Electrosurgical system

• US 20020052599A1
• Filed: 10/29/2001
• Published: 05/02/2002
• Est. Priority Date: 10/31/2000
• Status: Active Grant

• Current Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Original Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Inventors: Goble, Colin C.O.
• Granted Patent: US 6,893,435 B2
• Time in Patent Office: Days
• US Class Current: 606/40
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/1445 at the distal end of a shaft, e.g. forceps or scissors at the end of a rigid rod
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

An electrosurgical system has an electrosurgical generator and a bipolar electrosurgical instrument, the generator being arranged to perform a treatment cycle in which radio frequency energy is delivered to the instrument as an amplitude-modulated radio frequency power signal in the form of a succession of pulses characterized by periods of a least 100 milliseconds between successive pulses and by a predetermined pulse mark-to-space ratio. Energy delivery between pulses is substantially zero and the mark-to-space ratio is typically 1:4 or less. Each burst is of sufficiently high power to form vapor bubbles within tissue being treated and the time between successive pulses is sufficiently long to permit condensation of the vapor. The treatment cycles may each include an initial period and a subsequent period, the pulse duty cycle being increased or energy being delivered continuously in the subsequent period in order that tissue coagulation can be achieved quickly despite increasing tissue impedance.

Claims

1. An electrosurgical generator comprising a source of radio frequency (r.f.) energy, at least a pair of output terminals for connection to a bipolar electrosurgical instrument and for delivering r.f. energy from the source to the instrument, and a pulsing circuit for the source, wherein the pulsing circuit and the source are so arranged as to deliver into a resistive load, when connected across the output terminals, an amplitude-modulated r.f. power signal in the form of a succession of pulses, which succession is characterised by periods of at least 100 ms between successive pulses and by a predetermined pulse mark-to-space ratio.

2. A generator according to claim 1, wherein the depth of amplitude modulation in the said r.f. signal is at least 90% and the pulse mark-to-space ratio is less than 2:

3.

3. A generator according to claim 1, arranged such that the pulse mark-to-space ratio remains constant at a predetermined value over the major part of the said succession of pulses.

4. A generator according to claim 1, arranged such that the pulsing frequency remains constant at a predetermined value over the major part of the said succession of pulses.

5. A generator according to claim 1, arranged such that the pulse mark-to-space ratio and the pulsing frequency remain constant throughout the said succession of pulses until the pulses are terminated.

6. A generator according to claim 1, arranged such that at least one of the pulse mark-to-space ratio and the pulsing frequency is automatically preset at the start of the said succession of pulses to a value which is dependent on an instrument identification signal received by the generator.

7. A generator according to claim 1, arranged such that at least one of the pulse mark-to-space ratio and the pulsing frequency is automatically preset at the start of the said succession of pulses to a value which is dependent on the load resistance across the output terminals at the said start.

8. A generator according to claim 1, arranged such that at least one of the pulse mark-to-space ratio and the pulsing frequency after the start of the said succession of pulses is unaffected by the load resistance over at least the major part of a treatment period constituted by said succession of pulses.

9. An electrosurgical generator according to claim 1, arranged so as to be capable of delivering a peak power of at least 100 W into any resistive load connected across the generator output in the range of from 20 Ω

to 250 Ω

.

52. An electrosurgical system comprising an electrosurgical generator and a bipolar electrosurgical instrument coupled to an output of the generator, the generator being such as to provide a succession of controlled bursts of electrosurgical energy to the instrument at a predetermined pulse mark-to-space ratio, wherein each burst has a sufficiently high power to form at least one vapour bubble within tissue being treated by the instrument, and the time duration between successive bursts is sufficiently long to permit recondensation of the or each vapour bubble, the peak delivered power being between the bursts being substantially zero, wherein the generator is as claimed in claim 1.

55. An integrated electrosurgical generator and instrument system, wherein the instrument is removably connectible to the generator and includes an instrument identification element, and wherein the generator is as claimed in any of claims 1 to 49 and includes a sensing circuit for sensing the identification element, the pulsing circuit of the generator being arranged automatically to adjust the mark-to-space ratio of the signal pulses in response to the identification element as sensed by the sensing circuit.

56. A system according to claim 55, comprising a plurality of bipolar electrosurgical forceps instruments which are selectively connectible to the generator and contain respective identification elements, wherein the electrodes of the instruments define different tissue contact areas, and wherein the respective identification elements, the sensing circuit and/or the pulsing circuit are selected and configured to set the said mark-to-space ratio to a lower value for an instrument with electrodes defining a comparatively large tissue contact area and to a higher value for an instrument with electrodes defining a comparatively small tissue contact area.

57. A system according to claim 55, wherein the identification elements, the sensing circuit and/or the pulsing circuit are selected and configured to decrease the pulse frequency when an instrument with a comparatively large tissue contact area is selected.

10. An electrosurgical generator comprising a source of radio frequency (r.f.) energy, at least a pair of output terminals for connection to a bipolar electrosurgical instrument and for delivering r.f. energy from the source to the instrument, and a pulsing circuit for the source, wherein the pulsing circuit and the source are so arranged as to deliver into a resistive load, when connected across the output terminals, an amplitude-modulated r.f. power signal in which the periods between successive pulses are at least 100 ms, the depth of amplitude modulation is at least 90% and the pulse mark-to-space ratio is less than 2:

3.

11. A generator according to claim 10, wherein the mark-to-space ratio is less than or equal to 1:

3 over at least a load value range of 5 Ω

to 45 Ω

.

12. A generator according to claim 10, wherein the mark-to-space ratio is less than or equal to 1:

4 over at least a load value of 5 Ω

to 30 Ω

.

13. A generator according to claim 10, wherein the r.f. current during each of a plurality of successive said pulses reaches at least 3 amps r.m.s when the load is 20 Ω

.

14. A generator according to claim 10, wherein the pulse repetition rate is less than 1 Hz.

15. A generator according to claim 14, wherein the pulsing circuit and the r.f. source are arranged to generate a succession of treatment pulses of r.f. energy at the output terminals, the periods between successive such pulses being Is or longer.

16. A generator according to claim 10, wherein the pulsing circuit and the r.f. source are arranged to generate a succession of treatment pulses of r.f. energy at the output terminals, the periods between successive such pulses being 300 ms or longer.

17. A generator according to claim 10, arranged such that the peak voltage of the said r.f. signal remains below 200V peak when a resistive load is connected across the output terminals.

18. A generator according to claim 10, such that when any resistive load in the range of from 10 Ω

to 250 Ω

is connected to the output terminals, the r.f. energy delivered in each pulse is at least 2 J.

19. A generator according to claim 10, arranged such that the maximum value of the peak delivered power is delivered when the load resistance is less than 20 Ω

.

20. A generator according to claim 19, wherein the said maximum value of the peak delivered power is at least 200 W.

21. A generator according to claim 10, arranged such that the crest factor of the r.f. output voltage waveform during each pulse when delivering r.f. power is less than or equal to 1.5.

22. A generator according to claim 10, wherein the pulsing circuit is arranged automatically to adjust the mark-to-space ratio of the signal pulses in response to a sensing circuit associated with the output terminals.

23. A generator according to claim 22, wherein the sensing circuit is arranged to be responsive to an identification element housed in an instrument connected to the output terminals.

24. A generator according to claim 22, in which the sensing circuit is arranged to detect an initial value of a load impedance associated with the start of r.f. energy application.

25. A generator according to claim 24, wherein the pulsing circuit is arranged such that the pulse mark-to-space ratio increases with increasing sensed initial load impedance.

26. A generator according to claim 22, wherein the pulsing circuit is arranged to adjust the peak r.f. output power in response to the sensing circuit.

27. A generator according to claim 26, wherein the pulsing circuit is arranged to decrease the peak power with increasing sensed initial load impedance.

28. A generator according to claim 22, wherein the pulsing circuit is arranged to adjust the pulsing frequency in response to the sensing circuit.

29. A generator according to claim 28, wherein the pulsing circuit is arranged to increase the pulse frequency with increasing sensed initial load impedance.

30. A generator according to claim 10, wherein the pulsing circuit and the source are so arranged that the r.f. power signal comprises, during an initial period, the said succession of pulses having the said 100 ms periods between successive pulses and the said predetermined mark-to-space ratio and, during a subsequent period, a signal of a different characteristic.

31. A generator according to claim 30, including control circuitry with means for monitoring at least one electrical parameter associated with the output terminals, the control circuitry being arranged such that the transition from the initial period to the subsequent period is controlled in response to the at least one monitored parameter.

32. A generator according to claim 31, wherein the monitored parameter is one of the power delivered into a resistive load, the resistance of the load, and the voltage across the output terminals.

33. A generator according to claim 30, arranged to cause the r.f. power signal, during the subsequent period, to provide continuous energy delivery or more nearly continuous energy delivery than during the initial period.

34. A generator according to claim 30, arranged to cause the source to deliver the r.f. power signal as an amplitude-modulated signal which, during at least part of the subsequent period, has a second predetermined pulse duty cycle which is greater than the initial pulse duty cycle.

35. A generator according to claim 30, arranged such that the source delivers an r.f. power signal which has a peak power during the subsequent period which is lower than the peak power in the subsequent period.

36. A generator according to claim 34, wherein the pulse duty cycle is fixed at a first predetermined pulse duty cycle during the initial period and at a second, greater predetermined pulse duty cycle during the subsequent period, and wherein the subsequent period follows the initial period directly.

37. A generator according to claim 30, arranged to cause the source to deliver the r.f. power signal as a continuous r.f. signal during the said subsequent period.

39. A generator according to claim 38, wherein the control circuitry is arranged to cause the r.f. power signal to provide, during the subsequent period, continuous energy delivery or more nearly continuous energy delivery than during the initial period.

40. A generator according to claim 38, wherein the control circuitry is arranged to cause the source to deliver the r.f. power signal as an amplitude-modulated signal which, during at least part of the subsequent period, has a second predetermined pulse duty cycle which is greater than the initial pulse duty cycle.

41. A generator according to claim 40, wherein the control circuitry is arranged such that the source delivers an r.f. power signal which has a peak power during the subsequent period which is lower than the peak power in the subsequent period.

42. A generator according to claim 40, wherein the control circuitry is arranged such that the pulse duty cycle is fixed at a first predetermined pulse duty cycle during the initial period and at a second greater predetermined pulse duty cycle during the subsequent period, and wherein the subsequent period follows the initial period directly.

43. A generator according to claim 38, wherein the control circuitry is arranged to cause the source to deliver the r.f. power signal as a continuous r.f. signal during the said subsequent period.

44. A generator according to claim 43, wherein the control circuitry is arranged such that the pulse duty cycle is fixed at a predetermined value during the said initial period and such that the subsequent period follows the initial period directly.

45. A generator according to claim 38, wherein the control circuitry is arranged such that the pulse duty cycle of the r.f. power signal increases in more than one step.

46. A generator according to any of claim 38, wherein the control circuitry is arranged such that the pulse duty cycle of the said succession of pulses increases progressively.

47. A generator according to any of claim 38, wherein the at least one parameter is representative of the energy being delivered into a resistive load.

48. A generator according to claim 38, wherein the at least one parameter is the resistance of the load.

53. An integrated electrosurgical generator and instrument system, wherein the generator is as claimed in claim 38 and the instrument comprises a pair of forceps.

54. A system according to claim 53, wherein the generator is arranged so as to be capable of delivering a peak power of at least 100 W into a resistive electrical load in the range from 20 Ω

to 250 Ω

.

38. An electrosurgical generator comprising a source of radio frequency (r.f.) energy, at least a pair of output terminals for connection to a bipolar electrosurgical instrument and for delivering r.f. energy to the instrument, a pulsing circuit for the source, and control circuitry including means for monitoring at least one electrical parameter associated with the output terminals, wherein the arrangement of the control circuitry, the pulsing circuit and the source is such that, with the output terminals connected to a resistive load, the control circuitry causes the source to deliver into the load an amplitude-modulated r.f. power signal which, at least in an initial period, is a succession of pulses with a predetermined initial pulse duty cycle and, in a subsequent period, has a different characteristic, the transition from the initial period to the subsequent period being controlled by the control circuitry in response to the at least one monitored parameter.

49. A method of electrosurgically coagulating tissue between the electrodes of a bipolar electrosurgical instrument, in which radio frequency (r.f.) energy is applied to the tissue via the electrodes in a succession of pulse bursts with a duty cycle of 40% or less, wherein the instantaneous r.f. current at the start of each successive burst is higher than the instantaneous r.f. current at the end of the previous burst.

50. An electrosurgical system comprising an electrosurgical generator and a bipolar electrosurgical instrument coupled to an output of the generator, the generator being such as to provide a succession of controlled bursts of electrosurgical energy to the instrument at a predetermined pulse mark-to-space ratio, wherein each burst has a sufficiently high power to form at least one vapour bubble within tissue being treated by the instrument, and the time duration between successive bursts is sufficiently long to permit recondensation of the or each vapour bubble, the peak delivered power being between the bursts being substantially zero.

51. A system according to claim 50, wherein the time duration is at least 100 ms.

58. A method of electrosurgically coagulating tissue between the electrodes of a bipolar electrosurgical instrument, in which a succession of controlled bursts of r.f. energy are applied across the electrodes at a predetermined mark-to-space ratio, each burst being of sufficiently high power to form vapour bubbles within the tissue, and the time duration between successive bursts is sufficiently long to permit condensation of the bubbles.