Systems and methods for controlling tissue ablation using multiple temperature sensing elements

• US 5,769,847 A
• Filed: 04/24/1996
• Issued: 06/23/1998
• Est. Priority Date: 06/27/1994
• Status: Expired due to Term

• Current Assignee: EP Technologies Incorporated (Boston Scientific Corporation)
• Original Assignee: EP Technologies Incorporated (Boston Scientific Corporation)
• Inventors: Panescu, Dorin Nmi, Swanson, David K., Fleischman, Sidney D., Whayne, James G.
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US08/638,989
• Time in Patent Office: 790 Days
• Field of Search: 606/27-32, 606/37-42, 606/45-52, 607/100-102, 128/642
• US Class Current: 606/42
• CPC Class Codes: A61B 18/00 Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body eye surgery A61F9/007; ear surgery A61F11/00
• CPC Class Codes: A61B 18/12 by passing a current through the tissue to be heated, e.g. high-frequency current
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 2017/00088 using thermistors
• CPC Class Codes: A61B 2017/00092 using thermocouples
• CPC Class Codes: A61B 2017/00154 pulsed
• CPC Class Codes: A61B 2017/003 Steerable
• CPC Class Codes: A61B 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00095 high, i.e. heat conducting
• CPC Class Codes: A61B 2018/00101 low, i.e. thermally insulating
• CPC Class Codes: A61B 2018/00107 Coatings on the energy applicator
• CPC Class Codes: A61B 2018/00148 with metal
• CPC Class Codes: A61B 2018/0016 Energy applicators arranged in a two- or three dimensional array
• CPC Class Codes: A61B 2018/00357 Endocardium
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00636 Sensing and controlling the application of energy
• CPC Class Codes: A61B 2018/00654 with individual control of each of a plurality of energy emitting elements
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/0069 : using fuzzy logic
• CPC Class Codes: A61B 2018/00702 : Power or energy
• CPC Class Codes: A61B 2018/00726 : Duty cycle
• CPC Class Codes: A61B 2018/00761 : Duration
• CPC Class Codes: A61B 2018/00791 : Temperature
• CPC Class Codes: A61B 2018/00797 : measured by multiple temperature sensors
• CPC Class Codes: A61B 2018/00803 : with temperature prediction
• CPC Class Codes: A61B 2018/00821 : measured by a thermocouple
• CPC Class Codes: A61B 2018/00886 : Duration
• CPC Class Codes: A61B 2018/124 : switching the output to different electrodes, e.g. sequentially
• CPC Class Codes: A61B 2018/1253 : monopolar
• CPC Class Codes: A61B 2018/126 : bipolar
• CPC Class Codes: A61B 2018/128 : generating two or more frequencies
• CPC Class Codes: A61B 2018/1467 : using more than two electrodes on a single probe
• CPC Class Codes: G01K 1/026 : arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
• CPC Class Codes: G01K 3/14 : in respect of space

Abstract

A system and associated method ablate body tissue using multiple emitters of ablating energy. The system and method convey ablating energy individually to each emitter in a sequence of power pulses. The system and method periodically sense temperature at each emitter and compare the sensed temperatures to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison. The system and method individually vary the power pulse to each emitter based upon the signal for that emitter to maintain the temperatures at all emitters essentially at the desired temperature during tissue ablation.

Claims

1. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually from the source to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein power delivered to each emitter for ablating tissue is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTYCYCLE

a processing element coupled to each temperature sensing element for periodically reading the temperature measured by each temperature sensing element and comparing the temperature to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

a temperature controller coupled to the power controller and the processing element for causing the power controller to individually vary the power pulse to each emitter based upon the signal for that emitter to maintain the temperatures at all emitters essentially at the desired temperature during tissue ablation.

2. A system according to claim 1

wherein the temperature controller includes means for causing the power controller to vary the power pulse by individually varying the amplitude of the power pulse based upon the signal for that emitter, while maintaining the duty cycle of the power pulses essentially the same for all emitters.

3. A system according to claim 2

wherein the means for causing the power controller to vary the power pulse by varying amplitude maintains the duty cycle at 1/N, where N is the number of energy emitters.

4. A system according to claim 2

wherein the the means for causing the power controller to vary the power pulse by varying amplitude varies amplitude by varying either voltage or current.

5. A system according to claim 2

wherein the the means for causing the power controller to vary the power pulse by varying amplitude individually turns off an energy emitter when the temperature measured at the emitter equals or exceeds the desired temperature by a predetermined amount and individually turns on the emitter when the temperature measured at the emitter is less than the desired temperature by a predetermined amount.

6. A system according to claim 1

wherein the temperature controller includes means for causing the power controller to vary the power pulse by individually varying the duty cycle of the emitter based upon the signal for that emitter, while maintaining the amplitude of the power pulses essentially the same for all emitters.

7. A system according to claim 6

wherein the means for causing the power controller to vary the power pulse by varying duty cycle individually turns off an energy emitter when the temperature measured at the emitter equals or exceeds the desired temperature by a predetermined amount and individually turns on the emitter when the temperature measured at the emitter is less than the desired temperature by a predetermined amount.

8. A system according to claim 1

wherein the temperature controller includes means for causing the power controller to vary the power pulse by individually varying both the duty cycle and the amplitude of the power pulse for each energy emitter based upon the signal for that emitter.

9. A system according to claim 8

wherein the means for causing the power controller to vary the power pulse by varying both duty cycle and amplitude individually turns off an energy emitter when the temperature measured at the emitter equals or exceeds the desired temperature by a predetermined amount and individually turns on the emitter when the temperature measured at the emitter is less than the desired temperature by a predetermined amount.

10. A system according to claim 8

wherein the means for causing the power controller to vary the power pulse by varying both duty cycle and amplitude varies amplitude by varying either voltage or current.

11. A tissue ablation system comprising

an ablating element comprising at least one structure supporting at least two zones for emitting ablating energy E(J), where J=2 to N, N being the total number of zones,

at least one temperature sensing element supported in proximity with each zone E(J) for measuring a temperature condition localized with respect to the zone E(J), the localized temperature condition being designated TEMP(J),

a power controller coupled to a source of ablating energy and to the zones E(J) including a switching element to convey ablating energy individually to each zone E(J) in a power pulse having a duty cycle DUTYCYCLE_E(J) and an amplitude AMP_E(J), DUTYCYCLE_E(J) being set to be essentially the same for all E(J), wherein the power P_E(J) delivered to each zone E(J) is expressed as follows:

space="preserve" listing-type="equation">P.sub.E(J) ˜

AMP.sub.E(J).sup.2 ×

DUTYCYCLE.sub.E(J)

a processing element coupled to the at least one temperature sensing element including

means for periodically reading the temperature condition measured by each temperature sensing element TEMP(J),

means for comparing the read temperature condition TEMP(J) to a desired temperature condition TEMP_SET to generate a signal SIGNAL(J) based upon the comparison, and

a temperature controller coupled to the power controller and the processing element including control means for causing the power controller to vary the power pulse to each zone E(J) based upon SIGNAL(J) by varying AMP_E(J) while keeping DUTYCYCLE_E(J) essentially the same for all E(J), to maintain TEMP(J)≈

TEMP_SET for all E(J).

12. A system according to claim 11

wherein the control means keeps DUTYCYCLE_E(J) set at 1/N for all E(J).

13. A system according to claim 11

wherein the control means varies AMPE(J) by varying either voltage or current.

14. A tissue ablation system comprising

an ablating element comprising at least one structure supporting at least two zones for emitting ablating energy E(J), where J=2 to N, N being the total number of zones,

at least one temperature sensing element supported in proximity with each zone E(J) for measuring a temperature condition localized with respect to the zone E(J), the localized temperature condition being designated TEMP(J),

a power controller coupled to a source of ablating energy and to the zones E(J) including a switching element to convey ablating energy individually to each zone E(J) in a power pulse having a duty cycle DUTYCYCLE_E(J) and an amplitude AMP_E(J), AMP_E(J) being set to be essentially the same for all E(J), wherein the power P_E(J) delivered to each zone E(J) is expressed as follows:

space="preserve" listing-type="equation">P.sub.E(J) ˜

AMP.sub.E(J).sup.2 ×

DUTYCYCLE.sub.E(J)

a processing element coupled to the at least one temperature sensing element including

means for periodically reading the temperature condition measured by each temperature sensing element TEMP(J),

means for comparing the read temperature condition TEMP(J) to a desired temperature condition TEMP_SET to generate a signal SIGNAL(J) based upon the comparison, and

a temperature controller coupled to the power controller and the processing element including control means for causing the power controller to vary the power pulse to each zone E(J) based upon SIGNAL(J) by varying DUTYCYCLE_E(J) while keeping AMP_E(J) essentially the same for all E(J), to maintain TEMP(J)≈

TEMP_SET for all E(J).

17. A system according to claim 14 or 15 or 16

wherein the control means varies AMP_E(J) by varying either voltage or current.

15. A tissue ablation system comprising

an ablating element comprising at least one structure supporting at least two zones for emitting ablating energy E(J), where J=2 to N, N being the total number of zones,

at least one temperature sensing element supported in proximity with each zone E(J) for measuring a temperature condition localized with respect to the zone E(J), the localized temperature condition being designated TEMP(J),

a power controller coupled to a source of ablating energy and to the zones E(J) including a switching element to convey ablating energy individually to each zone E(J) in a power pulse having a duty cycle DUTYCYCLE_E(J) and an amplitude AMP_E(J), AMP_E(J) being set to be essentially the same for all E(J), wherein the power P_E(J) delivered to each zone E(J) is expressed as follows:

space="preserve" listing-type="equation">P.sub.E(J) ˜

AMP.sub.E(J).sup.2 ×

DUTYCYCLE.sub.E(J)

a processing element coupled to the at least one temperature sensing element including

means for periodically reading the temperature condition measured by each temperature sensing element TEMP(J),

means for identifying the lowest read temperature condition TEMP_SMIN of all TEMP(J), and

means for comparing the lowest read temperature condition TEMP_SMIN to a desired temperature condition TEMP_SET to generate a signal based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element including control means for causing the power controller to vary the power pulse to each zone E(J) based upon the signal by varying AMP_E(J) for all E(J) to maintain TEMP_SMIN ≈

TEMP_SET.

16. A tissue ablation system comprising

an ablating element comprising at least one structure supporting at least two zones for emitting ablating energy E(J), where J=2 to N, N being the total number of zones,

at least one temperature sensing element supported in proximity with each zone E(J) for measuring a temperature condition localized with respect to the zone E(J), the localized temperature condition being designated TEMP(J),

a power controller coupled to a source of ablating energy and to the zones E(J) including a switching element to convey ablating energy individually to each zone E(J) in a power pulse having a duty cycle DUTYCYCLE_E(J) and an amplitude AMP_E(J), AMP_E(J) being set to be essentially the same for all E(J), wherein the power P_E(J) delivered to each zone E(J) is expressed as follows:

space="preserve" listing-type="equation">P.sub.E(J) ˜

AMP.sub.E(J).sup.2 ×

DUTYCYCLE.sub.E(J)

a processing element coupled to the at least one temperature sensing element including

means for periodically reading the temperature condition measured by each temperature sensing element TEMP(J),

means for identifying the lowest read temperature condition TEMP_SMIN of all TEMP(J), and

means for comparing the lowest read temperature condition TEMP_SMIN to a desired temperature condition TEMP_SET to generate a signal based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element including control means for causing the power controller to vary the power pulse to each zone E(J) based upon the signal by varying AMP_E(J) for all E(J) to maintain TEMP_SMIN ≈

TEMP_SET while also varying the DUTYCYCLE_E(J) of each zone E(J) where TEMP(J)>

TEMP_SMIN to maintain TEMP(J)≈

TEMP_SET for each such zone.

18. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters,

a processing element coupled to the at least one temperature sensing element for periodically reading the temperature measured by each temperature sensing element and selecting one of the measured temperatures based upon preestablished criteria for comparison to a desired temperature to generate a signal, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to convey ablating energy to the emitters based upon the signal.

19. A system according to claim 18

wherein the processing element includes means for selecting the highest one of the measured temperatures.

20. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein ablating power delivered to each emitter is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTYCYCLE

a processing element coupled to the at least one temperature sensing element for periodically reading the temperature measured by each temperature sensing element and selecting one of the measured temperatures based upon preestablished criteria for comparison to a desired temperature to generate a signal, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to vary the power pulses to the emitters based upon the signal.

21. A system according to claim 20

wherein the processing element includes means for selecting the highest one of the measured temperature.

22. A system according to claim 20

wherein the temperature controller includes means for causing the power controller to vary the power pulses by varying the amplitudes of the power pulses for all emitters based upon the signal to maintain the amplitudes of the power pulses essentially the same for all emitters.

23. A system according to claim 20

wherein the means for causing the power controller to vary the power pulses by varying amplitudes varies amplitudes by varying either voltage or current.

24. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually to each emitter,

a processing element coupled to the at least one temperature sensing element for periodically reading the temperature measured by each temperature sensing element and selecting one of the measured temperatures based upon preestablished criteria and for comparing the temperature measured by each temperature sensor to the selected one of the measured temperatures to generate a signal individually for each emitter based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to individually control the conveyance of ablating energy to each emitter based upon the signal for that emitter.

25. A system according to claim 24

wherein the temperature controller includes means for causing the power controller to individually turn off and turn on an energy emitter based upon the signal for that emitter.

26. A system according to claim 24

wherein the the processing element includes means for selecting the lowest one of the measured temperatures.

27. A system according to claim 24

wherein the processing element includes means for deriving a difference between the temperature measured by each temperature sensor and the selected one of the measured temperatures and compares the difference to a predetermined value to generate the signal.

28. A system according to claim 27

wherein the temperature controller includes means for causing the power controller to individually turn off an energy emitter when the difference for that emitter equals or exceeds the predetermined value and individually turn on the emitter when the difference for that emitter is less than the predetermined value.

29. A tissue ablation system comprising

an ablating element comprising at least one structure supporting at least two zones for emitting ablating energy E(J), where J=2 to N, N being the total number of zones,

at least one temperature sensing element supported in proximity with each zone E(J) for measuring a temperature condition localized with respect to the zone E(J), the localized temperature condition being designated TEMP(J),

a power controller coupled to a source of ablating energy and to the zones E(J) including a switching element to convey ablating energy individually to each zone E(J) in a power pulse having a duty cycle DUTYCYCLE_E(J) and an amplitude AMP_E(J), wherein the power P_E(J) delivered to each zone E(J) is expressed as follows:

space="preserve" listing-type="equation">P.sub.E(J) ˜

AMP.sub.E(J).sup.2 ×

DUTYCYCLE.sub.E(J)

a processing element coupled to the at least one temperature sensing element including

means for periodically reading the temperature condition measured by each temperature sensing element TEMP(J),

means for comparing each read temperature condition TEMP(J) to a prescribed low threshold temperature condition TEMP_LOWTHRESH and a prescribed high threshold temperature condition TEMP_HITHRESH, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to turn off a given zone E(J) when TEMP(J) for that zone≧

TEMP_HITHRESH and for turn on the given zone E(J) when TEMP(J) for that zone<

TEMP_LOWTHRESH.

30. A system according to claim 29

wherein the power controller includes means for establishing and maintaining essentially the same AMP_E(J) for all E(J) during operation of the temperature controller.

31. A system according to claim 29

wherein the temperature controller includes means for causing the power controller to adjust AMP_E(J) for at least one zone E(J) according to prescribed criteria.

32. A system according to claim 29

wherein the processing element further includes

means for identifying the lowest read temperature condition TEMP_SMIN of all TEMP(J), and

means for comparing the lowest read temperature condition TEMP_SMIN to a prescribed low temperature condition TEMP_LOW to generate a signal based upon the comparison, and

wherein the temperature controller includes means for causing the power controller to adjust AMP_E(J) based upon the signal to maintain TEMP_SMIN above TEMP_LOW.

33. A system according to claim 29

wherein the temperature controller includes means for causing the power controller to adjust DUTYCYCLE_E(J) for at least one zone E(J) based upon prescribed criteria.

34. A system for ablating body tissue comprising

an emitter of ablating energy supported on a structure,

at least two temperature sensing elements supported in proximity with the energy emitter for measuring temperatures at the emitter,

a power controller coupled to a source of ablating energy and to the energy emitter to convey ablating energy to the emitter,

a processing element coupled to the at least two temperature sensing elements for periodically reading the temperature measured by each temperature sensing element and selecting the hottest one of the measured temperatures and for comparing the selected hottest temperature to a desired temperature to generate a signal based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to convey energy to the emitter based upon the signal.

35. A system for ablating body tissue comprising

an emitter of ablating energy supported on a structure,

at least two temperature sensing elements supported in proximity with the energy emitter for measuring temperatures at the emitter,

a power controller coupled to a source of ablating energy and to the energy emitter to convey ablating energy to the emitter,

a processing element coupled to the at least two temperature sensing elements for periodically reading the temperature measured by each temperature sensing element and deriving therefrom a prediction of the hottest tissue temperature at the emitter and for comparing the predicted hottest temperature to a desired temperature to generate a signal based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to convey energy to the emitter based upon the signal.

36. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperatures at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually to each emitter,

a processing element coupled to the at least two temperature sensing elements for periodically reading the temperatures measured by the temperature sensing elements for each emitter and selecting for each emitter the hottest one of the measured temperatures and for comparing the hottest one of the temperatures for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to individually convey energy to each emitter based upon the signal for that emitter to maintain the hottest temperature at all emitters essentially at the desired temperature during tissue ablation.

37. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperatures at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein power delivered to each emitter for ablating tissue is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTYCYCLE

a processing element coupled to the at least two temperature sensing elements for periodically reading the temperatures measured by the temperature sensing elements for each emitter and selecting for each emitter the hottest one of the measured temperatures and for comparing the hottest one of the temperatures for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to individually vary the power pulse to each emitter based upon the signal for that emitter to maintain the hottest temperature at all emitters essentially at the desired temperature during tissue ablation.

38. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperatures at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein power delivered to each emitter for ablating tissue is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTYCYCLE

a processing element coupled to the at least two temperature sensing elements for periodically reading the temperatures measured by the temperature sensing elements for each emitter and predicting for each emitter the hottest tissue temperature and for comparing the predicted hottest temperature for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

a temperature controller coupled to the power controller and to the processing element for causing the power controller to individually vary the power pulse to each emitter based upon the signal for that emitter to maintain the predicted hottest temperature at all emitters essentially at the desired temperature during tissue ablation.

39. A method for ablating body tissue using multiple emitters of ablating energy comprising the steps of

conveying ablating energy individually to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein power delivered to each emitter for ablating tissue is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTY CYCLE

periodically sensing temperature at each emitter,

comparing the sensed temperatures to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

individually varying the power pulse to each emitter based upon the signal for that emitter to maintain the temperatures at all emitters essentially at the desired temperature during tissue ablation.

40. A method according to claim 39

wherein the pulse power varying step includes individually varying the amplitude of the power pulse based upon the signal for that emitter, while maintaining the duty cycle of the power pulses essentially the same for all emitters.

41. A method according to claim 39

wherein the pulse power varying step includes individually varying the duty cycle of the emitter based upon the signal for that emitter, while maintaining the amplitude of the power pulses essentially the same for all emitters.

42. A method according to claim 39

wherein the pulse power varying step includes individually varying both the duty cycle and the amplitude of the power pulse for each energy emitter based upon the signal for that emitter.

43. A method according to claim 39

and further including the step of individually turning off an energy emitter when the temperature measured at the emitter equals or exceeds a predetermined amount and individually turning on the emitter when the temperature measured at the emitter is less than the predetermined amount.

44. A method for ablating body tissue using multiple emitters of ablating energy comprising the steps of

conveying ablating energy to the emitters,

periodically sensing temperature at each emitter,

selecting one of the sensed temperatures based upon preestablished criteria for comparison to a desired temperature to generate a signal, and

controlling the conveyance of ablating energy to all emitters based upon the signal.

45. A method according to claim 44

wherein the selecting step selects the highest one of the sensed temperatures.

46. A method according to claim 44

wherein the selecting step selects for each emitter a prediction of the hottest tissue temperature based upon the sensed temperatures at that emitter.

47. A method for ablating body tissue using multiple emitters of ablating energy comprising the steps of

conveying ablating energy individually to each emitter,

periodically sensing temperature at each emitter,

selecting one of the sensed temperatures based upon preestablished criteria,

comparing the sensed temperature at each emitter to the selected one of the sensed temperatures to generate a signal individually for each emitter based upon the comparison, and

individually controlling the conveyance of ablating energy to each emitter based upon the signal for that emitter.

48. A method according to claim 47

wherein the controlling step includes the step of individually turning off and turning on an energy emitter based upon the signal for that emitter.

49. A method according to claim 47

wherein the selecting step selects the lowest one of the sensed temperatures.

50. A method for ablating body tissue comprising the steps of

conveying ablating energy to an emitter,

periodically sensing at least two temperatures at the emitter,

selecting the hottest one of the selected temperatures,

comparing the selected hottest temperature to a desired temperature to generate a signal based upon the comparison, and

controlling the conveyance of energy to the emitter based upon the signal.

51. A method for ablating body tissue comprising the steps of

conveying ablating energy to an emitter,

periodically sensing at least two temperatures at the emitter,

predicting the hottest tissue temperature at the emitter based upon the sensed temperatures,

comparing the predicted hottest tissue temperature to a desired temperature to generate a signal based upon the comparison, and

controlling the conveyance of energy to the emitter based upon the signal.

52. A method ablating body tissue using multiple emitters of ablating energy comprising the steps of

conveying ablating energy individually to each emitter,

periodically sensing at least two temperatures at each emitter,

selecting for each emitter the hottest one of the sensed temperatures,

comparing the hottest one of the temperatures for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

individually controlling the conveyance of energy to each emitter based upon the signal for that emitter to maintain the hottest temperature at all emitters essentially at the desired temperature during tissue ablation.

53. A method ablating body tissue using multiple emitters of ablating energy comprising the steps of

conveying ablating energy individually to each emitter,

periodically sensing at least two temperatures at each emitter,

predicting the hottest tissue temperature at each emitter based upon temperatures sensed at that emitter,

comparing the predicted hottest tissue temperature for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

individually controlling the conveyance of energy to each emitter based upon the signal for that emitter to maintain the predicted hottest tissue temperature at all emitters essentially at the desired temperature during tissue ablation.

54. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy individually from the source to each emitter in a sequence of power pulses, each power pulse having a duty cycle and an amplitude, wherein power delivered to each emitter for ablating tissue is expressed as follows:

space="preserve" listing-type="equation">POWER˜

AMPLITUDE.sup.2 ×

DUTYCYCLE

an element coupled to each temperature sensing element and to the power controller to vary the power pulses conveyed by the power controller including

means for periodically sensing temperature at each emitter using the at least one temperature sensing element,

means for comparing the sensed temperatures to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

means for causing the power controller to individually vary the power pulse to each emitter based upon the signal for that emitter to maintain the temperatures at all emitters essentially at the desired temperature during tissue ablation.

55. A system according to claim 54

wherein the element includes means for individually varying the amplitude of the power pulse based upon the signal for that emitter, while maintaining the duty cycle of the power pulses essentially the same for all emitters.

56. A system according to claim 54

wherein the element includes means for individually varying the duty cycle of the emitter based upon the signal for that emitter, while maintaining the amplitude of the power pulses essentially the same for all emitters.

57. A system according to claim 54

wherein the element includes means for individually varying both the duty cycle and the amplitude of the power pulse for each energy emitter based upon the signal for that emitter.

58. A system according to claim 54

wherein the element includes means for individually turning off an energy emitter when the temperature measured at the emitter equals or exceeds a predetermined amount and individually turning on the emitter when the temperature measured at the emitter is less than the predetermined amount.

59. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing temperature at each emitter using the at least one temperature sensing element,

means for selecting one of the sensed temperatures based upon preestablished criteria for comparison to a desired temperature to generate a signal, and

means for causing the power controller to convey ablating energy to all emitters based upon the signal.

60. A system according to claim 59

wherein the means for selecting one of the sensed temperatures comprises means for selecting the highest one of the sensed temperatures.

61. A system according to claim 59

wherein the means for selecting one of the sensed temperatures comprises means for selecting for each emitter a prediction of the hottest tissue temperature based upon the sensed temperatures at that emitter.

62. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least one temperature sensing element supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing temperature at each emitter using the at least one temperature sensing element,

means for selecting one of the sensed temperatures based upon preestablished criteria,

means for comparing the sensed temperature at each emitter to the selected one of the sensed temperatures to generate a signal individually for each emitter based upon the comparison, and

means for causing the power controller to individually control the conveyance of ablating energy to each emitter based upon the signal for that emitter.

63. A system according to claim 62

wherein the means for causing the power controller to individually control the conveyance of ablating energy comprises means for individually turning off and turning on an energy emitter based upon the signal for that emitter.

64. A system according to claim 62

wherein the means for selecting one of the sensed temperatures comprises means for selecting the lowest one of the sensed temperatures.

65. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing at least two temperatures at the emitter using the at least two temperature sensing elements,

means for selecting the hottest one of the selected temperatures,

means for comparing the selected hottest temperature to a desired temperature to generate a signal based upon the comparison, and

means for causing the power controller to conveyance of energy to the emitter based upon the signal.

66. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing at least two temperatures at the emitter using the at least two temperature sensing elements,

means for predicting the hottest tissue temperature at the emitter based upon the sensed temperatures,

means for comparing the predicted hottest tissue temperature to a desired temperature to generate a signal based upon the comparison, and

means for causing the power controller to convey energy to the emitter based upon the signal.

67. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing at least two temperatures at each emitter using the at least two temperature sensing elements,

means for selecting for each emitter the hottest one of the sensed temperatures,

means for comparing the hottest one of the temperatures for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

means for causing the power controller to individually control the conveyance of energy to each emitter based upon the signal for that emitter to maintain the hottest temperature at all emitters essentially at the desired temperature during tissue ablation.

68. A system for ablating body tissue including multiple emitters of ablating energy supported adjacent body tissue by at least one supporting structure comprising

at least two temperature sensing elements supported in proximity with each energy emitter for measuring temperature at the emitter,

a power controller coupled to a source of ablating energy and to each energy emitter to convey ablating energy to the emitters, and

an element coupled to each temperature sensing element and to the power controller to control the conveyance of ablating energy to the emitters including

means for periodically sensing at least two temperatures at each emitter using the at least two temperature sensing elements,

means for predicting the hottest tissue temperature at each emitter based upon temperatures sensed at that emitter,

means for comparing the predicted hottest tissue temperature for each emitter to a desired temperature established for all emitters to generate a signal individually for each emitter based upon the comparison, and

means for causing the power controller to individually control the conveyance of energy to each emitter based upon the signal for that emitter to maintain the predicted hottest tissue temperature at all emitters essentially at the desired temperature during tissue ablation.