Power modulated endometrial lining tissue ablation
A system is configured to delivering radiofrequency power to the endometrial lining tissue of a uterine cavity, including modulating the delivered power so that a measured impedance of the endometrial lining tissue tracks a target impedance as a function of time, wherein the target tissue impedance is derived from a function that approximates a preferred endometrial lining tissue ablation impedance curve that is determined based upon a measured impedance of the endometrial lining tissue after RF power has been delivered for a predetermined initial time period.
1. A method for performing an endometrial lining tissue ablation procedure, the method comprising:
positioning a radiofrequency (RF) applicator within a uterine cavity, wherein the RF applicator is electrically coupled with an RF generator;
delivering RF power from the RF generator to endometrial lining tissue within the uterine cavity via the RF applicator;
after delivering the RF power to the endometrial lining tissue for an initial time period, measuring an initial impedance of the endometrial lining tissue using an impedance measurement circuit provided by the RF applicator;
based upon the measured initial impedance, determining a target impedance of the endometrial lining tissue as a function of time for a duration of the endometrial lining ablation procedure; and
modulating the RF power delivered to the endometrial lining tissue during the endometrial lining ablation procedure so that an impedance of the endometrial lining tissue tracks the target impedance.
2. The method of claim 1 , wherein the target impedance of the endometrial lining tissue for the duration of the endometrial lining ablation procedure is based in part upon scaling a preexisting endometrial lining tissue ablation impedance curve based upon the measured initial impedance of the endometrial lining tissue.
3. The method of claim 1 , wherein the controller is configured to determine the target impedance of the endometrial lining tissue for the duration of the endometrial lining ablation procedure based in part upon impedance data obtained from prior performed endometrial lining tissue ablation procedures.
4. The method of claim 1 , wherein the RF applicator comprises an electrode carrier including one or more bipolar electrode pairs thereon.
5. The method of claim 1 , wherein the RF power is delivered to the endometrial lining tissue at a substantially constant power level during the initial time period.
6. The method of claim 5 , wherein a duration of the initial time period and the substantially constant power level of the delivered RF power during the initial time period are together sufficient such that the measured initial impedance is representative of an electrical conductivity of the endometrial lining tissue.
7. The method of claim 2 , wherein the target impedance of the endometrial lining tissue for the duration of the endometrial lining ablation procedure is determined according to a formula, I t =I max −((I max −I o )*S), where
I t is a target tissue impedance for a given time t during the endometrial lining ablation procedure,
I max is a target maximum impedance of the endometrial lining tissue,
I o is a projected impedance of the endometrial lining tissue for the given time t during the endometrial lining ablation procedure derived from a function approximating the preexisting endometrial lining tissue ablation impedance curve, and
S is a scaling factor equal to (I max −I meas )/(I max −I io ), where I meas is the measured initial impedance of the endometrial lining tissue, t initial , and I io is a projected initial impedance of the endometrial lining tissue derived from the function approximating the preexisting endometrial lining tissue ablation impedance curve.
8. The method of claim 7 , wherein the duration of the endometrial lining ablation procedure is about 120 seconds, I max is about 50 ohms, and the function approximating the preexisting endometrial lining tissue ablation impedance curve is I t =4+(49 (T/120) ), where T is a given time (in seconds) during the endometrial lining ablation procedure.
9. The method of claim 1 , wherein the RF power is delivered to the endometrial lining tissue until (i) the impedance of the endometrial lining tissue reaches a target maximum tissue impedance, or (ii) a duration of the endometrial lining ablation procedure reaches a target completion time, whichever occurs first.
10. The method of claim 1 , wherein the delivery of the RF power to the endometrial lining tissue is modulated by causing one of increasing, decreasing, or maintaining constant a delivered RF current to the endometrial lining tissue at regular power adjustment intervals.
11. The method of claim 10 , wherein, at each power adjustment interval, an amperage of the delivered RF current is not increased or decreased more than a predetermined adjustment limit.
12. The method of claim 11 , wherein the predetermined adjustment limit is about 3%.
13. A method for performing an endometrial lining tissue ablation procedure, the method comprising:
positioning a radiofrequency (RF) applicator within a uterine cavity, wherein the RF applicator is electrically coupled with an RF generator;
delivering RF power from the RF generator to endometrial lining tissue within the uterine cavity via the RF applicator;
after delivering the RF power to the endometrial lining tissue for an initial time period, measuring an initial impedance of the endometrial lining tissue using an impedance measurement circuit provided by the RF applicator;
modulating the RF power delivered to the endometrial lining tissue during the endometrial lining ablation procedure so that an impedance of the endometrial lining tissue tracks a target impedance of the endometrial lining tissue as a function of time for a duration of an endometrial lining ablation procedure derived from impedance data obtained from prior performed endometrial lining tissue ablation procedures; and
stopping delivery of the RF power to the endometrial lining tissue when (i) the impedance of the endometrial lining tissue reaches a target maximum tissue impedance, or (ii) the duration of the endometrial lining ablation procedure reaches a target completion time, whichever occurs first.
14. The method of claim 13 , wherein the delivery of the RF power to the endometrial lining tissue is modulated by causing one of increasing, decreasing, or maintaining constant a delivered RF current to the endometrial lining tissue at regular power adjustment intervals.
15. The method of claim 13 , wherein, at each power adjustment interval, an amperage of the delivered RF current is not increased or decreased more than a predetermined adjustment limit.
16. The system of claim 13 , wherein the target impedance of the endometrial lining tissue for the duration of the endometrial lining ablation procedure is determined according to a formula, I t =I max −((I max −I o )*S), where
I t is a target tissue impedance for a given time t during the endometrial lining ablation procedure,
I max is a target maximum impedance of the endometrial lining tissue,
I o is a projected impedance of the endometrial lining tissue for the given time t during the endometrial lining ablation procedure derived from a function approximating a preexisting endometrial lining tissue ablation impedance curve, and
S is a scaling factor equal to (I max −I meas )/(I max −I io ), where I meas is the measured initial impedance of the endometrial lining tissue, and I io is a projected initial impedance of the endometrial lining tissue derived from the function approximating the preexisting endometrial lining tissue ablation impedance curve.
17. The system of claim 16 , wherein the duration of the endometrial lining ablation procedure is about 120 seconds, I max is about 50 ohms, and the function approximating the preexisting endometrial lining tissue ablation impedance curve is I t =4+(49 (T/120) ), where T is a given time (in seconds) during the endometrial lining ablation procedure.