Electrosurgical power control

• US 20060293649A1
• Filed: 06/22/2005
• Published: 12/28/2006
• Est. Priority Date: 06/22/2005
• Status: Active Grant

• Current Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Inventors: Drucker, Karen, Iki, Kobi, Mitchell, Mathew E., Lorang, Douglas M.
• Granted Patent: US 7,655,003 B2
• Time in Patent Office: Days
• US Class Current: 606/32
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/18 by applying electromagnetic radiation, e.g. microwaves radiation therapy A61N5/00
• CPC Class Codes: A61B 2017/00026 Conductivity or impedance, e.g. of tissue
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00678 upper
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00875 Resistance or impedance

Abstract

A method and apparatus include determining a value of a parameter associated with operation of an electrosurgical probe having a particular probe design, and determining whether the value of the parameter is within a range of values that has been predetermined for the particular probe design to indicate that the probe is treating tissue in a desired manner. Power is delivered to the probe according to an algorithm based upon a determination that the value of the parameter is outside the range of values The algorithm delivers power in a pulsed profile including portions of low power and portions of high power. In one embodiment, the tissue treatment is ablation, the parameter is impedance, and the method limits tissue necrosis to less than 200 microns. In another embodiment, the tissue treatment is shrinkage, the parameter is temperature, and the method limits power delivery when the probe is not shrinking tissue.

Claims

1. A method comprising:

determining a value of a parameter, the parameter being associated with operation of an electrosurgical probe having a particular probe design;

determining whether the value of the parameter is within a range of values that has been predetermined for the particular probe design to indicate that the probe is treating tissue in a desired manner; and

delivering power to the probe according to an algorithm based upon a determination that the value of the parameter is outside the range of values, the algorithm comprising a pulsed profile including portions of low power and portions of high power.

2. The method of claim 1 wherein the parameter comprises an impedance.

3. The method of claim 2 wherein the range of the impedance is between approximately 50 ohms and approximately 4000 ohms.

4. The method of claim 2 wherein the desired manner of tissue treatment comprises ablation.

5. The method of claim 4 further comprising limiting the low power in the pulsed profile to a duration that causes substantially no noticeable delay in initiating ablation.

6. The method of claim 5 wherein the duration of the pulsed low power is between approximately 50 milliseconds and approximately 500 milliseconds.

7. The method of claim 4 wherein the low power in the pulsed profile comprises a power setting between approximately 0 watts and approximately 50 watts.

8. The method of claim 4 further comprising providing the high power in the pulsed profile with a duration substantially equal to a minimum length sufficient to initiate ablation.

9. The method of claim 4 wherein the high power comprises a power setting between approximately 40 watts and approximately 300 watts.

10. The method of claim 1 wherein the parameter comprises a temperature.

11. The method of claim 10 wherein the range of the temperature is between approximately 65°

C. and approximately 90°

C.

12. The method of claim 11 wherein the range of the temperature is between approximately 75°

C. and approximately 90°

C.

13. The method of claim 10 wherein the desired manner of tissue treatment comprises shrinkage.

14. The method of claim 13 further comprising limiting the low power in the pulsed profile to a duration that limits a delay in initiating shrinkage.

15. The method of claim 13 wherein the low power in the pulsed profile comprises a power setting between approximately 0 watts and approximately 20 watts.

16. The method of claim 13 further comprising providing the high power in the pulsed profile with a duration that is greater than a time needed for the temperature to reach a lower limit of the range when the probe is shrinking tissue and that is less than a time needed for the temperature to reach a lower limit of the range when the probe is not shrinking tissue.

17. The method of claim 13 wherein the high power comprises a power setting between approximately 10 watts and approximately 300 watts.

18. The method of claim 1 further comprising delivering power to the probe according to a second algorithm different from the algorithm to treat tissue in the desired manner based upon a determination that the value of the parameter is within the range of values.

19. The method of claim 18 further comprising switching from the algorithm to the second algorithm upon a determination that the parameter is greater than a lower limit of the range of values by a margin.

20. The method of claim 18 further comprising switching from the second algorithm to the algorithm upon a determination that the parameter is less than a lower limit of the range of values by a margin.

21. The method of claim 1 further comprising:

determining a specific number of values of the parameter, the specific number being greater than one; and

determining, for less than all of the specific number of values, whether the values of the parameter are within the predetermined range of values.

22. An apparatus comprising one or more computer readable media having instructions stored thereon and configured to result in at least the following:

determining a value of a parameter associated with operation of an electrosurgical probe having a particular probe design;

determining whether the value of the parameter is within a range of values that has been predetermined for the particular probe design to indicate that the probe is treating tissue in a desired manner; and

delivering power to the probe according to an algorithm based upon a determination that the value of the parameter is outside the range of values, the algorithm comprising a pulsed profile including portions of low power and portions of high power.

23. A method comprising:

making one or more determinations that an impedance value encountered by an electrosurgical probe is less than a threshold value; and

limiting tissue necrosis to less than 200 microns by delivering power to the electrosurgical probe, in response to at least one of the one or more determinations that the impedance is less than the threshold value, according to an algorithm having a pulsed profile of low and high power.

24. An apparatus comprising:

an electrosurgical probe configured to deliver power to tissue; and

a control module configured to make one or more determinations that an impedance value encountered by the electrosurgical probe is less than a threshold value, and to limit tissue necrosis to less than 200 microns by delivering power to the electrosurgical probe in response to at least one of the one or more determinations that the impedance is less than the threshold value according to an algorithm having a pulsed profile of low and high power.

25. A method comprising:

determining whether a probe is delivering power in an ablative mode or a non-ablative mode;

delivering power according to a first algorithm when in the ablative mode;

delivering power according to a second algorithm different from the first algorithm when in the non-ablative mode, the second algorithm comprising a pulsed profile including portions of low power and portions of high power, the portions of high power being of sufficient durations to initiate the ablative mode and the durations being less than 250 milliseconds.

26. A method comprising:

determining a rate at which a temperature of a probe approaches a range of temperatures that has been predetermined to enable shrinkage of tissue;

determining whether the rate is within a range of rates that has been predetermined to indicate that a distance from the probe to tissue is small enough to enable shrinkage of tissue at a temperature in the range of temperatures; and

delivering power to the probe according to an algorithm based upon a determination that the rate is outside the range of rates, the algorithm comprising a pulsed profile including portions of low power and portions of high power.

27. The method of claim 26 wherein the range of rates has been predetermined based on the probe design.