[MR imaging of orbital tumors].

Nine cases of pathologically confirmed orbital tumors were evaluated with magnetic resonance imaging (MRI) at 0.5T. Seven cases were examined with orbit-coil using 7-mm-thick sections and two cases were examined with head-coil using 10-mm-thick sections. All lesions were clearly demonstrated on T1-weighted images as low intensity. However, the lesions were indistinct on T2-weighted images because of low contrast between the lesions and surrounding orbital fat and artefact produced by eye movement. Two of three cases with meningioma examined with orbit-coil were clearly discriminated from the optic nerve. Meningioma in the remaining case examined with head-coil was discriminated from the optic nerve by administration of Gd-DTPA. Adenoma of the right lacrimal gland was shown as an enlarged gland on T1-weighted images. Pseudotumors (four cases) showed very low intensity on T1-weighted images. Three cases of four pseudotumors showed low intensity on T2-weighted images. Among them one was moderately low intensity, and histological examination of the lesion showed prominent fibrotic changes. Pseudotumor of the remaining case examined with the head-coil showed same intensity with fat on T2-weighted images. Intraorbital infiltrating foci of chronic lymphocytic leukemia showed low intensity with fat on T1-weighted images, and the same intensity with fat on T2-weighted images. MRI may be useful to discriminate pseudotumor with fibrotic changes (chronic inflammatory lesions) from lymphoma or leukemic infiltration.