Ratio of directly necrotized volume to total volume of a submucosal myoma predicts shrinkage after microwave endometrial ablation

Abstract

To explore parameters relating to shrinkage of submucosal myomas after microwave endometrial ablation. Fourteen patients underwent microwave endometrial ablation at 2.45 GHz using a curved microwave applicator to treat menorrhagia caused by a submucosal myoma. The size of myomas was measured on magnetic resonance images before, one month after, and six months after the operation. The average radius r was defined as half of the size of the myoma measured in three dimensions. The protrusion ratio alpha was defined as the ratio of the thickness of the protruding part of a myoma in the uterine cavity to the size of the myoma before the operation. The ratio of the directly necrotized volume by microwave irradiation to the total volume (RODNeV) of preoperative myomas was calculated using the following formula: (1) where d is the depth of myoma tissue directly necrotized by microwave irradiation. The relationships of preoperative alpha, r and RODNeV to postoperative shrinkage were then examined. Two-dimensional plots showing shrinkage of submucosal myomas versus the RODNeV indicated that shrinkage at six months after microwave endometrial ablation depends on the RODNeV. Myomas with a RODNeV greater than 0.17 had shrunk more than 50% at six months after the operation. RODNeV is closely related to postoperative necrosis and shrinkage of the submucosal myoma after microwave endometrial ablation. Prediction of the shrinkage rate of submucous myomas appears to be possible by calculating the RODNeV preoperatively.