High field resolution magnetic resonance imaging of malignant choroidal melanoma.

High resolution surface receiver coil nuclear magnetic resonance imaging (MRI) of the eye and paraorbital areas was performed in a patient with a malignant choroidal melanoma before and after local radiotherapy using ruthenium application. The resulting improvement in signal-to-noise ratio allows for a reduction in the imaging voxel size to 0.31 X 0.31 X 3 mm3 which provided useful morphological information with respect to delineation of tumoral mass. In the same MRI session using a standard head coil imaging method, T1 and T2 relaxation time values were calculated in regions of interest of 3 X 3 mm by means of transversal scan images of orbital and cranial tissues performed in scan times of 7 to 9 minutes. The procedure presented here combines in one single session high resolution imaging performance, previously unobservable in MRI and in other noninvasive imaging techniques, with fast and reliable measurement of T1 and T2 relaxation times within small regions of interest. MRI, a non ionizing technique, offers within reasonable acquisition times not only a good multiplanar description of the site, size and volume of normal and pathologic orbital structures, but, in addition, the prospect of soft tissue differentiation and of accurately documenting the response to and side effects of the therapy of ocular tumors.