目的：探讨儿童幕上原始神经外胚层肿瘤（sPNET）的MRI表现特点。方法：收集经手术及病理证实的20例sPNET，所有病例均行常规MRI平扫和增强扫描，并行DWI扫描。结果：20例sPNET分别位于大脑半球的额、颞、顶、枕、岛叶及侧脑室内，14例为巨大囊实性肿瘤，4例以实性为主伴发小囊性变肿瘤，2例肿瘤体积小且以钙化为主。所有病例瘤周无水肿或水肿较轻，合并出血5例，3例术后复查沿蛛网膜下腔播散。MR平扫肿瘤呈混杂信号，肿瘤实性部分T1WI呈等或稍低信号，T2WI呈等或稍高信号，DWI呈高信号，ADC图呈低信号，囊变部分信号复杂。增强检查肿瘤实性部分呈中等或明显强化。结论：sPNET影像学表现有一定特征，尤其是DWI，这可能有助于肿瘤定性诊断，同时能够提供肿瘤浸润的范围、有无蛛网膜下腔种植转移，对疾病分期和制定治疗方案有重要价值。

Objective: To investigate the MRI features of the supratentorial primitive neuroectodermal tumor(sPNET) in children. Methods: Twenty cases of sPNET confirmed by operation and pathology were collected, all patients underwent conventional MRI scan, enhanced scan, and diffusion-weighted imaging(DWI) scan. Results: Twenty cases of sPNET were all located in supratentorial cerebral hemisphere(frontal, temporal, top, occipital, insular lobe, lateral ventricle). Fourteen cases were shown huge cystic-solid mixed masses, 4 cases were manifestated great solid tumor with microcystic, 2 cases were small tumor size and calcification. No edema or peritumoral edema around the tumor, hemorrhage in 5 cases, 3 cases of postoperative examination spreaded along the subarachnoid. MR scan was shown mixed signal, the solid part of tumor was shown equal or slightly low signal on T1WI, equal or slightly hyperintense on T2WI, high signal on DWI, and slightly low signal on ADC map. The signal of cystic region was consistent with cerebrospinal fluid and the region of cyst with hemorrhage was shown complex signal. The solid part of the tumor was enhanced moderately or markedly. Conclusion: There were some imaging features with sPENT. DWI was especially beneficial to nature of tumor diagnosis, providing information of tumor invasion and whether implantation metastasis along the subarachnoid existed. It was beneficial to clinical staging and treatment plan.