Patent Description:
Various techniques for controlling bipolar ablation procedures and electroporation procedures have been published.

For example, <CIT> describes electroporation systems, methods of controlling electroporation systems to limit electroporation arcs through intra-cardiac catheters, and catheters for electroporation systems. One method of controlling an electroporation system including a direct current (DC) energy source, a return electrode connected to the DC energy source, and a catheter connected to the DC energy source is disclosed. The catheter has at least one catheter electrode. The method includes positioning the return electrode near a target location within a body and positioning the catheter electrode adjacent the target location within the body. A system impedance is determined with the return electrode positioned near the target location and the catheter electrode positioned within the body. The system impedance is adjusted to a target impedance to arcing from the catheter electrode.

<CIT> describes a medical device system configured to detect an improper energy transmission configuration therein. The condition may be detected by way of a detection of a condition where an energy-transmitting electrode of the medical device system becomes too close to or becomes in contact with an object resulting in an inability of the electrode to properly transmit energy. For example, if the energy-transmitting electrode is a first electrode configured in its operational state to transmit energy to bodily tissue adjacent the first electrode, but the first electrode is inadvertently contacting a second electrode, such contact may cause at least some energy transmitted by the first electrode to follow an unintended path away from its intended path to the adjacent tissue. Such a condition may be detected based at least upon an analysis of information acquired from a sensing device system.

For further background, <CIT> describes an ablation system that comprises an ablation catheter and a console. The ablation catheter comprises: a shaft including a proximal end, a distal portion and a distal end; an ablation element configured to deliver energy to tissue; and a force maintenance assembly comprising a force maintenance element and configured to control and/or assess contact force between the ablation element and cardiac tissue. The console is configured to operably attach to the ablation catheter and comprises: an energy delivery assembly configured to provide energy to the ablation element.

<CIT> describes an ablation catheter having a deformable tip. The ablation catheter includes a catheter body and a deformable tip secured to the catheter body. The catheter body can include a fluid delivery lumen. The deformable tip includes one or more valves that are configured to open in response to deformation of the deformable tip. The ablation catheter is configured to permit liquid communication between an interior of the deformable tip and an exterior of the deformable tip. RF energy is transmitted from the interior of the deformable tip to the exterior of the deformable tip via liquid exiting the deformable tip. <CIT> discloses a system to detect shunt conditions between ablation electrodes.

The invention is defined the appended independent claim <NUM>, further embodiments are described in the dependent claims. The methods of surgery described here below are not claimed.

Procedures for ablating soft tissue, such as irreversible electroporation (IRE) and radio frequency ablation (RFA) procedures, may comprise applying bipolar ablation pulses, e.g., between two ablation electrodes of a catheter, which is inserted into a patient organ for ablating the tissue in question.

In principle, it is possible to use a flexible catheter, which conforms to the tissue intended to be ablated. In some cases, however, the catheter flexibility may enable undesired proximity or even physical contact between two or more electrodes of the catheter. Such proximity or contact may divert at least part of the ablation energy, for example, to undesired locations on tissue of a patient, and may also cause inadequate ablation of the tissue intended to be ablated.

Embodiments of the present invention that are described hereinbelow provide improved techniques for controlling IRE and bipolar RFA procedures while retaining a safe distance between ablation electrodes of one or more ablation catheters inserted into the patient organ to carry out the tissue ablation.

In some embodiments, a system for ablating tissue comprises a catheter, a pulse generator and a controller. The catheter is configured for insertion into a body of a patient, and comprising at least a first electrode, a second electrode and a third electrode, which are disposed at a distal end of the catheter and are configured to be placed in contact tissue intended to be ablated.

In some embodiments, the pulse generator is configured to apply one or more bipolar ablation pulses between the first and second electrodes, also referred to herein as active electrodes, for ablating the tissue in contact with the first and second electrodes.

In some embodiments, the controller is configured to control the pulse generator to apply the one or more bipolar ablation pulses between the active electrodes. The controller is further configured to receive a signal indicative of a voltage, measured between the third electrode and a reference when applying the ablation pulses to the active electrodes. Note that the aforementioned ablation pulses are not applied to the third electrode, and therefore, in the present configuration, the third electrode is also referred to herein as a non-active electrode.

In some embodiments, the controller is configured to issue a notification in response to detecting that the voltage violates a predefined criterion.

Additionally or alternatively, based on the sensed voltage described above, the controller is configured to estimate the distance between given active and non-active electrodes, and to issue a notification in case the estimated distance is smaller than a distance threshold indicative of the minimal distance allowed between the given electrodes.

Based on the disclosed techniques, the controller is configured to sense and notify the user of the ablation system when at least a portion of the energy of the ablation pulses is diverted from the active electrode to the non-active electrode. Thus, the disclosed techniques improve the quality of bipolar ablation procedures, and enable the use of flexible catheter while improving the patient safety in IRE and bipolar RFA procedures.

<FIG> is a schematic pictorial illustration of an ablation system <NUM> in the course of a cardiac ablation procedure, in accordance with an embodiment of the invention. In some embodiments, a physician <NUM> performs the ablation procedure on tissue <NUM> of a patient <NUM>, using an ablation catheter <NUM> whose distal end <NUM> is flexible, so as to conform with tissue <NUM>, and comprises multiple ablation electrodes <NUM>. The ablation procedure may comprise either an irreversible electroporation (IRE) procedure or a bipolar radiofrequency ablation (RFA) procedure, or possibly a combination of both kinds of ablation procedures.

In some embodiment, physician <NUM> is performing the cardiac ablation procedure using ablation system <NUM>. To begin the procedure, physician <NUM> inserts catheter <NUM> into the body of patient <NUM>, and then navigates the catheter, using a control handle <NUM>, to a target site within, or external to, a heart <NUM> of patient <NUM>. Subsequently, physician <NUM> places distal end <NUM> in contact with tissue <NUM> of heart <NUM>, such as myocardial or epicardial tissue.

In some embodiment, physician <NUM> selects from among electrodes <NUM>, a pair of electrodes 30a and 30b to carry out the bipolar ablation. System <NUM> comprises a pulse generator, also referred to herein as an electrical signal generator (SIG GEN) <NUM>, or a generator <NUM> for brevity. Physician <NUM> controls generator <NUM> to generate ablation pulses <NUM>, with signal parameters selected, for example, to serve as either IRE signals or RFA signals, or any suitable combination thereof.

In some embodiments, signals <NUM> are carried through catheter <NUM>, over different respective channels, to ablation electrodes 30a and 30b, such that the ablation current flows from one of the electrodes in the pair through tissue <NUM> of patient <NUM>, and returns through the other electrode of the pair.

In some embodiments, ablation system <NUM> further comprises a controller (CTRL) <NUM>, which is configured to receive, from physician <NUM> or from another user, prior to and/or during the ablation procedure, setup parameters <NUM> suitable for the procedure. For example, using one or more suitable input devices, such as a keyboard, mouse, or touch screen, physician <NUM> defines the ablation mode (IRE, RFA), the parameters of the ablation pulses (for example power, duration), and one or more pairs of ablation electrodes <NUM> to be used for the ablation.

In some embodiments, physician <NUM> may also input, using the aforementioned input devices, additional setup parameters <NUM> for ablation pulse <NUM>, such as but not limited to a maximum power, a maximum current amplitude, a maximum voltage amplitude, duration of the signal, and/or any other relevant parameters. In response to receiving setup parameters <NUM>, controller <NUM> is configured to control signal generator <NUM>, to generate signals <NUM> in accordance with the setup parameters. Moreover, controller <NUM> is configured to display the setup parameters on a display <NUM>, which may comprise the aforementioned touch screen.

In some embodiments, controller <NUM> is configured to track the respective positions of ablation electrodes <NUM> in the patient's body during the procedure, using any suitable tracking technique. For example, distal end <NUM> may comprise at least a magnetic position sensor (not shown), which is configured, in the presence of external magnetic fields generated by magnetic field-generators <NUM>, to output position signals indicative the positions of the respective sensor.

In some embodiments, based on the position signals, controller <NUM> is configured to estimate the positions of distal end <NUM> and electrodes <NUM>. In alternative embodiments, for each electrode, controller <NUM> may receive multiple signals indicative of respective impedances measured between each electrode and multiple external electrodes <NUM> disposed on the body surface of patient <NUM> at various different locations. In some embodiments, controller <NUM> is configured to compute the ratios between the received impedances so as to estimate the position of the respective electrode within the body of patient <NUM>. As yet another alternative, the controller <NUM> may use both magnetic-based tracking and impedance-based tracking, as described, for example, in <CIT>.

In some embodiments, distal end <NUM> may have additional sensors, such as but not limited to contact force sensors, configured to produce contact signals indicative of the contact between an electrode <NUM> and tissue <NUM>. Based on the position signals and contact signal, controller <NUM> is configured to display which ablation electrodes <NUM> are in contact with tissue <NUM>. In the present example, electrodes 30a and 30b are in contact with tissue <NUM>, and in response to instructions from physician <NUM>, controller <NUM> is configured to control signal generator <NUM> to apply ablation pulses <NUM> to tissue <NUM> via electrodes 30a and 30b. Note that other electrodes <NUM> of distal end <NUM> are not receiving ablation pulses <NUM>, and are referred to herein as "non-activated electrodes," whereas in the present example, electrodes 30a and 30b are also referred to herein as "activated electrodes.

In some embodiments, controller <NUM> displays, on display <NUM>, an image <NUM> of the patient's anatomy, with the position and orientation of distal end <NUM> overlaid on image <NUM>. Additionally or alternatively, based on signals received from additional sensors disposed on distal end <NUM>, controller <NUM> is configured to track the temperature and/or impedance of tissue <NUM>, and to control signal generator <NUM> responsively thereto.

In some embodiments, ablation system <NUM> comprises a control console <NUM> having controller <NUM>, signal generator <NUM> and display <NUM>. Catheter <NUM> is electrically connected to console <NUM> via an electrical interface <NUM>, such as a port or socket. Signals <NUM> are thus carried to distal end <NUM> via interface <NUM>. Similarly, signals for tracking the position of distal end <NUM> and/or signals for tracking the temperature and/or impedance sensed in tissue <NUM> may be received by controller <NUM> via interface <NUM>. Magnetic field-generators <NUM> and external electrodes <NUM> are connected to console <NUM> via cables <NUM> and <NUM>, respectively.

In some embodiments, controller <NUM> typically comprises both analog and digital elements. Thus, controller <NUM> may comprise multiple analog-to-digital converters (ADCs) for receiving analog signals from catheter <NUM> and from signal generator <NUM>. Controller <NUM> may further comprise multiple digital-to-analog converters (DACs) for transmitting analog control signals to signal generator <NUM> and other system components. Alternatively, these control signals may be transmitted in digital form, provided that signal generator <NUM> is configured to receive digital control signals. Controller <NUM> typically comprises digital filters for extracting signals at given frequencies from the received signals.

Typically, the functionality of controller <NUM>, as described herein, is implemented at least partly in software. For example, controller <NUM> may comprise a programmed digital computing device comprising at least a central processing unit (CPU) and suitable memory, such as any suitable type of random access memory (RAM). Program code, comprising software programs and/or data are loaded into the RAM for execution and processing by the CPU. The program code and/or data may be downloaded to the controller in electronic form, over a network, for example. Alternatively or additionally, the program code and/or data may be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. Such program code and/or data, when provided to the processor, produce a machine or special-purpose computer, configured to perform the tasks described herein.

In other embodiments, controller <NUM> may comprise a general-purpose controller, which is programmed in software to carry out the functions described herein. The software may be downloaded to the controller in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.

This particular configuration of system <NUM> is shown by way of example, in order to illustrate certain problems that are addressed by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such a system. Embodiments of the present invention, however, are by no means limited to this specific sort of example system, and the principles described herein may similarly be applied to other sorts of ablation systems used in medical ablation procedures.

<FIG> are schematic pictorial illustrations of two shapes of distal end <NUM> of catheter <NUM>, in accordance with embodiments of the invention. Items similar to those in <FIG> are marked with the same labels.

In some embodiments, distal end <NUM> of catheter <NUM> comprises a "Lasso" type catheter, having multiple electrodes <NUM> mounted on a flexible arm, which is configured to conform to the shape of tissue <NUM> of patient <NUM>. For example, when ablating a pulmonary vein (PV) of heart <NUM>, distal end <NUM> is configured to conform to the inner diameter of the PV, so as to carry out a PV isolation procedure.

In other embodiments, distal end <NUM> may comprise any other suitable type of catheter, for example, a multi-arm catheter, such as but not limited to a basket catheter. Note that in both embodiments, electrodes <NUM> are disposed at distal end <NUM>, using any suitable configuration, e.g., along a longitudinal axis of an arm, or at different arms of the distal end.

Reference is now made to <FIG>. In some embodiments, distal end <NUM> forms a loop, but none of electrodes <NUM> are positioned in close proximity or making contact with one another.

Reference is now made to <FIG>. In some embodiments, distal end <NUM> is configured to form a tighter loop compared to that of <FIG>. In this arrangement, an electrode 30c is placed, in contact with or close proximity to, electrode 30b.

In the example of <FIG>, when applying one or more bipolar ablation pulses <NUM> between electrodes 30a and 30b at least some of the current flowing through electrode 30b may leak (e.g., parasitically) through electrode 30c. As a result of the reduction in power that is actually applied to tissue <NUM>, the bipolar ablation between electrodes 30a and 30b is likely to be inadequate.

<FIG> is a schematic pictorial illustration of generator <NUM>, in accordance with an embodiment of the invention. In some embodiments, generator <NUM> may be integrated in console <NUM> (as shown in <FIG> above), or may be positioned at any other suitable module of system <NUM>.

In some embodiments, generator <NUM> comprises multiple channels, configured to conduct ablation pulses <NUM> between pulse generator <NUM> and respective electrodes <NUM> of catheter <NUM>, as described in detail herein.

In some embodiments, generator <NUM> comprises pulse-generation circuits (PGCs) <NUM>, <NUM>, <NUM> and <NUM>, which are connected to, and are configured to, apply one or more bipolar ablation pulses <NUM> to electrodes 30a, <NUM>, 30b and 30c, respectively.

In some embodiments, PGC <NUM> comprises a pulse generating apparatus (PGA) <NUM> connected to an output transformer, referred to herein as a transformer <NUM>, which is configured to transfer ablation pulses <NUM> between PGA <NUM> and electrode 30a of catheter <NUM>. PGC <NUM> further comprises a channel <NUM> (shown as "Ch. <NUM>" in <FIG>) made from electrical conductors (e.g., electrical leads or electrical traces) for connecting and disconnecting between PGC <NUM> and electrode 30a of catheter <NUM>.

In the present example, a first coil of transformer <NUM> receives one or more of the ablation pulses from PGA <NUM>, and a second coil of transformer <NUM>, which is connected, via channel <NUM>, to a corresponding channel of catheter <NUM>, applies one or more ablation pulses <NUM> to electrode 30a.

In some embodiments, PGC <NUM> comprises switches <NUM> and <NUM>, configured to connect and disconnect between transformer <NUM> and channel <NUM>, wherein switch <NUM> is further configured to connect and disconnect between transformer <NUM> and an electrical trace <NUM>. Note that when switch <NUM> is closed (as shown in <FIG>), transformer <NUM> transfers the one or more ablation pulses to electrode 30a, which is now activated for applying ablation pulses <NUM> to tissue <NUM>.

In some embodiments, the structure of PGC <NUM> repeats in the other PGCs of generator <NUM>. For example, PGC <NUM> comprises: (i) a PGA <NUM>, for producing the ablation pulses as described above for PGA <NUM>, (ii) a channel <NUM> having the same features of channel <NUM>, and (iii) a transformer <NUM>, which is configured to transfer, via channel <NUM>, ablation pulses <NUM> between PGA <NUM> and electrode <NUM>. Similarly, PGC <NUM> comprises: (i) a PGA <NUM>, for producing the ablation pulses as described above for PGA <NUM>, (ii) a channel <NUM> having the same features of channel <NUM>, and (iii) a transformer <NUM>, which is configured to transfer, via channel <NUM>, ablation pulses <NUM> between PGA <NUM> and electrode 30b.

In some embodiments, PGC <NUM> comprises: (i) a PGA <NUM>, for producing the ablation pulses as described above for PGA <NUM>, (ii) a channel <NUM> having the same features of channel <NUM>, and (iii) a transformer <NUM>, which is configured to transfer, via channel <NUM>, ablation pulses <NUM> between PGA <NUM> and electrode 30c. Note that in the example of <FIG>, generator <NUM> has ten PCGs (wherein only PGCs <NUM>, <NUM>, <NUM> and <NUM> are shown) for connecting and disconnecting between each PGA with a respective electrode of catheter <NUM>.

In other embodiments, generator <NUM> may have any other suitable number of PGCs for connecting and disconnecting between a corresponding number of electrodes of catheter <NUM>. In yet other embodiments, instead of PGAs described above, generator <NUM> may comprise a single pulse generator (not shown), which is controlled by controller <NUM> and is configured to supply the ablation pulses to transformers <NUM>, <NUM>, <NUM> and <NUM>.

In some embodiments, generator comprises a similar routing and switching configuration for each PGC. For example, switches <NUM> and <NUM> are configured to connect and disconnect between transformer <NUM> and channel <NUM>, switches <NUM> and <NUM> are configured to connect and disconnect between transformer <NUM> and channel <NUM>, and switches <NUM> and <NUM> are configured to connect and disconnect between transformer <NUM> and channel <NUM>.

In some embodiments, generator <NUM> comprises an electrical conductor, referred to herein as a back-patch (BP) <NUM>, which is configured to electrically connect between the transformers of generator <NUM>. BP <NUM> may serve as a reference for voltage measurement during the application of ablation pulses <NUM>.

In some embodiments, generator <NUM> further comprises switches <NUM>, <NUM>, <NUM> and <NUM> for connecting and disconnecting between BP <NUM> and transformers <NUM>, <NUM>, <NUM> and <NUM>, respectively. In the example of <FIG>, switches <NUM> and <NUM> are closed for connecting between BP <NUM> and transformers <NUM> and <NUM>, and switches <NUM> and <NUM> are opened for disconnecting between BP <NUM> and transformers <NUM> and <NUM>, respectively.

In some embodiments, generator <NUM> further comprises: (i) a switch <NUM> for connecting and disconnecting between transformers <NUM> and <NUM> of neighbor electrodes 30a and <NUM>, (ii) a switch <NUM> for connecting and disconnecting between transformers <NUM> and <NUM> of neighbor electrodes <NUM> and 30b, (ii) a switch <NUM> for connecting and disconnecting between transformer <NUM> and an additional transformer (not shown) of electrode 30b and a neighbor electrode (not shown), and (iv) a switch <NUM> for connecting and disconnecting between transformers <NUM> and <NUM>, via trace <NUM>.

In some embodiments, controller <NUM> is configured to control generator <NUM> to apply ablation pulses <NUM>: (i) to electrode 30a via transformer <NUM> and channel <NUM>, and (ii) to electrode 30b via transformer <NUM> and channel <NUM>. Note that in this operative mode, switches <NUM>, <NUM> and <NUM> are closed, so as to apply ablation pulses <NUM> to electrode 30a, and similarly, switches <NUM>, <NUM> and <NUM> are closed, so as to apply ablation pulses <NUM> to electrode 30b.

In the present example, controller <NUM> is configured to control generator <NUM> to apply bipolar ablation pulses <NUM> having an amplitude of about 900V activated in opposite phase between channels <NUM> and <NUM>. For example, when channel <NUM> outputs about +900V to electrode 30a, channel <NUM> outputs about -900V to electrode 30b. Therefore, the total amplitude of bipolar ablation pulses <NUM> applied between electrodes 30a and 30b, is about 1800V.

In the context of the present disclosure, the terms "about" or "approximately" for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein.

In some embodiments, during the ablation described above, the voltage amplitude on BP <NUM>, which serves for connecting between transformers <NUM> and <NUM>, is virtually zero. Similarly, transformers <NUM> and <NUM> are idle and the electrodes connected to channels <NUM> and <NUM> are not receiving any ablation pulses.

In some embodiments, when applying bipolar ablation pulses <NUM> between electrodes 30a and 30b, controller <NUM> is configured to receive a signal. The signal is indicative of a voltage, which is measured between: (i) a point <NUM> of channel <NUM> connected to electrode 30c, and (ii) any suitable reference point on BP <NUM>, such as a reference point <NUM>.

In some embodiments, when distal end <NUM> is arranged as shown in <FIG>, electrodes <NUM>, 30a, 30b and 30c are sufficiently far from one another (e.g., about <NUM> or more between any pair of adjacent electrodes). Therefore, when about 1800V is applied between electrodes 30a and 30b (e.g., about +900V voltage is applied to electrode 30a, and at the same time, about -900V is applied to electrode 30b), the voltage measured between points <NUM> and <NUM> is about zero.

In some embodiments, when measuring electrical current flowing through activated electrodes, such as electrodes 30a and 30b, the typical impedance measured on each activated electrode is typically constant, e.g., about <NUM>Ω.

In other embodiments, when distal end <NUM> is arranged as shown in <FIG>, electrodes 30b and 30c are in close proximity with one another, e.g., at a distance smaller than about <NUM>, or even in direct contact with one another.

In some embodiments, in the example of <FIG>, when about 1800V is applied between electrodes 30a and 30b, the electrical current associated with ablation pulses <NUM>, may flow into electrode 30b. However, due to the close proximity (or physical contact) between electrodes 30b and 30c, voltage has been formed between 30b to electrode 30c. Moreover, when electrodes 30b and 30c are (unintentionally) placed in contact with one another, the surface area of the "combined" electrode (comprising electrodes 30b and 30c) is larger compared to that of electrode 30b. Therefore, the impedance measured on the combined electrode is substantially different than about <NUM>Ω measured in the example described in <FIG> above. Moreover, the measured electrical current flowing through the combined electrode substantially differs from the measured electrical current flowing through electrode 30b in the example described in <FIG> above.

Additionally or alternatively, the voltage measured between points <NUM> and <NUM> is substantially larger than zero. For example, (i) when the distance between electrodes 30b and 30c is about <NUM>, the voltage measured between points <NUM> and <NUM> is about 400V, and (ii) when electrodes 30b and 30c are in direct contact the voltage measured between points <NUM> and <NUM> is more than about 800V.

In some embodiments, controller <NUM> is configured to issue a notification in response to detecting that the voltage measured between points <NUM> and <NUM>, violates a predefined criterion. For example, controller <NUM> is configured to hold a threshold for the voltage measured between points <NUM> and <NUM>, and to issue the notification in case the measured voltage exceeds (i.e. is larger than) the threshold voltage. Additionally or alternatively, controller <NUM> is configured to hold a predefined pulse shape of the voltage measured between points <NUM> and <NUM>. The pulse shape may have a predefined waveform, e.g., the waveform may comprise the voltage amplitude plotted as a function of the measurement time.

In some embodiments, controller <NUM> is configured to hold a preassigned threshold of inter-electrode distance (e.g., about <NUM>), also referred to herein as a distance threshold. Based on the voltage measured between points <NUM> and <NUM>, controller <NUM> is configured to detect whether the distance between electrodes 30b and 30c is smaller than the distance threshold.

In some embodiments, because the measured voltage increases when the distance between electrodes 30b and 30c is reduced, controller <NUM> is configured, based on the measured voltage, to estimate the distance between electrodes 30b and 30c. For example, when the measured voltage is between about 400V and 550V, the distance between electrodes 30b and 30c is smaller than about <NUM>.

Additionally or alternatively, controller <NUM> is configured to issue a notification in response to detecting that the current flowing through an active electrode (in the present example, electrode 30b) and/or through a non-active electrode (such as electrode 30c), violates a respective predefined criterion.

In some embodiments, in order to measure of the signal indicative of the voltage between points <NUM> and <NUM>, controller <NUM> is configured to disconnect electrode 30c from transformer <NUM>. For example, by having switches <NUM> and <NUM> opened.

<FIG> is a flow chart that schematically illustrates a method for detecting contact and proximity between ablation electrodes 30b and 30c during a bipolar ablation procedure.

The method begins with a catheter insertion step <NUM>, with the insertion of catheter <NUM> into heart <NUM> or any other suitable organ in the body of patient <NUM>. As described in <FIG> above, catheter <NUM> comprises at least electrodes 30a, 30b and 30c, disposed at distal end <NUM> for being placed in contact with tissue <NUM> of heart <NUM>.

At a tissue ablating step <NUM>, controller <NUM> controls generator <NUM> to apply one or more bipolar ablation pulses <NUM> between electrodes 30a and 30b, for ablating tissue <NUM>, which is in contact with electrodes 30a and 30b, as described in <FIG>, <FIG> above.

At a signal receiving step <NUM>, when applying ablation pulses <NUM>, controller <NUM> receives a signal indicative of the voltage measured between points <NUM> and <NUM>, which constitutes the voltage between electrode 30c and BP <NUM> that serves as a reference, as described in <FIG> above.

At a first decision step <NUM>, controller <NUM>, which holds one or more thresholds of electrical parameters, such as voltage threshold, checks whether the measured parameter exceeds the respective threshold. Additionally or alternatively, controller <NUM> may hold a distance threshold, and estimates the distance between electrodes 30b and 30c, based on the measured voltage. In some embodiments, controller <NUM> checks whether the estimated distance is smaller or larger than the distance threshold.

In some embodiments, in step <NUM> controller <NUM> may detect that the voltage measured between points <NUM> and <NUM> is larger than the voltage threshold, and/or the estimated distance is smaller than the distance threshold. In such embodiments, the method proceeds to an alerting and adjusting step <NUM>, with issue notification by controller <NUM> to stop applying bipolar ablation pulses <NUM>. Additionally or alternatively, controller <NUM> may automatically control generator <NUM> to stop applying bipolar ablation pulses <NUM> between electrodes 30a and 30b.

In some embodiments, controller <NUM> may also issue a notification to physician <NUM> to adjust the position of the electrodes of distal end <NUM> relative to tissue <NUM>, because an active electrode (e.g., electrode 30b) and a non-active electrode (e.g., electrode 30c) are in contact with one another or positioned in too close proximity to one another.

In some embodiments, after adjusting the position of the electrodes of distal end <NUM> relative to tissue <NUM>, controller <NUM> may estimate the need to apply additional bipolar ablation pulses <NUM> to tissue <NUM>, and in case more ablation is needed, the method loops back to step <NUM> for applying the ablation pulses as described above.

In other embodiments, in step <NUM> controller <NUM> may detect that the voltage measured between points <NUM> and <NUM> is smaller than the voltage threshold, and/or the estimated distance is larger than the distance threshold. In such embodiments, the method proceeds to an ablation continuation step <NUM>, and controller <NUM> controls generator <NUM> to continue applying one or more bipolar ablation pulses <NUM> between electrodes 30a and 30b, in accordance with ablation plan.

At a second decision step <NUM>, controller <NUM> checks whether the ablation procedure has been completed, e.g., in case sufficient bipolar ablation pulses <NUM> have been applied to tissue <NUM>. In case the ablation procedure has not been completed, the method loops back to step <NUM>. In case the ablation has been completed, the method proceeds to a catheter extraction step <NUM>, which concludes the method, so that physician <NUM> extracts catheter <NUM> out of the body of patient <NUM>.

Although the embodiments described herein mainly address bipolar ablation procedures using a flexible catheter, e.g., lasso type, having multiple electrodes, the methods and systems described herein can also be used in other applications, such as in bipolar ablation procedures using other sorts of catheters, for maintaining predefined distance between electrodes of such catheters. Moreover, the embodiments described herein may be also used in various types of electroporation procedures, such as but not limited to irreversible electroporation, and in electrosurgical procedures.

Claim 1:
A system (<NUM>) for detecting contact and proximity between ablation electrodes by sensing changes in voltage morphology of non-activated electrodes, the system comprising:
a catheter (<NUM>), which is configured for insertion into a body of a patient (<NUM>), the catheter (<NUM>) comprising at least a first electrode (30a), a second electrode (30b) and a third electrode (30c), which are disposed at a distal end (<NUM>) of the catheter (<NUM>) and are configured to contact tissue within the body;
a pulse generator (<NUM>), which is configured to apply one or more bipolar ablation pulses between the first and second electrodes (30a, 30b), for ablating the tissue in contact with the first and second electrodes (30a, 30b); and
a controller (<NUM>), which is configured to:
(i) control the pulse generator (<NUM>) to apply the one or more bipolar ablation pulses between the first and second electrodes (30a, 30b), and
(ii) detect that a distance between (i) at least one of the first and second electrodes, and (ii) the third electrode, is smaller than a distance threshold;
characterized in that:
the controller is configured to receive a signal indicative of a voltage, measured between the third electrode and a reference during application of the ablation pulses,
the distance is detected by detecting that the voltage violates a predefined criterion, and
the controller is further configured to issue a notification in response to detecting that the voltage violates the predefined criterion.