Apparatus and methods for electrosurgical ablation and resection of target tissue

• US 20010025177A1
• Filed: 02/28/2001
• Published: 09/27/2001
• Est. Priority Date: 01/07/1992
• Status: Active Grant

• Current Assignee: ArthroCare Corporation (Smith & Nephew PLC)
• Original Assignee: ArthroCare Corporation (Smith & Nephew PLC)
• Inventors: Woloszko, Jean, Eggers, Philip E., Thapliyal, Hira V., Davison, Paul O.
• Granted Patent: US 7,429,262 B2
• Time in Patent Office: Days
• 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 18/1402 Probes for open surgery
• CPC Class Codes: A61B 18/148 having a short, rigid shaft for accessing the inner body transcutaneously, e.g. for neurosurgery or arthroscopy
• CPC Class Codes: A61B 18/1482 having a long rigid shaft for accessing the inner body transcutaneously in minimal invasive surgery, e.g. laparoscopy
• CPC Class Codes: A61B 18/1485 having a short rigid shaft for accessing the inner body through natural openings
• CPC Class Codes: A61B 18/149 bow shaped or with rotatable body at cantilever end, e.g. for resectoscopes, or coagulating rollers
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2017/00026 Conductivity or impedance, e.g. of tissue
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/00097 one of the thermometric elements being an electrode or the heating element
• CPC Class Codes: A61B 2017/00101 using an array of thermosensors
• CPC Class Codes: A61B 2017/00247 Making holes in the wall of the heart, e.g. laser Myocardial revascularization
• CPC Class Codes: A61B 2017/00292 mounted on or guided by flexible, e.g. catheter-like, means
• CPC Class Codes: A61B 2017/003 Steerable
• CPC Class Codes: A61B 2017/22001 Angioplasty, e.g. PCTA
• CPC Class Codes: A61B 2017/22038 with a guide wire
• CPC Class Codes: A61B 2018/00029 open
• CPC Class Codes: A61B 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00119 with metal oxide nitride
• CPC Class Codes: A61B 2018/0016 : Energy applicators arranged in a two- or three dimensional array
• CPC Class Codes: A61B 2018/00178 : Electrical connectors
• CPC Class Codes: A61B 2018/00196 : reciprocating lengthwise
• CPC Class Codes: A61B 2018/00327 : Ear, nose or throat
• CPC Class Codes: A61B 2018/00392 : Transmyocardial revascularisation
• CPC Class Codes: A61B 2018/00505 : Urinary tract
• CPC Class Codes: A61B 2018/00577 : Ablation
• CPC Class Codes: A61B 2018/00583 : Coblation, i.e. ablation using a cold plasma
• CPC Class Codes: A61B 2018/00642 : with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/0066 : without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/00678 : upper
• CPC Class Codes: A61B 2018/00702 : Power or energy
• CPC Class Codes: A61B 2018/00726 : Duty cycle
• CPC Class Codes: A61B 2018/00761 : Duration
• CPC Class Codes: A61B 2018/00791 : Temperature
• CPC Class Codes: A61B 2018/00797 : measured by multiple temperature sensors
• CPC Class Codes: A61B 2018/00821 : measured by a thermocouple
• CPC Class Codes: A61B 2018/00827 : Current
• CPC Class Codes: A61B 2018/00875 : Resistance or impedance
• CPC Class Codes: A61B 2018/00886 : Duration
• CPC Class Codes: A61B 2018/1213 : creating an arc
• CPC Class Codes: A61B 2018/124 : switching the output to different electrodes, e.g. sequentially
• CPC Class Codes: A61B 2018/1253 : monopolar
• CPC Class Codes: A61B 2018/126 : bipolar
• CPC Class Codes: A61B 2018/1273 : including multiple generators in one device
• CPC Class Codes: A61B 2018/1467 : using more than two electrodes on a single probe
• CPC Class Codes: A61B 2018/1472 : for use with liquid electrolyte, e.g. virtual electrodes
• CPC Class Codes: A61B 2018/1497 : Electrodes covering only part of the probe circumference
• CPC Class Codes: A61B 2018/162 : located on the probe body
• CPC Class Codes: A61B 2018/165 : Multiple indifferent electrodes
• CPC Class Codes: A61B 2090/378 : using ultrasound
• CPC Class Codes: A61B 2218/002 : Irrigation
• CPC Class Codes: A61F 2/2493 : Transmyocardial revascularisation [TMR] devices
• CPC Class Codes: A61M 25/0133 : Tip steering devices
• CPC Class Codes: A61M 25/0147 : with movable mechanical means, e.g. pull wires
• CPC Class Codes: A61M 25/0158 : with magnetic or electrical means, e.g. by using piezo materials, electroactive polymers, magnetic materials or by heating of shape memory materials

Abstract

An electrosurgical system and method for ablating, resecting, or cutting body structures, with minimal or no damage to tissue adjacent to the treatment site. The system includes an electrosurgical probe having a shaft with a shaft distal end bifurcated to provide first and second arms. First and second electrode supports are disposed on the first and second arms, respectively. At least one active electrode, in the form of a loop or partial loop, is arranged between the first and second electrode supports. A return electrode, also in the form of a loop or partial loop, is arranged between the first and second electrode supports distal to the active electrode. The active and return electrodes are configured to promote substantially high electric field intensities and associated high current densities between the active portion and the target site when a high frequency voltage is applied to the electrodes. These high current densities are sufficient to break down the tissue by processes including molecular dissociation of tissue components. In one embodiment, the high frequency voltage imparts energy to the target site to effect the vaporization and volumetric removal of a layer of tissue without causing substantial tissue damage beyond the layer of tissue ablated. In another embodiment, a fragment of target tissue is removed, with minimal or no damage to surrounding tissue, by a process including the molecular dissociation of tissue components, and the tissue fragment is retrieved for biopsy.

Claims

1. An electrosurgical probe, comprising:

a bifurcated shaft including a first arm and a second arm;

a first electrically insulating electrode support disposed on the first arm distal end, and a second electrically insulating electrode support disposed on the second arm distal end; and

an active electrode disposed between the first and second electrode supports.

2. The probe of

claim 1

, wherein the active electrode is arranged at a non-perpendicular angle with respect to the longitudinal axis of the probe.

3. The probe of

claim 1

, wherein the active electrode comprises a substantially U-shaped wire loop.

4. The probe of

claim 1

, wherein the active electrode is configured to promote high electric field intensities at a surface of the active electrode when a high frequency voltage is applied to the active electrode.

5. The probe of

claim 1

, wherein the active electrode is roughened or pointed in order to promote high current densities at a surface of the active electrode when a high frequency voltage is applied to the active electrode.

6. The probe of

claim 1

, further comprising a return electrode, wherein the return electrode is configured to promote low current densities at a surface of the return electrode.

7. The probe of

claim 6

, wherein the return electrode is located distal to the active electrode.

8. The probe of

claim 7

, wherein the active electrode and the return electrode each comprise a filament, and each filament is selected from the group consisting of substantially U-shaped, C-shaped, D-shaped, and V-shaped.

9. The probe of

claim 6

, wherein the active electrode lies in a first plane, and the first plane is non-perpendicular to the longitudinal axis of the probe.

10. The probe of

claim 9

, wherein the first plane is arranged at an angle in the range of from about 45°

to 85°

with respect to the longitudinal axis of the probe.

11. The probe of

claim 9

, wherein the return electrode lies in a second plane, and the second plane is substantially parallel to the first plane.

12. The probe of

claim 1

, wherein the shaft distal end is adapted for penetration into a target tissue or organ.

13. The probe of

claim 1

, wherein the shaft includes a first bend and a second bend.

14. An electrosurgical probe for treating a target tissue of a patient, comprising:

a probe proximal end and a probe distal end;

an elongate body including a first shaft, the first shaft located at the probe distal end, and the first shaft bifurcated to provide a first arm and a second arm;

a first electrically insulating electrode support disposed on the first arm distal end, and a second electrically insulating electrode support disposed on the second arm distal end;

an active electrode disposed between the first and second electrode supports; and

a return electrode disposed between the first and second electrode supports at a location distal to the active electrode.

15. The probe of

claim 14

, wherein the first and second electrode supports are disposed axially on the first and second arms, respectively.

16. The probe of

claim 14

, wherein the active electrode comprises an active electrode filament and active electrode first and second ends, the active electrode first and second ends coupled to the first and second electrode supports, respectively.

17. The probe of

claim 16

, wherein the active electrode filament is arcuate.

18. The probe of

claim 16

, wherein the active electrode filament is selected from the group consisting of substantially U-shaped, C-shaped, D-shaped, and V-shaped.

19. The probe of

claim 14

, wherein the return electrode comprises a return electrode filament and return electrode first and second ends, the return electrode first and second ends coupled to the first and second electrode supports, respectively.

20. The probe of

claim 19

, wherein the return electrode filament is selected from the group consisting of substantially U-shaped, C-shaped, D-shaped, and V-shaped.

21. The probe of

claim 14

, wherein the active electrode and the return electrode are separated by an electrode gap in the range of from about 0.010 to about 0.100 inches, and the electrode gap is substantially the same over the entire distance between the first and second electrode supports.

22. The probe of

claim 14

, wherein each of the first and second electrode supports includes a curved portion, the active electrode and the return electrode emanating from the curved portion.

23. The probe of

claim 22

, wherein each of the curved portions includes a proximal curved portion and a distal curved portion, the active electrode emanating from the proximal curved portion, and the return electrode emanating from the distal curved portion, and wherein the proximal curved portion is longer than the distal curved portion.

24. The probe of

claim 23

, wherein the return electrode includes a return electrode filament and the active electrode includes an active electrode filament, and the return electrode filament is longer than the active electrode filament.

25. The probe of

claim 16

, wherein the active electrode first and second ends lie in a first plane, and the return electrode first and second ends lie in a second plane, and the first and second planes are substantially parallel to each other.

26. The probe of

claim 14

, wherein the active electrode lies in a first plane, the return electrode lies in a second plane, and the first plane and the second plane are substantially parallel to each other.

27. The probe of

claim 26

, wherein the first plane is arranged at an angle in the range of from about 50°

to 80°

with respect to the longitudinal axis of the probe.

28. The probe of

claim 14

, wherein the active electrode and the return electrode are arranged at an angle in the range of from about 45°

to 85°

with respect to the longitudinal axis of the probe.

29. The probe of

claim 14

, wherein the active electrode and the return electrode are separated by an electrode gap in the range of from about 0.010 to about 0.100 inches.

30. The probe of

claim 14

, wherein the active electrode and the return electrode are separated by an electrode gap, and the electrode gap is substantially the same over the entire distance between the first and second electrode supports.

31. The probe of

claim 14

, wherein the first shaft includes a first bend and a second bend.

32. The probe of

claim 14

, wherein each of the first arm and the second arm includes a first bend and a second bend.

33. The probe of

claim 31

, wherein the first bend is at a first angle and the second bend is at a second angle, and the first and second angles are substantially the same.

34. The probe of

claim 33

, wherein the first angle is in the range of from about 10°

to 30°

.

35. The probe of

claim 31

, wherein the first bend is distal to a point of bifurcation of the first shaft, and the second bend is distal to the first bend.

36. The probe of

claim 14

, wherein the elongate body further includes a second shaft, the second shaft coupled axially to the first shaft proximal end.

37. The probe of

claim 36

, wherein the elongate body further includes a third shaft, the third shaft coupled axially to the second shaft proximal end.

38. The probe of

claim 37

, wherein the probe further includes a bipolar connector unit for independently coupling the active electrode and the return electrode to opposite poles of a high frequency power supply.

39. The probe of

claim 38

, wherein the bipolar connector unit is disposed on the third shaft.

40. The probe of

claim 37

, wherein the third shaft comprises a low friction polymer.

41. The probe of

claim 37

, wherein the third shaft comprises a material selected from the group consisting of polyethylene and polytetrafluoroethylene.

42. The probe of

claim 14

, further comprising an attachment unit for removably affixing the probe to a surgical instrument, the attachment unit disposed on the elongate body.

43. The probe of

claim 42

, wherein the surgical instrument is an endoscope.

44. The probe of

claim 43

, wherein the endoscope is a resectoscope.

45. The probe of

claim 42

, wherein the elongate body further includes a second shaft, and the attachment unit is disposed on the second shaft.

46. The probe of

claim 42

, wherein the attachment unit comprises a clamp, the clamp including a first wall, a second wall and a base, wherein the base partially encircles the elongate body.

47. The probe of

claim 14

, wherein each of the active electrode and the return electrode includes a filament, each filament comprising a metal wire.

48. The probe of

claim 14

, wherein the active electrode comprises a wire having a substantially rectangular cross-section, and having a width in the range of from about 0.005 to about 0.050 inches.

49. The probe of

claim 14

, wherein the active electrode comprises a wire having a substantially rectangular cross-section, and the long axis of the rectangle lies substantially parallel to the longitudinal axis of the probe.

50. The probe of

claim 14

, wherein the return electrode comprises a round wire having a diameter in the range of from about 0.005 to about 0.050 inches.

51. The probe of

claim 14

, wherein the active electrode and the return electrode comprise a metal selected from the group consisting of:

molybdenum, platinum, iridium, titanium, tantalum, tungsten, stainless steel, nickel, and their alloys.

52. The probe of

claim 51

, wherein the metal comprises an alloy selected from the group consisting of:

platinum/tungsten, platinum/iridium, and platinum/molybdenum.

53. The probe of

claim 14

, wherein the active electrode is coated with a material selected from the group consisting of:

chromium and titanium nitride.

54. The probe of

claim 14

, wherein the active electrode comprises a rectangular wire having a width in the range of from about 0.010 to 0.020 inches, and the return electrode comprises a round wire having a diameter in the range of from about 0.015 to 0.030 inches.

55. The probe of

claim 14

, wherein the active electrode is adapted for ablating the target tissue via a cool ablation process involving molecular dissociation of the target tissue components.

56. The probe of

claim 14

, wherein the probe is adapted for ablating the target tissue during axial movement of the probe in a proximal direction, wherein ablation of the target tissue is effected via a process involving molecular dissociation of the target tissue components.

57. The probe of

claim 14

, wherein the probe is adapted for removing a fragment of the target tissue for biopsy, wherein the fragment is removed via a cool ablation process involving molecular dissociation of the target tissue components.

58. The probe of

claim 14

, wherein the first and second electrode supports each comprise an electrically insulating material selected from the group consisting of:

a silicone rubber, a ceramic, and a glass.

59. An electrosurgical probe for treating a target tissue of a patient, comprising:

an elongate body including a first shaft, the first shaft distal end bifurcated to provide a first arm and a second arm;

a first electrically insulating electrode support disposed on the first arm distal end, and a second electrically insulating electrode support disposed on the second arm distal end, wherein each of the first and second arms includes a first bend and a second bend; and

an active electrode disposed between the first and second electrode supports.

60. The probe of

claim 59

, wherein the first bend is away from the longitudinal axis of the probe and the second bend is towards the longitudinal axis of the probe.

61. The probe of

claim 59

, wherein the first bend is at a first angle with respect to the longitudinal axis of the probe and the second bend is at a second angle with respect to the longitudinal axis of the probe, and wherein the first angle and the second angle are substantially equal.

62. The probe of

claim 61

, wherein the first angle is in the range of from about 10°

to 35°

.

63. The probe of

claim 61

, wherein the first angle is in the range of from about 15°

to 25°

.

64. The probe of

claim 59

, further comprising a return electrode disposed between the first and second electrode supports at a location distal to the active electrode.

65. The probe of

claim 64

, wherein the return electrode comprises a round wire.

66. The probe of

claim 59

, wherein the active electrode comprises a wire having a substantially rectangular cross-section.

67. The probe of

claim 64

, wherein the active electrode and the return electrode comprise a metal selected from the group consisting of:

molybdenum, platinum, iridium, titanium, tantalum, tungsten, stainless steel, nickel, and their alloys.

68. The probe of

claim 64

, wherein the active electrode and the return electrode are arranged at an angle in the range of from about 45°

to 85°

with respect to the longitudinal axis of the probe.

69. An electrosurgical probe for treating a target tissue of a patient, comprising:

an elongate body including a first shaft, the first shaft bifurcated to provide a first arm and a second arm;

a first electrically insulating electrode support disposed on the first arm distal end, and a second electrically insulating electrode support disposed on the second arm distal end; and

an active electrode disposed between the first and second electrode supports, wherein the active electrode is arranged at an acute angle with respect to the longitudinal axis of the probe.

70. The probe of

claim 69

, wherein the active electrode is arranged at an angle in the range of from about 45°

to 85°

with respect to the longitudinal axis of the probe.

71. The probe of

claim 69

, wherein the active electrode is arranged at an angle in the range of from about 50°

to 70°

with respect to the longitudinal axis of the probe.

72. The probe of

claim 69

, further comprising a return electrode disposed between the first and second electrode supports at a location distal to the active electrode, wherein the return electrode is arranged at an acute angle with respect to the longitudinal axis of the probe.

73. The probe of

claim 72

, wherein the active electrode lies in a first plane, and the return electrode lies in a second plane, and the first and second planes are substantially parallel to each other.

74. A method of treating a target tissue of a patient using an electrosurgical probe, the method comprising:

a) positioning the probe distal end in at least close proximity to the target tissue, wherein the probe includes an active electrode, and a return electrode located distal to the active electrode;

b) applying a high frequency voltage between the active and return electrodes, the high frequency voltage sufficient to ablate a portion of the target tissue; and

c) manipulating the probe distal end such that the electrode assembly moves with respect to the target tissue, wherein at least a portion of the target tissue is ablated.

75. The method of

claim 74

, wherein the tissue ablated in said step c) is vaporized to form low molecular weight ablation by-products.

76. The method of

claim 74

, wherein said step c) comprises axially reciprocating the electrode assembly with respect to the target tissue.

77. The method of

claim 76

, wherein during said step c) each proximal stroke of the reciprocating electrode assembly removes a layer or fragment of the target tissue.

78. The method of

claim 74

, further comprising the step of:

d) prior to said step b), advancing the probe distal end towards the target tissue.

79. The method of

claim 78

, wherein the target tissue comprises tissue of the prostate gland, and said step d) comprises advancing the probe distal end transurethrally.

80. The method of

claim 78

, wherein the target tissue comprises uterine tissue, and said step d) comprises advancing the probe distal end through the cervix of the uterus.

81. The method of

claim 74

, further comprising the step of:

e) prior to said step b), delivering an electrically conductive fluid to the electrode assembly or to the target tissue to provide a current flow path between the active electrode and the return electrode.

82. The method of

claim 81

, wherein said step b) causes electric current to flow through the electrically conductive fluid in a distal direction.

83. The method of

claim 74

, wherein the high frequency voltage applied in said step b) is in the range of from about 50 volts RMS to about 500 volts RMS, at a frequency in the range of from about 20 KHz to about 1 MHz.

84. The method of

claim 74

, wherein the tissue ablated in said step c) is vaporized at a temperature in the range of from about 45°

C. to 90°

C. to form low molecular weight ablation by-products, and the method further comprises;

f) aspirating the low molecular weight ablation by-products from the target site.

85. The method of

claim 74

, further comprising the step of:

g) resecting a fragment of the target tissue; and

h) harvesting the fragment of target tissue for tissue analysis.

86. The method of

claim 85

, wherein said step g) involves inserting the probe distal end within the target tissue to a depth of at least 4 mm.

87. The method of

claim 85

, wherein said step g) involves dragging the active electrode over the target tissue.

88. The method of

claim 86

, wherein said step g) involves electrosurgical molecular dissociation of target tissue components.

89. The method of

claim 74

, wherein the probe distal end includes a bifurcated shaft having first and second arms, a first electrode support and a second electrode support disposed on the first and second arms, respectively, the active electrode disposed between the first and second electrode supports, and the return electrode disposed between the first and second electrode supports.

90. The method of

claim 74

, wherein the probe further comprises an attachment unit adapted for attaching the probe to an endoscope.

91. The method of

claim 74

, wherein the active electrode lies in a first plane and the return electrode lies in a second plane, wherein the first plane and the second plane are substantially parallel to each other.

92. The method of

claim 74

, wherein the active electrode and the return electrode are arranged at an acute angle with respect to the longitudinal axis of the probe.

93. The method of

claim 89

, wherein each of the first arm and the second arm includes a first bend and a second bend.

94. A method of treating hypertrophied target tissue of a patient, comprising:

a) positioning the distal end of an electrosurgical probe in at least close proximity to the target tissue, the probe including an electrode assembly disposed on the probe distal end, the electrode assembly having an active electrode and a return electrode, the return electrode spaced distally from the active electrode;

b) applying a high frequency voltage between the active and return electrodes, the high frequency voltage sufficient to ablate the target tissue; and

c) reciprocating the probe distal end with respect to the target tissue, wherein at least a portion of the target tissue is electrosurgically ablated.

95. The method of

claim 94

, wherein, during said step c), at least one fragment of the target tissue is resected during proximal motion of the electrode assembly.

96. The method of

claim 94

, further comprising:

d) prior to or after said step c), inserting the probe distal end within the target tissue;

e) thereafter, while applying the high frequency voltage of said step b), electrosurgically resecting at least one fragment of the target tissue; and

f) harvesting the at least one fragment of the target tissue for biopsy.

97. The method of

claim 94

, further comprising:

g) delivering an electrically conductive fluid to the electrode assembly, wherein the electrically conductive fluid provides a current flow path between the active electrode and the return electrode, and said step b) causes electric current to flow through the electrically conductive fluid in a distal direction.

98. The method of

claim 96

, wherein said step d) comprises inserting the probe within the target tissue to a depth of at least 4 mm.

99. The method of

claim 94

, wherein the probe distal end includes a bifurcated shaft having first and second arms, and a first electrode support and a second electrode support disposed on the first and second arms, respectively.

100. The method of

claim 94

, wherein the return electrode and the active electrode each comprise a wire loop.

101. The method of

claim 94

, wherein the active electrode lies in a first plane and the return electrode lies in a second plane, wherein the first plane and the second plane are substantially parallel to each other.

102. The method of

claim 94

, wherein the active electrode and the return electrode are arranged at an acute angle with respect to the longitudinal axis of the probe.

103. An electrosurgical probe, comprising:

a shaft having a shaft proximal end and a shaft distal end; and

an electrode assembly disposed on the shaft, the electrode assembly including an active electrode and a return electrode, wherein the return electrode is spaced distally from the active electrode.

104. The probe of

claim 103

, wherein the active electrode and the return electrode each comprise a wire loop.

105. The probe of

claim 104

, wherein each of the active electrode and the return electrode is substantially U-shaped, C-shaped, D-shaped, or V-shaped.

106. The probe of

claim 103

, wherein the active electrode is spaced from the return electrode by an electrode gap in the range of from about 0.010 to about 0.100 inches.

107. The probe of

claim 106

, wherein the active electrode comprises an active electrode filament, and the electrode gap is substantially constant over the entire length of the active electrode filament.

108. The probe of

claim 103

, wherein the shaft includes a first bend and a second bend.

109. The probe of

claim 103

, wherein the active electrode and the return electrode are arranged at an acute angle with respect to the longitudinal axis of the probe.

110. The probe of

claim 103

, further comprising a first electrode support and a second electrode support, wherein the active electrode and the return electrode are disposed between the first electrode support and the second electrode support.

111. A bipolar electrosurgical probe, comprising:

a shaft having a shaft proximal end and a shaft distal end; and

a first loop electrode and a second loop electrode disposed at the shaft distal end.

112. The probe of

claim 111

, wherein the first loop electrode comprises an active electrode and the second loop electrode comprises a return electrode, and the return electrode is spaced distally from the active electrode.

113. The probe of

claim 112

, wherein the active electrode lies in a first plane and the return electrode lies in a second plane, and the first plane is located proximal to the second plane.

114. The probe of

claim 113

, wherein the first plane and the second plane are substantially parallel to each other.

115. The probe of

claim 111

, wherein the first loop electrode and the second loop electrode each comprise a wire filament, each wire filament comprising a metal selected from the group consisting of:

molybdenum, platinum, iridium, titanium, tantalum, tungsten, stainless steel, nickel, and their alloys.

116. The probe of

claim 115

, wherein each wire filament is substantially U-shaped, C-shaped, D-shaped, or V-shaped.

117. The probe of

claim 112

, wherein the active electrode is spaced proximally from the return electrode by an electrode gap, the electrode gap in the range of from about 0.010 to about 0.100 inches.

118. The probe of

claim 117

, wherein the electrode gap is substantially constant over the entire length of the active electrode.

119. The probe of

claim 111

, wherein the first loop electrode and the second loop electrode are arranged at an acute angle with respect to the longitudinal axis of the probe.

120. An electrode assembly for electrosurgical treatment of a target tissue, comprising:

an active electrode arranged between a first electrode support and a second electrode support; and

a return electrode disposed distal to the active electrode.

121. The electrode assembly of

claim 120

, wherein the return electrode is arranged between the first electrode support and the second electrode support.

122. The electrode assembly of

claim 120

, wherein the active electrode comprises an active electrode first end, an active electrode second end and an active electrode filament, the active electrode first end emanating from the first electrode support, the active electrode second end emanating from the second electrode support, and the active electrode filament suspended between the first electrode support and the second electrode support.

123. The electrode assembly of

claim 122

, wherein the active electrode filament is substantially C-shaped, D-shaped, U-shaped, or V-shaped.

124. The electrode assembly of

claim 123

, wherein the return electrode comprises a return electrode filament, the active electrode filament spaced proximally from the return electrode filament by an electrode gap, and the electrode gap remains substantially constant over a distance between the active electrode first end and the active electrode second end.

125. The electrode assembly of

claim 124

, wherein the electrode gap is in the range of from about 0.010 to about 0.100 inches.

126. The electrode assembly of

claim 120

, wherein the first and second electrode supports each comprise an electrically insulating material selected from the group consisting of a silicone rubber, a ceramic, and a glass.

127. The electrode assembly of

claim 120

, wherein the active electrode lies in a first plane and the return electrode lies in a second plane, wherein the first plane is located proximal to the second plane.

128. The electrode assembly of

claim 120

, wherein each of the active electrode and the return electrode is in the form of a wire loop.

129. The electrode assembly of

claim 128

, wherein each wire loop comprises a metal selected from the group consisting of:

molybdenum, platinum, iridium, titanium, tantalum, tungsten, stainless steel, nickel, and their alloys.