Claims
- 1. An electrosurgery system for electrosurgically cutting or vaporising living tissue, comprising an electrosurgical generator and an electrode assembly having at least one treatment electrode and an adjacent return electrode, wherein the generator and the assembly are arranged to deliver to the treatment and return electrodes radio frequency (r.f.) energy simultaneously at at least two frequencies, one of which is in a lower frequency range of from 50 kHz to 50 MHz and the other of which is greater than 300 MHz, the r.f. current delivered in the lower frequency range being limited such that the current-to-frequency ratio of energy delivered in the lower frequency range remains below a value of 17 mA r.m.s. per 100 kHz.
- 2. A system according to claim 1, arranged to deliver the said r.f. energy to the electrode assembly at both of the two frequencies along a single feeder between the generator and the electrodes.
- 3. A system according to claim 1, comprising a generator unit having a pair of r.f. output terminals, an electrosurgical instrument which includes a handpiece, a shaft mounted in the handpiece and the electrode assembly located at a distal end of the shaft, and a feeder cable arranged to connect the generator unit output terminals to the handpiece, wherein the instrument includes a current limiting capacitor connected in series between the feeder cable and the treatment electrode for limiting the current at the lower frequency to the said current range.
- 4. A system according to claim 3, wherein the capacitor is located at the distal end of the shaft.
- 5. A system according to claim 4, wherein the shaft comprises at least a pair of supply conductors for delivering the r.f. energy to the electrode assembly, and wherein the capacitor is formed as the coaxial combination of an elongate inner conductor, a tubular heat-resistant dielectric tube around the inner conductor, and a tubular outer conductor around the dielectric tube, one of the said inner and outer conductors of the combination being connected to one of the supply conductors of the shaft and the other being connected to the treatment electrode.
- 6. A system according to claim 5, wherein the treatment electrode is monolithically integral with the capacitor inner conductor.
- 7. A system according to claim 3, wherein the capacitor has a value of 5 pF or less.
- 8. A system according to claim 3, wherein the capacitor is located in the handpiece and has a value in the range of from 20 pF to 100 pF.
- 9. A system according to claim 1, comprising a generator unit having a pair of output terminals, an electrosurgical instrument which includes a handpiece, a shaft mounted in the handpiece, and the electrode assembly located at the distal end of the shaft, and a feeder cable arranged to connect the generator unit output terminals to the handpiece, wherein the system includes a low frequency source to generate r.f. energy in the said lower frequency range, and a current limiting impedance coupled in series between the low frequency source and the feeder cable.
- 10. A system according to claim 9, wherein the current limiting impedance is a capacitor the value of the which is in the range of from 300 pF to 1 nF.
- 11. A system according to claim 1, including a balun associated with the electrode assembly, the balun being configured to operate at the said frequency greater than 300 MHz.
- 12. A system according to claim 1, having a handheld electrosurgical instrument which includes an elongate shaft mounted in the handpiece, and the electrode assembly located at a distal end of the shaft wherein:
the shaft comprises at least a pair of supply conductors forming a coaxial feeder structure for delivering electrosurgical r.f. energy from the generator to the electrode assembly; the treatment electrode is electrically coupled to an inner supply conductor of the shaft; the return electrode is electrically coupled to an outer supply conductor of the shaft and is set back from the treatment electrode; the shaft carries a balun adjacent the electrode assembly, the balun being electrically coupled to the outer supply conductor; and the shaft, the return electrode and the balun are covered in an insulative material.
- 13. A system according to claim 12, wherein the electrode assembly includes a current limiting capacitor in series between the inner supply conductor and the treatment electrode for limiting the current supplied to the electrodes at the lower frequency such that the said ratio remains within the said range.
- 14. A system according to claim 1, wherein the source impedance at the treatment electrode at an operating frequency in the lower frequency range is greater than 100 kilohm.
- 15. A system according to claim 1, wherein the current at an operating frequency in the lower frequency range is limited by means for increasing the source impedance at that frequency.
- 16. A system according to claim 15, wherein the current limiting means comprises a capacitance in series with the treatment electrode.
- 17. A system according to claim 16, wherein the current limiting means comprises a resonant impedance converter associated with an output of the generator.
- 18. A system according to claim 17, wherein the impedance converter comprises a parallel resonant circuit.
- 19. A system according to claim 17, including a coaxial feeder between the generator output and the electrode assembly, and wherein the impedance converter comprises an inductance associated with the generator output which resonates with the capacitance of the feeder at the operating frequency in the lower frequency range.
- 20. A system according to claim 19, wherein the generator is arranged such that the r.f. energy in the lower frequency range is pulse modulated.
- 21. A system according to claim 20, wherein the pulse duty cycle is at least 10%.
- 22. A system according to claim 1, arranged such that the peak voltage in the lower frequency range when in a cutting/vaporisation mode is in excess of 500 V.
- 23. A system according to claim 1, wherein the energy in the said lower frequency range is delivered at a frequency of 100 kHz or higher.
- 24. A system according to claim 1, wherein the energy in the said lower frequency range is delivered at a frequency of 5 MHz or below.
- 25. A system according to any preceding claim, wherein the r.f. current delivered in the lower frequency range remains below 50 mA r.m.s.
- 26. A method of operating an electrosurgical tissue cutting or vaporising system using an electrosurgical instrument having an active electrode and an adjacent return electrode, wherein the method comprises supplying to the electrodes radio frequency energy simultaneously at at least two frequencies, one of which is in a lower frequency range of 50 kHz to 50 MHz and the other of which is greater than 300 MHz, the current in the lower frequency range whilst the instrument is set to operate in a tissue cutting or vaporising mode being such that the current-to-frequency ratio of energy delivered in the lower frequency range remains below a value of 17 mA r.m.s. per 100 kHz.
- 27. A method according to claim 26, including maintaining the current-to-frequency ratio below the said value by driving the active electrode from a source impedance which is between 100 kilohm and 500 kilohm at the operating frequency in the lower frequency range.
- 28. A method according to claim 26, wherein the tissue cutting or vaporising mode is characterised by a peak voltage in the lower frequency range between 500 V and 2000 V.
- 29. A method of electrosurgically treating tissue using an electrosurgical instrument having an active electrode and an adjacent return electrode, comprising successively (a) cutting or vaporising tissue, and (b) coagulating tissue, wherein both steps (a) and (b) are performed by delivering radio frequency energy to the electrodes at a frequency greater than 300 MHz, and wherein step (a) is characterised by simultaneously supplying r.f. energy at a frequency within a lower frequency range of from 50 kHz to 50 MHz, the r.m.s. current in the lower frequency range being limited to a value such that the current-to-frequency ratio of energy delivered in the lower frequency range remains below 17 mA r.m.s. per 100 kHz.
- 30. A method according to claim 29, wherein the r.f. energy delivered in the lower frequency range is pulsed, and the current-to-frequency ratio of energy delivered within each r.f. pulse burst in the lower frequency range remains below the said current-to-frequency ratio value.
- 31. A system according to claim 30, wherein the r.f. current in the lower frequency range during the pulse bursts remains below 50 mA r.m.s.
- 32. A method of electrosurgically cutting or vaporising tissue using an electrosurgery system which comprises an electrosurgical generator and an electrode assembly having at least a treatment electrode and an adjacent return electrode, wherein the method comprises bringing the treatment electrode to a position on or adjacent the tissue to be cut or vaporised, applying to the electrodes a first radio frequency (r.f.) signal component at at least one frequency in the range of from 50 kHz to 50 MHz to establish an arc between the treatment electrode and the tissue, and simultaneously applying to the electrodes a second r.f. signal component at at least one second frequency which is greater than 300 MHz to cause a current at the second frequency to flow along the arc established by the first r.f. signal component, the level of the average current above 300 MHz being at least on order of magnitude greater than the average current in the frequency range of from 50 kHz to 50 MHz during a cutting or vaponsation operation.
- 33. A method according to claim 32, wherein the average current in the frequency range of from 50 kHz to 50 MHz is small enough to have no clinical effect or negligible clinical effect on the patient in the absence of the second r.f. signal component.
- 34. An electrosurgery system comprising an electrosurgical generator, a feed structure and an electrode assembly, the electrode assembly having at least one active electrode and at least one adjacent return electrode, each of which is coupled to the generator via the feed structure, wherein the generator and feed structure are capable of delivering radio frequency (r.f.) power to the active and return electrodes in lower and upper frequency ranges simultaneously, and wherein the lower frequency range is below 100 MHz and the upper frequency range is above 300 MHz.
- 35. A system according to claim 34, wherein the return electrode is an element which is resonant at an operating frequency in the upper frequency range.
- 36. A system according to claim 35, wherein the operating frequency is above 1 GHz.
- 37. A system according to claim 34, wherein the electrode assembly has associated therewith a sleeve balun operable at an operating frequency in the upper frequency range.
- 38. An electrosurgery system comprising an elecrosurgical generator and a handheld electrosurgical instrument, wherein the generator is capable of delivering to the instrument radio frequency power in lower and upper frequency ranges, the upper range containing frequencies at least three times the frequencies of the lower frequency range, wherein the instrument includes (a) an instrument shaft which comprises a coaxial feeder having an inner conductor and an outer conductor and (b) an electrode assembly at an end of the shaft, the assembly comprising a first electrode electrically coupled to the inner conductor and a second electrode in the form of a conductive sleeve set back from the first electrode and surrounding a portion of said outer conductor, and wherein the sleeve has an end portion which includes an electrical connection to said outer conductor, the remainder of the sleeve being spaced from said outer conductor.
- 39. A system according to claim 38, wherein the first electrode is capacitively coupled to said inner conductor.
- 40. A system according to claim 39, wherein the first electrode is coupled to said inner conductor by a capacitor which comprises an elongate coaxial assembly inside said feeder outer conductor.
- 41. A system according to claim 40, wherein the coaxial assembly comprises a solid dielectric tube containing an axial wire, the tube having an outer conductive layer.
- 42. A system according to claim 40, wherein the coaxial asembly comprises an axial rod and an insulative tube with an inner conductive layer, the rod supported coaxially within the tube and spaced from the inner layer.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9905210.2 |
Mar 1999 |
GB |
|
RELATED APPLICATION
[0001] This application is a continuation-in-part of application Ser. No. 09/517,639 filed Mar. 3, 2000.
Provisional Applications (2)
|
Number |
Date |
Country |
|
60229537 |
Sep 2000 |
US |
|
60141261 |
Jun 1999 |
US |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09517631 |
Mar 2000 |
US |
Child |
09945833 |
Sep 2001 |
US |