Magnetic resonance imaging of the ovarian cyst : its diagnostic value of endometrial cyst

Abstract

The role of magnetic resonance imaging (MRI) in diagnosing the ovarian cyst was reviewed with emphasis on its diagnostic value of endometrial cyst. 94 cystic ovarian masses in 77 patients were evaluated using 0.15 Tesla MRI just before laparotomy at Okayama University Hospital from 1984 to 1987 and these images were followed up by histopathological data. From these obtained images, 6 parameters; that is (1) laterality and (2) delineation of the cyst, (3) presence or absence of septal image, and (4) homogeneity, (5) signal intensity and (6) T1 value of the cyst contents, were extracted and analyzed respectively. In 95.5% of endometrial cysts, homogenous internal pattern was observed in all 3 images (short spin echo (SE), inversion recovery (IR) and long SE) and its signal intensity was at the same level or higher than that of myometrium. On the other hand, in all cases of follicular cyst, para-ovarian cyst, corpus luteum cyst and in 95.0% of serous cystadenoma and in 90.9% of mucinous cystadenoma, cyst contents showed either lower signal intensity than the myometrium or similar to it in T1 contrast images (short SE and IR). 93.1% of dermoid cyst showed heterogenous signal intensity in all 3 images and their signal intensity levels were widely ranging. High signal intensity of cyst contents in all 3 images could be observed in 72.7% of endometrial cyst, 5.0% of serous cystadenoma with internal hemorrhage, 9.1% of mucinous cystadenoma with internal hemorrhage and 3.4% of dermoid cyst consisted of fatty tissue only. Endometrial cyst showed markedly shortened T1 value (209.6 +/- 102.7 ms) and the other hemorrhagic cyst showed comparatively short value (360-970 ms). On the other hand, T1 value of non hemorrhagic cyst was as high as the level of urine. All of endometrial cysts were clearly defined from the other pelvic structures. In result, endometrial cysts were found to exhibit the characteristic findings in MRI images such as homogenous high signal intensity of internal fluid and clear delineation of cyst contour. The diagnostic accuracy of MRI in endometrial cyst were considered 96.8% in our cases.