Electrosurgery system and instrument

• US 6,547,786 B1
• Filed: 05/18/2000
• Issued: 04/15/2003
• Est. Priority Date: 05/21/1999
• Status: Expired due to Fees

• Current Assignee: Gyrus Medical Co.
• Original Assignee: Gyrus Medical Co.
• Inventors: Goble, Colin Charles Owen
• Primary Examiner(s): VRETTAKOS, PETER J
• Application Number:
  US09/572,338
• Time in Patent Office: 1,062 Days
• Field of Search: 606/28-31, 606/34, 606/41, 606/42, 607/101, 607/102, 600/549
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety

Abstract

In an electrosurgery system having a radio frequency generator and an instrument with a treatment electrode, the generator includes a circuit for sensing thermionic emission from the electrode as means of controlling the supply of radio frequency power to the electrode. Thermionic emission is sensed by detecting d.c. voltage at the output of the generator, or an a.c. representation of the d.c. voltage, using a detector with an isolated output, and generator output power is controlled so as to limit the d.c. voltage or the a.c. representation to a predetermined threshold. Accordingly, the temperature of the electrode can be limited to avoid electrode destruction. The invention also has application to reducing nerve stimulation due to electrosurgical treatment.

Claims

1. An electrosurgery system comprising a generator which includes a source of radio frequency (r.f.) energy for feeding to a treatment electrode of an electrosurgical instrument, the generator comprising:

a circuit for sensing thermionic emission from the treatment electrode,

the sensing circuit having an input stage arranged substantially to remove r.f. signals at an operating frequency or frequencies of the generator to yield an averaged representation of r.f. output of the generator, and

a detection stage coupled to the input stage to receive the averaged representation,

wherein the generator is arranged to generate a modulated r.f. output for feeding to the treatment electrode of the electrosurgical instrument, and the sensing circuit is arranged such that substantial removal of the r.f. signals at the generator operating frequency results in an averaged signal being fed to the detection stage which produces a sensing circuit signal as a measure of an amplitude of the averaged signal;

wherein the sensing circuit input stage comprises a filter having a passband including the frequency of the modulation but excluding the generator operating frequency, the averaged signal being an a.c. signal having a frequency equal to the modulation frequency; and

wherein the generator has an output stage having a pair of output lines coupled to respective generator output terminals, each output line having a series-connected isolation capacitor, and a series inductor in one of the output lines between the respective isolating capacitor and output terminal, the inductor being coupled to the input stage of the sensing circuit.

2. A system according to claim 1, wherein the input stage comprises a parallel resonant circuit tuned to the modulation frequency and having an inductance inductively coupled to said series inductance, and wherein the detection circuit is coupled across the resonant circuit to detect the amplitude of the signal developed across the resonant circuit.

3. An electrosurgical generator comprising a radio frequency (r.f.) power source operable at a generator operating frequency, and an output stage including a pair of r.f. power output terminals, the output stage being DC-isolated from the source, the generator further comprising means for modulating the r.f. power signal generated by the source, and a sensing circuit AC-coupled to and DC-isolated from the output stage and operable to generate an averaged AC signal containing a modulation component representative of a DC shift in the power signal delivered to the output terminals.

4. A generator according to claim 3, wherein the modulation means produces amplitude modulation in the r.f. power signal at a predetermined modulation frequency, and wherein the generator further comprises a filtering element associated with the sensing circuit for substantially removing an r.f. component at the operating frequency from the input to the sensing circuit to yield the averaged AC signal.