弥散MRI诊断颅内表皮样囊肿的价值

目的:探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)图诊断颅内表皮样囊肿的价值.材料和方法:分析19例表皮样囊肿常规MRI和DWI的信号特征,定量测定表皮样囊肿、正常脑实质和脑脊液的ADC值.结果:17例表皮样囊肿T1WI、T2WI呈等或稍高于脑脊液信号,2例T1WI呈高低混杂信号.肿瘤边缘弧线形增强或不增强.19例肿瘤DWI呈明显高于脑实质和脑脊液信号,肿瘤较脑脊液的平均ADC值显著减低,较脑实质的平均ADC值显著增高.结论:DWI优于常规MRI发现颅内表皮样囊肿,DWI上表皮样囊肿的高信号可能是肿瘤组织的T2余辉效应所致.

The Value of Diffusion-weighted MRI in Diagnosis of Intracranial Epidermoid Cysts

Purpose: To evaluate the value of MR diffusionweighted imaging and apparent diffusion coefficients(ADC) map in diagnosis of intracranial epidermoid cysts.Materials and Methods: The signal characteristics of 19 patients with epidermoid cysts on conventional MRI and DWI were analysed.The ADC values of epidermoid cysts,normal cerebral parenchyma and CSF were measured quantitatively.Results: Seventeen epidermoid cysts exhibited equivalent or slightly high signal intensity relative to CSF on T1WI and T2WI,2 tumors exhibited heterogeneously lower and high signal intensity on T1WI.The tumors had rim enhancement or no enhancement.On DWI,19 epidermoid cysts presented strikingly hyperintense signal relative to those of cerebral parenchyma and CSF,the mean ADC of tumors was significantly lower than that of CSF,and significantly higher than that of cerebral parenchyma.Conclusion: DWI is superior to conventional MR imaging in finding intracranial epidermoid cysts,the hyperintense signal of epidermoid cysts on DWI is probably caused by the T2 shine-through effect in tumor tissue.