[Magnetic resonance tomography in ophthalmology. I. Choroid melanoma]

The value of magnetic resonance tomography (MRT) for the diagnosis of choroidal melanomas is illustrated with reference to 26 cases. The geometric dimensions of the tumors are in good agreement with findings obtained by ultrasonography. The relaxation time T2 varies between 85 and 120 msec in contrast to 145-210 msec in subretinal hemorrhages and 190-400 msec in secondary retinal detachments. In contrast to A-scan a differential diagnosis is possible even with lesions less than 1.5 mm in prominence. In solutions of melanin the relaxation time T2 decreases with increasing melanin concentration. This leads to an interpretation that the pigment content of the melanoma is responsible for the relatively short relaxation times. Thus, the relaxation time T2 is a useful factor in predicting metastasis.