Prognostic application of magnetic resonance imaging in patients with endometriomas treated with gonadotrophin-releasing hormone analogue.

We evaluated the usefulness of magnetic resonance imaging (MRI) for assessing the response of patients with endometriomas to medical therapy. MRI was performed before and after treatment in 20 consecutive patients with at least one endometrioma with a maximal diameter >10 mm diagnosed by laparoscopy who received 900 microg of buserelin acetate daily for 6 months. Patients were categorized as good responders (group I, n = 13) and poor responders (group II, n = 7) depending on the results of a third-look laparoscopy performed 6 months after treatment. We determined the ratio of the signal intensity (SI) of the endometrioma to the SI of the gluteus maximus muscle on T2-weighted images [T2SI/M (muscle) SI] and the volume of the endometrium. The volume decreased by >50% in 61.5% of the good-response group and 57.1% of the poor-response group. There was no significant difference between the two groups. The T2SI/MSI decreased in 12 of 13 patients in group I but in only one of seven patients in group II, a significant difference (P < 0.05) between the two groups. In the good-response group, there was a positive linear correlation between the decrease in the volume of the endometrioma and the decrease in the T2SI/MSI after treatment (r = 0. 561, P < 0.05). Therefore, the T2SI/MSI determined from MR images may be useful in assessing the therapeutic response of patients with endometriomas.