Minimal Device and Method for Effecting Hyperthermia Derived Anesthesia

• US 20080262490A1
• Filed: 03/06/2006
• Published: 10/23/2008
• Est. Priority Date: 03/04/2005
• Status: Active Grant

• Current Assignee: Intervention Technology Pty, Ltd.
• Original Assignee: Intervention Technology Pty, Ltd.
• Inventors: Williams, Donald V.
• Granted Patent: US 9,031,667 B2
• Time in Patent Office: Days
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1477 Needle-like probes
• CPC Class Codes: A61B 2018/00434 Neural system
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/143 multiple needles
• CPC Class Codes: A61N 1/06 for high-frequency therapy
• CPC Class Codes: A61N 1/36017 with leads or electrodes penetrating the skin
• CPC Class Codes: A61N 1/36021 for treatment of pain
• CPC Class Codes: A61N 1/403 for thermotherapy, e.g. hyperthermia

Abstract

A method and device for inducing anaesthesia in mammals by the application of RF energy to create hyperthermia derived neural anaesthesia. An RF generator drives a plurality of electrodes placed in tissue surrounding the target nerve fibre to desiccate the desired length of nerve fibre to be desiccated in a single deployment. The device allows high-speed selection/de-selection of bipolar electrode pairs or sets under continuous RF excitation. Activation of electrode pairs is adapted in response to sensed current density and temperature (by electrodes not in the current discharge activation phase) in order to create lesions of complex and well defined shape necessary for the production of hyperthermia derived neural anaesthesia.

Claims

1-28. -28. (canceled)

29. A device for supplying RF electrical power to biological tissue, comprising

(a) an RF generator device with a resonant output stage comprising a tank circuit inductively coupled to said RF generator device,

(b) a plurality of electrodes capable of being placed in biological tissue, and

(c) a selector mechanism operating a plurality of switches capable of connecting said electrodes dynamically across the outputs of said tank circuit in any possible combination,

wherein said biological tissue represents the damping of said resonant output stage.

30. The device of claim 29, wherein the resonant frequency of said resonant output stage is close to, but not identical to, the frequency of said RF generator device.

31. The device of claim 29, wherein the output power level of said RF generating device is self-regulating and relatively insensitive to changes in the impedance of the biological tissue between the electrodes.

32. The device of claim 29, wherein the output power level of said RF generating device is self-regulating and insensitive to changes that occur during dynamic switching of said selector mechanism.

33. The device of claim 29, wherein the orientation and degree of insertion of a portion of said electrodes defines a volume, and said volume is bounded by further electrodes excluding other tissue from hyperthermic effects.

34. The device of claim 29, further comprising current measuring means whereby the impedance between a selected pair of said electrodes can be sensed.

35. The device of claim 34, wherein said electrodes are activated only momentarily for the purpose of sampling current distribution and impedance.

36. The device of claim 29, further comprising a plurality of temperature sensing means for measuring temperature in said biological tissue.

37. The device of claim 29, wherein said electrodes are provided with thermal detectors.

38. A method for inducing desiccation of elongate nerve tissue in mammalian tissue by producing a thermal lesion, comprising

(a) inserting a plurality of electrodes into mammalian tissue containing elongate nerve tissue,

(b) selecting the orientation and degree of insertion of said electrodes to define a volume containing at least a substantial portion of said elongate nerve tissue, and

(c) applying a controlled distribution of RF current between pairs or sets of said electrodes to heat said volume to the extent of effective desiccation,

wherein said electrodes are connected to an RF generator device with a resonant output stage comprising a tank circuit inductively coupled to said RF generator device, and a selector mechanism operating a plurality of switches capable of connecting said electrodes dynamically across the outputs of said tank circuit in any possible combination, and

wherein said biological tissue represents the damping of said resonant output stage.

39. The method of claim 38, wherein said elongate nerve tissue is sufficiently desiccated to produce an anesthetic effect.

40. The method of claim 38, further comprising measuring the distribution of changing impedances in said mammalian tissue by sensing current during momentary activation of selected electrodes.

41. The method of claim 40, wherein the electrodes activated momentarily are not the same as those used for heating.

42. The method of claim 40, wherein selected electrodes are activated alternately with (1) power and duration sufficient for heating said volume, and (2) momentary activation sufficient for current sensing but not for heating.

43. The method of claim 40, wherein said measuring the distribution of changing impedances is used to represent the accumulation of coagulum around individual electrodes, and wherein a uniform distribution of coagulum between active discharge electrodes is created by adapting the activation of electrode patterns.

44. The method of claim 40, further comprising the steps of

(d) testing the perfusion of said thermal lesion by a method comprising the steps of

(i) waiting for a period of time longer than the RF discharge period to allow re-perfusion of electrolytes into said volume, and

(ii) measuring changes in tissue impedance;

and

(e) re-energizing said electrodes if significant measured changes in tissue impedance occur.

45. The method of claim 38, wherein the frequency of said RF current is between about 100 kHz and 700 kHz.

46. The method of claim 45, wherein said frequency is approximately 500 kHz.

47. The method of claim 38, further comprising repeating steps (a)-(c) at intervals of from about 6 months to about 2 years.

48. The method of claim 38, wherein the volume containing at least a substantial portion of said elongate nerve tissue is bounded by electrodes excluding other tissue from hyperthermic effects.

49. The method of claim 38, wherein said electrodes are mounted in probes with hollow cannulas through which chemicals such as anesthetics or other therapeutic or ablative fluids can be injected.