Vascular Perfusion of Choroidal Melanoma by 3Tesla MRI

Abstract

Abstract: : Purpose: To describe the vascular perfusion patterns of choroidal melanoma by 3Tesla(3T) MRI. Standard magnetic resonance imaging (MRI) occurs at 1.5Tesla. Recent advances in supermagnets have led to the development of 3T MRI units with improved visualization of orbital and ocular structures. The addition of contrast material can demonstrate the vascular perfusion of ocular lesions. We examined the vascular perfusion of eleven patients with intraocular masses (nine choroidal melanomas, one metastatic tumor and one subretinal hemorrhage) on a 3T MRI. There were three demonstrable patterns of vascular perfusion: 0-10% suggestive of a benign or treated lesion, overlapping 15-50% enhancement, strong rapid enhancement 50->100% suggestive of a highly malignant process. Methods: Patients 18 years of age or older with ocular masses were examined by 3T MRI with a vascular perfusion study. Contrast material was injected into the antecubital vein at time zero. Images of the globe and orbit were acquired at time zero and sequentially at 1-minute intervals for 5 minutes. Contrast enhancement of the mass was measured as a percent increase over baseline followed by washout of the contrast material from the mass. Simultaneous images of brain and muscle were used as controls (muscle enhances brightly, brain does not normally enhance). Results: All of the uveal lesions in this study were well visualized on both T1 weighted images and T2 weighted images. The shape and location of these lesions correlated well to those observed on clinical examination. Orbital perfusion studies of these lesions demonstrated enhancement in nine of eleven suspected lesions. The enhancement ranged from zero to 130%. There were three patterns of enhancement: 0-10%, 15-50% and 50->100%. Only benign lesions or lesions following plaque brachytherapy with I 131 demonstrated enhancement under 10%. There were four choroidal melanomas with overlapping (15-50%) levels of enhancement and four lesions (three melanomas, one metastatic tumor) with strong, rapid enhancement (50->100%). Three patients had subsequent vascular perfusion studies following plaque brachytherapy. All of these patients experienced a decline in the contrast enhancement following treatment (range 3-7 months following treatment). Conclusion: 3T MRI vascular perfusion studies can demonstrate the perfusion patterns of ocular masses. There are three patterns of perfusion, and these patterns seem to correspond to the benign or malignant nature of the lesion. Further studies are anticipated.

Keywords: melanoma • oncology • imaging/image analysis: clinical