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Objective: To correlate CT and MR patterns of ovarian mature cystic teratomas (MCT)., Subjects and Methods: CT and MR findings in 25 histologically proven ovarian MCT were retrospectively reviewed. MCT characterization at CT and MR was based on detection of fat and/or a Rokitansky protuberance. MR signal intensity and CT density numbers of fat were correlated., Results: At pathology, 24/25 tumors contained fat, 1/25 a water content, and 23/25 a Rokitansky protuberance. Twenty one MCT contained fat with a density number less than-20 HU (mean density: -95 HU) and a signal intensity superior or equal to sub-cutaneous fat on T1 images, however, only six of these had a signal intensity equal to sub-cutaneous fat on T1 and T2 images and 12 had a reversed chemical shift artifact. Three contained fat with a density number ranging from -13 to +8 HU and a signal intensity inferior to subcutaneous fat on T1 images. CT showed a Rokitansky protuberance in 21/23, containing adipose tissue in 16 and calcified structures in 21. Standard MR showed a Rokitansky protuberance in 14/23 and characterized adipose tissue in eight cases, and calcified material in six cases. Finally, CT characterized 24/25 (96%) MCT. Standard MR characterized 22/25 (88%) MCT, and standard MR with fat-suppression sequences characterized 23/25 (92%) MCT., Conclusion: Standard MR is less effective than CT in characterizing fat and has the same difficulty as CT in characterizing fat mixed with hair when its density is high. When fat cannot be identified by either technique, diagnosis of a Rokitansky protuberance is more easily made at CT than at MR.

Objective: The aim of this study is to analyze the ability of MR fat suppression techniques to characterize fat components of ovarian mature cystic teratomas (MCT) shown by CT., Subjects and Methods: MR images of eight MCTs of the ovary were obtained using standard sequences followed by a SPIR (spectral presaturation with inversion recovery) sequence in six cases and by Dixon sequences in two cases. In all cases correlation with CT and pathologic findings was achieved., Results: MR fat suppression sequences showed to be as accurate as CT in detecting fat inside the cystic part of the teratomas (8/8)., Conclusion: MR fat suppression sequences should be performed when presence of fat is suspected on images of ovarian tumors produced by standard MR sequences.

MRI findings in three cases of pseudomyxoma peritonei, in two cases associated with visceral invasion, are described. MR imaging using the same morphologic criteria as described in ultrasonography and CT suggested the diagnosis in all three cases. In T 1 weighted images (SE 400/28 ms) the hypointensity of signals of both implants and mucoid ascites was found to approach that of muscle tissue. In T 2 weighted images (SE 1600/40, 80, 120 ms), however, there was general hyperintensity of signals, which was more pronounced in mucoid ascites than in implants, and which approached signal intensities of water. Invasion of the viscera was very well depicted in all cases.