Electrosurgical generator

• US 4,378,801 A
• Filed: 12/10/1980
• Issued: 04/05/1983
• Est. Priority Date: 12/17/1979
• Status: Expired due to Term

• Current Assignee: Linvatec Corporation (Jefferies Financial Group, Inc.)
• Original Assignee: Optical Research Associates (Synopsys Incorporated)
• Inventors: Oosten, Roger L.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US06/215,046
• Time in Patent Office: 846 Days
• Field of Search: 128/303.13, 128/303.14, 128/303.17, 128/303.18
• US Class Current: 606/37
• 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 2018/0066 without feedback, i.e. open loop control

Abstract

A fixed high frequency oscillator, variable frequency divider, and low frequency timer are provided to produce a high frequency output pulse group which is terminated at different intervals by both the variable frequency divider and the timer. The characteristics of the frequency divider may be varied to produce a number of modes of generator operation, all of which utilize a single high frequency output. The generator includes apparatus for producing a voltage spike as one of the pulses of each output group with a crest ratio of at least 3:1 in the cut command group and at least 14:1 in the fulgurate mode. The spike reionizes the current path through tissue without excessive tissue destruction due to wasted power and is minimized in dessicate mode where reionization arcing is undesirable. A pair of opto-isolated hand-held switches allow the user to select continuously between two preset modes of operation without risking shock.

Claims

1. A generator for electrosurgery comprising first and second command switches for selecting command status of operation;

a command control means coupled to said first and second command switches for preventing simultaneous activation of said first and second command switches;

a first mode switch for selecting a mode of operation when the first command switch is activated;

a second mode switch for selecting a mode of operation when the second command switch is activated;

a mode control means coupled to said first and second mode switches for determining the mode of operation indicated by said first and second command switches and said first and second mode switches, said command control means being coupled to said mode control means by first and second command lines;

first, second, third and fourth voltage amplifiers, each said voltage amplifier being coupled to said mode control means so that one of said voltage amplifiers corresponding to the mode of operation indicated by said first and second mode switches and said first and second command switches is activated by said mode control means;

a first NAND gate having two inputs, the inputs of said first NAND gate being coupled respectively to the said first and second command lines;

high frequency oscillator means and low frequency oscillator means coupled to the output of said first NAND gate so that said high and low frequency oscillator means are activated by said first NAND gate when either command line is activated;

a three-input NAND gate, the output of said high frequency oscillator means being coupled to a first input of said three-input NAND gate, the output of said low frequency oscillator means comprising a duty cycle interrupt signal and being coupled to a second input of said three-input NAND gate, variable frequency divider means, the output of said high frequency oscillator means also being coupled to said variable frequency divider means, said variable frequency divider means also being coupled to the output of said mode control means, the output of said variable frequency divider means being coupled to the third input of said three-input NAND gate and comprising a waveform interrupt signal comprised of a high voltage portion and a low voltage portion, the wave-length of said waveform interrupt signal being an integer multiple of the wave-length of the output of said high frequency oscillator means, the ratio of the length of said high voltage portion to the length of said low voltage portion being altered by said variable frequency divider means corresponding to the mode of operation indicated by said first and second mode switches and said first and second command switches;

a voltage controlled main amplifier means, the output of said three-input NAND gate being coupled to the input of said voltage controlled main amplifier means and comprising groups of pulses, said voltage controlled main amplifier means including means for selectively increasing the amplitude of a pulse of each said group of pulses from said three-input NAND gate, said voltage controlled main amplifier means being coupled to said first, second, third and fourth voltage amplifiers so that said voltage amplifiers control the output level of said voltage controlled main amplifier means;

a DC voltage supply and an isolation transformer means, the output of said voltage controlled main amplifier means being coupled through the primary winding of said isolation transformer means to said DC voltage supply, said isolation transformer means having first and second secondary windings, the side taps of said first secondary winding being coupled through first and second blocking capacitors, respectively, to first and second output terminals for monopolar operation, one side tap of said second secondary winding being coupled through a third blocking capacitor to a third terminal for bipolar operation, the other side tap of said second secondary winding being coupled directly to a fourth output terminal for bipolar operation.

2. The apparatus as claimed in claim 1 including a plurality of gain control means coupled to each of said first, second, third and fourth amplifiers for adjustment of the output voltage of said amplifiers.

3. The apparatus as claimed in claim 2 in which said first and second amplifiers are coupled to one of said gain control means, and said third and fourth amplifiers are coupled to a second of said gain control means.

4. The apparatus as claimed in claim 1 wherein each of said first and second command control switches comprises a plurality of switches connected in parallel.

5. The apparatus as claimed in claim 1 including isolation means comprising a power supply and opto-isolator, said first and second command switches being coupled to said isolation means and said isolation means being coupled to said command control means.

6. The apparatus as claimed in claim 1 wherein said voltage controlled main amplifier means includes an output stage, said output stage comprising a constant-current amplifier.

7. The apparatus as claimed in claim 6 wherein said output stage functions as a constant-current amplifier over a human tissue impedance range of 25 to 2000 ohms.

8. The apparatus as claimed in claim 6 wherein the input of said output stage includes an isolation transformer.

9. The apparatus as claimed in claim 1 including first and second display means for displaying the power output level corresponding to each of said first and second command switches.

10. The apparatus as claimed in claim 1 wherein the initial pulse of each group of pulses has a crest ratio in the range of 3:

1 to 18;

1.

11. The apparatus as claimed in claim 1 wherein said means for selectively increasing the amplitude of a pulse of each said group of pulses is a resonant circuit, said resonant circuit comprising a resistor, capacitor and transformer coupled in parallel, said circuit being tuned to a resonant frequency not equal to the frequency of said high-frequency oscillator means.

12. The apparatus as claimed in claim 1 wherein said high-frequency oscillator means produces an output frequency of 450 kilohertz.

13. The apparatus as claimed in claim 1 wherein said low frequency oscillator means produces an output frequency of 5 kilohertz.

14. The apparatus as claimed in claim 1 wherein said ratio of the length of said high voltage portion to the length of said low voltage portion varies in the range of 0:

20 to 19;

1.