WO2016132339A1

WO2016132339A1 - Method and system for radiofrequency ablation with means for activating electrode pairs in a bipolar mode, identifying electrodes with temperature deviations and calculating a remaining ablation time for a unipolar mode

Info

Publication number: WO2016132339A1
Application number: PCT/IB2016/050943
Authority: WO
Inventors: David Prutchi; Benjamin PATEL
Original assignee: Renal Dynamics Ltd.
Priority date: 2015-02-22
Filing date: 2016-02-22
Publication date: 2016-08-25

Abstract

There is provided a system for radiofrequency (RF) ablation, comprising a controller programmed to activate (104) pairs of RF electrodes to deliver bipolar RF energy to an inner wall of a target lumen for a total ablation time at a temperature within a target temperature range, wherein the RF electrodes are coupled to an ablation device at a distal end region of an intravascular catheter and adapted to apply RF energy to the inner wall to ablate a target tissue. The controller is further programmed to identify (106) electrodes that deviated from a lower limit of the target temperature range, calculate (108), for each identified electrode, a remaining time as the total ablation time minus the time spent within the target temperature range and activate (110) each identified electrode to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

Description

METHOD AND SYSTEM FOR RADIOFREQUENCY ABLATION WITH MEANS FOR ACTIVATING ELECTRODE PAIRS IN A BIPOLAR MODE, IDENTIFYING ELECTRODES WITH TEMPERATURE DEVIATIONS AND CALCULATING A REMAINING ABLATION TI ME FOR A UNIPOLAR MODE

FIELD AND BACKGROUND OF THE PRESENT INVENTION

The present invention, in some embodiments thereof, relates to systems and methods for radiofrequency (RF) ablation and, more particularly, but not exclusively, to methods and systems for intravascular radiofrequency (RF) ablation of target tissue.

Target tissues located within body lumens, such as blood vessels, may be accessed for treatment in a minimally invasive manner, for example, by threading a catheter percutaneously, through the vascular system, to reach the target tissue.

Ablation using RF energy has been found to be particularly effective for performing certain treatment procedures, for example, for performing renal denervation.

International Patent Application Publication No. WO2014/118733 discloses "An ablation device and/or method of ablation may include placing one or more ablation electrodes in contact with a target tissue in a lumen. An electrical insulator may be positioned between the electrode and a lumen fluid and an electrical signal (for example a radio frequency signal) may be conveyed between the electrodes to heat and/or ablate the target tissue. Ablation may be bipolar and/or an in-lumen dispersive electrode may be supplied for unipolar ablation. Ablation progress may be sensed and ablation may be adjusted to produce a desired level and/or geometry of ablation."

International Patent Application Publication No. WO2014/118734 discloses "An ablation device and/or method of ablation may include placing one or more ablation electrodes in contact with a target tissue in a lumen. An electrical insulator may be positioned between the electrode and a lumen fluid and an electrical signal (for example a radio frequency signal) may be conveyed between the electrodes to heat and/or ablate the target tissue. Ablation may be bipolar and/or an in-lumen dispersive electrode may be supplied for unipolar ablation. Ablation progress may be sensed and ablation may be adjusted to produce a desired level and/or geometry and/or distribution of ablation."

SUMMARY OF THE PRESENT INVENTION

According to an aspect of some embodiments of the present invention there is provided a system for radiofrequency (RF) ablation of target tissue, comprising: a controller programmed to: activate pairs of a plurality of RF electrodes to deliver bipolar RF energy to an inner wall for a total ablation time at a temperature within a target temperature range, wherein the RF electrodes are coupled to an ablation device at a distal end region of an intravascular catheter and adapted to apply RF energy to the inner wall of a target lumen to ablate a target tissue, identify which one or both electrodes of each pair deviated from a lower limit of the target temperature range, calculate, for each identified electrode, a remaining time to reach the total ablation time as the total ablation time minus the time spent within the target temperature range, and activate each identified electrode to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

Optionally, the controller is programmed to continue activation of the pairs of the plurality of RF electrodes to deliver bipolar RF energy for the entire duration of the total ablation time when the temperature of one or both of the electrodes of each pair drops below the lower limit of the target temperature range.

Optionally, the controller is programmed to simultaneously start activation of the pairs to deliver the bipolar RF energy, and to simultaneously start activation of the identified electrodes to deliver the unipolar RF energy.

Optionally, the controller is further programmed to ramp-up the temperature of each of the plurality of RF electrodes to a predefined temperature within the target temperature range before activation for the total ablation time delivering RF bipolar energy begins. Optionally, a number of bipolar channels during the ramp-up is equal to the number of electrode pairs. Optionally, the ramp-up is performed for a predefined period of time.

Optionally, a number of bipolar channels during the bipolar RF energy delivery is equal to the number of the plurality of electrodes. Optionally, the electrodes are arranged in pairs on a plurality of struts positioned along the long axis of the lumen and around the circumference of the inner wall of the lumen, each electrode included in a first bipolar channel with another electrode on the same strut and in a second bipolar channel with a different electrode on a neighboring strut.

Optionally, the controller is further programmed to, after termination of the bipolar energy delivery for the total ablation time, to ramp-up the temperature of each of the identified RF electrodes from the temperature reached at the termination of the bipolar energy delivery to a predefined temperature within the target temperature range before activation for the remaining time begins during RF unipolar energy delivery.

Optionally, the controller is further programmed to: detect when one of the electrodes of each pair exceeds an upper limit of the target temperature range during the bipolar energy delivery; terminate or reduce the bipolar energy delivery of both electrodes of each pair at a termination time before than the total ablation time; calculate, for both electrodes, the remaining time to reach the total ablation time as the total ablation time minus the time spent in the target temperature range before the bipolar energy termination; and activate both electrodes to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

Optionally, the controller is further programmed to measure impedances of each of the plurality of electrodes, and designate the pairs according to electrodes having measured impedance values indicative of adequate contact between respective electrodes and the inner wall of the body lumen. Optionally, the controller is further programmed to activate the designated pairs when a number of electrodes having measured impedance values indicative of adequate contact is below a predefined threshold.

Optionally, the system further comprises a display adapted to graphically present status of each of the plurality of electrodes, the status selected from the group consisting of: manually deselected electrode, electrode with inadequate contact or no contact with the inner wall, electrode with marginal contact with the inner wall, and electrode with good contact with the inner wall. Optionally, the display is adapted to graphically present a schematic diagram of the ablation device including each electrode, wherein the electrodes are color coded according to the status.

Optionally, the system further comprises a display adapted to graphically present status of each of the plurality of electrodes, the status selected from the group consisting of: energy being delivered to the electrode, and completion of the total ablation time within the target temperature range.

Optionally, the system further comprises a display adapted to graphically present for each electrode that achieved the total ablation time within the target temperature range, at least one of: an average temperature, average impedance during RF energy delivery, and an average power of RF energy delivery. Optionally, the system further comprises a display adapted to graphically present for all electrodes that achieved the total ablation time within the target temperature range, at least one of: an average temperature of all the electrodes, an average impedance of all the electrodes during RF energy delivery, and an average power of all the electrodes.

Optionally, the controller is further programmed to monitor an impedance of each electrode of each pair, and terminate energy delivery to both electrodes of the pair when the impedance of at least one of the electrodes is outside of a predefined impedance range.

According to an aspect of some embodiments of the present invention there is provided a method for radiofrequency (RF) ablation of target tissue, comprising: providing a total ablation time; providing a target temperature range; activating pairs of a plurality of RF electrodes to deliver bipolar RF energy to an inner wall of a body lumen for the total ablation time at a temperature within the target temperature range; identifying which one or both electrodes of each pair deviated from the target temperature range; calculating, for each identified electrode, a remaining time to reach the total ablation time as the total ablation time less the time spent within the target temperature range; and activating each identified electrode to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

Optionally, one electrode of each pair reached the total ablation time at the target temperature range, and the other electrode of each pair deviated from the target temperature range before the total ablation time.

Optionally, each electrode of each pair deviated from the target temperature range for different periods of time, each electrode of each pair having different remaining times.

Optionally, a total activation time of each electrode, including bipolar and unipolar RF energy is less than or equal to two times the total ablation time.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Some embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the present invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the present invention may be practiced.

In the drawings:

FIG. 1 is a flowchart of a method of activating electrodes for RF ablation, in accordance with some embodiments of the present invention;

FIG. 2A is a schematic diagram of a distal end portion of a catheter including an arrangement of electrodes for performing the RF ablation method of FIG. 1, in accordance with some embodiments of the present invention;

FIG. 2B is a schematic diagram of components of a system for performing the RF ablation method of FIG. 1, in accordance with some embodiments of the present invention;

FIGs. 3A-3D are graphs depicting electrode temperature profiles, in accordance with some embodiments of the present invention;

FIG. 4 is a flowchart depicting some option features for the method described with reference to FIG. 1, in accordance with some embodiments of the present invention;

FIG. 5 is a flowchart of an example of an implementation of the method of FIG. 1 and/or FIG. 4, in accordance with some embodiments of the present invention;

FIGs. 6A-6D are screen captures of an example implementation of a presentation on a display representing electrode parameters, in accordance with some embodiments of the present invention; and

FIG. 7 includes histological images obtained as part of an experiment using the systems and/or methods described herein, that produced surprising results. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE PRESENT INVENTION

An aspect of some embodiments of the present invention relates to systems and methods for performing RF ablation according to a predefined total ablation time, including applying bipolar RF ablation for the duration of the predefined total ablation time using multiple electrodes, and for those electrodes that did not reach a predefined target temperature range or dropped below the predefined target temperature range before completing the total ablation time, applying unipolar RF ablation for the remaining time (i.e., total ablation time minus bipolar time within target temperature range). The systems and/or methods deliver, using each electrode, RF bipolar energy followed sequentially by RF unipolar energy, for the total ablation time within the target temperature range.

Bipolar RF energy may continue (for each electrode) for the predefined total ablation time, even if the lower threshold value of the target temperature range is never reached by the electrode. In such a case, the electrode may be activated to apply unipolar RF energy for the entire duration of the total ablation time.

Optionally, bipolar RF energy delivery is initiated simultaneously for all electrodes, and optionally terminated simultaneously for all the electrodes. Optionally, unipolar energy delivery is initiated simultaneously for all electrodes that have been identified as requiring the additional unipolar energy. The unipolar energy delivery may terminate at different times for each electrode, according to the amount of remaining time calculated for each electrode.

Optionally, bipolar energy is shutoff or reduced for both electrodes paired together, such as when one electrode reaches a temperature higher than the higher threshold value of the target temperature range. The shutoff may be performed as a safety mechanism, to prevent or reduce tissue damage from the high temperature. Each of the electrodes may then be activated for unipolar energy delivery for the remaining time. Optionally, RF bipolar energy is delivered using multiple channels for each electrode, optionally two channels. Each electrode participates in two different RF bipolar channels, one with each neighboring electrode.

Before explaining at least one embodiment of the present invention in detail, it is to be understood that the present invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The present invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to the drawings, FIG. 1 is a flowchart of a method of activating electrodes for RF ablation, in accordance with some embodiments of the present invention. Reference is also made to FIG. 2A, which is a schematic diagram of a distal end portion of a catheter including an arrangement of electrodes which may be used to perform the RF ablation method of FIG. 1, in accordance with some embodiments of the present invention, and to FIG. 2B, which is a schematic diagram of components of a system which may be used to perform the RF ablation method of FIG. 1, including the ablation device of FIG. 2A, in accordance with some embodiments of the present invention. It is noted that other RF systems with different design implementations may be suitable for performing the method of FIG. 1. As described herein, inventors discovered that the systems and/or methods described herein produce surprising and/or unexpected results, for example, an ability to ablate renal nerves in a renal denervation procedure. Chronic swine studies performed by inventors resulted in an overall 77% reduction in norepinephrine (NEPI), which is a biomarker representing efficacy of renal denervation therapy in a swine model. The 77% reduction compares favorably to other published renal denervation data performed by an RF based system, which range, for example, from 47%, 54%, and 74%. Moreover, the overall achieved 77% NEPI reduction is similar to published surgical denervation data of 77%.

The methods and/or systems described herein allow for each RF electrode to receive a full dose of treatment, which includes the electrode remaining within the target temperature range for the full duration of the target ablation time. The methods and/or systems described herein may allow to deliver the full dose for each RF electrode to generate a contained tissue ablation region, that is adequate for providing treatment (i.e., not too small), while the size of the ablation region is not exceeded by excessive treatment and/or allowed temperatures are not exceeded (i.e., not too big).

In some cases it may be desired to ablate tissue in a given area to an effective level (for example effective ablation may occur for heating to a temperature of between 60° and 72° C for a time between 20 and 180 sec). Tissue and/or contact with electrodes may be heterogeneous. Tissue may heat and/or ablate unevenly. Overheating and/or over-ablating tissue may have serious consequences (for example heating to over 90° C and/or over-ablating may cause blood coagulation and/or blood clots and/or damage to arteries and/or internal bleeding etc.). The systems and/or methods described herein may automatically generate a controlled ablation region.

Typically the majority of the impedance and/or ablation occur at the location and/or near the ablation electrode(s). Sometimes, unipolar ablation may cause deeper lesions than bipolar ablation. For example, bipolar ablation may be used to achieve spreading of a lesion along a tissue surface. For example, unipolar ablation may be used to deepen a lesion.

Unipolar ablation may optionally follow bipolar ablation. For example, after bipolar ablation achieves a large and/or shallow and/or heterogeneous lesion, unipolar ablation may be used to fill in the gaps left by unevenly ablated regions of the bipolar treatment, such as due to uneven temperatures reached by the RF electrodes. Each unipolar electrode may ablate a small area and/or to achieve a deeper lesion and/or even out a lesion (for example to ablate a portion of a less well done portion of a lesion).

Optionally, the systems and/or methods described herein are used to perform a renal denervation procedure. The renal denervation procedure is a minimally invasive, endovascular catheter based procedure using radiofrequency ablation aimed at treating resistant hypertension and/or other physiological effects believed to be related to renal nerves. Radiofrequency signals (e.g., pulses) may be applied to the inner wall of the renal arteries, using the systems and/or methods described herein, to ablate renal nerves in the vascular wall (e.g., adventitia layer). The ablation may cause reduction of renal sympathetic afferent and/or efferent activity, which may lead to a reduction in blood pressure and/or other sympathetic system related physiological effects. A steerable catheter with a radio frequency (RF) energy electrode tip, as described herein, delivers RF energy to the renal artery via standard femoral artery access. A series of ablations may be delivered along each renal artery according to the systems and/or methods described herein. Alternatively, other procedures are possible, for example, device 200 may be designed for insertion into other lumens and/or blood vessels, for example, the hepatic artery, the esophagus (i.e., digestive tract), and the trachea (i.e., respiratory tract). Device 200 may be designed for ablation of other tissues, for example, other nerves, or tumors (cancerous and/or benign).

An ablation device 200 is disposed at a distal end portion of a catheter 202, optionally a steerable catheter, for intravascular delivery and/or delivery within other body lumens. Ablation device 200 may include multiple struts 204 arranged parallel (or proximately parallel) to one another. Ablation device 200 may be expandable and retractable. In the expanded state, struts 204 are designed to be positioned along the long axis of the body lumen and around the circumference of the inner wall of the lumen. Struts 204 and/or device 200 may be arranged to expand into a shape, for example, a tent and/or an umbrella and/or an expandable basket and/or a malecot.

Each strut 204 may include one or more electrodes (ablation electrodes), optionally two electrodes arranged as neighboring pairs on the same strut: 206A and 206B, 206C and 206D, 206E and 206F, and 206G and 206H. Each ablation electrode may be made, for example, of between 80% and 95% Platinum and/or between 20% and 5% Iridium. The ablation electrodes may range for example between 0.5 and 4 millimeters (mm) long and/or have an electrically active area for example of between 0.1 and 1 mm and/or have a diameter ranging from 0.01 to 0.05 inch (0.25 to 1.27 mm). The electrically active area of the ablation electrodes may be in contact with a target tissue. The distance between ablation electrodes may range for example between 0.5 and 3 mm or more. Different struts may include different numbers of electrodes, and/or electrodes of different shapes and/or structures.

The distal portion of catheter 202 optionally includes a dispersive electrode 208 for performing unipolar RF energy application. Alternatively, the dispersive electrode may be located at other positions, for example, on the outer skin of the patient. Dispersive electrode 202 may have a length ranging, for example, between 4 to 20 mm and/or have a diameter ranging between 2 and 5 French (between 0.67 and 1.67 mm). The dispersive electrode may have an electrically active area ranging, for example, 20 to 50 times or more than the electrically active area and/or surface of contact of the ablation electrodes. For example, the electrically active area of the dispersive electrode may range between 50 to 150 mm 2 (e.g., between 50 to 100 mm 2 , between 100 to 150 mm 2 , or between 75 to 120 mm 2 ). Optionally, the electrically active surface of the disperse electrode may be in electrical contact with a fluid in a lumen of a patient. In some embodiments, the dispersive electrode may be coated with a material such as porous titanium nitride (TiN) or iridium oxide (IrOx). The coating may increase microscopic surface area of the electrode in electrical contact with lumen fluid.

Ablation device 200 may include a radially expanding tubular insulation member 210 designed to prevent or reduce RF ablation energy from being shunted through flowing blood, which may improve delivery of the RF energy to the target tissue within the luminal wall. Additional details of insulation member 210 are described, for example, in International Patent Application Publication Nos. WO2014/118733 and/or WO2014/118734, incorporated herein by reference in their entirety.

Electrodes 206A-H of ablation device 200 communicate with a controller 220 through an optional ablation device interface 222, for example, through wires and/or wirelessly.

Optionally, controller 220 includes a data input interface 224 for communication with a user interface 226, for input and/or output. Interface 226 may include one or more of: a graphical user interface (GUI), a display, a keyboard, a mouse, a touchscreen, press buttons and/or dials. The user may provide ablation related parameters via interface 226, and/or interface 226 may provide a graphical display related to the ablation procedure, as described herein. Data input interface 224 may be in communication with a memory 228, for example, to retrieve data and/or store data, such as ablation related parameters, as described herein.

Controller 220 may be implemented, for example, as standalone device (e.g., hardware and/or software), as a hardware card that is plugged-in to an existing device, and as a software module installed on a computer.

Controller 220 may include an RF control module 230 to control the electrodes in order to apply the ablation methods described with reference to FIG. 1. Controller 220 may include an RF generator module to generate the RF energy. Controller 220 may have a number of channels that convey an electrical signal bipolarly through the target tissue between the electrode pairs, and/or unipolarly through a target tissue between the ablation electrode and the dispersive (reference) electrode. The electrodes may be activated in accordance with a switch configuration set by a multiplexer. Multiplexed RF channels may be used to transmit radio frequency (RF) ablation energy to the electrodes, optionally simultaneously as described herein. The RF channels may optionally be used to transmit an auxiliary signal. For example, an auxiliary signal may be used to measure impedance between pairs of electrodes. When measuring impedance a sensor may optionally include an electrode. A sensor for measuring impedance may include one or more of an ablation electrode and/or a dispersive electrode. For example, an auxiliary signal may be similar to an ablation signal but at a lower power (optionally minimizing and/or avoiding tissue damage during measurements). The RF channels may optionally include means to measure electrode/tissue impedance. In some embodiments, measurements may be made with high accuracy and/or repeatability. The RF channels may optionally be controlled by RF control module 230 (e.g., a microcontroller and/or single-board computer).

Controller 200 may optionally be programmed to calculate the temperature of some or all of the electrodes and/or near some or all of the electrodes. For example, temperature measurements may be sensed by means of a thermocouple attached to each electrode and the output of the means is forwarded to the controller for calculation. Interaction with the user (e.g., a physician performing the ablation procedure) may optionally be via a graphical user interface (GUI) presented on, for example, a touch screen or another display of user interface 226.

Temperature may be measured individually at one, some and/or all of the electrodes. Temperature measurements may be performed by the thermocouple. The thermocouple may optionally be formed between the main electrode's wire and an auxiliary thermocouple wire. Temperature measurement range may be for example between 30°C to 100°C or more. Temperature measurement accuracy range between +0.2 to +1 °C or may be more accurate. Temperature measurement repeatability may range for example between 0.1 to 0.5 °C or less. Target temperatures may range for example between 60 to 80 °C.

Optionally, controller 220 is programmed to measure electrode impedance. The measurements may be used to estimate contact (estimated contact) between electrode and tissue as surrogate for thermal contact between electrode interface and target tissue (for example a low impedance of a unipolar signal between an ablation electrode and a dispersive electrode may indicate good contact between the ablation electrode and the target tissue). Optionally, power being converted to heat at electrode/tissue interface may be estimated (estimated power), for example, based on the estimated contact, applied power and/or electrode temperature. Together with the time of RF application to the tissue, the estimated contact and/or estimated power and/or electrode temperature may optionally be used to calculate energy transferred to target tissue and/or resulting target tissue temperature locally at individual ablation electrode locations. Optionally, the results may be reported in real-time on user interface 226.

Optionally, controller 220 may measure the complex bipolar and unipolar electrode impedance at the ablation frequency. Optionally, when not ablating, an auxiliary signal may include an auxiliary current not meant to cause significant physiological effect. Electrode impedance measurements may optionally be possible within the 100Ω to lkQ range within a minimum accuracy ranging for example between 2 to 10%, and within the 100Ω to 2kQ range with a minimum accuracy ranging for example between 5 to 20%. Minimum repeatability within the 100Ω to 2kQ range may range for example between 2 to 10%. Ablation interruptions may range from 1 to 100 milliseconds when measuring unipolar impedance during bipolar ablation segments. Alternatively, impedance is measured without interrupting the current. Impedance measurements may be taken at a minimum rate ranging for example between 50 to 200 samples for use by the control algorithm.

Optionally, controller 220 supplies power for RF ablation. For example, controller 200 may be rechargeable and/or battery-powered. The ablation generator may operate, for example, around the 460 kilohertz (kHz) frequency and/or ranging, for example, between 400 and 600 kHz or other RF frequency ranges assigned to ISM (Industrial, Scientific, and Medical) applications within the low-frequency (LF: 30 to 300 kHz), medium-frequency (300 kHz to 3 MHz), and high-frequency (HF 3 to 30 megahertz (MHz))) portions of the RF spectrum. The controller may have a number of channels that allow ablation to be conducted bipolarly between electrode pairs through the target tissue. The generator may optionally be able to deliver ablation energy to be conveyed simultaneously between one, some and/or all bipolar ablation electrode pairs in the catheter. The generator may supply a maximum power of, for example, between 3- 10W (watt) per bipolar channel. The generator may optionally be able to ablate unipolarly between one, some and/or all of the contact electrodes and the dispersive electrode. Each channel may have a minimum voltage compliance of 100 volt (V). In some embodiments, the minimum voltage compliance may permit, for example, an average of between 2 and 10W to be delivered per bipolar electrode pair presenting an impedance in the vicinity of for example 1.5 kQ.

As used herein, the term "controller" may include an electric circuit that performs a logic operation on input or inputs. For example, such a controller may include one or more integrated circuits, microchips, microcontrollers, microprocessors, all or part of a central processing unit (CPU), graphics processing unit (GPU), digital signal processors (DSP), field-programmable gate array (FPGA) or other circuit suitable for executing instructions or performing logic operations. The instructions executed by the controller may, for example, be pre-loaded into the controller or may be stored in a separate memory unit such as a RAM, a ROM, a hard disk, an optical disk, a magnetic medium, a flash memory, other permanent, fixed, or volatile memory, or any other mechanism capable of storing instructions for the controller. The controller may be customized for a particular use, or can be configured for general-purpose use and can perform different functions by executing different software.

At 102, a predefined total ablation time and/or a predefined target temperature range are provided. The total ablation time and/or the target temperature range may be received manually from the user (e.g., using the user interface 226), retrieved from a location on associated memory 228, and/or automatically calculated by a module. The total ablation time is, for example, about 10 seconds-90 seconds, or about 15-70 seconds, or about 20-60 seconds, or about 15-30 seconds, or about 20 seconds, or other smaller, larger or intermediate ranges.

The total ablation time may include the time the electrode spends in the bipolar ramp-up phase (as described herein) and the active bipolar phase. Alternatively, the ablation time includes the time the electrode spends in the active bipolar phase, excluding any ramp-up time.

The total ablation time and/or target temperature range may be selected based on one or more factors, for example, the target tissue type (e.g., nerves, tumor, vessel wall, connective tissue), and/or the target lumen (e.g., blood vessel, air filled lumen, artery, vein), such as according to a mathematical model, empirical measurements, and/or experimental results.

Reference is now made to FIG. 3A, which is a graph depicting an example of an RF electrode temperature versus time graph, to help understand the method of FIG. 1, in accordance with some embodiments of the present invention. The graph plots temperature on the y-axis (e.g., of the RF electrode and/or tissue being ablated) versus time on the x-axis. Region 302 defines bipolar RF energy application, including a ramp- up sub-region 304A and an active energy delivery sub-region 304B. Region 306 defines unipolar RF energy application, including a ramp-up sub-region 308A and an active energy delivery sub-region 308B. The measured temperature profile (of the electrode and/or tissue) is represented by a solid line 318.

The target temperature range is defined by an upper limit 310, (for example, about 80 degrees Celsius, or about 76 degrees, or about 84 degrees, or about 90 degrees) and one or more lower limits, such as a higher lower-limit 312 and a lower lower-limit 314 (selected, for example, from the values about 60 degrees, or about 54 degrees, or about 66 degrees, or about 70 degrees). The upper limit represents the maximum allowable temperature. Higher temperatures may cause damage, for example, leading to uncontrolled ablation, blood coagulation within the blood vessel, or other adverse effects. The lower-limit represents the lower temperature at which ablation occurs to achieve the desired results. Optionally, the predefined target temperature range includes a temperature setpoint 316, which is a target temperature within the range that the controller tries to achieve, for example, about 72 degrees Celsius, or about 70, or about 68, or about 66, or about 72, or about 74 or about 76, or about 78, or about 80, or about 60, or other smaller, intermediate or larger temperatures.

Referring now back to FIG. 1, at 104, each pair of RF electrodes is activated to deliver bipolar RF energy to the inner wall of the body lumen, for a duration of the total ablation time, at a temperature within the target temperature range, optionally the setpoint temperature.

As discussed herein, electrodes may not both achieve the same temperature, as one or both electrodes may not remain within the target range for the entire time duration, or one or both electrodes may not achieve the target range at all. Electrodes may not heat up evenly. Optionally, the RF control module is programmed to ramp-up the temperature of each RF electrode to reach the temperature setpoint within the target temperature range, before activation for the total ablation time begins. The ramp-up may be controlled to be performed for a predefined period of time, for example about 5, 10, 15, or 20 seconds, to reach the target temperature setpoint at the end of the ramp-up time.

It is noted that the duration of time within the target temperature range is not yet measured during the ramp-up stage.

Optionally, the number of bipolar channels activated during the ramp-up is equal to the number of electrode pairs. Optionally, the ramp-up channels are designated based on electrodes located on the same strut. For example, when the ablation device includes 8 electrodes arranged as 4 pairs, the ramp-up is performed for 4 bipolar channels. For example, with reference to FIG. 2A, the 4 channels are electrodes 206A and 206B, 206C and 206D, 206E and 206F, and 206G and 206H.

Optionally, the RF control module is programmed to simultaneously start activation of the electrode pairs to deliver the bipolar RF energy simultaneously.

Optionally, during the active bipolar energy delivery phase, the bipolar energy is delivered using a bipolar channel that is equal to the number of individual electrodes. For example, when the ablation device includes 8 electrodes arranged as 4 pairs, the active bipolar energy delivery is performed for 8 bipolar channels. Optionally, each individual electrode is included in two channels, in a first bipolar channel with another electrode on the same strut, and in a second bipolar channel with a different electrode on a neighboring strut. For example, with reference to FIG. 2A, the 8 channels are electrodes 206A and 206B, 206C and 206D, 206E and 206F, 206G and 206H, 206H and 206A, 206B and 206C, 206D and 206E, and 206F and 206G.

The intra- strut bipolar channel may generate ablations in the tissue along the length of the lumen when the long axis of each strut is positioned along the length of the lumen. The neighboring inter-strut bipolar channel may generate ablation regions along the circumference of the lumen. The combination of the intra-strut and extra-strut based bipolar channels may generate a ring-like ablation pattern around the circumference of the inner wall of the lumen.

The RF control module is programmed to continue activation of both electrodes of each pair to deliver bipolar RF energy for the entire duration of the total ablation time when the temperature of one or both of the electrodes of each pair drops below the lower limit of the target temperature range.

Bipolar (or multipolar) ablation may proceed by applying a high current designed to result in the desired power delivered to the tissue, for example, an average of between 0.5 and 10W (e.g., 0.5W, 1W, 5W, 10W etc.) between one or more pairs of ablation electrodes. During the application of current, the temperature at one, some or all of the ablation electrodes and/or the current and/or the impedance between pairs of electrodes may optionally be monitored, as described herein. Application of current may continue, for example, between 5-200 milliseconds (e.g., 50-200 milliseconds, 100-200 milliseconds, or 150-200 milliseconds) at a power ranging, for example, between 0.5 to 10 W between each pair of ablation electrodes. Current application may be interrupted for a short period, for example, between 50-200 milliseconds at which time impedance and/or temperature may be tested (e.g., measured) at the location of one or more of the ablation electrodes and/or other locations. For example, impedance may be tested. Alternatively, temperature and/or impedance are measured without interrupting the current. Optionally, when testing impedance a sensor may include an electrode, for example an ablation electrode and/or a dispersive electrode. Testing may optionally include measuring an impedance. For example measuring impedance may include applying a small current between the ablation electrode and a dispersive electrode.

At 106, the electrodes of each pair that deviated from the target temperature range are identified by the RF control module. For each pair, there may be no electrodes, one electrode, or both electrodes that deviated from the target temperature range. As used herein, the term "deviated" means reaching the temperature range and falling below the temperature range, or never reaching the range and remaining below the range for the entire duration of treatment.

At 108, for each electrode identified as not having completed the total ablation time duration within the target temperature range, the remaining time required to reach the total ablation time is calculated as the total ablation time minus the time within the target temperature range. For example, when the total ablation time is 20 seconds, and an electrode spent 5 seconds within the target temperature range during the bipolar phase, the remaining time is 20-5 = 15 seconds. At 110, each identified electrode is activated to deliver unipolar RF energy to the inner wall at the target temperature range for the calculated remaining time.

Optionally, an upper limit for unipolar treatment duration is predefined, for example, manually by the user, automatically by a software module, and/or retrieved from storage. The upper limit may define the maximal treatment time for the unipolar energy delivery, irrespective of the calculated remaining time. When the calculated remaining time is greater than the upper limit, the unipolar ablation is continued for the upper limit time instead of the remaining time. For example, when the remaining time is 15 seconds and the upper limit is 12 seconds, unipolar treatment continues for 12 seconds. When the calculated remaining time is less than the upper limit, the unipolar ablation is continued for the remaining time.

Optionally, the RF control module is programmed, after termination of the bipolar energy delivery for the total ablation time, to ramp-up the temperature of each of the identified RF electrodes to the predefined temperature within the target temperature range before activation for the remaining time begins. Ramp-up is performed unipolarly for each identified electrode. During the ramp-up period, the temperature of each electrode is increased from the final temperature at the end of the bipolar phase, to the temperature setpoint, which may be the same or different than the bipolar temperature setpoint.

Optionally, the unipolar ramp-up period is a pre-defined period of time, optionally equal to the bipolar ramp-up period of time.

Optionally, the RF control module is programmed to simultaneously ramp-up the identified electrodes. Activation of the identified electrodes (after the ramp-up) to deliver the unipolar RF energy may be performed simultaneously.

It is noted that the total activation time of each electrode, including bipolar and unipolar RF energy, is less than or equal to two times the total ablation time. For example, when the total ablation time is 20 seconds, and an electrode is activated in the bipolar state for 20 seconds without reaching the target temperature, the electrode will spend another 20 seconds in the unipolar state.

Unipolar ablation may be performed by passing current between each identified electrode and the dispersive electrode. Unipolar ablation may proceed by applying a high current designed to result in the desired power delivered to the tissue, for example, an average of between 0.5 and 10W (e.g., 0.5W, 1W, 5W, 10W etc.) between one or more ablation electrodes and a dispersive electrode. During the application of current, the temperature at one, some or all of the ablation electrodes and/or the current and/or the impedance between the electrodes (e.g., an ablation electrode and dispersive electrode) may optionally be monitored, as described herein. Application of current may continue for example between 50-200 milliseconds and/or between 200 milliseconds and 20 seconds and/or between 20 seconds and 200 seconds at a power of 0.5-10 W between each ablation electrode and the dispersive electrode. High current application may be interrupted for a short period for example between 0.5-100 milliseconds at which time impedance and/or temperature may be tested (e.g. measured) at the location of one or more of the ablation electrodes and/or other locations. Optionally, when testing impedance a sensor may include an electrode, for example, an ablation electrode and/or a dispersive electrode. For example, local impedance may be tested by applying a small current between one of the ablation electrodes and the dispersive electrode. After testing, application of current may optionally be resumed (e.g., if local ablation has not been completed and/or if there are no signs of local overheating and/or over- ablation). The interruption of current application may optionally be short enough that the target tissue does not significantly cool and/or ablation is not adversely affected. Alternatively, temperature and/or impedance are measured without interrupting the current.

Reference is now made to FIGs. 3B-3D, which are graphs depicting some example cases of electrode temperature profiles, in accordance with some embodiments of the present invention. Each figure graphically illustrates a different case of temperature profiles achieved by the electrodes, and the control of the RF control module.

FIG. 3B depicts the case of a first electrode of the electrode pair reaching the total ablation time within the target temperature range, represented by line 320A. The second other electrode deviated from the target temperature range (i.e., fell below the lower limit), not meeting the total ablation time, represented by line 320B. The second electrode proceeds through the unipolar ramp-up period, followed by the active unipolar phase for the calculated remaining period of time. It is noted that the first electrode is not activated unipolarly, since the total ablation time has been reached. FIG. 3C depicts the case where neither of the paired electrodes achieved the total ablation time within the target temperature range. Each electrode deviated from the target temperature range for different periods of time, and therefore each electrode has a different calculated remaining time. Both electrodes are activated unipolarly for different periods of time, according to their respective calculated remaining times, to complete the total ablation time. Line 322A represents the temperature profile of the first electrode, and line 322B represents the temperature profile of the second electrode.

FIG. 3D depicts the case where the RF control modules detects when one of the electrodes exceeds an upper limit of the target temperature range during the bipolar energy delivery phase, the time of exceeding the upper limit represented by line 324. The temperature profile of the first electrode that reached the upper limit is represented by line 326A. The temperature profile of the second electrode (that did not reach the upper limit) is represented by line 326B.

Upon detection that the electrode reached the upper limit, the RF control module terminates the bipolar energy delivery of both electrodes before the total ablation time has been reached for the bipolar energy delivery phase. It is noted that since the power has been cut or reduced, the temperature drops during the remaining time duration in the bipolar energy delivery phase. Both electrodes are then activated unipolarly, proceeding to the ramp-up and active unipolar energy delivery phases. It is noted that when electrodes pairs are controlled simultaneously, the unipolar phase is initiated for all pairs at the same time. As such, the electrodes that had bipolar power cut or reduced cannot immediately enter the unipolar state, but wait until the remaining electrode pairs completed the bipolar state.

The remaining time to reach the total ablation time for both electrodes is calculated as the total ablation time less the time spent in the allowed temperature range (i.e., before exceeding the upper limit and power cut). It is noted that the remaining time is the same for both electrodes.

Both electrodes are activated for the same remaining time duration in the unipolar stage, to deliver unipolar RF energy to the inner wall at the target temperature range.

FIG. 4 is a flowchart depicting some optional features for the method described with reference to FIG. 1, in accordance with some embodiments of the present invention. The method of FIG. 4 includes optional features that may be performed before the method of FIG. 1, during the method of FIG. 1, and/or after the method of FIG. 1. Each block of the method of FIG. 4 may be graphically presented on a visual display (e.g., screen) optionally part of a graphical visual interface (GUI), for example, as described below with reference to FIGs. 6A-6D.

Optionally, at 402, the intra-luminal positioning of the electrodes of the ablation device at the distal end portion of the catheter is verified. The position of the electrodes is verified according to measured and/or calculated unipolar electrode impedances of each electrode. The impedances are compared against one or more predefined values, for example, a range, indicative of appropriate electrical contact with the inner wall of the vessel. Alternatively or additionally, initial temperatures are measured for each electrode.

Impedance may optionally be measured by conveying an auxiliary signal between two or more electrodes. There may optionally be one range for bipolar impedance (e.g., for conveying a signal between two ablation electrodes) and/or another range for unipolar impedance (e.g., for conveying a signal between an ablation electrode and a dispersive electrode). A high initial impedance may be a sign of poor or inadequate contact between an electrode and the target tissue. A low initial impedance may be a sign that a signal is being shunted away from the target (e.g., because an insulator is not properly contacting tissue surrounding an ablation electrode). If the initial impedance is outside of the set range, for a particular electrode and/or pair of electrodes, the electrode and/or electrodes may optionally not be used for ablation until they are repositioned.

The RF control module 230 may be programmed to measure the impedances of each electrode. The electrode pairs may be designated according to electrodes having measured impedance values indicative of adequate contact between respective electrodes and the inner wall of the body lumen.

The RF control module 230 may be programmed to activate the designated electrode pairs when the number of electrodes having measured impedance values indicative of adequate contact is below a predefined threshold, for example, when less than or equal to 3/8 electrodes have insufficient contact (i.e., greater than or equal to 5/8 electrodes have good contact). Alternatively, the user may manually select or deselect electrodes for energy delivery. Ablation may be allowed to proceed when there are enough electrodes in good contact with the inner wall to achieve the desired ablation treatment.

Electrodes may be displayed on the GUI in a color coded manner according to the impedance values, as described herein.

At 404, ablation proceeds as described with reference to FIG. 1. Temperature may be monitored as described herein. The highest temperature of each bipolar pair is monitored for exceeding the upper allowed temperature range, in which case power to both electrodes may be shut down or reduced, as described herein.

RF control module 230 may be programmed to monitor the real-time impedance of each electrode during treatment. Module 230 may terminate energy delivery to both paired electrodes when the impedance of at least one of the electrodes falls outside of the predefined impedance range (i.e., good contact with inner wall has been lost).

Real-time status of the each electrode may be presented on the GUI, as described herein. For example, the time each electrode spent within the allowed temperature range, such as blue for active electrodes and green for electrodes that have completed the total ablation time within the target temperature range.

Optionally, at 406, a summary of the electrode parameters for the duration of the ablation treatment is presented, for example, including one or more of: average temperature for each electrode, average impedance for each electrode, average power for each electrode.

FIG. 5 is a flowchart of an example of an implementation of the method of FIG. 1 and/or FIG. 4, in accordance with some embodiments of the present invention. User input and/or presentations to the user may be provided via GUI. Values described represent default values, which may be adjusted manually by the user and/or automatically by a software module, or other default values may be used. Values may be selected based on, for example, a mathematical model, empirical measurements, and/or experiments.

At block 502 (which is an optional implementation of block 402), the ablation device is connected to the control unit, for example: controller 220 (e.g., wirelessly and/or by plugging in cables). The catheter having the ablation device on the distal end of the catheter is positioned in the vessel, for example, the renal artery. The mode of ablation operation may be selected by the user, such as automatic (following the method of FIG. 1), manual bipolar, or manual unipolar.

The unipolar impedances may be measured as described herein. Electrodes that have been manually deselected by the user are grayed out on the GUI and/or removed from the designated electrodes for performing ablation.

Electrodes are color coded according to measured impedance within a predefined range indicative of sufficient contact. Electrodes with impedance values lower than about 300 or greater than about 1 kilo-ohms are colored grey representing improper contact with the vessel wall. Such electrodes are not used for ablation. Ablation is allowed when the number of grey colored electrodes is less than or equal to three, representing enough electrodes with good contact to ablate.

Optionally, electrodes with impedance values between about 100 and 250 ohms may be colored yellow, representing sufficient contact for ablation, but not the best contact possible.

Electrodes with impedance values between about 250 and 450 ohms are colored green, representing optimal contact. Alternatively, all electrodes suitable for ablation (e.g., non-grey electrodes) may be colored green.

Electrodes that initially, or during the procedure are detected as having an error condition, for example, defined by medical device standards, such as improper power delivery, may be colored red or have their green (or yellow) color changed to red.

At 504 (which is an optional implementation of block 504), electrodes are constantly or periodically monitored after the user presses a button to start the ablation process. Impedance and/or temperature limits may be checked for each electrode. When one electrode of the pair exceeds the temperature or falls out of the impedance limits, RF energy may be terminated to both. The colors of electrodes in which the impedance and/or temperature limits are within the allowed ranges are updated according to the time spent within the target temperature. Electrodes that have completed the total time at the target temperature are colored green, representing ablation completion. Electrodes that are still being activated are colored blue, representing RF energy being delivered.

When auto mode is selected, the method according to FIG. 1 is performed.

Electrodes are activated in bipolar RF, and ramped up to about 68 degrees Celsius (or other values), using 4 bipolar channels for 8 active electrodes (based on electrodes sharing the same strut), for about 10 seconds (or other values).

The electrodes are activated in bipolar RF, to attempt to hold the temperature at 68 degrees Celsius, using 8 bipolar channels (based on both electrodes sharing the same strut and with an electrode on a neighboring strut), to achieve a total time of 30 seconds (i.e., 10 second ramp-up + 20 seconds hold time).

Electrodes that did not achieve at least 15 seconds within the target temperature range in bipolar RF are activated in unipolar mode, using 8 channels (i.e., one for each electrode). Electrodes are ramped-up to the target temperature of 68 degrees Celsius for 10 about seconds, and held at the target temperature for 20 seconds minus the time spent within the target temperature range in the bipolar state.

When all electrodes have completed the total ablation time, the RF delivery is complete.

Alternatively, when the selected mode is manual and bipolar, the bipolar procedure is executed (i.e., 4 channel ramp-up for 10 seconds, and hold for 20 seconds at target temperature using 8 channels).

Alternatively, when the selected mode is manual and unipolar, the unipolar procedure is executed (i.e., 8 channel ramp-up for 10 seconds, and hold for remaining time at target temperature).

At 506, after the ablation procedure has completed, the average temperature and/or impedance values over the delivery duration for each electrode may be displayed on the GUI. The average temperature, impedance, and power, for all electrodes that participated in the energy delivery may be displayed. Electrodes are colored according to time spent within the temperature range, based on a higher lower-limit, and a lower- lower limit.

When the user presses an exit button, the catheter placement screen may be displayed for the next procedure.

Reference is now made to FIGs. 6A-6D, which are screen captures of an example implementation of a presentation on a display representing data according to the method of FIG. 1 and/or FIG. 4, and/or FIG. 5, in accordance with some embodiments of the present invention. Data may be displayed as a GUI on a screen. Data may be graphically presented on the display based on a schematic of the ablation device on the distal end region of the catheter including each electrode, as colored dots (or rectangles or other shaped) superimposed on the location of each electrode.

FIG. 6A is a screen capture of the GUI, showing all electrodes, colored green, having appropriate unipolar impedances that represent suitable contact to perform the ablation procedure. Actual measured values are displayed for each electrode around the schematic. The initial temperature measured at each electrode is displayed. FIG. 6A may be presented during box 402 and/or box 502.

The display graphically presents the initial status of each electrode: manually deselected electrode (e.g., grey), electrode with inadequate contact or no contact with the inner wall (e.g., grey), electrode with marginal contact with the inner wall (e.g., yellow or green), electrode with good contact with the inner wall (e.g., green), and/or electrode with an error (e.g., red).

FIG. 6B is a screen capture of the GUI, graphically presenting the status of all electrodes during RF energy delivery. Electrodes colored green have completed the total ablation time within the target temperature. Electrodes colored blue are delivering RF energy within the remaining time, to try and reach the total ablation time. Real-time impedance and temperatures are displayed for each electrode.

FIG. 6B may be presented during FIG. 1, and/or box 404 and/or box 504.

FIG. 6C is a screen capture of the GUI, summarizing electrode parameters during the treatment. The GUI graphically presents for each electrode that achieved the total ablation time within the target temperature range, one or more of: an average temperature during the ablation, average impedance during RF energy delivery, and an average power of RF energy delivery.

Data is not displayed for electrodes that did not achieve the total ablation time within the target temperature range. The electrode may be shown as yellow.

FIG. 6C may be presented during box 406 and/or box 506.

FIG. 6D is a screen capture of the GUI, providing a simplified summary of the data shown within FIG. 6C. The display graphically presents, using data of electrodes that achieved the total ablation time within the target temperature range, one or more of: an average temperature of all the electrodes during the ablation, an average impedance of all the electrodes during RF energy delivery, and an average power of all the electrodes during the ablation.

FIG. 6D may be presented during box 406 and/or box 506.

Inventors performed experiments, in the form of bilateral renal denervation, using the systems and/or methods described herein. The experiments produced surprising results, of an overall renal norepinephrine reduction of 77%.

Methods: 8 pigs underwent bilateral denervation using the systems and/or methods described herein. Each pig underwent 2 successive 1 minute treatments with a 72°C set point. A single size basket was used to treat all renal arteries having diameters between 4.08-6.45 mm.

Results: Norepinephrine levels at 7 days (79+109 nanogram/gram, n=6) were reduced 88.1% (p<0.001) relative to published baseline levels in naive animals. Overall renal norepinephrine reduction for 16 kidneys (6 at 7 days, 6 at 30 days, 4 at 90 days) was 77%.

FIG. 7 includes histological slides depicting cross sectional slices of renal arteries, illustrating deep tissue ablation at relatively low treatment power, which produced the unexpected renal norepinephrine reduction of 77%. Dotted lines represent regions of ablation damage. Renal nerves are marked as 'N' or 'nerves' . Image 702, obtained at 7 days, shows damage at a depth of 2.3 mm. Image 704, obtained at 30 days, shows damage at a depth of 1.7 mm. Image 706, obtained at 90 days, shows resolution of damage and benign tissue effects.

Conclusion: The systems and/or methods described herein produced the unexpected result of a renal norepinephrine decrease of 77% after a renal denervation procedure. The 77% reduction compares favorably to other published renal denervation data performed by other RF based systems, which range, for example, from 47%, 54%, and 74%. Moreover, the overall achieved 77% NEPI reduction is similar to published surgical denervation data of 77%.

It is expected that during the life of a patent maturing from this application many relevant ablation devices and electrodes will be developed and the scope of the terms ablation device and electrodes are intended to include all such new technologies a priori.

As used herein the term "about" refers to ± 10 %. The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof. Throughout this application, various embodiments of this present invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the present invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts. As used herein, the term "treating" includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition.

It is appreciated that certain features of the present invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the present invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the present invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

WHAT IS CLAIMED IS:

1. A system for radiofrequency (RF) ablation of target tissue, comprising:

a controller programmed to:

activate pairs of a plurality of RF electrodes to deliver bipolar RF energy to an inner wall for a total ablation time at a temperature within a target temperature range, wherein the RF electrodes are coupled to an ablation device at a distal end region of an intravascular catheter and adapted to apply RF energy to the inner wall of a target lumen to ablate a target tissue,

identify which one or both electrodes of each pair deviated from a lower limit of the target temperature range,

calculate, for each identified electrode, a remaining time to reach the total ablation time as the total ablation time minus the time spent within the target temperature range, and

activate each identified electrode to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

2. The system of claim 1, wherein the controller is programmed to continue activation of the pairs of the plurality of RF electrodes to deliver bipolar RF energy for the entire duration of the total ablation time when the temperature of one or both of the electrodes of each pair drops below the lower limit of the target temperature range.

3. The system of claim 1, wherein the controller is programmed to simultaneously start activation of the pairs to deliver the bipolar RF energy, and to simultaneously start activation of the identified electrodes to deliver the unipolar RF energy.

4. The system of claim 1, wherein the controller is further programmed to ramp-up the temperature of each of the plurality of RF electrodes to a predefined temperature within the target temperature range before activation for the total ablation time delivering RF bipolar energy begins.

5. The system of claim 4, wherein a number of bipolar channels during the ramp-up is equal to the number of electrode pairs.

6. The system of claim 1, wherein a number of bipolar channels during the bipolar RF energy delivery is equal to the number of the plurality of electrodes.

7. The system of claim 6, wherein the electrodes are arranged in pairs on a plurality of struts positioned along the long axis of the lumen and around the circumference of the inner wall of the lumen, each electrode included in a first bipolar channel with another electrode on the same strut and in a second bipolar channel with a different electrode on a neighboring strut.

8. The system of claim 4, wherein the ramp-up is performed for a predefined period of time.

9. The system of claim 1, wherein the controller is further programmed to, after termination of the bipolar energy delivery for the total ablation time, to ramp-up the temperature of each of the identified RF electrodes from the temperature reached at the termination of the bipolar energy delivery to a predefined temperature within the target temperature range before activation for the remaining time begins during RF unipolar energy delivery.

10. The system of claim 1, wherein the controller is further programmed to:

detect when one of the electrodes of each pair exceeds an upper limit of the target temperature range during the bipolar energy delivery;

terminate or reduce the bipolar energy delivery of both electrodes of each pair at a termination time before than the total ablation time;

calculate, for both electrodes, the remaining time to reach the total ablation time as the total ablation time minus the time spent in the target temperature range before the bipolar energy termination; and

activate both electrodes to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

11. The system of claim 1, wherein the controller is further programmed to measure impedances of each of the plurality of electrodes, and designate the pairs according to electrodes having measured impedance values indicative of adequate contact between respective electrodes and the inner wall of the body lumen.

12. The system of claim 11, wherein the controller is further programmed to activate the designated pairs when a number of electrodes having measured impedance values indicative of adequate contact is below a predefined threshold.

13. The system of claim 1, further comprising a display adapted to graphically present status of each of the plurality of electrodes, the status selected from the group consisting of: manually deselected electrode, electrode with inadequate contact or no contact with the inner wall, electrode with marginal contact with the inner wall, and electrode with good contact with the inner wall.

14. The system of claim 13, wherein the display is adapted to graphically present a schematic diagram of the ablation device including each electrode, wherein the electrodes are color coded according to the status.

15. The system of claim 1, further comprising a display adapted to graphically present status of each of the plurality of electrodes, the status selected from the group consisting of: energy being delivered to the electrode, and completion of the total ablation time within the target temperature range.

16. The system of claim 1, further comprising a display adapted to graphically present for each electrode that achieved the total ablation time within the target temperature range, at least one of: an average temperature, average impedance during RF energy delivery, and an average power of RF energy delivery.

17. The system of claim 1, further comprising a display adapted to graphically present for all electrodes that achieved the total ablation time within the target temperature range, at least one of: an average temperature of all the electrodes, an average impedance of all the electrodes during RF energy delivery, and an average power of all the electrodes.

18. The system of claim 1, wherein the controller is further programmed to monitor an impedance of each electrode of each pair, and terminate energy delivery to both electrodes of the pair when the impedance of at least one of the electrodes is outside of a predefined impedance range.

19. A method for radiofrequency (RF) ablation of target tissue, comprising:

providing a total ablation time;

providing a target temperature range;

activating pairs of a plurality of RF electrodes to deliver bipolar RF energy to an inner wall of a body lumen for the total ablation time at a temperature within the target temperature range;

identifying which one or both electrodes of each pair deviated from the target temperature range;

calculating, for each identified electrode, a remaining time to reach the total ablation time as the total ablation time less the time spent within the target temperature range; and

activating each identified electrode to deliver unipolar RF energy to the inner wall at the target temperature range for the remaining time.

20. The method of claim 19, wherein one electrode of each pair reached the total ablation time at the target temperature range, and the other electrode of each pair deviated from the target temperature range before the total ablation time.

21. The method of claim 19, wherein each electrode of each pair deviated from the target temperature range for different periods of time, each electrode of each pair having different remaining times.

22. The method of claim 19, wherein a total activation time of each electrode, including bipolar and unipolar RF energy is less than or equal to two times the total ablation time.