Control system for neurosurgery

• US 5,720,744 A
• Filed: 06/06/1995
• Issued: 02/24/1998
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Valleylab Inc. (Medtronic Plc)
• Inventors: Sodnicar, Matthew J., Orszulak, James H., Eggleston, Jeffrey L.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/470,533
• Time in Patent Office: 994 Days
• Field of Search: 606/34, 606/38, 606/40, 606/50, 606/51
• US Class Current: 606/40
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1442 Probes having pivoting end effectors, e.g. forceps
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

A control system and method for the operation of neurosurgical bipolar electrodes for application to the tissue and bodily fluids of a patient provides a source of high frequency energy connected to bipolar electrodes. Contacting surfaces are on the bipolar electrodes of highly electrically conductive material with resistance per unit area substantially less than the impedance of the tissue and bodily fluids. A current transducer attached to the source of high frequency energy responds to the RMS current applied through the tissue and bodily fluids between the contact surfaces as a measure relative to the instantaneous values of the RMS current. A current transducer attached to the source of high frequency energy responds to the RMS current through a capacitor applied across the contact surfaces to provide a signal correlated to the instantaneous values of the RMS voltage between the contacts and across the tissue and bodily fluids. A control connects to the source of high frequency energy for initially regulating the RMS current applied through the tissue and bodily fluids by the contacting surfaces in response to the impedance until the signal divided by the measure reaches a predetermined value. The control regulates the RMS power applied to the tissue and bodily fluids by the contacting surfaces in accord with the impedance until the signal divided by the measure reaches a predefined value. The control responds to the measure and the signal so that the RMS voltage applied to the impedance being treated between the contacting surfaces is regulated while monitored until a prescribed value is reached. The control regulates the RMS voltage applied to the tissue and bodily fluids by the contacting surfaces in accord with the impedance by changing the RMS voltage to a percentage of that applied until the prescribed value is obtained so that the tissue and bodily fluids being treated are moist but coagulated at the surface and not completely dry and carbonized or turned to eschar.

Claims

1. A control system for neurosurgical bipolar electrodes for application by a surgeon to tissue and bodily fluids of a patient, the tissue and bodily fluids having a tissue impedance, the control system comprising:

a source of high frequency energy having an output and an operating frequency;

a tank network in the source of high frequency energy, the tank network having at least a tank capacitor and at least a tank inductor, the at least tank capacitor and the at least tank inductor tuned to the operating frequency of the source of high frequency energy, the tank network connected to the output of the source of high frequency energy;

bipolar electrodes connected to the output of the source of high frequency energy;

contact surfaces on the bipolar electrodes, the contact surfaces comprised of highly electrically conductive material with resistance per unit area substantially less than the tissue impedance;

a first current transducer inductively coupled to the bipolar electrodes, the first current transducer responsive to the tissue impedance, the first current transducer providing a measure relative to a first current through the tissue and bodily fluids;

a second current transducer attached to the source of high frequency energy to respond to a second current through a second capacitor applied across the contact surfaces, the second current transducer providing a signal of changes in the second current, the signal representative of a voltage across the tissue and bodily fluids between the contact surfaces;

a control connected to the source of high frequency energy for initially regulating the first current applied through the tissue and bodily fluids by the contact surfaces and for responding to the tissue impedance until the signal divided by the measure is a predetermined value, the control connected for then regulating power applied to the tissue and bodily fluids by the contact surfaces until the signal divided by the measure is a predefined value, the control for thereafter responding to the signal divided by the measure so that the voltage across the tissue and bodily fluids being treated between the contact surfaces is regulated while monitored until the signal divided by the measure is a prescribed value, so that the tissue and bodily fluids being treated are moist but coagulated at the surface and not completely dry and carbonized.

2. The control system for neurosurgical bipolar electrodes of claim 1 wherein the control includes a microprocessor, the microprocessor for dividing the signal by the measure, the microprocessor having memory for the predetermined value, the predefined value and the prescribed value and the microprocessor able to compare the predetermined value, the predefined value and the prescribed value to the signal divided by the measure in real time.

3. The control system for neurosurgical bipolar electrodes of claim 2 wherein the control has feedback technique programmed into the microprocessor for maintaining the current substantially constant until the signal divided by the measure is the predetermined value of sixteen.

4. The control system for neurosurgical bipolar electrodes of claim 2 wherein the control has feedback technique programmed into the microprocessor for maintaining the power substantially constant until the signal divided by the measure is the predefined value of five hundred and twelve.

5. The control system for neurosurgical bipolar electrodes of claim 2 wherein the control has feedback technique programmed into the microprocessor for maintaining the voltage substantially regulated until the signal divided by the measure is the prescribed value of one thousand and twenty four.

6. The control system for neurosurgical bipolar electrodes of claim 2 wherein the control has feedback technique programmed into the microprocessor for maintaining the voltage at a percentage of its substantially regulated level after the signal divided by the measure is the prescribed value of one thousand and twenty four.

7. The control system for neurosurgical bipolar electrodes of claim 2 wherein the microprocessor calculates the signal and the measure then multiplies them to calculate power in real time.

8. The control system for neurosurgical bipolar electrodes of claim 1 wherein the source of high frequency energy has a surgeon power knob limiting the source of high frequency energy to a range of between about 1 and 70 watts of output.

9. The control system for neurosurgical bipolar electrodes of claim 1 wherein the contact surfaces are composed of a metal selected from the group consisting of a noble metal, nickel and alloys thereof selected for their electrically and thermally conductive characteristics.

10. The control system for neurosurgical bipolar electrodes of claim 1 wherein a switch is located between the source of high frequency energy and the bipolar electrodes for the surgeon to activate and make a connection therebetween.

11. The control system for neurosurgical bipolar electrodes of claim 2 wherein the control has feedback technique programmed into the microprocessor for maintaining the voltage at fifty percent of its substantially regulated level after the signal divided by the measure is the prescribed value of one thousand and twenty four.

12. A method for controlling a system for neurosurgical bipolar electrodes for application to tissue and bodily fluids of a patient, the tissue and bodily fluids having a tissue impedance, the method comprising the steps of:

providing a source of high frequency energy having an output stage and an operating frequency;

connecting bipolar electrodes to the source of high frequency energy, the bipolar electrodes having contact surfaces of highly electrically conductive material having resistance per unit area substantially less than the tissue impedance;

contacting the tissue and bodily fluids with the contact surfaces;

connecting a tank network to the output stage of the source of high frequency energy, the tank network including at least a tank capacitor and at least a tank inductor, the at least tank capacitor and the at least tank inductor tuned to the operating frequency;

inductively coupling a first current transducer to the bipolar electrodes;

responding with the first current transducer to the tissue impedance at the particular instant of treatment of the tissue and bodily fluids;

providing with the first current transducer a measure relative to the instantaneous values of current through the tissue and bodily fluids;

inductively coupling a second current transducer to the source of high frequency energy to respond to current through a second capacitor applied across the contact surfaces;

generating a signal with the second current transducer, the signal generated in response to the tissue impedance;

the signal correlated to an instantaneous value of voltage between the contact surfaces;

connecting a control to the source of high frequency energy for initially regulating current applied through the tissue and bodily fluids by the contact surfaces;

responding with the control to the tissue impedance until the signal divided by the measure reaches a predetermined value;

connecting the control for then regulating power applied to the tissue and bodily fluids by the contact surfaces in accord with the tissue impedance until the signal divided by the measure reaches a predefined value;

responding thereafter with the control to the signal divided by the measure so that voltage between the contact surfaces is regulated while monitored until the signal divided by the measure is a prescribed value, so that the tissue and bodily fluids being treated are moist but coagulated at the surface and not completely dry and carbonized.

13. A control system for neurosurgical bipolar electrodes for application by a surgeon to tissue and bodily fluids of a patient, the tissue and bodily fluids having a tissue impedance, the control system comprising:

a source of high frequency energy having an output and an operating frequency;

a tank network in the source of high frequency energy, the tank network having at least a tank capacitor and at least a tank inductor, the at least tank capacitor and the at least tank inductor tuned to the operating frequency of the source of high frequency energy, the tank network as the output of the source of high frequency energy for generating an output power and an output voltage;

bipolar electrodes connected to the output of the source of high frequency energy;

contact surfaces on the bipolar electrodes, the contact surfaces comprised of highly electrically conductive material with resistance per unit area substantially less than the tissue impedance;

a first current transducer inductively coupled to the bipolar electrodes the first current transducer responsive to the tissue impedance, the first current transducer providing a measure relative to a first current through the tissue and bodily fluids;

a second current transducer attached to the source of high frequency energy to respond to a second current through a second capacitor applied across the contact surfaces, the second current transducer providing a signal of changes in the second current, the signal representative of the output voltage;

a control connected to the source of high frequency energy for regulating the first current, the output power and the output voltage and for responding to the tissue impedance, the control connected for receiving the measure and the signal in real time;

a microprocessor in the control, the microprocessor for receiving from the control and thereafter relating the measure to the signal, the microprocessor having memory for a predetermined value and for assessing when the signal divided by the measure equals the predetermined value, the microprocessor having memory for predefined value and for assessing when the signal divided by the measure equals the predefined value, the microprocessor having memory for a prescribed value and for assessing when the signal divided by the measure equals the prescribed value, and

the control connected to the source of high frequency energy for regulating the first current applied to the tissue and bodily fluids by the contact surfaces in accord with the tissue impedance until the signal divided by the measure is the predetermined value, the control for thereafter responding to the signal divided by the measure so that the output power is regulated while monitored until the signal divided by the measure is the value, the control connected for finally regulating the output voltage by changing the output voltage to a percentage of that applied to the tissue and bodily fluid until the prescribed value is obtained so that the tissue and bodily fluids being treated are moist but coagulated at the surface and not completely dry and carbonized.

14. The control system for neurosurgical bipolar electrodes of claim 13 wherein the control has feedback technique programmed into the microprocessor for maintaining the voltage at fifty percent of its substantially regulated level after the signal divided by the measure is the prescribed value of one thousand and twenty four.

15. The control system for neurosurgical bipolar electrodes of claim 13 wherein the control has feedback technique programmed into the microprocessor for maintaining the voltage at one hundred percent of its substantially regulated level until the signal divided by the measure is the prescribed value of one thousand and twenty four.