only the electrode 18 that is guaranteed to be in contact with biological tissue.

[0066] On the other hand, when the pressure P is less than the threshold value Pth, it can be determined that the target electrode 18x is not in contact with biological tissue. Therefore, when the pressure P is less than the threshold value Pth, the control unit 28 controls the power supply unit 26 to perform monopolar voltage application using the target electrode 18x. The pressure P applied to the electrode 18 can be measured using a known measurement method. For example, the pressure P can be measured by providing a known pressure sensor on the electrode 18. The threshold value Pth can be set appropriately based on the designer's empirical knowledge or experiments or simulations conducted by the designer, and is set in advance and stored in the control unit 28.

[0067] When the electrodes 18 are divided into multiple groups and monopolar and bipolar voltage applications are performed on a group-by-group basis, the contact determination of the target electrode 18x based on the impedance Z and pressure P described above may be performed on a group-by-group basis. Contact determination based on the impedance Z and contact determination based on the pressure P may be combined. Contact determination may be performed periodically during ablation, and the monopolar and bipolar voltage applications may be switched depending on the result of the determination. The voltage application method may be selected or switched depending on the number of times and duration of voltage application to the target electrode 18x, the temperature of the target electrode 18x, and the like.

[0068] The embodiments of the present disclosure have been described in detail above. The above-described embodiments merely illustrate specific examples of implementing the present disclosure. The content of the embodiments does not limit the technical scope of the present disclosure, and many design modifications, such as changing, adding, or deleting components, are possible within the scope of the concept of the present disclosure defined in the claims. A new embodiment with design modifications will combine the effects of the combined embodiments and modifications. In the above-described embodiments, the content that allows such design modifications is emphasized by using notations such as "in this embodiment" or "in this embodiment," but design modifications are also permitted even in content without such notation. Any combination of the components included in each embodiment is also valid as an aspect of the present disclosure. Hatching on cross sections in the drawings does not limit the material of the hatched object.

[0069] Embodiments may be specified by the following items: [Item 1] A power supply device (8) for performing ablation using irreversible electroporation, comprising: a power supply unit (26) electrically connected to a catheter (4) having a plurality of electrodes (18) and a return electrode plate (6) and applying a voltage to the plurality of electrodes (18) and the return electrode plate (6), and a control unit (28) controlling the power supply unit (26) to perform a combination of monopolar application, which applies a voltage between the electrodes (18) and the return electrode plate (6), and bipolar application, which applies a voltage between the electrodes (18). [Item 2] The control unit (28) controls the power supply unit (26) to perform monopolar application after bipolar application. [Item 3] The power supply device (8) according to item 1 or 2, wherein the control unit (28) is capable of executing a plurality of application modes with different ratios of time spent performing monopolar application to time spent performing bipolar application in a single ablation treatment. [Item 4] The power supply device (8) according to any of items 1 to 3, wherein the catheter (4) has a shaft (10) and a plurality of splines (16) arranged in a direction around the axis of the shaft (10), at least one electrode (18) is provided on each spline (16), and the control unit (28) controls the power supply unit (26) to apply a voltage between the electrode (18) provided on a given spline (16) and the electrode (18) provided on a spline (16) adjacent to the given spline (16) in bipolar application. [Item 5] A power supply device (8) according to any one of items 1 to 4, wherein the catheter (4) has a shaft (10) and a plurality of splines (16) arranged in a direction around the axis of the shaft (10), each of the splines (16) being provided with at least one electrode (18), the plurality of splines (16) being switchable between a first deployed state in which they are curved to a predetermined degree and a second deployed state in which they are curved more sharply than the first deployed state, and a control unit (28) controls the power supply unit (26) to apply voltage in a monopolar manner when the plurality of splines (16) are in the first deployed state, and to apply voltage in a bipolar manner when the plurality of splines (16) are in the second deployed state.[Item 6] The power supply device (8) according to any one of Items 1 to 5, wherein the control unit (28) applies a voltage for impedance measurement between a target electrode (18x) among the plurality of electrodes (18) to which an ablation voltage is to be applied and the return electrode (6), or between the target electrode (18x) and another electrode (18) to measure an impedance (Z), and controls the power supply unit (26) to perform bipolar application using the target electrode (18x) when a difference (ΔZ) between the measured impedance (Z) and a reference impedance (Z0) that is a reference point for determining whether the target electrode (18x) is in contact with biological tissue is equal to or greater than a predetermined threshold (Zth), and to perform monopolar application using the target electrode (18x) when the difference (ΔZ) is less than the threshold (Zth). [Item 7] The power supply device (8) according to any one of Items 1 to 6, wherein the control unit (28) controls the power supply unit (26) to perform bipolar voltage application using the target electrode (18x) when pressure (P) applied to a target electrode (18x) among the plurality of electrodes (18) to which an ablation voltage is applied is equal to or greater than a predetermined threshold (Pth), and to perform monopolar voltage application using the target electrode (18x) when the pressure (P) is less than the threshold (Pth). [Item 8] An ablation system (1) for performing ablation using irreversible electroporation, comprising: a catheter (4) having a plurality of electrodes (18), a return electrode (6), and the power supply device (8) according to any one of Items 1 to 7.

[0070] The present disclosure may be utilized in power supply devices and ablation systems.

[0071] 1 Ablation system, 4 Catheter, 6 Patient electrode, 8 Power supply device, 10 Shaft, 16 Spline, 18 Electrode, 26 Power supply unit, 28 Control unit.

Claims

1. A power supply device for performing ablation using irreversible electroporation, comprising: a power supply unit electrically connected to a catheter having a plurality of electrodes and a return electrode plate, and applying a voltage to the plurality of electrodes and the return electrode plate; and a control unit that controls the power supply unit to perform a combination of monopolar application, which applies a voltage between the electrodes and the return electrode plate, and bipolar application, which applies a voltage between the electrodes.

2. The power supply device according to claim 1, wherein the control unit controls the power supply unit to execute the monopolar application after the bipolar application.

3. The power supply device according to claim 1 or 2, wherein the control unit is capable of executing a plurality of application modes with different ratios of the time during which the monopolar application is performed to the time during which the bipolar application is performed in one ablation treatment.

4. A power supply device as described in claim 1 or 2, wherein the catheter has a shaft and a plurality of splines arranged in a direction around the axis of the shaft, at least one of the electrodes is provided on each spline, and the control unit controls the power supply unit to apply a voltage between the electrode provided on a specified spline and the electrode provided on a spline adjacent to that spline in the bipolar voltage application.

5. The power supply device according to claim 1 or 2, wherein the catheter has a shaft and a plurality of splines arranged in a direction around the axis of the shaft, each spline is provided with at least one of the electrodes, the plurality of splines are switchable between a first deployed state in which they are curved to a predetermined degree and a second deployed state in which they are curved more sharply than the first deployed state, and the control unit controls the power supply unit to apply the monopolar voltage when the plurality of splines are in the first deployed state, and to apply the bipolar voltage when the plurality of splines are in the second deployed state.

6. The power supply device according to claim 1, wherein the control unit applies a voltage for impedance measurement between a target electrode to which an ablation voltage is applied among the plurality of electrodes and the return electrode plate, or between the target electrode and another of the electrodes, to measure impedance, and controls the power supply unit to perform the bipolar application using the target electrode when the difference between the measured impedance and a reference impedance that is a reference point for determining whether the target electrode is in contact with biological tissue is equal to or greater than a predetermined threshold, and to perform the monopolar application using the target electrode when the difference is less than the threshold.

7. The power supply device of claim 1, wherein the control unit controls the power supply unit to perform the bipolar application using the target electrode when the pressure on the target electrode to which the ablation voltage is applied is equal to or greater than a predetermined threshold, and to perform the monopolar application using the target electrode when the pressure is less than the threshold.

8. An ablation system for performing ablation using irreversible electroporation, comprising: a catheter having a plurality of electrodes; a return electrode; and the power supply device according to claim 1 or 2.

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