Magnetic resonance imaging of uveal melanomas.

A series of 31 patients who presented with uveal mass lesions was studied with magnetic resonance imaging (MRI). Uveal melanoma was the presumed clinical diagnosis in 23 of the cases. Ten (43%) of these suspected melanomas provided useful images on both spin-lattice (T1)- and spin-spin (T2)-weighted studies and these had characteristic features. The features include a high-intensity image on T1-weighted studies with progressively decreasing relative intensity on T2-weighted images. These findings are consistent with short T1 and T2 relaxation times. In contrast, three cases of carcinoma metastatic to the choroid demonstrated a relatively high signal intensity on both T1- and T2-weighted images. The short relaxation times exhibited by uveal melanomas are in contrast with the relatively long T1 and T2 times found in other malignant neoplasms. These characteristics may provide a noninvasive method for differentiation of malignant melanoma from other mass lesions within the uveal tract.