Radiofrequency ablation with independently controllable ground pad conductors

• US 7,736,357 B2
• Filed: 08/29/2005
• Issued: 06/15/2010
• 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: Goldberg, S. Nahum, Lee, Fred T. Jr., Haemmerich, Dieter Georg, Sampson, Lisa Ann, Winter, Thomas Charles III
• Primary Examiner(s): Cohen; Lee S
• Application Number:
  US11/214,398
• Publication Number:
  US 20070049919A1
• Time in Patent Office: 1,751 Days
• Field of Search: 606 34- 35, 606 41- 42, 606/32
• 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 radio frequency 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 at least one ablation electrode and the at least two ground pad conductors to ablate tissue at the ablation site;

wherein the power supply switches an application of the voltage first between the at least one ablation electrode and a first ground pad conductor, and second between the at least one ablation electrode and a second ground pad conductor according to a predetermined time schedule.

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

3. The radiofrequency ablation system of claim 1 wherein the power supply applies the voltage independently between the at least one ablation electrode and the at least two ground pad conductors also as a function of an impedance between the at least one ablation electrode and the at least two ground pad conductors.

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

5. The radiofrequency ablation system of claim 4 wherein the predetermined value is a constant value.

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

7. The radio frequency ablation system of claim 1 wherein the at least two ground pad conductors are actively cooled.

8. 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;

independent power regulation circuitry controlling the power applied to tissue at the ablation site, wherein the power applied to the tissue at the ablation site is a function of the current passing through a first ground pad conductor and the current passing through a second ground pad conductor;

a clock circuit controlling a switching of the power regulation circuitry according to a predetermined time schedule; and

a power source configured for regulation by the independent power regulation circuitry.

9. The radio frequency ablation power supply of claim 8 wherein the power regulation circuitry is electronically controlled switches interposed between the power source and each of the at least two additional electrical connectors for alternating connecting the power source and the two additional electrical connectors.

10. The radiofrequency ablation power supply of claim 8 further including inputs receiving a temperature signal associated with the at least two ground pad conductors and wherein the power regulation circuitry controls the power associated with current through the at least two ground pad conductors as a function of temperature at the at least two ground pad conductors.

11. The radiofrequency ablation power supply of claim 8 wherein the power regulation circuitry controls the power associated with current through each of the at least two ground pad conductors, as a function of impedance between the ablation electrode and the at least two ground pad conductors.

12. The radiofrequency ablation power supply of claim 8 wherein the power regulation circuitry limits the power associated with the at least two ground pad conductors to at least one of predetermined value.

13. The radiofrequency ablation power supply of claim 12 wherein the predetermined value is a constant value.

14. The radiofrequency ablation power supply of claim 8 further including a 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.

15. The radiofrequency ablation power supply of claim 8 further providing user controls allowing user modification of the power applied to tissue at the ablation site by controlling the current passing through the first ground pad conductor and the power applied to tissue at the ablation site by controlling the current passing through the second ground pad conductor.

16. 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 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;

wherein the radiofrequency voltage is switched according to a fixed periodic schedule from between the at least one ablation electrode and a first ground pad conductor to between the at least one ablation electrode and a second ground pad conductor.

17. The method of radiofrequency ablation of claim 16 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.

18. The method of radiofrequency ablation of claim 16 further including the step of controlling the current between the ablation electrode and each ground pad conductor as a function of impedance between electrode and the ground pad conductors.

19. The method of radiofrequency ablation of claim 16 wherein the power dissipated between the ablation electrode and each of the ground pad conductors is limited to a predetermined value.