Temperature-controlled pulsed RF ablation

Abstract

To provide a system for radiofrequency (RF) ablation.SOLUTION: Described embodiments include a system that includes a radiofrequency-current (RF-current) generator and a processor. The processor is configured to cause the RF-current generator to generate a plurality of pulses of RF current to be applied to tissue of a subject, each of the pulses having a power whose maximum value is greater than 80 W and a duration that is less than 10 s, where an intermission between successive ones of the pulses is less than 10 s. The processor is further configured to, while each one of the pulses is applied to the tissue, receive at least one signal that indicates a measured temperature of the tissue, and, in response to the measured temperature, control the power of the pulse. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of radiofrequency (RF) ablation, such as for the treatment of cardiac arrhythmias. [Background technology]

[0002] Radiofrequency (RF) ablation is a treatment that uses heat to kill unwanted tissue. RF ablation originated in the 1980s as a treatment for cardiac arrhythmias and has since found clinical applications in many diseases, becoming a common treatment for certain types of cardiac arrhythmias and certain cancers. During RF ablation, an electrode is inserted adjacent to the target site, typically under medical imaging guidance. The tissue surrounding the electrode within the target area is then destroyed by heating it with RF current.

[0003] U.S. Patent No. 9,072,518 describes an ablation system and method that uses high-voltage pulses to ablate tissue and create lesions. One or more electrodes can be positioned at target locations using a variety of different electrophysiology devices, such as catheters, surgical probes, and clamps. The electrodes can be connected to a power supply line, and in some cases, power to the electrodes can be controlled on an electrode-by-electrode basis. High-voltage pulse sequences typically result in a lesser total amount of heating than that observed in heat-based radiofrequency energy ablation protocols.

[0004] WO 1996 / 010950 describes a method for treating ventricular tachycardia, which involves inserting an electrode catheter into a cardiac ventricle. The ventricular wall of the heart is contacted with an ablation electrode at the site where the abnormal electrical pathway is located. Radiofrequency waves are delivered to the tissue through the ablation electrode for a time sufficient to identify the site of the abnormal electrical pathway and preheat the tissue. A short, high-voltage electrical pulse is then delivered to the tissue via the same electrode, thereby forming a non-conductive lesion.

[0005] U.S. Patent Application Publication No. 2017 / 0209208 to Govari et al., the disclosure of which is incorporated herein by reference, describes a method including selecting a first maximum radio frequency (RF) power delivered by an electrode in the range of 70 W to 100 W and selecting a second maximum RF power delivered by the electrode in the range of 20 W to 60 W. The method also includes selecting a tolerable force on the electrode in the range of 5 g to 50 g, selecting a maximum tolerable temperature of the tissue to be ablated in the range of 55°C to 65°C, and selecting an irrigation rate for supplying irrigation fluid to the electrode in the range of 8 to 45 mL / min. The method further includes performing tissue ablation using the selected values by initially using the first power, switching to the second power after a predefined time of 3 to 6 seconds, and terminating the ablation after a total ablation time of 10 to 20 seconds. Summary of the Invention [Means for solving the problem]

[0006] According to some embodiments of the present invention, there is provided a system including a radio frequency current (RF current) generator and a processor. The processor is configured to cause the RF current generator to generate multiple pulses of RF current for application to tissue of a subject, each pulse having a power greater than 80 W and a duration less than 10 seconds, with an intermission between successive pulses being less than 10 seconds. The processor is further configured to receive at least one signal indicative of a measured temperature of the tissue while each pulse is applied to the tissue, and to control the power of the pulses in response to the measured temperature.

[0007] In some embodiments, the processor is configured to drive the RF current generator to apply fewer than seven pulses.

[0008] In some embodiments, the intermission is 2 to 5 seconds.

[0009] In some embodiments, the duration of each pulse is 2 to 5 seconds.

[0010] In some embodiments, the processor is configured to drive the RF current generator to apply each of the pulses such that the power of the pulse first rises to a maximum value and then levels off at the maximum value.

[0011] In some embodiments, the maximum value is greater than 100W.

[0012] In some embodiments, the maximum value is greater than 120W.

[0013] In some embodiments, the maximum value is equal to a predefined target power value.

[0014] In some embodiments, the processor is configured to control the power of the pulses by alternately decreasing and increasing the power of the pulses.

[0015] In some embodiments, the processor is configured to control the power of the pulses by reducing the power of the pulses in response to the measured temperature approaching a threshold temperature.

[0016] In some embodiments, the threshold temperature is between 40°C and 65°C.

[0017] In some embodiments, the threshold temperature is between 40°C and 55°C.

[0018] In some embodiments, no RF energy is applied to the tissue during the intermission.

[0019] According to some embodiments of the present invention, a method is further provided, including generating a plurality of pulses of high-frequency (RF) current for applying to a subject's tissue, each pulse having a power with a maximum value greater than 80 W and a duration less than 10 seconds, and an intermission between consecutive pulses among the pulses being less than 10 seconds. This method further includes receiving at least one signal indicating the measured temperature of the tissue while applying each pulse to the tissue, and controlling the power of the pulse in response to the measured temperature.

[0020] In some embodiments, the tissue includes the subject's heart tissue.

[0021] A more complete understanding of the present disclosure will be obtained by reading the following detailed description of the embodiments of the present disclosure in conjunction with the drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram of an ablation system used for performing an ablation treatment according to an embodiment of the present invention. [Figure 2A] It schematically shows the distal end of a probe used in the system according to an embodiment of the present invention. [Figure 2B] It schematically shows the distal end of a probe used in the system according to an embodiment of the present invention. [Figure 2C] It schematically shows the distal end of a probe used in the system according to an embodiment of the present invention. [Figure 2D] It schematically shows the distal end of a probe used in the system according to an embodiment of the present invention. [Figure 3] It is a schematic diagram of the application of pulsed RF ablation according to some embodiments of the present invention.

Modes for Carrying Out the Invention

[0023] Overview In a conventional system, radio frequency (RF) ablation is typically performed at a continuous power level of about 20 to 50 watts with a contact force of about 10 g under perfusion for about 1 minute. Such a protocol generally results in a damage depth of about 5 mm. To achieve a greater depth, such as 6 - 10 mm, it is typically necessary to increase the duration for which the RF current is applied or increase the power level of the current. However, both of these options may be undesirable, for example, due to the possibility of forming steam pops within the tissue.

[0024] To address this issue, U.S. Patent Application Publication No. 2017 / 0209208 describes a range of values for contact force and perfusion rate that facilitate the application of a continuous power of about 100 watts. During the ablation procedure, the temperature of the tissue being ablated is carefully monitored and recorded at high speed. If the monitored temperature exceeds a pre-set maximum temperature limit, the RF power supplied to the tissue is reduced. Alternatively or additionally, the impedance to the RF energy supplied to the tissue can be monitored, and if the impedance increases beyond a pre-set value, the supply of RF energy can be stopped. The high power of the RF current facilitates shortening the duration of the RF current to less than 1 minute. In addition, monitoring of tissue temperature and / or impedance substantially eliminates the risk of forming steam pops.

[0025] Embodiments of the present invention further enhance the effectiveness and safety of ablation procedures by applying RF energy in a plurality of short high-power pulses, typically a plurality of short high-power pulses of 100 W or more, rather than a continuous current. The interruption following each pulse allows the tissue to cool so that subsequent pulses can be applied again at high power. The temperature of the tissue can be monitored as described above between each pulse, and the amplitude of the pulse can be adjusted accordingly. Advantageously, this protocol facilitates rapidly and safely achieving a relatively large damage depth.

[0026] Description of the System 1, which is a schematic illustration of an ablation system 12 used to perform an ablation procedure in accordance with one embodiment of the present invention. By way of example, it is assumed that the procedure involves ablation of a portion of the myocardium of a heart 16 of a human patient 18. However, it will be understood that embodiments of the present invention may be equally applied to any ablation procedure on living tissue.

[0027] To perform ablation, physician 14 inserts probe 20 into a lumen of patient 18 so that a distal end 22 of probe 20 enters the patient's heart 16. Distal end 22, described in more detail below with reference to Figures 2A-2D, includes one or more electrodes 24 that are brought into contact with respective locations of the myocardium by the physician. Probe 20 further includes a proximal end 28 that connects to an operator console 48 via a suitable electrical interface, such as a port or socket.

[0028] System 12 is controlled by a system processor 46, typically located in an operator console 48. Generally, processor 46 may be embodied as a single processor or as a set of processors networked or clustered together. Processor 46 is typically a programmable digital computing device including a central processing unit (CPU), random access memory (RAM), non-volatile secondary storage such as a hard drive or CD-ROM drive, a network interface, and / or peripheral devices. Program code, including software programs, and / or data are loaded into RAM for execution and processing by the CPU, generating results for display, output, transmission, or storage, as is known in the art. Program code and / or data may be downloaded to a computer in electronic form, for example, over a network, or alternatively or additionally, may be provided and / or stored on non-transitory tangible media such as magnetic, optical, or electronic memory. When such program code and / or data is provided to the processor, it results in a machine or special-purpose computer configured to perform the tasks described herein.

[0029] During the procedure, processor 46 typically tracks the position and orientation of probe distal tip 22 using any suitable method known in the art. For example, processor 46 may use a magnetic tracking method in which a magnetic transmitter outside the patient's 18 generates a signal in a coil positioned at the probe's distal tip. The Carto® system manufactured by Biosense Webster uses such a tracking method. The path of distal tip 22 is typically displayed on screen 62 as a three-dimensional representation 60 of the patient's 18's heart. The progress of the ablation procedure is also typically displayed on screen 62 as graphics 64 and / or alphanumeric data 66.

[0030] To control the associated components of system 12, processor 46 can load and execute the associated software modules stored in memory 50. Typically, memory 50 stores a temperature module 52, a power control module 54, a force module 56, and an infusion module 58, and these functions will be described below. (Generally, any associated processing function described below may be said to be executed by either the processor or a module that is executed by the processor to perform the function.)

[0031] Console 48 includes an RF current generator 47 configured to generate the RF current used in the ablation procedure. Console 48 further includes control means 49 used by physician 14 to communicate with processor 46. Console 48 may further include any other suitable hardware or software elements to facilitate communication between processor 46 and probe 20.

[0032] Now refer to FIGS. 2A - 2D, which schematically show the distal end 22 of probe 20 according to one embodiment of the present invention. FIG. 2A is a cross-sectional view along the length of the probe, FIG. 2B is a cross-sectional view along the cut line IIB-IIB shown in FIG. 2A, FIG. 2C is a perspective view of a section of the distal end, and FIG. 2D is a schematic cross-sectional view of a force sensor 90 incorporated into the proximal portion 92 of the distal end.

[0033] As shown in FIG. 2A , the insertion tube 70 extends along the length of the probe and terminates at its distal end in a conductive cap electrode 24A used for ablation. (The conductive cap electrode 24A is also referred to herein as the “ablation electrode” or simply “cap.”) The cap electrode 24A has a generally flat conductive surface 84 at its distal end and a substantially circular edge 86 at its proximal end. Proximal to the ablation electrode 24A is typically another electrode, such as a ring electrode 24B. Typically, the insertion tube 70 comprises a flexible, biocompatible polymer, while the electrodes 24A and 24B comprise a biocompatible metal, such as gold or platinum. The ablation electrode 24A is typically perforated with an array of irrigation apertures 72. In one embodiment, there are 36 apertures 72 evenly distributed over the electrode 24A.

[0034] Electrical conductors 74 transmit radio frequency (RF) electrical energy from console 48 (FIG. 1) through insertion tube 70 to electrode 24A, thus energizing the electrode for ablating the myocardial tissue it contacts. As described below, power control module 54 controls the level of RF power dissipated through electrode 24A. During the ablation procedure, irrigation fluid exiting through openings 72 washes the tissue being treated, the fluid flow rate being controlled by irrigation module 58. Irrigation fluid is delivered to electrode 24A by tubing (not shown) within insertion tube 70.

[0035] Temperature sensors 78 are mounted within the conductive cap electrode 24A at locations arranged axially and circumferentially around the distal tip of the probe. In one embodiment of the disclosure discussed herein, the cap 24A includes six such sensors, with one group of three sensors located distally near the tip and another group of three sensors located slightly more proximal. This distribution is shown by way of example only; more or fewer sensors may be mounted in any suitable location within the cap. The sensors 78 may comprise thermocouples, thermistors, or any other suitable type of miniature temperature sensor. The sensors 78 are connected by leads (not shown in the schematic) that extend the entire length of the insertion tube 70. Thus, a temperature signal is carried over the leads to the temperature module 52.

[0036] In the disclosed embodiment, cap 24A has a relatively thick sidewall 73, on the order of 0.5 mm thick, to provide the desired thermal insulation between temperature sensor 78 and the irrigation fluid inside central cavity 75 of the tip. Irrigation fluid exits cavity 75 through opening 72. Sensor 78 is mounted on a rod 77 that fits into a longitudinal inner diameter 79 of sidewall 73. Rod 77 may comprise a suitable plastic material, such as polyimide, and may be held in place at the distal end by a suitable adhesive 81, such as epoxy. U.S. Pat. No. 9,445,725, incorporated herein by reference, describes a catheter having a temperature sensor mounted in a configuration similar to that described above.

[0037] The configuration described above provides an arrangement of six sensors 78, however, other configurations and numbers of sensors will be apparent to those skilled in the art, and all such configurations and numbers are within the scope of the present invention.

[0038] In the description herein, distal end 22 is assumed to define a set of orthogonal x, y, and z axes, with the z axis of this set corresponding to distal end axis 95. For simplicity, and by way of example, the y axis is assumed to be in the plane of the paper, the x, y plane is assumed to correspond herein to the plane defined by edge 86, and the origin of the x, y, and z axes is assumed to be the center of the circle.

[0039] 2D is a schematic cross-sectional view of force sensor 90, according to one embodiment of the present invention. Sensor 90 comprises spring 94, herein assumed to comprise a plurality of helices 96 connecting cap 24A to proximal portion 92. A position sensor 98 is secured distally to spring 94, herein assumed to comprise one or more coils coupled to force module 56 by conductors 100.

[0040] An RF transmitter 102, typically a coil, is secured proximal to the spring 94, and RF energy for the transmitter 102 is supplied via conductors 104 from the console 48 under the control of the force module 56. The RF energy from the transmitter passes through the sensor 98 and generates a corresponding signal in the sensor's conductors 100.

[0041] In operation, when a force is exerted on the cap 24A, the sensor 98 moves relative to the transmitter 102, causing the movement to cause a change in the sensor signal. The force module 56 uses the change in the sensor signal to provide a metric of the force acting on the cap 24A. This metric is typically indicative of the magnitude and direction of the force.

[0042] A more detailed description of a sensor similar to sensor 90 is provided in U.S. Patent Application Publication No. 2011 / 0130648, which is incorporated herein by reference.

[0043] Returning to FIG. 1 , the temperature module 52 receives signals from the six temperature sensors 78 within the cap 24A and uses those signals to determine the maximum of the six measured temperatures. The temperature module is typically configured to calculate the maximum temperature at a fixed rate, such as every 20-40 milliseconds. In some embodiments, the maximum temperature is determined at a frequency of at least 30 Hz. The calculated maximum temperature is also referred to herein as the measured temperature, and this measured temperature is registered as the temperature of the tissue being ablated. The temperature module passes the measured temperature value to the power control module 54 so that the power control module can control the RF current in response to the measured temperature.

[0044] The power control module 54 can supply RF power to the cap 24A in any suitable range, such as from 1 W to 130 W, 140 W, or 150 W. The power control module also measures the impedance of the cap 24A, i.e., the impedance to the RF current delivered by the cap 24A. The impedance is typically measured at a predefined rate, such as every 400 to 600 milliseconds. If the impedance increases from the previous impedance measurement by more than a predefined value, such as 7 Ω, the power control module can stop RF delivery to the cap 24A because the increase in impedance may indicate an undesirable change in the tissue being ablated, such as charring or steam popping.

[0045] Typically, before an ablation procedure, the physician defines an RF pulse profile by selecting relevant parameters such as the number of pulses, the maximum (or “target”) power of each pulse, the duration of each pulse, and the time between consecutive pulses. The power control module then causes the RF generator 47 to generate a plurality of pulses of RF current for application to the subject's tissue according to the defined profile. Each of these pulses is supplied by the generator to the probe 20. As further described below with reference to FIG. 3, while the probe is applying a pulse, the power control module controls the power of the pulse in response to the measured temperature received from the temperature module 52. For example, the power control module can reduce the delivered power in response to a measured temperature approaching a threshold temperature set by the physician 14, such as to reduce the likelihood of undesirable effects such as charring within the tissue being ablated, coagulation on the cap 24A, and / or steam pops.

[0046] Typically, during an ablation session, the processor 46 causes the screen 62 to display the values of the parameters selected by the physician. The processor 46 can also cause the screen 62 to display to the physician the progress of the RF delivery by methods known in the art. The progress display can be graphical, such as a simulation of the dimensions of the lesion being generated by the ablation, and / or alphanumeric.

[0047] As described above, the force module 56 measures the force applied to the cap 24A. In some embodiments, the allowable force for ablation is in the range of 5 g to 35 g. Similarly, the perfusion module 58 manages the rate at which perfusion fluid is delivered to the probe tip. In some embodiments of the present invention, this rate can be set in the range of 8 to 45 mL / min.

[0048] Pulsed RF ablation As explained above in overview and with reference to Figure 1, the embodiments described herein provide for the safe application of short, high-power pulses of RF current to tissue (e.g., cardiac tissue) of a subject, such as to achieve relatively deep lesions in a relatively short period of time. In this regard, reference is now made to Figure 3, which is a schematic illustration of the application of pulsed RF ablation, according to some embodiments of the present invention.

[0049] 3 shows multiple RF current pulses 106, including a first pulse 106a, a second pulse 106b, and a third pulse 106c. The pulses 106 are applied by the processor 46 to tissue of the patient 18 using the RF generator 47 and the probe 20.

[0050] 3 further illustrates the temperature 108 at the interface between the tissue and the probe 20 as measured during the application of the pulse 106. As discussed above with reference to FIG. 1, the temperature 108, which may be more succinctly described as the "tissue temperature," may be calculated by the temperature module 52 by taking the maximum of the individual measurements received from the temperature sensor 78.

[0051] 3 further illustrates the power 110 of the pulses 106. As described in detail below, the amplitude, and therefore the power, of each pulse 106 is controlled by the processor 46 in response to the measured temperature 108.

[0052] The temperature 108 and power 110 of the pulse 106 are plotted along a common time axis, with times of particular interest t0-t8 marked. The data in Figure 3 are based on the results of actual experimental procedures that were performed, although specific numerical values have been omitted from Figure 3 for the sake of generality.

[0053] Typically, each pulse 106 has a maximum power of greater than 80 W, e.g., greater than 100 W or greater than 120 W. (In other words, the power of each pulse may exceed 80 W, 100 W, or 120 W for at least one instant during application of the pulse.) Typically, the duration of each pulse is less than 10 seconds, e.g., the pulse duration may be 2 to 5 seconds. Thus, for example, the duration between time t0 when the first pulse 106a begins and time t7 when the first pulse ends may be 2 to 5 seconds.

[0054] Each pair of consecutive pulses is separated by an intermission, during which no energy is typically applied to the tissue. Typically, the intermission is less than 10 seconds, e.g., 2-5 seconds. For example, the duration between time t7 and the start of the second pulse, t8, can be 2-5 seconds. As explained above in the overview, the intermission facilitates cooling of the tissue between pulse applications.

[0055] Typically, each pulse is applied such that the power of the pulse initially rises to a previously mentioned maximum power value and then levels off at that maximum power value. Typically, this maximum value is equal to a predefined target power value P, which, as noted above, may be greater than 80 W, greater than 100 W, or greater than 120 W. Following this initial plateau, the power of the pulse typically oscillates as the pulse is controlled in response to the measured temperature of the tissue, as will be described in more detail shortly.

[0056] During the application of each pulse, processor 46 controls the power of the pulse in response to the measured temperature 108. For example, the processor may reduce the power of the pulse in response to the measured temperature approaching, reaching, or exceeding a threshold temperature T, which may be, for example, 40° C. to 65° C. (e.g., 40° C. to 55° C.). Similarly, the processor may increase the power of the pulse in response to the measured temperature being sufficiently lower than T. Thus, typically, the processor alternately reduces and increases the power of each pulse in response to the temperature 108.

[0057] In some embodiments, the processor continuously uses the temperature readings to calculate a small change in power required to control each pulse, and then adjusts the power of the pulse by only this required change. For example, as described in U.S. Patent Application Publication No. 2017 / 0209208, the small required change is

[0058]

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[0059] Figure 3 demonstrates the use of the control technique described above. Specifically, the power of the first pulse rises from time t0 until it reaches the target power at time t1. Thereafter,

[0060]

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[0061]

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[0062] In general, an ablation procedure can include the application of any number of pulses greater than one. Typically, however, the desired lesion depth can be reached in fewer than seven pulses, such that fewer than seven (e.g., fewer than six) pulses are applied. During each pulse, the power 110 can reach the target power P any number of times.

[0063] Typically, while each pulse is applied, the processor measures the impedance across the pulse, as described above with reference to Figure 1. As further described above, the processor can cease application of RF current in response to a significant increase in this measured impedance.

[0064] It will be understood that the above-described embodiments are given by way of example, and that the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof not disclosed in the prior art that would occur to one skilled in the art upon reading the foregoing description.

[0065] [Embodiment] (1) A system comprising: a radio frequency current (RF current) generator; an electrode operably connected to the RF current generator; a processor, the processor comprising: causing the RF current generator to generate a plurality of pulses of RF current for application to tissue of the subject, each of the pulses having a power greater than 80 W and a duration less than 10 seconds, with an intermission between successive pulses of less than 10 seconds; receiving at least one signal indicative of a measured temperature of the tissue from a temperature measurement device operably connected to the processor while each of the pulses is applied to the tissue; and controlling the power of the pulses in response to the measured temperature. (2) The system according to Embodiment 1, wherein the processor is configured to drive the RF current generator to apply less than 7 pulses. (3) The system according to Embodiment 1, wherein the intermission is 2 to 5 seconds. (4) The system according to Embodiment 1, wherein the duration of each pulse is 2 to 5 seconds. (5) The system according to Embodiment 1, wherein the processor is configured to drive the RF current generator to apply each of the pulses such that the power of the pulse first rises to the maximum value and then stays at the maximum value.

[0066] (6) The system according to Embodiment 1, wherein the maximum value is greater than 100 W. (7) The system according to Embodiment 6, wherein the maximum value is greater than 120 W. (8) The system according to Embodiment 1, wherein the maximum value is equal to a pre-defined target power value. (9) The system according to Embodiment 1, wherein the processor is configured to control the power of the pulse by alternately reducing and increasing the power of the pulse. (10) The system according to Embodiment 1, wherein the processor is configured to control the power of the pulse by reducing the power of the pulse in response to the measured temperature approaching a threshold temperature.

[0067] (11) The system according to Embodiment 10, wherein the threshold temperature is 40°C to 65°C. (12) The system according to Embodiment 11, wherein the threshold temperature is 40°C to 55°C. (13) The system according to Embodiment 1, wherein no RF energy is applied to the tissue during the intermission. (14) A method, Generating a plurality of pulses of high-frequency (RF) current for application to a subject's tissue by a high-frequency current (RF current) generator, each of the pulses having a maximum value greater than 80 W and a duration of less than 10 seconds, and an intermission between consecutive pulses being less than 10 seconds; Applying the pulses to the tissue via an electrode in contact with the tissue and operably connected to the RF current generator; Receiving at least one signal indicative of a measured temperature of the tissue from a temperature sensing device while each of the pulses is being applied to the tissue, and controlling the power of the pulses in response to the measured temperature. A method comprising. (15) The method according to embodiment 14, wherein the intermission is 2 to 5 seconds.

[0068] (16) The method according to embodiment 14, wherein the duration of each pulse is 2 to 5 seconds. (17) The method according to embodiment 14, wherein the tissue includes the subject's heart tissue. (18) The method according to embodiment 14, wherein applying the pulses includes applying each of the pulses such that the power of the pulse first rises to the maximum value and then remains at the maximum value. (19) The method according to embodiment 14, wherein controlling the power of the pulses includes reducing the power of the pulses in response to the measured temperature approaching a threshold temperature. (20) The method according to embodiment 19, wherein the threshold temperature is 40°C to 65°C.

Claims

1. A system comprising: a radio frequency (RF) current generator; an electrode operably connected to the RF current generator; a processor, wherein the processor is configured to: cause the RF current generator to generate a plurality of pulses of RF current for application to a subject's tissue, each pulse having a maximum value greater than 80 W and a duration of less than 10 seconds, and an intermission between consecutive pulses of less than 10 seconds; receive from a temperature measuring device operably connected to the processor at least one signal indicative of a measured temperature of the tissue while each pulse is being applied to the tissue; increase the power of each pulse until the power of the pulse reaches the maximum value; after the maximum value is reached, add to the power of the pulse the minimum of the value of the formula a(Tt−1−Tt) / T + b(T−Tt) / T using the current measured temperature Tt, the immediately preceding measured temperature Tt−1, a predetermined temperature T, and constants a and b, and the value of the formula (P−Pt) / P using the current pulse power value Pt and the maximum value P of the power of the pulse, and increase or decrease the power; reduce the power of the pulse to 0 when the duration of the pulse reaches a predefined pulse duration. A system.

2. The system according to claim 1, wherein the processor is configured to drive the RF current generator to apply fewer than 7 pulses.

3. The system according to claim 1, wherein the intermission is 2 to 5 seconds.

4. The system according to claim 1, wherein the duration of each pulse is 2 to 5 seconds.

5. The system according to claim 1, wherein the maximum value is greater than 100 W.

6. The system according to claim 1, wherein the maximum value is greater than 120 W.

7. The system according to claim 1, wherein the maximum value is equal to a predefined target power value.

8. The system according to claim 1, wherein the predetermined temperature is 40° C. to 65° C.

9. The system according to claim 1, wherein the predetermined temperature is 40° C. to 55° C.

10. The system according to claim 1, wherein no RF energy is applied to the tissue during the intermission.

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