Power control technique for beam-type electrosurgical unit

Abstract

An electrosurgical generator in an electrosurgical unit (ESU) controls the repetition rate and the energy content of bursts of RF energy delivered to a gas jet supplied by the ESU, in order to maintain RF leakage current within acceptable limits while still achieving a sufficient state of ionization in the gas jet to reliably initiate the conduction of arcs to the tissue. The repetition rate of the RF bursts is substantially reduced in an inactive state when no arcs are delivered. A relatively small number of the RF bursts delivered during the inactive state have an increased or boosted energy content to assure an adequate ionization state in the gas jet.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation in part of application Ser. No. 849,950, filed Apr. 8, 1986 for "Electrosurgical Conductive Gas Stream Technique of Achieving Improved Eschar for Coagulation", now U.S. Pat. No. 52patent application Ser. No. 849,950.

The RF logic and arc sense circuit 86 receives a control signal 110 from the resonant output circuit 100. The control signal 110 relates to the condition of power delivery to the patient tissue, and is employed primarily to detect 242 252 in a linearly increasing or ramp fashion once the circuit 250 is triggered by a pulse signal 122 from the pulse generator 118 (FIG. 3). The linearly increasing ramp signal is applied to the noninverting input terminal of a comparator 254. The width control signal 138 is applied to the inverting input terminal of the comparator 254. When the ramp signal applied to the noninverting input terminal exceeds the analog level established by the signal 138, the modulated width output signal 142 is delivered by the ramp generator 140. The time width to the occurrence of the signal 142 created by the ramp generator 140 is determined by the analog level of the signal 138. Active pulses have a wider time width, because the output signal from the analog switch 238 will be greater in analog value. The booster target pulse will have a greater value than the normal target pulses, since the analog output signal from the analog switch 248 is greater than that of the analog switch 242. The ramp generator 140 establishes a convenient means for controlling the width of the drive pulses 102 and 104.

The RF drive pulse generator 144 includes a flip-flop 256 which is triggered by the pulse signal 122. The flip-flop 256 is reset by the modulated width pulse signal 142. A transistor circuit 258 includes a transistor 260 which is triggered into conduction by the output signal from the flip-flop 256. The output drive pulse signal 104 goes to a low level when transistor 260 commences conducting. When the output signal from the flip-flop 256 cease ceases, transistor 260 becomes nonconductive and transistor 262 becomes conductive. The drive pulse signal 104 goes high, and the drive pulse signal 102 goes low, thus terminating the width of the drive pulse delivered by the RF drive circuit 98 (FIG. 2) to the resonant output circuit 100 (FIG. 2).

The various improvements associated with the present invention have been described above. The preferred form of the present invention has been shown and described with a degree of detail. It should be understood, however, that this detailed description has been made by way of preferred example, and that the scope of the present invention is defined by the appended claims.

Claims

1. In an electrosurgical unit which includes means for conducting a predetermined gas in a jet to tissue and means for transferring electrical energy in ionized conductive pathways in the gas jet, said electrical energy transferring means operatively transferring arcs to the tissue in the ionized conductive pathways in an active state to thereby create a predetermined electrosurgical effect on the tissue, said electrical energy transferring means operatively creating substantially only ionized conductive pathways in the gas jet in an inactive state to allow arc initiation upon transition to the active state, said electrical energy transferring means including electrosurgical generator means for generating target bursts of radio frequency electrical energy at a predetermined inactive repetition rate in the inactive state and for generating active bursts of radio frequency electrical energy at a predetermined active repetition rate in the active state, said electrical energy transferring means applying the bursts of radio frequency energy to the gas jet, and an improvement to said electrosurgical generator means comprising, in combination:

repetition rate changing means for changing the predetermined repetition rate of the target bursts to a value substantially less than the predetermined repetition rate of the active bursts.

2. An invention as defined in claim 1 wherein said improved generator means further comprises:

arc sensing means for sensing a condition indicative of the occurrence of an arc initiation to the tissue in ionized conductive pathways during the inactive state and for supplying an active signal upon sensing said initiation condition; and wherein:

said repetition rate changing means is responsive to the active signal for operatively changing the repetition rate from the inactive rate to the active rate upon receipt of the active signal.

3. An invention as defined in claim 1 wherein said generator means further comprises:

arc sensing means for sensing a condition indicative of the absence of at least one arc in the ionized conductive pathways during the active state and for supplying a target signal upon sensing said absence condition; and

said repetition rate changing means is responsive to the target signal for operatively changing the repetition rate from the active rate to the inactive rate upon receipt of the target signal.

4. An invention as defined in claim 1 wherein:

the target bursts are generated in a plurality of repeating sequences during the inactive state, each sequence includes a plurality of target bursts; and

said generator means further includes booster means for increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts.

5. An invention as defined in claim 1 wherein said improved generator means further comprises:

arc sensing means for sensing a condition indicative of the occurrence of an arc initiation to the tissue in the ionized conductive pathways during the inactive state and for supplying an active signal upon sensing said initiation condition, said arc sensing means further sensing a condition indicative of the absence of at least one arc in the ionized pathways during the active state and for supplying a target signal upon sensing said absence condition; and

said repetition rate changing means is responsive to the active and target signals for operatively changing the repetition rate from the inactive rate to the active rate upon in response to the receipt of the active signal and for operatively changing the repetition rate from the active rate to the inactive rate upon in response to the receipt of the target signal.

6. An invention as defined in claim 5 wherein:

the target bursts are generated in a plurality of repeating sequences during the inactive state, each sequence includes a plurality of target bursts; and

said generator means further includes booster means for increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts.

7. An invention as defined in claim 6 wherein said generator means further includes:

temporary disabling means responsive to the target signal for temporarily disabling the booster means for a predetermined disabled time period after the target signal is supplied, the target bursts applied to the gas jet during this predetermined disabled time period being normal target bursts, said temporary disabling means further responding to the expiration of the predetermined disabled time period to thereafter enable said booster means to commence operating as recited, the predetermined disabled time period being at least the time period of one sequence of target bursts.

8. An invention as defined in claim claims 2, 5 or 7 wherein:

said means supplies the active signal upon sensing initiation condition is the first arc to the tissue occurring while in the inactive state.

9. An invention as defined in claims 3, 5 or 7 wherein:

said arc sensing means supplies the target signal upon sensing absence condition is the absence of a predetermined plurality of consecutive arcs in the active state.

10. An invention as defined in claim 9 wherein:

said generator means further includes means for establishing a predetermined active power level of electrical energy to be delivered to the gas jet in the active state; and

said arc sensing means is also responsive to the predetermined active power level and operatively supplies the target signal upon the absence of a relatively fewer predetermined plurality of consecutive arcs when the predetermined active power level is relatively higher and supplies the target signal upon the absence of a relatively greater predetermined plurality of consecutive arcs when the active power level is relatively lower.

11. An invention as defined in claims 4 or 6 wherein:

the booster target bursts are consecutive in each sequence.

12. An invention as defined in claim 11 wherein the number of booster target bursts in each sequence is in a range of less than ten percent of the total number of target bursts in each sequence.

13. An invention as defined in claims 4 or 6 wherein:

the booster target bursts have an energy content established at least in part by a peak to peak peak-to-peak voltage of at least one cycle of the radio frequency electrical energy of each booster target bursts; and

the peak to peak peak-to-peak voltage of at least one cycle of each booster target burst is substantially greater than the peak to peak peak-to-peak voltage of any cycle of each normal target burst.

14. An invention as defined in claim 7 wherein said generator means further comprises:

drive pulse generator means for generating driving pulses of energy having time width durations corresponding to the amount of energy contained in each pulse, said drive pulse generator means also generating the driving pulses at repetition rates corresponding to the repetition rates of the bursts;

drive means receptive of the drive driving pulses and operative for creating charging pulses having a time width related to the drive driving pulses;

conversion means receptive of each charging pulse and operative for converting each charging pulse into one said radio frequency burst, each burst having an energy content which relates to the energy content of the corresponding charging pulse which created the burst; and

pulse width adjusting means connected to said drive pulse generator means and operative for adjusting the width of driving pulses which control the charging pulses that established the booster target bursts and the normal target bursts to achieve the recited energy characteristics of the target bursts in the active and inactive states.

15. An invention as defined in claims 1, 4 or 6 wherein said repetition rate changing means establishes a substantially constant repetition rate in the inactive state and a different substantially constant repetition rate in the active state.

16. In an electrosurgical unit which includes means for conducting a predetermined gas in a jet to tissue and means for transferring electrical energy in ionized conductive pathways in the gas jet, said electrical energy transferring means operatively transferring arcs to the tissue in the ionized conductive pathways in an active state to thereby create a predetermined electrosurgical effect on the tissue, said electrical energy transferring means operatively creating substantially only ionized conductive pathways in the gas jet in an inactive state to allow arc initiation upon transition to the active state, said electrical energy transferring means including electrosurgical generator means for generating target bursts of radio frequency electrical energy at a predetermined repetition rate in the inactive state and for generating active bursts of radio frequency electrical energy at a predetermined repetition rate in the active state, said electrical energy transferring means applying the bursts of radio frequency energy to the gas jet, and an improvement to said electrosurgical generator means comprising, in combination:

means for generating the target bursts in a plurality of repeating sequences during the inactive state, each sequence including a plurality of target bursts; and

booster means for substantially increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts.

17. An invention as defined in claim 16 wherein the number of booster target bursts in each sequence is in a range of less than ten percent of the total number of target bursts in each sequence.

18. An invention as defined in claim 17 wherein:

the booster target busts bursts are consecutive in each sequence.

19. An invention as defined in claim 17 wherein:

the energy content of the booster target bursts is approximately three times the energy content of the normal target burst.

20. An invention as defined in claim 19 wherein the number of target bursts in each sequence is approximately less than five percent of the total number of target bursts in each sequence.

21. An invention as defined in claim 16 wherein said booster means further comprises:

means for delaying the application of booster target bursts for a predetermined time after said generator means transitions from delivering active bursts to delivering normal target bursts.

22. A method of operating an electrosurgical unit for conducting electrosurgery on tissue, comprising:

conducting a predetermined gas in a jet to tissue;

transferring electrical energy to the gas jet in an active state by generating active bursts of radio frequency electrical energy occurring at a predetermined active repetition rate to create arcs in ionized conductive pathways in the gas jet and to transfer arcs in the ionized conductive pathways to the tissue for achieving a predetermined electrosurgical effect on the tissue;

transferring electrical energy to the gas jet in an inactive state by generating target bursts of radio frequency electrical energy occurring at a predetermined inactive repetition rate to create substantially only ionized conductive pathways in the gas jet which allow arc initiation upon transition to the active state; and

establishing the predetermined inactive repetition rate of the target bursts at a predetermined value which is substantially less than the predetermined active repetition rate of the active bursts.

23. A method as defined in claim 22 further comprising:

sensing a condition indicative of the occurrence of arc initiation to the tissue in ionized conductive pathways during the inactive state; and

terminating the predetermined inactive repetition rate of the target bursts in response to the sensed initiation condition.

24. A method as defined in claim 23 wherein the sensed initiation condition is the first arc initiated to the tissue in the inactive state. 25. A method as defined in claim 22 further comprising:

sensing a condition indicative of the absence of at least one arc in the ionized conductive pathways during the active state; and

establishing the predetermined inactive repetition rate of the target bursts in response to the sensed absence condition. 26. A method as defined in claim 25 wherein the sensed absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 27. A method as defined in claim 22 further comprising:

sensing a condition indicative of the occurrence of an arc initiation to the tissue in the ionized conductive pathways during the inactive state;

establishing the active repetition rate in response to the sensed initiation condition;

sensing a condition indicative of the absence of at least one arc in the ionized pathways during the active state; and

establishing the inactive repetition rate in response to the sensed absence

condition. 28. A method as defined in claim 27 wherein the sensed absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 29. A method as defined in claim 28 wherein the sensed initiation condition is the first arc initiated to the tissue during the inactive state. 30. A method as defined in claim 27 further comprising:

generating target bursts in a plurality of repeating sequences during the inactive state, each sequence including a plurality of target bursts; and

increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts. 31. A method as defined in claim 30 further comprising:

temporarily ceasing the generation of booster target bursts for a predetermined disabled time period upon sensing the absence condition, the predetermined disabled time period being at least the time period of one sequence; and

beginning the generation of booster target bursts after the expiration of the predetermined disabled time period. 32. A method as defined in claim 31 wherein the sensed absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 33. A method as defined in claim 31 further comprising:

sensing a predetermined active power level of electrical energy delivered to the gas jet in the active state;

establishing the inactive repetition rate in response to sensing the absence of a relatively fewer predetermined plurality of consecutive arcs when the predetermined active power level is relatively higher; and

establishing the inactive repetition rate in response to sensing the absence of a relatively greater predetermined plurality of consecutive arcs when the predetermined active power level is relatively lower.

34. A method as defined in claim 33 further comprising:

consecutively generating the booster target bursts in each sequence. 35. A method as defined in claim 34 further comprising:

generating a number of booster target bursts in each sequence in a range of less than ten percent of the total number of target bursts in each sequence. 36. A method as defined in claim 27 further comprising:

generating target bursts in a plurality of repeating sequences during the inactive state, each sequence including a plurality of target bursts; and

increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target

bursts being normal target bursts. 37. A method as defined in claim 36 further comprising:

sensing a condition indicative of the absence of at least one arc in the ionized conductive pathways during the active state;

temporarily ceasing the generation of booster target bursts for a predetermined disabled time period upon sensing the absence condition, the predetermined disabled time period being at least the time period of one sequence; and

beginning the generation of booster target bursts after the expiration of the predetermined disabled time period. 38. A method as defined in claim 37 wherein the sensed absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 39. A method as defined in claim 37 further comprising:

sensing a predetermined active power level of electrical energy delivered to the gas jet in the active state;

establishing the inactive repetition rate in response to sensing the absence of a relatively fewer predetermined plurality of consecutive arcs when the predetermined active power level is relatively higher; and

establishing the inactive repetition rate in response to sensing the absence of a relatively greater predetermined plurality of consecutive arcs when the predetermined active power level is relatively lower. 40. A method as defined in claim 36 further comprising:

generating a number of booster target bursts in each sequence in a range of less than ten percent of the total number of target bursts in each

sequence. 41. A method as defined in claim 36 further comprising:

generating a number of booster target bursts in each sequence at approximately five percent of the total number of target bursts in each sequence; and

increasing the energy content of the booster target bursts to a value approximately three times greater than the energy content of the normal target bursts. 42. A method of operating an electrosurgical unit for conducting electrosurgery on tissue, comprising:

conducting a predetermined gas in a jet to tissue;

transferring electrical energy to the gas jet in an active state by generating active bursts of radio frequency electrical energy occurring at a predetermined active repetition rate to create the arcs in ionized conductive pathways in the gas jet and to transfer arcs in the ionized conductive pathways to the tissue for achieving a predetermined electrosurgical effect on the tissue;

transferring electrical energy to the gas jet in an inactive state by generating target bursts of radio frequency electrical energy occurring at a predetermined inactive repetition rate to create substantially only ionized conductive pathways in the gas jet which allow arc initiation upon transition to the active state, the target bursts occurring in a plurality of repeating sequences and each sequence including a plurality of target bursts; and

increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts. 43. A method as defined in claim 42 further comprising:

generating a number of booster target bursts in each sequence in a range of less than ten percent of the total number of target bursts in each sequence. 44. A method as defined in claim 43 further comprising:

consecutively generating the booster target bursts in each sequence. 45. A method as defined in claim 43 further comprising:

increasing the energy content of the booster target bursts to a value approximately three times greater than the energy content of the normal target bursts. 46. A method as defined in claim 45 further comprising:

generating a number of booster target bursts in each sequence at approximately five percent of the total number of target bursts in each sequence. 47. A method as defined in claim 42 further comprising:

delaying the generation of booster target bursts for a predetermined time after ceasing the delivery of active bursts and commencing the delivery of

normal target bursts. 48. An electrosurgical generator for an electrosurgical unit which includes means for conducting a predetermined gas in a jet to tissue and means for transferring arcs of electrical energy in ionized conductive pathways in the gas jet in an active state to create a predetermined electrosurgical effect on the tissue, the arcs in the active state resulting from bursts of radio frequency electrical energy occurring at a predetermined active repetition rate; said electrosurgical generator comprising:

burst generator means operative during an inactive state for generating bursts of radio frequency electrical energy to create substantially only ionized conductive pathways in the gas jet to allow arc initiation in the gas jet upon transition from the inactive state to the active state, the inactive state occurring other than during the occurrence of the active state; and

repetition rate establishing means for controlling the burst generator means to establish a repetition rate of the bursts in the inactive state which is substantially less than the predetermined repetition rate of the

bursts during the active state. 49. An electrosurgical generator as defined in claim 48 further comprising:

arc sensing means for sensing a condition indicative of the occurrence of an arc initiation to the tissue in ionized conductive pathways during the inactive state and for supplying an active signal upon sensing said initiation condition; and wherein:

said repetition rate establishing means is responsive to the active signal for operatively terminating the predetermined inactive repetition rate. 50. An electrosurgical generator as defined in claim 49 wherein:

said initiation condition is the first arc to the tissue occurring while in the inactive state. 51. An electrosurgical generator as defined in claim 48 further comprising:

arc sensing means for sensing a condition indicative of the absence of at least one arc in the ionized conductive pathways during the active state and for supplying a target signal upon sensing said absence condition; and

said repetition rate establishing means is responsive to the target signal for establishing the predetermined inactive repetition rate.

52. An electrosurgical generator as defined in claim 51 wherein:

said absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 53. An electrosurgical generator as defined in claim 48 further comprising:

arc sensing means for sensing a condition indicative of the occurrence of an arc initiation to the tissue in the ionized conductive pathways during the inactive state and for supplying an active signal upon sensing said initiation condition, and further sensing a condition indicative of the absence of at least one arc in the ionized pathways during the active state and for supplying a target signal upon sensing said absence condition; and

said repetition rate establishing means is responsive to the active and target signals for operatively terminating the predetermined inactive repetition rate in response to the active signal and for operatively establishing the predetermined inactive repetition rate in response to the target signal. 54. An electrosurgical generator as defined in claim 53 wherein:

said absence condition is the absence of a predetermined plurality of

consecutive arcs in the active state. 55. An electrosurgical generator as defined in claim 54 wherein:

said initiation condition is the first arc to the tissue occurring while in the inactive state. 56. An electrosurgical generator as defined in claim 53 wherein:

said burst generator means generates target bursts in a plurality of repeating sequences during the inactive state, each sequence includes a plurality of target bursts; and said burst generator means further includes:

booster means for increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts. 57. An electrosurgical generator as defined in claim 56 wherein said burst generator means further includes:

temporary disabling means responsive to the target signal for temporarily disabling the booster means for a predetermined disabled time period after the target signal is supplied, the predetermined disabled time period being at least the time period of one sequence of target bursts; and

reenabling means responsive to the expiration of the predetermined disabled time period for thereafter enabling said booster means to commence

operating as recited. 58. An electrosurgical generator as defined in claim 57 wherein:

said absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 59. An electrosurgical generator as defined in claim 57 wherein:

said arc sensing means is further responsive to a predetermined active power level of electrical energy delivered to the gas jet in the active state and operatively supplies the target signal upon the absence of a relatively fewer predetermined plurality of consecutive arcs when the predetermined active power level is relatively higher and supplies the target signal upon the absence of a relatively greater predetermined plurality of consecutive arcs when the active power level is relatively lower. 60. An electrosurgical generator as defined in claim 59 wherein:

the booster target bursts are consecutive in each sequence. 61. An electrosurgical generator as defined in claim 60 wherein the number of booster target bursts in each sequence is in a range of less than ten percent of the total number of target bursts in each sequence. 62. An electrosurgical generator as defined in claim 48 wherein:

the burst generator means generates target bursts in a plurality of repeating sequences during the inactive state, each sequence includes a plurality of target bursts; and said target burst generator means further includes:

booster means for increasing the energy content of a predetermined plurality of less than all of the target bursts occurring during each sequence, those target bursts of increased energy being booster target bursts and those other target bursts being normal target bursts. 63. An electrosurgical generator as defined in claim 62 further comprising:

arc sensing means for sensing a condition indicative of the absence of at least one arc in the ionized conductive pathways during the active state and for supplying a target signal upon sensing said absence condition; and wherein said burst generator means further includes:

temporary disabling means responsive to the target signal for temporarily disabling the booster means for a predetermined disabled time period after the target signal is supplied upon sensing the absence condition, the predetermined disabled time period being at least the time period of one sequence; and

reenabling means responsive to the expiration of the predetermined disabled time period for thereafter enabling said booster means to commence operating as recited. 64. An electrosurgical generator as defined in claim 63 wherein:

said absence condition is the absence of a predetermined plurality of consecutive arcs in the active state. 65. An electrosurgical generator as defined in claim 63 wherein:

said arc sensing means is further responsive to a predetermined active power level of electrical energy delivered to the gas jet in the active state and operatively supplies the target signal upon the absence of a relatively fewer predetermined plurality of consecutive arcs when the predetermined active power level is relatively higher and supplies the target signal upon the absence of a relatively greater predetermined plurality of consecutive arcs when the active power level is relatively lower. 66. An electrosurgical generator for an electrosurgical unit which includes means for conducting a predetermined gas in a jet to tissue and means for transferring arcs of electrical energy in ionized conductive pathways in the gas jet in an active state to create a predetermined electrosurgical effect on the tissue, the arcs in the active state resulting from bursts of radio frequency electrical energy occurring at a predetermined active repetition rate; said electrosurgical generator comprising:

burst generator means for generating a plurality of repeating sequences of bursts of radio frequency electrical energy during an inactive state to create substantially only ionized conductive pathways in the gas jet to allow arc initiation in the gas jet upon transition from the inactive state to the active state, each sequence including a plurality of bursts; and

booster means for increasing the energy content of a predetermined plurality of less than all of the bursts occurring during each sequence in the inactive state, those bursts of increased energy during the inactive state being booster target bursts and those other bursts being normal target bursts. 67. An electrosurgical generator as defined in claim 66 wherein the number of booster target bursts in each sequence is in a range of less than ten percent of the total number of target bursts in each sequence. 68. An electrosurgical generator as defined in claim 67 wherein:

the booster target bursts are consecutive in each sequence.

9. An electrosurgical generator as defined in claim 67 wherein:

the energy content of the booster target bursts is approximately three times the energy content of the normal target bursts. 70. An electrosurgical generator as defined in claim 69 wherein the number of booster bursts in each sequence is approximately five percent of the total number of bursts in each sequence. 71. An electrosurgical generator as defined in claim 66 wherein said booster means further comprises:

means for delaying the application of booster target bursts for a predetermined time after the transition from the delivery of active bursts to the delivery of normal target bursts.