Radiofrequency ablation with independently controllable ground pad conductors

• US 20070049919A1
• Filed: 08/29/2005
• Published: 03/01/2007
• Est. Priority Date: 05/11/2004
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Lee, Fred, Winter, Thomas, Haemmerich, Dieter, Goldberg, S., Sampson, Lisa
• Granted Patent: US 7,736,357 B2
• Time in Patent Office: Days
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/1477 Needle-like probes
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/124 switching the output to different electrodes, e.g. sequentially
• CPC Class Codes: A61B 2018/1425 Needle
• CPC Class Codes: A61B 2018/165 Multiple indifferent electrodes

Abstract

A radiofrequency ablation system provides multiple ground pads and active control of current flow through the ground pads to provide improved power sharing at the tissue near the ground pads reducing risk of patient skin burns for higher power ablation generators.

Claims

1. A radiofrequency ablation system comprising:

at least one ablation electrode for insertion into a patient at an ablation site;

at least two ground pad conductors for topical application to a portion of the patient'"'"'s skin; and

a power supply independently applying a radio frequency voltage between the ablation electrode and the ground pad conductors to ablate tissue at the ablation site.

2. The radiofrequency ablation system of claim 1 wherein the power supply switches an application of voltage first between the ablation electrode and a first ground pad conductor, and second between the ablation electrode and a second ground pad conductor.

3. The radiofrequency ablation system of claim 2 wherein the switching of application of the voltage is according to a predetermined time schedule.

4. The radiofrequency ablation system of claim 1 wherein the ground pad conductors include temperature sensors and wherein the power supply applies the voltage independently between the ablation electrode and the ground pad conductors as a function of temperature at the ground pad conductor.

5. The radiofrequency ablation system of claim 1 wherein the power supply applies the voltage independently between the electrode and the ground pad conductors as a function of an impedance between the electrode and the ground pad conductors.

6. The radiofrequency ablation system of claim 1 wherein the power supply independently controls the power dissipated between each of the ablation electrodes and ground pad conductors to at least one predetermined value.

7. The radio frequency ablation system of claim 1 wherein the predetermined value is a constant value.

8. The radiofrequency ablation system of claim 1 wherein the ground pad conductors are different mutually insulated conductive areas of an integral pad unit.

9. The radiofrequency ablation system of claim 1 wherein the ground pad conductors are actively cooled.

10. A radiofrequency ablation power supply comprising:

an electrical connector accepting a mating connector to an ablation electrode for insertion into a patient at an ablation site;

at least two additional electrical connectors accepting mating connectors for at least two ground pad conductors for topical application to a portion of the patient'"'"'s skin; and

independent power regulation circuitry controlling the power applied to tissue at the ablation site from current passing through a first ground pad conductor and the power applied to tissue at the ablation site from current passing through a second ground pad conductor.

11. The radiofrequency ablation power supply of claim 10 wherein the power regulation circuitry is electronically controlled switches interposed between a power source and each of the at least two additional electrical connectors for alternating connecting the power source and the two additional electrical connectors.

12. The radiofrequency ablation power supply of claim 11 further including a clock circuit controlling a switching of the electronically controlled switches according to a predetermined time schedule.

13. The radiofrequency ablation power supply of claim 10 further including inputs receiving a temperature signal associated with each ground pad conductor and wherein the power regulation circuitry controls the power associated with current through each of the ground pad conductors as a function of temperature at the ground pad conductor.

14. The radiofrequency ablation power supply of claim 10 wherein the power regulation circuitry controls the power associated with current through each of the ground pad conductors, a function of impedance between the ablation electrode each ground pad conductor.

15. The radiofrequency ablation power supply of claim 10 wherein the power regulation circuitry limits the power associated with each ground pad conductors to at least one predetermined value.

16. The radiofrequency ablation power supply of claim 10 wherein the predetermined value is a constant value.

17. The radiofrequency ablation power supply of claim 10 further ground pad verification circuit providing a signal indicating a number of ground pad conductors connected to the power supply to control the power supply based on that signal.

18. The radiofrequency ablation power supply of claim 10 further providing user controls allowing user modification of the power applied to tissue at the ablation site from current passing through the first ground pad conductor and the power applied to tissue at the ablation site from current passing through the second ground pad conductor.

19. A ground pad for use with a radiofrequency ablation system comprising:

a flexible pad element having a skin contacting surface;

at least two mutually insulated conductive areas exposed at the skin contacting surface and sized to provide a broad area electrical return for ablation;

a conductor assembly having an electrical conductor connected to each of the mutually insulated conductive areas to communicate with a ground connection at an ablation power supply.

20. The ground pad of claim 19 further including an adhesive on the skin side of the pad element to hold the pad element to the skin.

21. The ground pad of claim 19 further including an active cooling device cooling the ground pad.

22. A method of radiofrequency ablation comprising the steps of:

(a) inserting at least one ablation electrode into a patient at an ablation site;

(b) attaching at least two ground pad conductors in electrical communication with a portion of the patient'"'"'s skin; and

(c) applying a radiofrequency voltage between the ablation electrode and the ground pad conductors to ablate tissue at the ablation site while independently adjusting a current flow at each of the ground pad conductors to reduce risk of skin burns.

23. The method of radiofrequency ablation of claim 22 wherein the radiofrequency voltage is switched according to a schedule from between the ablation electrode and a first ground pad conductor to between the ablation electrode and a second ground pad conductor.

24. The method of radiofrequency ablation of claim 23 wherein the schedule is a fixed periodic schedule.

25. The method of radiofrequency ablation of claim 22 further including the step of controlling the current between the ablation electrode and each ground pad conductor as a function of temperature at the ground pad conductor.

26. The method of radiofrequency ablation of claim 22 further including the step of controlling the current between the ablation electrode and each ground pad conductor as a function of impedance between the electrode and the ground pad conductors.

27. The method of radiofrequency ablation of claim 22 wherein the power dissipated between the ablation electrode and each of the ground pad conductors is limited to a predetermined value.