Power Ramping During RF Ablation

• US 20080071257A1
• Filed: 09/18/2006
• Published: 03/20/2008
• Est. Priority Date: 09/18/2006
• Status: Active Grant

• Current Assignee: Cytyc Corporation (Hologic Incorporated)
• Original Assignee: Cytyc Corporation (Hologic Incorporated)
• Inventors: Taylor, Scott Dennis, Sampson, Russel M., Kotmel, Robert
• Granted Patent: US 8,486,060 B2
• Time in Patent Office: Days
• US Class Current: 606/32
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1485 having a short rigid shaft for accessing the inner body through natural openings
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00559 Female reproductive organs
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2218/002 Irrigation
• CPC Class Codes: A61B 2218/007 Aspiration

Abstract

A method for tissue ablation is described. An RF applicator including an electrode carrier with one or more bipolar electrodes thereon is positioned at a target tissue site for tissue ablation. A current at an initial current level is passed through the one or more bipolar electrodes to the target tissue site to apply an initial power density to destroy tissue for an initial time period. A vacuum source in fluid communication with the RF applicator is employed to remove moisture generated during ablation away from the target tissue site. After the initial time period, the power density is ramped up by increasing the current passed through the one or more bipolar electrodes to the target tissue site for a second time period.

Claims

1. A method for tissue ablation comprising:

positioning an RF applicator comprising an electrode carrier with one or more bipolar electrodes thereon at a target tissue site for tissue ablation;

passing a current at an initial current level through the one or more bipolar electrodes to the target tissue site to apply an initial power density to destroy tissue for an initial time period;

employing a vacuum source in fluid communication with the RF applicator to remove moisture generated during ablation away from the target tissue site; and

after the initial time period, ramping up the power density by increasing the current passed through the one or more bipolar electrodes to the target tissue site for a second time period.

2. The method of claim 1, wherein ramping up the power density comprises steadily increasing the current over the second time period.

3. The method of claim 1, wherein ramping up the power density comprises suddenly increasing the current from the initial current level to a second current level and applying the second current level for the second time period.

4. The method of claim 1, further comprising:

monitoring an impedance level at an interface between the target tissue site and the RF applicator;

where the initial time period is a time period after which a threshold decrease in the impedance level from an initial impedance level is detected.

5. The method of claim 4, where the second time period is a time period beginning when the threshold decrease in impedance level is detected and ending when the impedance level is detected as having returned to substantially the initial impedance level, the method further comprising:

after the second time period, decreasing the power density to the initial power density.

6. The method of claim 5, further comprising:

after decreasing the power density to the initial power density, steadily increasing the power density over a third time period.

7. The method of claim 4, where:

the target tissue site is a tubal ostium in a female uterine cavity;

the initial power density is approximately 5 watts per square centimeter;

the decrease in impedance level detected is a decrease of approximately 25%; and

the power density is increased during the second time period at a rate of approximately 1 watt per square centimeter per second.

8. The method of claim 4, where:

the target tissue site is a tubal ostium in a female uterine cavity;

the initial power density is approximately 5 watts per square centimeter;

the decrease in impedance level detected is a decrease of approximately 33%; and

the power density is increased during the second time period at a rate of approximately 2.5 watts per square centimeter per second.

9. The method of claim 4, where:

the target tissue site is a tubal ostium in a female uterine cavity;

the initial power density is approximately 5 watts per square centimeter;

the decrease in impedance level detected is a decrease of approximately 50%; and

the power density is increased during the second time period to a level of approximately 10 to 15 watts per square centimeter.

10. The method of claim 1, where the initial time period is determined empirically as a time period after which an initial depth of tissue destruction has been achieved.

11. The method of claim 10, where:

the target tissue site is a tubal ostium in a female uterine cavity;

the initial power density is approximately 5 watts per square centimeter;

the initial time period is between approximately 45 and 60 seconds;

the power density is increased during the second time period at a rate of approximately 1 watt per square centimeter per second; and

the second time period is between approximately 5 and 10 seconds.

12. The method of claim 10, where:

the target tissue site is a tubal ostium in a female uterine cavity;

the initial power density is approximately 5 watts per square centimeter;

the initial time period is between approximately 10 and 60 seconds;

the power density is increased during the second time period at a rate of approximately 0.5 to 2.5 watts per square centimeter per second; and

the second time period is between approximately 5 and 10 seconds.