Endometrial cysts of the ovary: MR imaging.

Magnetic resonance (MR) images of 15 cases of ovarian endometrial cyst were reviewed. With a high-field-strength (1.5-T) MR imager, T1- and T2-weighted images were obtained in axial and sagittal planes, with 5-mm section thickness. MR findings highly suggestive of an endometrial cyst included adhesions to the surrounding organs (e.g., loss of clear margin of the uterine body and tethered appearance of the rectum); a distinct low-intensity zone surrounding a cyst loculus on both T1- and T2-weighted images produced by a thick fibrous capsule; loculus contents with short T1 and long T2 values, attributed to hemorrhagic fluid; and prominent low intensity (shading) within a loculus on T2-weighted images, the mechanism of which is yet to be determined.