Struma ovarii: MRI findings.

We describe the MRI findings in three cases of struma ovarii. In all three cases, MRI showed a multilocular cystic mass with a variable signal intensity within loculi. Some loculi or small cysts within septations showed low signal intensity on T1 weighted images and very low signal intensity on T2 weighted images, corresponding pathologically to gelatinous colloid material in large follicles. In one case, with Gd-DTPA enhanced T1 weighted images, the thick septations and locally thickened wall showed marked enhancement, corresponding microscopically to thyroid tissue.