Ovarian cystic teratomas: MR imaging.

Magnetic resonance (MR) imaging characteristics of ovarian cystic teratomas were evaluated in 18 patients with 23 surgically proved tumors. The fat within the tumor demonstrated characteristic intensity similar to that of subcutaneous fat and a pathognomic pattern of chemical shift artifact that helped differentiate ovarian cystic teratomas from endometrial cysts. In addition to fat, MR images of ovarian cystic teratomas had several other characteristics that allowed confident diagnosis, including gravity-dependent layering or floating debris, palm tree-like protrusions or rounded nodules (dermoid plugs), and, occasionally fat-fluid levels and globular calcification. MR images were diagnostic in 20 tumors and were able to depict a tumor measuring 2 cm in diameter. MR imaging appears to be valuable in problematic cases in which other modalities are not diagnostic.