Electrosurgery system

• US 6,398,781 B1
• Filed: 03/06/2000
• Issued: 06/04/2002
• Est. Priority Date: 03/05/1999
• Status: Expired due to Fees

• Current Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Original Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Inventors: Goble, Colin C. O., Goble, Nigel M, Amoah, Francis E
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): RUDDY, DAVID M
• Application Number:
  US09/519,469
• Time in Patent Office: 820 Days
• Field of Search: 606/29, 606/32-34, 606/38, 606/39-42, 606/48, 606/50, 607/101-102, 607/97-99, 607/154-156
• US Class Current: 606/41
• 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 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00601 Cutting
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/1213 creating an arc

Abstract

An electrosurgery system has an electrosurgical generator operable to generate electrosurgical power at a frequency in the UHF band (typically 2.45 GHz), a feed structure, and an electrode assembly for delivering the electrosurgical power to tissue to be cut. The electrode assembly has an elongate active electrode which, at the operating frequency, is λ/8 in length (λ being the wavelength in air) and has an active surface area of less than 30 square millimeters. A return electrode set back proximally from the active electrode is arranged so as to be capacitively coupled to tissue adjacent the active electrode and is isolated from the feed structure in respect of unbalanced currents. Tissue cutting occurs due to thermal dissipation of UHF power in the tissue substantially without arcing, resulting from the lossy dielectric behavior of the tissue.

Claims

1. An electrosurgery system that cuts tissue comprising an electrosurgical generator, a feed structure and an electrode assembly, the electrode assembly comprising at least an exposed active electrode and a return electrode which are coupled to the generator via the feed structure, wherein the generator and the feed structure are capable of delivering radio frequency (r.f) power to the active electrode at a UHF operating frequency of at least 1 GHz, the active electrode comprises an elongate electrically conductive member which is less than λ

/8 in length and cuts the tissue by direct electrical contact between the active electrode and the tissue, where λ

is the wavelength in air of the delivered power at the operating frequency, and the surface area of the active electrode is less than 30 square millimeters.

2. A system according to claim 1, wherein the return electrode is located adjacent the active electrode so as to be capacitively coupled in use of the system to tissue adjacent the active electrode.

3. A system according to claim 2, wherein the active electrode has a proximal end attached to the feed structure, and a free distal end, and wherein the return electrode forms part of the electrode assembly and comprises a conductive lamina located laterally of the active electrode and set back from the distal end of the active electrode.

4. A system according to claim 2, wherein the feed structure comprises the coaxial combination of an inner supply conductor and an outer supply conductor, the active electrode is coupled to the inner conductor, and the return electrode is coupled to the outer supply conductor, such that the feed structure has an open-circuit end.

5. A system according to claim 2, wherein the isolating means isolates the return electrode from the feed structure in respect of unbalanced currents.

6. A system according to claim 5, wherein said isolating means comprises a open-ended quarter-wave conductor.

7. A system according to claim 6, wherein said return electrode is in the form of a conductive sleeve.

8. A system according to claim 4, including a balun associated with said outer conductor.

9. A system according to any of claim 2, wherein the return electrode is of annular cross-section and coaxial with the active electrode, such that the assembly comprises an open-circuit coaxial structure.

10. A system according to claim 1, wherein the operating frequency is in the region of 2.45 GHz.

11. A system according to claim 10, wherein the active electrode has a length in the region of 4 mm and a diameter equal to or less than 1 mm.

12. A system according to claim 1, wherein the generator and feed structure are capable of delivering to the active electrode sufficient power at UHF to yield a power density of at least 5 W/mm².

13. A system according to claim 1, wherein the generator and feed structure are capable of delivering between 13 and 125 W of UHF power to the active electrode.

14. A system according to claim 1, wherein the surface area of the active electrode is at least 1.5 square millimeters.

15. A system according to claim 1, wherein the return electrode is of elongate construction and has a length less than or equal to λ

/4.

16. A method of electrosurgically cutting tissue comprising applying to the tissue an electrode assembly having an exposed active electrode electrically coupled to a radio frequency (r.f.) source, and activating the source to feed UHF energy at an operating frequency of at least one GHz to the electrode at a voltage level sufficient to cause cell rupture within the tissue due to dielectric heating of the tissue by direct electrical contact between the active electrode and the tissue without arcing at the exposed electrode.

17. A method according to claim 16, including providing a capacitive return path from the tissue for UHF current.

18. A method according to claim 17, wherein the capacitive return path is provided by a return electrode adjacent said active electrode and arranging for the return electrode to be located adjacent but spaced from the tissue, the return electrode being coupled to said r.f. source.

19. A method according to claim 16, including providing said electrode assembly as an open-circuit coaxial structure, said active electrodes being formed as a projecting end portion of an inner conductor of said structure.

20. A method according to claim 16, including inserting a major part of said projecting portion into the tissue to be treated.

21. A method according to claim 20, including inserting said projecting portion to a depth of at least λ

_s/8 where λ

_s is the wavelength of the supplied UHF energy in said tissue.

22. A method according to claim 16, wherein the active electrode constitutes an at least approximate quarter wave transformer when inserted in the tissue to be treated.

23. A method according to claim 16, wherein the UHF power density at the active electrode when the source is activated is at least 5 W/mm².

24. A method according to claim 16, wherein the delivered UHF power is in the range of from 13 W to 125 W.

25. A method according to claim 16, wherein the tissue being electrosurgically cut is neurological tissue.

26. A method according to claim 16, wherein the tissue to which the electrode assembly is applied is in the region of the spine.

27. A method according to claim 16, wherein the tissue being electrosurgically cut is fatty tissue.

28. An electrosurgical instrument for cutting at a UHF operating frequency, wherein the instrument comprises a feed structure and an electrode assembly coupled to receive radio frequency (r.f.) power from the feed structure, and wherein:

the feed structure comprises a coaxial line having an inner supply conductor and an outer supply conductor,

the electrode assembly comprises an active electrode in the form of an exposed elongate electrically conductive member which is coupled to the said inner conductor, is less than λ

/8 in length, where λ

is the wavelength (in air) corresponding to the operating frequency and has a surface area no greater than 30 square millimeters, and a return electrode coupled to the outer supply conductor and located so as to be adjacent the active electrode and set back from the distal end of the active electrode, whereby the feed structure and electrode assembly together constitute an open-circuit coaxial line, and

means isolating the electrode assembly from at least a part of the outer supply conductor in respect of unbalanced currents at said operating frequency.

29. An instrument according to claim 28, wherein the active electrode is an exposed rod having a length in the region of 4 mm and a diameter less than 1 mm.

30. An instrument according to claim 29, comprising a handpiece and an elongate instrument shaft comprising a rigid or resilient coaxial feeder forming at least part of the said coaxial line, the shaft having a proximal end secured in the handpiece and a distal end mounting the electrode assembly, wherein the active electrode rod extends directly from an end of the coaxial line.

31. An instrument according to claim 28, wherein the surface are of the active electrode is at least 1.5 square millimeters.

32. An instrument according to 28, wherein the return electrode comprises an elongate member having a length less than or equal to λ

/4.

33. A method of electrosurgically cutting tissue comprising:

providing an electrosurgical generator, a feed structure and an electrode assembly, the generator having a UHF operating frequency and the electrode assembly including an exposed active electrode which is coupled to the generator via the feed structure and which comprises an elongate electrically conductive member of a length less than λ

/8, where λ

is the wavelength in air corresponding to said operating frequency,

applying the electrode assembly to the tissue, and

activating the generator to deliver energy at said UHF operating frequency via the feed structure at a voltage level sufficient to cause cell rupture within the tissue due to dielectric heating of the tissue without arcing at the exposed electrode, whereby the tissue is cut due to said cell rupture.