MR扩散加权成像对颅内囊性肿块的鉴别诊断价值

目的 :探讨MR扩散加权成像对颅内囊性肿块的鉴别诊断价值。方法 :搜集有手术病理结果的患者 3 1例 ,其中表皮样囊肿 9例 ,蛛网膜囊肿 15例 ,囊性颅咽管瘤 4例 ,颅底囊性变神经鞘瘤 3例。所有病例均行MR常规T1WI、T2 WI及DWI扫描 ,回顾性分析各组病例的MR常规及扩散加权成像表现。结果 :在MR扩散加权图像上 ,所有 7例表皮样囊肿均为显著高信号 ,而在指数扩散加权像及ADC图上为等信号 ;其余病变在扩散加权图像上为低信号或伴等信号。结论 :MR扩散加权成像有助于表皮样囊肿与其它颅内脑外囊性肿块的鉴别 ,表皮样囊肿的扩散加权高信号主要是由“T2余辉效应”而非水分子扩散受限所致。

The value of diffusion-weighted MR imaging in the differential diagnosis of intracranial cystic masses

Objective:To assess the value of diffusion-weighted echo planar MR Imaging (DWI) in the differential diagnosis of intracranial cystic masses.Methods:31 patients with histopathologic diagnosis were studied,including epidermoid cyst 9 cases,arachnoid cyst 15 cases,cystic craniopharygioma 4 cases and cystic neurilemmoma of base of the skull 3 cases.All patients were examined with T 1-weighted MR sequences,fast T 2-weighted sequences and DW echo planar sequences. Their findings on conventional and diffusion weighted MR images were retrospectively analyzed.Results:On diffusion- weighted images 7 epidermoid cysts appeared markedly hyperintense,but they showed isointense on exponential diffusion-weighted images and ADC maps;all the remaining lesions were hypointense or mixed hypo-and iso-intense on diffusion- weighted images.Conclusion:Diffusion-weighted echo planar MR imaging is useful in the differential diagnosis of epidermoid cysts from other intracranial-extraaxial cystic masses.The hyperintensity of epidermoid tumors on echo planar DW imaging is not caused by the diffusion restriction but by the T 2 shine-through effect.