Virtual shorting electrode for ire pulse generator

Abstract

The invention is entitled "Virtual short circuit electrode for IRE pulse generator". A medical device includes a probe including an insertion tube configured for insertion into a body lumen of a patient and a distal assembly connected distally to the insertion tube and including a plurality of electrodes configured to contact tissue within the body lumen. An electrical signal generator is configured to simultaneously apply biphasic electrical pulses to at least one set of two or more of the electrodes, the biphasic electrical pulses having energy sufficient to irreversibly electroporate the tissue contacted by the electrodes in the at least one set. A controller is coupled to measure a voltage difference between the electrodes in the at least one set over time and to adjust the biphasic electrical pulses applied to the electrodes in the at least one set so that the voltage difference does not exceed a predetermined threshold at any time during application of the biphasic electrical pulses.

Description

Technical Field

[0001] The present invention relates generally to medical devices, and more particularly to devices and methods for irreversible electroporation of physiological tissues. Background Technology

[0002] Irreversible electroporation (IRE) is a soft tissue ablation technique that applies short pulses of a strong electric field to create permanent and therefore lethal nanopores in the cell membrane, thereby disrupting cellular homeostasis (internal physical and chemical conditions). The cell death following IRE is due to apoptosis (programmed cell death) rather than necrosis (cell damage, which leads to cell destruction through the action of its own enzymes), as in all other heat- or radiation-based ablation techniques. IRE is commonly used for tumor ablation in areas where the precision and preservation of the extracellular matrix, blood flow, and nerves are crucial.

[0003] U.S. Patent Application Publication No. 2010 / 0125315 describes a method and system for providing treatment to a patient with an implanted electrode array. Electrical stimulation current is delivered from at least two electrodes to at least one electrode along at least two electrical pathways passing through the patient's tissue, and the electrical stimulation current is transferred between the electrical pathways by actively adjusting one or more finite resistances, each associated with one or more electrical pathways. Summary of the Invention

[0004] The embodiments of the present invention described below provide improved apparatus and methods for irreversible electroporation of body tissues.

[0005] Therefore, according to an embodiment of the present invention, a medical device including a probe is provided, the probe comprising: an insertion tube configured for insertion into a patient's body cavity; and a distal assembly distally connected to the insertion tube and including a plurality of electrodes configured to contact tissue within the body cavity. An electrical signal generator is configured to simultaneously apply biphasic electrical pulses to at least one set of two or more electrodes, the energy of the biphasic electrical pulses being sufficient to irreversibly electroperforate the tissue contacted by the electrodes in the at least one set. A controller is coupled to measure the voltage difference between the electrodes in the at least one set over time and to adjust the biphasic electrical pulses applied to the electrodes in the at least one set such that the voltage difference does not exceed a predetermined threshold at any time during the application of the biphasic electrical pulses.

[0006] In some embodiments, the controller is configured to adjust the amplitude of the biphase electrical pulses to compensate for the difference in the corresponding peak voltages measured at any pair of electrodes in at least one set. In one embodiment, the controller is configured to adjust the phase of the biphase electrical pulses to compensate for the phase shift between the corresponding voltage waveforms measured at any pair of electrodes in at least one set.

[0007] In another embodiment, the distal component includes a balloon that is distally connected to the insertion tube and configured to inflate within the body cavity with fluid flowing into the balloon through the insertion tube.

[0008] In another embodiment, the device includes a common electrode configured to be fixed to a position on the patient's body such that biphasic electrical pulses travel from multiple electrodes through the body to the common electrode, thereby performing irreversible electroporation of the tissue in a unipolar mode.

[0009] In yet another embodiment, at least one group includes a first group and a second group, wherein biphase electrical pulses are applied in a bipolar mode between electrodes in the first group and electrodes in the second group, and wherein a controller is coupled to measure the voltage difference between the electrodes in the first group and the second group over time, and to adjust the biphase electrical pulses applied to the electrodes in the first group and the second group such that the voltage difference between the electrodes in the first group and the second group includes a predetermined series of biphase electrical pulses.

[0010] According to an embodiment of the invention, a medical treatment method is also provided. The method includes providing a probe for insertion into a patient's body cavity, wherein the probe includes an insertion tube and a distal assembly distally connected to the insertion tube and including a plurality of electrodes configured to contact tissue within the body cavity. Biphasic electrical pulses are simultaneously applied to at least one group of two or more electrodes, the energy of the biphasic electrical pulses being sufficient to irreversibly electroperforate the tissue contacted by the electrodes in the at least one group. A voltage difference over time is measured between the electrodes in the at least one group, and the biphasic electrical pulses applied to the electrodes in the at least one group are adjusted such that the voltage difference does not exceed a predetermined threshold at any time during the application of the biphasic electrical pulses. Attached Figure Description

[0011] The invention will be more fully understood through the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein:

[0012] Figure 1 This is a schematic diagram of a medical device during an IRE procedure according to an exemplary embodiment of the present invention;

[0013] Figure 2 This is a schematic diagram of a biphase IRE pulse according to an exemplary embodiment of the present invention;

[0014] Figure 3 A schematic diagram of the bursting of a biphasic pulse according to an exemplary embodiment of the present invention;

[0015] Figure 4A block diagram illustrating the connections between an IRE pulse generator, controller, electrodes, and return patch according to an exemplary embodiment of the present invention;

[0016] Figure 5 According to an exemplary embodiment of the present invention Figure 4 A circuit diagram of the pulse routing and metering components; and

[0017] Figure 6 This is a circuit diagram of two adjacent modules of a pulse routing and metering component configured for a bipolar mode IRE according to an exemplary embodiment of the present invention. Detailed Implementation

[0018] Overview

[0019] IRE is primarily a non-thermal ablation process, raising tissue temperature by at most a few degrees Celsius within milliseconds. Therefore, it differs from RF (radio frequency) ablation, which raises tissue temperature by 20°C to 70°C and destroys cells through heating. IRE utilizes biphasic pulses (a combination of positive and negative pulses) to avoid muscle contraction caused by non-zero DC voltage components. Biphasic pulses are often also referred to as “bipolar” pulses. However, as detailed further below, IRE can be performed in either unipolar or bipolar mode. To avoid confusion, the term “bipolar” will be used below only in the context of bipolar mode of IRE.

[0020] Some IRE procedures use a balloon catheter with a balloon at its distal end and electrodes arranged around the surface of the balloon. The balloon is inflated within a body cavity, and then the electrodes are brought into contact with the tissue to be electroporated. To perform electroporation on tissue in small cavities within the body (e.g., in the left atrium of the heart), small-diameter balloons, for example, less than 15 mm in diameter, can be used.

[0021] IRE can be performed in bipolar or unipolar mode. In bipolar mode, the electroporation current flows along the same catheter from one electroporation electrode to another. In unipolar mode, the electroporation current flows between the electroporation electrode on the catheter and an external electrode (called a "return patch"). The return patch is typically attached to the subject's body surface, such as the skin of the subject's torso, via an electrical return connection to the IRE signal generator.

[0022] Electrodes arranged on small-diameter balloons and other types of electrode assemblies used in IRE procedures are typically small in size to allow for precise targeting of ablation energy. Generally, an electrical signal generator (also referred to herein as an "IRE pulse generator") that applies IRE pulses to the electrodes enables individual activation of each electrode via a corresponding channel of the generator. Due to their small size, each electrode contacts and ablates only a small area of ​​tissue.

[0023] In some cases, it may be desirable to apply IRE to a larger area of ​​tissue than can be covered by a single small electrode. This can be achieved by grouping two or more adjacent electrodes together by electrically shorting them, thus creating a larger effective electroporation area. However, the practical implementation of this method in hardware requires additional high-voltage switching devices between the individual output channels of the IRE pulse generator. These additional switching devices are costly, require dedicated control lines, and offer limited flexibility in forming different electrode groups.

[0024] The embodiments of the invention described herein address this problem by achieving a “virtual short circuit” in two or more electrode groups within an IRE system. The electrodes are “virtually short-circuited” in the sense that all electrodes in the group simultaneously apply the same voltage waveform with the same amplitude and phase to the tissue they contact. Therefore, the IRE current flows through a larger area of ​​tissue defined by the contact locations of all electrodes in the group.

[0025] However, this virtual short circuit cannot be reliably achieved simply by setting up an IRE pulse generator to apply the same waveform to all electrodes in the group. For example, local differences in tissue impedance and differences in contact impedance between the electrodes in the group and the tissue they contact can lead to differences in the amplitude and phase of the IRE waveform actually applied to the tissue by different electrodes. This non-uniformity in the waveform can cause the IRE current to flow through the tissue along unexpected paths and produce unsatisfactory ablation effects.

[0026] The embodiments of the invention described herein address this problem by measuring the voltage difference between the electrodes in the group over time. Based on these measurements, an IRE pulse generator adjusts the biphase electrical pulses applied to the electrodes in the group such that the voltage difference does not exceed a predetermined threshold at any time during the application of the biphase electrical pulses.

[0027] In the embodiments disclosed in this invention, during unipolar IRE surgery, an IRE pulse generator simultaneously applies biphasic IRE pulses to a selected group of electrodes on a probe. The energy of the biphasic IRE pulses is sufficient to electroporate the tissue contacted by the electrodes. A controller measures the voltage difference between the electrodes in the group over time and adjusts the amplitude and phase of the IRE pulses such that the voltage difference does not exceed a predetermined threshold at any time during the application of the IRE pulses. This method ensures that the group of electrodes is pulsed as if it were a single large-area electrode.

[0028] In bipolar IRE procedures, IRE pulses need to flow through the tissue from one set of electrodes to another. To achieve this, a controller adjusts the relative amplitude and phase of the IRE pulses applied to the two sets to generate a series of IRE pulses between the two sets for bipolar electroporation in the tissue between the two sets of electrodes. Furthermore, and similarly to unipolar IRE, the controller adjusts the amplitude and phase of the IRE pulses within each set so that the voltage difference between the electrodes in that set does not exceed a predetermined threshold at any time during the application of the IRE pulses.

[0029] System Description

[0030] Figure 1 This is a schematic illustration of a medical device 20 during an IRE procedure according to an embodiment of the present invention. A physician 22 performs the IRE procedure on a patient 24 using an electroporation catheter 26, with further details regarding the catheter described below. The embodiment shown in the figures is an example of an IRE procedure performed in a chamber of the heart 27 using a balloon 32. In alternative embodiments, the IRE procedure can be performed using other types of catheters with multiple electrodes, and can be performed not only in the heart 27 but also in other organs and tissues, as will be apparent to those skilled in the art upon reading this specification.

[0031] As shown in Figure 36, the electroporation catheter 26 includes a shaft 28 and a distal assembly 30, wherein the shaft serves as an insertion tube for inserting the distal assembly into the body cavity of the patient 24, in this case, into the chamber of the heart 27. The distal assembly 30 includes a balloon 32 with a plurality of electroporation electrodes 34. A portion of the distal assembly 30 and the shaft 28 is also shown in Figure 38. In an alternative embodiment, the distal assembly 30 may include a structure different from that of the balloon.

[0032] The medical device 20 also includes a controller 42 and an electrical signal generator configured as an IRE pulse generator 44 typically residing in a console 46; the controller and the signal generator may each include one or more circuit components. Further details of such a signal generator are described in U.S. Patent Application No. 16 / 701,989, filed December 3, 2019, and U.S. Patent Application No. 17 / 092,662, filed November 9, 2020, the disclosures of which are incorporated herein by reference. The catheter 26 is connected to the console 46 via an electrical interface 48 (e.g., a port or receptacle), through which IRE pulses are transmitted from the IRE pulse generator 44 to the distal assembly 30. The console 40 includes input devices 49, such as a keyboard and mouse, and a display screen 58.

[0033] Before and / or during electroporation, controller 42 receives setup parameters 51 for the procedure from physician 22 (or another operator). For example, using one or more suitable input devices, such as a keyboard, mouse, or touchscreen (not shown), physician 22 defines the electrical and timing parameters of the IRE pulse to be applied to the selected electrode 34. Controller 42 then transmits appropriate control signals to IRE pulse generator 44 for execution of the IRE.

[0034] The controller 42 may be further configured to track the corresponding position of the electrodes 34 during IRE surgery using any suitable tracking technology. For example, the distal assembly 30 may include one or more electromagnetic position sensors (not shown) that output signals that vary with the sensor's position in the presence of an external magnetic field generated by one or more magnetic field generators 50. Based on these signals, the controller 42 may determine the position of the electrodes 34. The magnetic field generators 50 are connected to the console 46 via cables 52 and interfaces 54. Alternatively, for each electrode 34, the controller 42 may determine a corresponding impedance between the electrode and a plurality of external electrodes 56 coupled to the patient 24 at various locations and connected to the console 46 via cables 39. The controller 42 calculates ratios between these impedances that indicate the position of each electrode 34. Alternatively, the controller may use both electromagnetic tracking and impedance-based tracking, as described, for example, in U.S. Patent No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0035] In some implementations, the controller 42 displays relevant images 60 of the subject's anatomy on the display screen 58, which are annotated, for example, to show the current position and orientation of the distal component 30.

[0036] The controller 42 and the IRE pulse generator 44 typically include both analog and digital components. Therefore, the controller 42 includes an analog front end with multiple inputs having corresponding analog-to-digital converters (ADCs) for monitoring the IRE pulse applied to each of the electrodes 34 by the IRE pulse generator 44. The controller 42 also includes multiple digital output circuitry for sending commands to the IRE pulse generator 44 to adjust the IRE pulses, as described below. Figures 4 to 6 As described in detail in the document.

[0037] The electrical IRE pulse generator 44 typically includes analog circuitry for generating and amplifying IRE pulses for electroporation, and digital input circuitry for receiving digital control signals from the controller 42.

[0038] Alternatively, the control signal can be transmitted from the controller 42 to the IRE pulse generator 44 in analog form, provided that the controller and the IRE pulse generator are configured accordingly.

[0039] Typically, the functionality of the controller 42 as described herein is implemented at least in part in software. For example, the controller 42 may include a programmable digital computing device, which includes at least a central processing unit (CPU) and random access memory (RAM). Program code (including software programs and / or data) is loaded into the RAM for execution and processing by the CPU. For example, the program code and / or data may be downloaded to the controller electronically via a network. Alternatively or otherwise, the program code and / or data may be provided and / or stored on a non-transitory tangible medium, such as magnetic, optical, or electronic memory. When such program code and / or data are provided to the controller, they create a machine or dedicated computer configured to perform the tasks described herein.

[0040] At the start of the IRE procedure, physician 22 inserts catheter 26 through sheath 62, with balloon 32 in a collapsed configuration, and only after the catheter leaves the sheath is the balloon inflated to its intended functional shape by fluid flowing into the balloon through shaft 28. This functional shape is illustrated in illustrations 36 and 38. By including balloon 32 in a collapsed configuration, sheath 62 also serves to minimize vascular trauma as the balloon is carried to the target location. Physician 22 navigates catheter 26 to the target location in patient 24's heart 27 by manipulating catheter 64 near the proximal end of catheter and / or by deflection from sheath 62. Physician 22 brings distal component 30 into contact with tissue (e.g., myocardial tissue) of heart 27. Next, under the control of physician 22 and controller 42, IRE pulse generator 44 generates IRE pulses that are delivered through catheter 26 to electroporation electrodes 34 via different corresponding channels.

[0041] In the unipolar mode of the IRE, electroporation current flows from one or more electroporation electrodes 34 to an external electrode or “return patch” 66, which is externally coupled between the patient 24 (typically on the skin of the subject’s torso) and the IRE pulse generator 44. A catheter 26 with a balloon 32 less than 15 mm in diameter is typically used for electroporation of tissue in small cavities within the body (e.g., the left atrium of the heart 27). Due to the small size of the electroporation electrodes 34 in these small-diameter balloons, stimulating only one electrode with an IRE pulse can result in electroporation occurring in an excessively small area. Shorting several electrodes 34 together in a group will create a significantly larger electroporation area. While this can be achieved by adding short-circuit switching devices between the individual output channels of the IRE pulse generator 44, such additions are costly. In the embodiments disclosed in this invention, at least two electrodes 34 are grouped together and effectively short-circuited by adjusting the amplitude and phase of the IRE pulse at each of these electrodes to be identical. To this end, the controller 42 monitors the amplitude and phase of the IRE pulse at each of the electrodes 34 in the group and sends a control signal to the IRE pulse generator 44 to equalize these amplitudes and phases.

[0042] In the bipolar mode of IRE, the electroporation current flows between two electrodes or electrode groups 34, thus requiring a series of IRE pulses between the electrodes. In the embodiments disclosed herein, the controller 42 monitors (as in the above-described embodiments of unipolar IRE) the amplitude and phase of the IRE pulses at each of the electrodes 34, but now modulates them to generate the desired IRE pulse train between the two electrodes or two groups of electrodes. Similar to unipolar IRE, the controller 42 further equalizes the amplitude and phase of the IRE pulses within each group.

[0043] More details about the IRE pulse generator 44 and controller 42 are below. Figures 4 to 6 As shown in the image.

[0044] although Figure 1 The document illustrates a specific type of electroporation procedure, but it should be noted that the implementation method described herein can be applied to any suitable type of multi-channel IRE procedure.

[0045] Figure 2 This is a schematic diagram of a biphase IRE pulse 100 according to an embodiment of the present invention.

[0046] Curve 102 shows the voltage V of the biphasic IRE pulse 100 as a function of time t during IRE surgery. The biphasic IRE pulse includes a positive pulse 104 and a negative pulse 106, where the terms "positive" and "negative" refer to the arbitrary polarity of the two electrodes to which the biphasic pulse is applied. In unipolar IRE, a biphasic pulse can be applied between a single electrode 34 and the return patch 66 or between a set of electrodes 34 and the return patch 66. For bipolar IRE, a biphasic pulse can be applied between two electrodes 34 or between two sets of electrodes 34. The amplitude of the positive pulse 104 is denoted as V+, and the pulse's duration is denoted as t+. Similarly, the amplitude of the negative pulse 106 is denoted as V-, and the pulse's duration is denoted as t-. The duration between the positive pulse 104 and the negative pulse 106 is denoted as t. 间隔 Typical values ​​for the parameters of the biphase pulse 100 are given in Table 1 below.

[0047] Figure 3 This is a schematic diagram of a biphasic pulse burst 200 according to an embodiment of the present invention.

[0048] During IRE surgery, the IRE signal is delivered to electrode 34 as one or more bursts 200 as shown by curve 202. The burst 200 includes N... T There are 204 pulse trains, each consisting of N pulses. P One biphase pulse 100. The length of the pulse train 204 is marked as t. T The period of the biphase pulse 100 within pulse train 204 is denoted as t. PP And the interval between consecutive strings is marked as Δ T No signal is applied during this interval. Typical values ​​for the parameters of burst 200 are given in Table 1 below.

[0049] Table 1: Typical values ​​of IRE signal parameters

[0050]

[0051]

[0052] Figure 4 To illustrate schematically, a system 20 according to an embodiment of the present invention includes the connection between an IRE pulse generator 44, a controller 42, an electrode 34, and a return patch 66. Figure 1 A detailed block diagram.

[0053] The IRE pulse generator 44, depicted by dashed box 404, includes a pulse generation component 406 and a pulse routing and metering component 408, wherein the routing and metering component is described below. Figures 5 to 6 The following is a more detailed description.

[0054] The controller 42 receives digital voltage and current signals 412 from the pulse routing and metering component 408, and transmits a digital command signal 418 from the setting parameter 51 to the pulse generation component 406, commanding the IRE pulse generator 44 to generate IRE pulses, such as those described above. Figures 2 to 3 The IRE pulses shown are sent as analog pulse signals 420 to the pulse routing and metering component 408. The pulse routing and metering component 408 is coupled to the electrode 34 via the output channel 422 and to the return patch 66 via the connection 424. Figure 4 Ten output channels 422, labeled CH1 to CH10, are shown. In the following description, a particular electrode is referred to by the name of the specific channel coupled to a particular electrode 34; for example, electrode CH5 refers to the electrode coupled to channel 422. Although Figure 4 This refers to ten channels 422, but the IRE pulse generator 44 may optionally include a different number of channels, such as 8, 16 or 20 channels, or any other suitable number of channels.

[0055] Figure 5 According to an embodiment of the present invention Figure 4 A circuit diagram of the pulse routing and metering component 408 is shown below. For clarity, circuits involving the measurement of current and voltage have been omitted. These circuits will be discussed later. Figure 6 Detailed description is provided below. Output channel 422 and connection 424 are in... Figure 5 Used with Figure 4 The same label is shown in the image.

[0056] The pulse routing and metering component 408 includes module 502, with one module for each output channel 422. (See below...) Figure 6 The diagram details a pair of adjacent modules 502, 504, configured for a bipolar IRE. Alternatively, the BP line 506 connected to the return patch 66 can be used as the return path for a unipolar IRE. Modules 502 receive pulse inputs via corresponding transformer secondary coils 508, 510, which are driven by the primary coil in the pulse generation assembly 406.

[0057] Each module 502 includes a switching device and a relay, denoted as FO of the i-th module. i SO i N i and BP i Switching device FO i All are fast switching devices, controlled by a field-programmable gate array (FPGA, not shown in the attached diagram), used to switch IRE ablation from one channel to another, while the switching device SO i N i and BPi It is a slower relay used to set the pulse routing and metering component 408 for IRE ablation of a given mode. Fast switching device FO i The typical switching time is less than 0.3μs, while the slow relay SO i N i and BP i The switching time is only 3ms.

[0058] Figure 6 The diagram shows two adjacent modules 601 and 602 of the pulse routing and metering component 408 for an IRE in bipolar mode according to an embodiment of the present invention. The use of module 601 for unipolar mode will be further described below.

[0059] Composed of modules 601 and 602 Figure 5 The counterpart to 504 is shown in the dashed box with the same label (504). Modules 601 and 602 are fed by pulse generation circuits 603 and 604, respectively, as shown in the reference. Figure 4 These pulse generation circuits include components of pulse generation assembly 406. Similar to... Figure 5 Modules 502, 601, and 602 of module 504 then feed channels CH1 and CH2 respectively. Figure 6 Two modules, 601 and 602, are shown to illustrate the connection 605 between the modules. Since the two modules are identical (and the same as the other modules in the pulse routing and metering component 408), only module 601 will be described in detail below.

[0060] The pulse generation component 406 includes a pulse generation circuit similar to circuits 603 and 604 of each channel of the IRE pulse generator 44. Pulse generation circuit 603 is coupled to module 601 via transformer 606. The fast switching device FO1 and slow relays SO1, N1, and BP1 are similar to... Figure 5 Mark it.

[0061] The voltage V1 and current I1 coupled to CH1 are in Figure 6 The voltage between channels CH1 and CH2 is shown in the figure, along with the current flowing to CH1 and returning from CH2.

[0062] V1 and I1 are measured by a metering module 612, which includes an operational amplifier 614 for measuring voltage and a differential amplifier 616 for measuring the current across a current-sensing resistor 618. Voltage V1 is measured from a voltage divider 620 (including resistors R1, R2, and R3) and an analog multiplexer 622. The analog multiplexer 622 is coupled to either resistor R1 or R2 such that the voltage divider 620 has a division ratio of R1 / R3 or R2 / R3. The metering module 612 also includes an analog-to-digital converter (ADC) 624 for converting the measured analog voltage V1 and current I1 into digital signals DV1 and DI1. These digital signals are sent to the controller 42 via a digital isolator 626 as signal 412 (…). Figure 4 The controller 42 uses the received digital signal 412 to generate a command signal 418 to be sent to the pulse generation component 406 to adjust the amplitude and phase of the IRE pulses coupled to channels CH1 and CH2.

[0063] For the purpose of "virtual short circuit," controller 42 receives signal 412 from the corresponding module 502. As an example of a bipolar IRE with "virtual short circuit electrodes," electrodes CH1, CH2, and CH3 (coupled to channels CH1, CH2, and CH3) are selected as one extended electrode, and electrodes CH4, CH5, and CH6 are selected as another extended electrode. The signals from electrodes CH1, CH2, and CH3 are used after passing through the tissue of patient 24. Figure 5 The relays shown are coupled to channels CH4, CH5, and CH6. Controller 42 receives signals 412 from channels CH1, CH2, and CH3 indicating the corresponding measured voltages and currents, and generates corresponding command signals 418 such that V1, V2, and V3 will each have the same amplitude and phase (i.e., a virtual short circuit). Similarly, controller 42 receives signals 412 from channels CH4, CH5, and CH6, and generates corresponding command signals 418 such that V4, V5, and V6 will each have the same amplitude and phase, but different from the amplitude and phase of V1, V2, and V3, so that a desired series of IRE pulses flows between the two sets of channels (and therefore between the two sets of electrodes 34 coupled to these channels).

[0064] As an example of a unipolar IRE with a "virtual short-circuit electrode," electrodes CH1, CH2, and CH3 are selected as an extended electrode, while the return patch 66 serves as the return electrode for the IRE ablation signals emitted from electrodes CH1, CH2, and CH3. The return patch 66 is coupled to the corresponding modules 502 of channels CH1, CH2, and CH3 via relays BP1, BP2, and BP3 through connection 424. Similar to the bipolar IRE described above, the controller 42 receives signals 412 from channels CH1, CH2, and CH3 and generates corresponding command signals 413 such that V1, V2, and V3 will each have the same amplitude and phase, thus effectively short-circuiting the electrodes 34 coupled to these channels.

[0065] Digital isolator 626 protects patients for 24 hours. Figure 1 It is protected from harmful voltages and currents.

[0066] The switching device FO1, relays SO1, BP1, N1, and 610, as well as the analog multiplexer 622, are driven by the controller 42. For simplicity, Figure 6 The corresponding control lines are not shown.

[0067] It should be understood that the above embodiments are cited by way of example, and the invention is not limited to the specific contents shown and described above. Rather, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should be apparent to those skilled in the art upon reading the above description, and which are not disclosed in the prior art.

Claims

1. A medical device for irreversible electroporation, the medical device comprising: The probe includes: An insertion tube, the insertion tube being configured for insertion into a patient's body cavity; and A distal assembly, the distal assembly being distally connected to the insertion tube and including a plurality of electrodes configured to contact tissue within the body cavity; A common electrode, configured to be fixed to the patient's body; An electrical signal generator configured to simultaneously apply biphasic electrical pulses in a unipolar mode between a group of two or more electrodes and a common electrode, such that the biphasic electrical pulses travel from the group of electrodes through the body to the common electrode, the energy of the biphasic electrical pulses being sufficient to irreversibly electroperforate the tissue contacted by the electrodes in the group; and A controller coupled to measure the voltage difference between the electrodes in the set over time and to regulate the biphase electrical pulses applied to the electrodes in the set such that the voltage difference does not exceed a predetermined threshold at any time during the application of the biphase electrical pulses.

2. The device of claim 1, wherein the controller is configured to adjust the amplitude of the biphase electrical pulses to compensate for the difference in the corresponding peak voltages measured at any pair of electrodes in the set.

3. The device of claim 1, wherein the controller is configured to adjust the phase of the biphase electrical pulses to compensate for phase shifts between corresponding voltage waveforms measured at any pair of electrodes in the set.

4. The device of claim 1, wherein the distal component includes a balloon distally connected to the insertion cannula and configured to inflate within the body cavity with fluid flowing into the balloon through the insertion cannula.

5. The device of claim 1, wherein the group comprises a first group and a second group, wherein the biphase electrical pulses are applied in a bipolar mode between the electrodes in the first group and the electrodes in the second group, and wherein the controller is coupled to measure the voltage difference between the electrodes in the first group and the second group over time, and to adjust the biphase electrical pulses applied to the electrodes in the first group and the second group such that the voltage difference between the electrodes in the first group and the second group comprises a predetermined series of biphase electrical pulses.

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