[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.


CONCLUSIONS
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.
Li
S
S
Radiology Department, Beijing Hospital, Beijing 100730.
Cai
K
K
Sun
N
N
Wang
Z
Z
Xia
Q
Q
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002830:Choroid Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008545:Melanoma / Q000175:diagnosis*; D008875:Middle Aged