Electrosurgical generator and system

• US 20020029036A1
• Filed: 08/09/2001
• Published: 03/07/2002
• Est. Priority Date: 06/23/1995
• Status: Abandoned Application

• Current Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Original Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Inventors: Goble, Colin Charles Owen, Goble, Nigel Mark
• Application Number:
  US09/924,485
• Publication Number:
  US 20020029036A1
• Time in Patent Office: Days
• US Class Current: 606/38
• CPC Class Codes: A61B 18/082 Probes or electrodes therefor
• 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 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 2017/00482 with a code
• CPC Class Codes: A61B 2018/00178 Electrical connectors
• CPC Class Codes: A61B 2018/00505 Urinary tract
• CPC Class Codes: A61B 2018/00589 Coagulation
• CPC Class Codes: A61B 2018/00625 Vaporization
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00755 Resistance or impedance
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00892 Voltage
• CPC Class Codes: A61B 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2018/1213 creating an arc
• CPC Class Codes: A61B 2018/126 : bipolar
• CPC Class Codes: A61B 2018/143 : multiple needles
• CPC Class Codes: A61B 2018/1432 : curved
• CPC Class Codes: A61B 2018/1435 : Spiral
• CPC Class Codes: A61B 2018/1472 : for use with liquid electrolyte, e.g. virtual electrodes
• CPC Class Codes: A61B 2018/162 : located on the probe body
• CPC Class Codes: A61B 2018/1861 : with an instrument inserted into a body lumen or cavity, e.g. a catheter
• CPC Class Codes: A61M 2205/6018 : providing set-up signals for the apparatus configuration
• CPC Class Codes: A61M 2205/6027 : Electric-conductive bridges closing detection circuits, with or without identifying elements, e.g. resistances, zener-diodes

Abstract

An electrosurgical system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid has a generator with control circuitry for rapidly reducing the delivered radio frequency output power by at least 50% within at most a few cycles of the peak radio frequency output voltage reaching a predetermined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporization or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning. In a blended mode, the output voltage is alternately limited to a value appropriate for coagulation and a value appropriate for cutting or vaporization.

Claims

1. An electrosurgical generator for supplying power to an electrosurgical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output connections for the delivery of radio frequency power to the instrurnent, and control circuitry operable to limit the radio frequency peak output voltage developed across the output connections to at least first and second predetermined threshold values and, in a blend mode of the generator, to alternate constantly between said first and second threshold values.

2. A generator according to claim 1, wherein the first threshold value is in the range of from 150V to 200V and the second threshold value is in the range of from 250V to 600V, the voltages being peak voltages.

3. A generator according to claim 2, wherein the control circuity is operable, in said blend mode, to limit said output voltage alternately to said first and second threshold values at an alternation rate in the range of from 5 Hz to 2kHz.

4. A generator according to claim 3, wherein the control circuit is operable, in said blend mode, to limit said output voltage alternately to said first and second threshold values at an alternation rate in the range of from 20 Hz to 1 kHz.

5. A generator according to claim 1, wherein the output stage includes a radio frequency switching device for delivering power signal to the output connections, wherein the control circuitry includes sensing means for deriving a sensing signal representative of the radio frequency peak output voltage developed across said output connections, and a reference signal generator for generating reference signals representative of said first and second threshold values, wherein the sensing means further includes a comparator arranged to compare said sensing signal with said reference signals to produce a control signal for actuating the switching device such as to reduce said delivered output power when the control signal produced by the comparator is indicative of the respective said threshold value having been reached, and wherein the reference signal generator and the comparator are operable, in said blend mode, to compare said sensing signal alternately with the reference signal representative of the first threshold value and the reference signal representative of the second threshold value.

6. A generator according to claim 5, wherein the reference signal generator includes a switching circuit operable to apply said reference signals alternately to a reference input of said comparator.

7. A generator according to claim 6, wherein said switching circuit is software-controlled.

8. An electrosurgical system comprising an electrosurgical generator for generating radio frequency power and an electrosurgical instrument coupled to the generator, the instrument having an electrode structure for operation immersed in an electrically conductive liquid, wherein the system has a first mode of operation in which tissue is treated by the application of heat in the region of the electrode structure without forming an electrode-enveloping vapour pocket, and a second mode of operation in which the tissue is locally vaporised by energy transmitted from the electrode structure via an electrode-enveloping vapour pocket, said first and second modes being defined by different respective electrical control parameters selected in the generator, and wherein the system has a third, blended mode of operation produced by constantly alternating between the first and second modes.

9. A system according to claim 8, wherein the said different control parameters are first and second radio frequency output voltage values, and wherein the generator includes control circuitry operable, when the blended mode is required, to limit the radio frequency output voltage of the generator alternately to said first and second values.