Electrosurgical generator

• US 6,238,387 B1
• Filed: 11/16/1998
• Issued: 05/29/2001
• Est. Priority Date: 08/23/1996
• Status: Expired due to Term

• Current Assignee: Microline Surgical, Inc. (Hoya Corporation)
• Original Assignee: Team Medical, LLC
• Inventors: Miller, Scott A. III
• Primary Examiner(s): PEFFLEY, MICHAEL F
• Application Number:
  US09/192,746
• Time in Patent Office: 925 Days
• Field of Search: 606/32-35, 606/38-42, 607/101, 607/102
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/0072 Current
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00767 Voltage
• CPC Class Codes: A61B 2018/00827 Current

Abstract

An electrosurgical generator is disclosed that provides radio-frequency electrical waveforms for performing surgical operations on a tissue mass. The various aspects of the present invention are embodied in an electrosurgical generator that includes a DC regulator, an amplifier, an energy recovery circuit, and a method of controlling these components to generate a desired electrical waveform for an electrosurgical operation.

Claims

1. An electrosurgical generator for use in the performance of a surgical operation on a tissue mass, comprising:

a signal generating means adapted to apply electrosurgical output pulses across a tissue mass at a predetermined frequency;

impedance measuring means which measures at least one of a complex impedance and a rate of change of the complex impedance across the tissue mass through the application of a predetermined measurement signal across the tissue mass only between said electrosurgical output pulses; and

control means which regulates the signal generating means based at least in part on said at least one of the complex impedance and rate of change of the complex impedance.

2. The electrosurgical generator of claim 1, wherein said predetermined measurement signal is at a different frequency than the electrosurgical output pulses.

3. The electrosurgical generator of claim 1, wherein the measurement includes measuring both of said complex impedance and the rate of change of the complex impedance across the tissue mass, and wherein the regulation is based on both of said measured complex impedance and measured rate of change of the complex impendence.

4. The electrosurgical generator of claim 1, wherein the impedance measuring means measures said complex impedance by dividing a voltage applied across the tissue mass by a current passing through the tissue mass.

5. The electrosurgical generator of claim 1, wherein the control means regulates a voltage output by said signal generating means based on said at least one of the complex impedance and rate of change of the complex impedance.

6. The electrosurgical generator of claim 1, wherein said at least one of the complex impedance and rate of change of the complex impedance corresponds with a tissue condition which is compared with a desired condition.

7. The electrosurgical generator of claim 1, said signal generating means including:

(a) dc regulator means for converting a first dc signal from a power source into a second dc signal having a predetermined voltage, including;

inductive input means for reducing current ripple in the first dc signal,

capacitive energy storage means for storing and releasing energy,

switch means for alternatively charging said capacitive energy storage means with the first dc signal and discharging said capacitive energy storage means to generate the second dc signal, and

inductive output means for reducing current ripple in the second dc signal;

(b) amplifier means for converting the second dc signal into the output signal having a predetermined frequency;

wherein said control means provides control signals to at least one of the dc regulator means and said amplifier means to establish at least one of said predetermined voltage and said predetermined frequency.

8. The electrosurgical generator of claim 7, said amplifier means comprising:

an amplifier input inductor for reducing current ripple of the second dc signal;

a resonant circuit connectable across the tissue mass, wherein said resonant circuit is connected in series with said amplifier input inductor and includes an inductor and a capacitor; and

amplifier switch means for alternately connecting and disconnecting a current return path of said amplifier means to a junction between said input inductor and said resonant circuit thereby providing an output signal.

9. The electrosurgical generator of claim 8, wherein said inductor and said capacitor of said resonant circuit are selected to provide a substantially zero voltage across said amplifier switch means and a substantially zero instantaneous rate of change of voltage across said amplifier switch mans prior to said connecting by said amplifier switch means thereby substantially reducing energy dissipation by said amplifier switch means.

10. The electrosurgical generator of claim 1, said signal generating means including:

(a) dc regulator means for converting a first dc signal from a power source into a second dc signal having a predetermined voltage;

(b) amplifier means for converting the second dc signal into the output signal into the output signal having predetermined frequency, including;

an input inductor for reducing current ripple in the second dc signal,

a resonant circuit connectable across the tissue mass, wherein said resonant circuit is connected in series with said input inductor and includes an inductor and a capacitor; and

switch means for alternately connecting and disconnecting a current return path of said amplifier to a junction between said input inductor and said resonant circuit;

wherein said control means for establishes at least one of said predetermined voltage and said predetermined frequency.

11. The electrosurgical generator of claim 10, wherein said inductor and said capacitor of said resonant circuit are selected so as provide a substantially zero voltage across said switch means and a substantially zero instantaneous rate of change of voltage across said switch means prior to said connecting by said switch means thereby substantially reducing energy dissipation by said switch means.

12. The electrosurgical generator of claim 10, further comprising:

energy recovery means electrically connected to said resonant circuit for selectively storing and releasing energy of output signal.

13. The electrosurgical generator of claim 1, wherein the control means regulates at least one of a voltage output, frequency, and pulse width of said electrosurgical output pulses in response to said at least one of the complex impedance and rate of change of the complex impedance.

14. An electrosurgical generator for providing an output signal for use in the performance of a surgical operation on a tissue mass comprising:

a signal generating means adapted to apply electrosurgical output pulses across a tissue mass including;

(a) dc regulator means for converting a first dc signal from a power source into a second dc signal having a pre-determined voltage;

(b) amplifier means for converting the second dc signal into an output signal having a predetermined frequency; and

,

(c) energy recovery means electrically connected to said amplifier means for selectively storing and releasing energy of the output signal;

impedance measuring means which measures at least one of a complex impedance and a rate of change of the complex impedance across the tissue mass through the application of a predetermined measurement signal across the tissue mass only between said electrosurgical output pulses; and

control means which regulates the signal generating means based at least in part on said at least one of the measured complex impedance and measured rate of change.

15. The electrosurgical generator of claim 14, said energy recovery means including:

energy storage means electrically connected to said amplifier means; and

energy recovery switching means, in connection with said control means, to alternately direct excess energy from the amplifier means to the energy recovery storage means and to return the excess energy from the energy storage means to the amplifier means.

16. The electrosurgical generator of claim 15, wherein the energy storage means is an inductor.

17. The electrosurgical generator of claim 15, wherein the energy recovery means comprises a transistor.

18. The electrosurgical generator of claim 15, said amplifier means including:

an amplifier input inductor for reducing current ripple of the second dc signal;

a resonant circuit connectable across the tissue mass, wherein said resonant circuit is connected in series with said amplifier input inductor and includes an inductor and a capacitor; and

amplifier switch means for alternately connecting and disconnecting a current return path of said amplifier means to a junction between said input inductor and said resonant circuit thereby providing an output signal.

19. The electrosurgical generator of claim 18, the energy recovery means including:

energy storage means in connection with said resonant circuit;

energy recovery switching means in connection with the control means, which alternately directs excess energy from the resonant circuit to the energy recovery storage means, and return the excess energy to the amplifier means.

20. The electrosurgical generator of claim 14, wherein said energy recovery means captures energy from the amplifier means at the end of each of said electrosurgical output pulses.