Microwave power and duration without extrauterine thermal damage in microwave endomyometrial ablation at 2.45 GHz.
OBJECTIVE
We investigated microwave power and duration of use, which does not affect extrauterine organs, in order to treat organic menorrhagia caused by myomas or adenomyosis.


METHODS
Electric fields around a microwave applicator at a frequency of 2.45 GHz were calculated using the finite element method with commercially available software for analysis of electromagnetic fields. Transient temperature distributions around the applicator were obtained by numerically solving the bioheat transfer equation during microwave irradiation for 120 s in the human uterus and swine liver. We compared areas enclosed by the 60 degrees C isotherm obtained using numerical simulations and necrosis areas after microwave irradiation. Postoperative avascular areas in a Gd-enhanced MRI of a uterus enlarged by adenomyosis after clinical microwave endomyometrial ablation were compared with numerical simulations.


RESULTS
There was good agreement between the calculated results and the experiments. At 40 W of output power for 50 s of duration and 64.5 W for 100 s, the depth of the necrotized uterine wall did not increase beyond 7 mm and 11 mm, respectively, either in the calculations or the experiments. Generally, the 50 degrees C isotherm was located approximately 2 mm external to the 60 degrees C isotherm in temperature distributions. The Gd-enhanced MRI after the operation depicted avascular areas, which agreed with the results of numerical simulations.


CONCLUSIONS
The myometrial portion of a uterine wall > or = 13 mm throughout the uterus irradiated for < or = 64.5 W for 100 s is sufficient to avoid thermal damage of the extrauterine organs during microwave endomyometrial ablation.
Kanaoka
Yasushi
Y
Department of Obstetrics and Gynecology, Osaka City University Graduate School of Medicine, Osaka, Japan. kanaokamd@med.osaka-cu.ac.jp
Hirai
Kouzo
K
Ishiko
Osamu
O
D000818:Animals; D017115:Catheter Ablation / Q000379:methods; D003198:Computer Simulation; D004715:Endometriosis / Q000601:surgery*; D005260:Female; D006801:Humans; D008595:Menorrhagia / Q000209:etiology / Q000601:surgery*; D008872:Microwaves / Q000627:therapeutic use*; D013552:Swine; D014591:Uterine Diseases / Q000601:surgery*