[The diagnostic value of high field MRI for choroidal melanoma].

OBJECTIVE

To clarify the characteristic magnetic resonance imaging (MRI) features of choroidal melanomas by the high field MRI to improve the accuracy of diagnosis and localization and to differentiate choroidal melanomas from other choroidal lesions.

METHODS

12 patients with choroidal melanomas were examined by GE 1.5T magnet and heat coil, fat suppression technique and GD-DPTA as contrast agent were also used. Ten patients underwent operations and the histopathologic diagnosis was confirmed.

RESULTS

The melanomas of the 12 patients had relatively high signals on T(1) weighted image and relatively low signals on T(2) weighted image. This is because of the paramagnetic properties of melanin. The melanomas with melanin can produce stable free radicals, both T(1) and T(2) relaxation times are shortened, with this we can differentiate melanomas from other choroidal lesions.

CONCLUSION

Sagittal, coronal, axial and oblique scanning with small feild of view for the orbit by MRI can be made to show the exact position of melanomas and differentiate them from other choroidal lesions.