Electrosurgery system and method

• US 6,228,081 B1
• Filed: 06/30/1999
• Issued: 05/08/2001
• Est. Priority Date: 05/21/1999
• Status: Expired

• Current Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Original Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Inventors: Goble, Colin C. O.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US09/343,542
• Time in Patent Office: 678 Days
• Field of Search: 606/32-35, 606/37-42
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor

Abstract

An electrosurgical generator has output terminals for connection to active and return electrodes respectively of an electrosurgical instrument and, connected to the output terminals via at least one isolation capacitor, a radio frequency (r.f.) source which may be pulsed by a pulsing circuit. To permit tissue removal at a high rate, the source and the pulsing circuit are arranged so as to generate a pulsed r.f. output signal having a peak-to-peak voltage of at least 1250V, a mark-to-space ratio not more than 1:1, and a pulse length not more than 100 μs.

Claims

1. An electrosurgical generator comprising a source of radio frequency (r.f.) energy, an active output terminal, a return output terminal, a d.c. isolation capacitance between the source and the active output terminal, and a pulsing circuit for the source, wherein the source and the pulsing circuit are arranged to generate a pulsed r.f. output signal at the output terminals, which signal has a peak-to-peak voltage of at least 1250V, a pulse mark-to-space ratio of no greater than 1:

1, and a pulse length of no greater than 100 μ

s.

2. A generator according to claim 1, wherein the pulse repetition rate is between 5 Hz and 15 kHz.

3. A generator according to claim 1, including a d.c. voltage detector connected between the active and return output terminals, and wherein the pulsing circuit forms part of a control circuit configured to control the r.f. energy delivered from the output terminals in response to a d.c. voltage detected by the detector.

4. A generator according to claim 3, wherein the control circuit and the detector are operable to control the delivered r.f. energy so as to limit the d.c. voltage.

5. An electrosurgical generator comprising a source of r.f. energy, a pair of output terminals coupled to the source, and a pulsing circuit for the source, wherein the pulsing circuit and the source are arranged, in a pulsed mode of operation, to deliver to the output terminals a peak current of at least 3 A into a 50 ohm load and a peak-to-peak voltage of at least 1250V into 1 kilohm load.

6. A generator according to claim 5, wherein the pulse repetition rate in the pulsed mode being less than 12 kHz, and wherein the generator is capable of delivering a peak power of at least 200 W in the pulsed mode.

7. An electrosurgery system comprising a generator having a source of radio frequency (r.f.) energy and, coupled to the generator, an bipolar electrosurgical instrument having an electrode assembly with at least a pair of electrodes for operating in a wet field, wherein the generator is adapted to deliver r.f. energy to the electrode assembly as a pulse modulated r.f. signal which, in use with the pair of electrodes immersed in liquid has a peak current of at least 3 A and a peak-to-peak voltage of at least 1250V.

8. A system according to claim 7, wherein the ratio of peak power to average power is greater than 4:

1.

9. A system according to claim 8, wherein the ratio of peak power of average power is greater than 20:

1.

10. A system according to claim 7, wherein the generator is capable of delivering a peak power of 200 W in a pulsed made of operation, the ratio of peak power is average power being at least 4:

1.

11. An electrosurgery system comprising a generator including a source of radio frequency (r.f.) energy and, coupled to the generator, an electrosurgical instrument having a treatment electrode, wherein the system includes an electrode temperature sensing arrangement and the generator is adapted to supply the r.f. energy to the electrode as a pulse modulated r.f. signal, the mark-to-space ratio of the modulation being dynamically variable in response to a temperature signal from the temperature sensing arrangement representative of the electrode temperature.

12. A system according to claim 11, wherein r.f. energy is delivered to the electrode as a pulsed signal having a pulse repetition rate between 5 Hz and 2 kHz and with a peak-to-peak voltage value of at least 1250V.

13. A system according to claim 12, wherein the generator includes a pulse modulator arranged to modulate the r.f. energy so as to produce a pulsed signal having alternate ‘

off’ and

‘

on’

periods during which the peak-to-peak output voltage of the generator us substantially zero and at least 1250V respectively, the duration of the ‘

on’

periods being controlled in response to the temperature signal reaching a predetermined threshold value.

14. A system according to claim 11, wherein the temperature sensing arrangement has a response time which is less than the modulation period.

15. A system according to claim 11, wherein the temperature sensing arrangement is responsive to thermionic emission from the electrode.

16. A system according to claim 15, wherein the temperate sensing arrangement includes a d.c. voltage detector arranged to detect a d.c. offset on the treatment electrode.

17. A system according to claim 16, wherein the temperature sensing arrangement and the pulse modulator are adapted to control the modulation of the generator output signal so as to limit the d.c. offset to a predetermined d.c. voltage level.

18. A system according to claim 17, wherein the predetermined d.c. voltage level is in the region of from 50V to 100V.

19. A system according to claim 11, wherein the mark-to-space ratio is 1:

1 or less during at least the majority of the time the generator is activated.

20. A system according to claim 19, wherein the peak-to-peak output voltage is greater than or equal to 1500V.

21. A method of operating an electrosurgery system including an electrosurgical r.f. generator and an electrode assembly having a treatment electrode coupled to the generator, wherein the method comprises applying to the electrode a pulse modulated r.f. signal produced by the generator, generating a temperature signal indicative of the temperature of the electrode, and dynamically varying at least the mark-to-space ratio of the pulse modulation of the r.f. signal in order to control the temperature of the electrode.

22. A method according to claim 21, wherein the pulse repetition rate of the r.f. signal is between 5 Hz and 2 kHz with a peak-to-peak voltage of at least 1250V.

23. A method according to claim 22, wherein the pulsed signal has alternate ‘

on’ and

‘

off’

periods during which the peak-to-peak output voltage of the generator is substantially zero and at last 1250V respectively, the duration of the ‘

on’

periods being controlled in response to the temperature signal reaching a predetermined threshold value.

24. A method according to claim 21, wherein the temperature signal is responsive to changes in electrode temperature occurring within one pulse cycle.

25. A method according to claim 21, including detecting a d.c. offset voltage on the treatment electrode due to thermionic emission from the electrode and generating the temperature signal as a function of the offset voltage.

26. A method according to claim 21, wherein the mark-to-space ratio of the pulse modulation is 1:

1 or less during at least the majority of the time the r.f. signal is applied to the electrode.

27. A method of performing electrosurgical tissue cutting or ablation in which r.f. energy is applied to an electrosurgical instrument so as to promote arcing at a treatment electrode of the instrument, wherein the energy is applied as a pulsed r.f. signal having a peak-to-peak voltage of at least 1250V, a pulse mark-to-space ratio of no greater than 1:

1 and a pulse length of no greater than 100 μ

s.

28. A method according to claim 27, wherein the mark-to-space ratio is dynamically regulated to maximise the temperature of the electrode without substantial electrode burning.

29. A method according to claim 27, wherein the electrosurgical instrument has an electrode assembly with at least two electrodes, including an active electrode and a return electrode, wherein the tissue cutting or ablation is performed in the presence of a conducting liquid supplied to the site of the operation such that electrosurgical currents pass from the active electrode to the return electrode through said liquid, and wherein application of the pulsed r.f. signal causes a layer of vapour to form and collapse repeatedly at the active electrode, the layer being formed when the pulsed signal is ‘

on’ and

collapsing when the said signal is ‘

off’

.

30. A method according to claim 27, wherein the peak current is at least 3 A.