Method and apparatus for plasma-mediated thermo-electrical ablation

• US 20070239156A1
• Filed: 03/22/2007
• Published: 10/11/2007
• Est. Priority Date: 05/03/2002
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Vankov, Alexander, Palanker, Daniel
• Granted Patent: US 7,789,879 B2
• Time in Patent Office: Days
• US Class Current: 606/42
• CPC Class Codes: A61B 18/042 using additional gas becoming plasma
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00601 Cutting
• CPC Class Codes: A61B 2018/00625 Vaporization
• CPC Class Codes: A61B 2018/1213 creating an arc
• CPC Class Codes: A61B 2018/122 ionizing, with corona
• CPC Class Codes: A61B 2018/1472 for use with liquid electrolyte, e.g. virtual electrodes
• CPC Class Codes: H05H 1/48 using an arc H05H1/26 takes precedence
• CPC Class Codes: H05H 2245/32 Surgery, e.g. scalpels, blades or bistoury; Treatments inside the body

Abstract

An apparatus and method for cutting a material including conducting and non-conducting materials such as biological tissue, cellulose or plastic while the material is submerged in a conductive liquid medium. The apparatus has a cutting electrode with an elongate cutting portion having an aspect ratio (length to width) of 1 or more and a return electrode. The two electrodes are immersed in the conductive medium and a voltage is applied between them to heat the medium, thus producing a vapor cavity around the elongate cutting portion and ionizing a gas inside the vapor cavity to produce a plasma. The voltage applied between the electrodes is modulated in pulses having a modulation format selected to minimize the size of the vapor cavity, its rate of formation and heat diffusion into the material while the latter is cut with an edge of the elongate cutting portion. The modulation format includes pulses ranging in duration from 10 μs to 10 ms, as well as minipulses and micropulses, as necessary. The apparatus and method of invention allow the user to perform efficient thermal ablation and electrosurgical procedures in particular at power levels as low as 10 mW with minimal thermal and cavitation damage.

Claims

1. (canceled)

2-34. -34. (canceled)

35. A system for plasma-mediated thermo-electrical ablation comprising:

a cutting electrode having an elongate cutting portion having a length that is greater than a width, wherein the width is less than 250 μ

m;

a return electrode; and

a voltage control unit configured to provide a plurality of voltage pulses to the cutting electrode, wherein the voltage control unit comprises

a voltage source and

a pulse control, wherein the pulse control is configured to control the modulation format of the voltage applied to the cutting electrode from the voltage source, so that the voltage applied comprises a plurality of pulses separated by a pulse interval of greater than 1 ms, wherein each pulse comprises a plurality of minipulses having a duration of between about 0.1 μ

sec and 10 μ

sec and a duration between minipulses of between about 0.1 μ

sec and 10 μ

sec.

36. The system of claim 35, wherein the voltage control unit is further configured so that the plurality of pulses applied comprise minipulses of alternating positive and negative polarities.

37. The system of claim 35, wherein the voltage control unit is further configured so that the plurality of pulses applied comprise minipulses wherein the peak power of the minipulses vary.

38. The system of claim 35, wherein the voltage control unit is further configured so that the plurality of pulses applied comprise minipulses wherein the duration of each minipulse is less than about 5 μ

sec.

39. The system of claim 35, further comprising a charge transfer prevention device.

40. The system of claim 39, wherein the charge transfer prevention device comprises a circuit with a separating capacitor.

41. The system of claim 35, further comprising a low impedance line electrically connecting the voltage control unit to the cutting electrode.

42. The system of claim 35, further comprising a ballast resistor electrically connected between the cutting electrode and the voltage control unit.

43. The system of claim 35, wherein said elongate cutting portion has a width between about 1 μ

m and about 100 μ

m.

44. The system of claim 35, wherein said elongate cutting portion has a circular cross section.

45. The system of claim 35, wherein said elongate cutting portion has at least one bend.

46. The system of claim 35, wherein said elongate cutting portion forms a loop.

47. The system of claim 35, wherein said cutting electrode comprises a wire electrode.

48. The system of claim 35, further comprising a ballast resistor electrically connected between the cutting electrode and the voltage control unit.

49. The system of claim 35, wherein the elongate cutting portion has a diameter between about 10 microns and about 200 microns and extends from an insulator by about 20 microns to about 1 mm, and wherein said insulator has a diameter between about 0.1 mm and about 1 mm, and wherein the elongate cutting portion has a bent tip, whereby said elongate cutting portion is suitable for capsulotomy.

50. The system of claim 35, wherein the ratio of the length to width of the cutting portion is larger than five.

51. The system of claim 35, wherein the pulse control comprises a peak power control and a duration control configured to adjust pulse duration and pulse interval.

52. A system for plasma-mediated thermo-electrical ablation comprising:

a cutting electrode having an elongate cutting portion having a length that is greater than a width, wherein the width is less than 250 μ

m; and

a voltage control unit configured to provide the cutting electrode with a plurality of pulses that are separated by a pulse interval of greater than 1 ms, wherein each of the pulses comprises a plurality of minipulses that are separated by a minipulse interval;

wherein the voltage control unit comprises

a voltage source, and

a pulse control having a duration control configured to allow adjustment of the duration of the minipulses between about 0.1 μ

sec and 10 μ

sec, and further configured to allow adjustment of the pulse interval of the minipulses between about 0.1 and 10 μ

sec.

53. A system for plasma-mediated thermo-electrical ablation comprising:

a cutting electrode having an elongate cutting portion having a length that is at least five times greater than a width, wherein the width is less than 100 μ

m;

a return electrode; and

a voltage control unit configured to provide a plurality of pulses that are separated by a pulse interval of greater than 1 ms, wherein each pulse comprises a plurality of minipulses that are separated by a minipulse interval;

wherein the voltage control unit comprises

a voltage source, and

a pulse control configured to produce vaporization and ionization at the cutting portion of the cutting electrode during each pulse, and to terminate plasma discharge between the pulses.