高场磁共振对脉络膜黑色素瘤的诊断价值

The diagnostic value of high field MRI for choroidal melanoma

目的评价高场磁共振（ＭＲＩ）对脉络膜黑色素瘤的诊断价值。方法采用ＧＥ１．５Ｔ磁共振扫描仪，对１２例黑色素瘤患者进行矢、冠、轴及斜位扫描，同时行脂肪抑制技术、增强扫描及病理检查。结果１２例黑色素瘤在Ｔ１ＷＩ均表现为不同程度的高信号，在Ｔ２ＷＩ上为低信号。其主要原因为黑色素瘤中的黑色素为顺磁性物质，可同时缩短Ｔ１和Ｔ２弛豫时间，以此可以同脉络膜其他病变相鉴别。１２例中有７例合并视网膜脱离。结论磁共振可在矢、冠、轴及斜位以小视野对眼眶进行扫描，并为临床治疗及手术准确定位；脉络膜黑色素瘤具有特殊的ＭＲＩ表现。

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.