弥散加权成像、氢质子波谱成像及三维动脉自旋标记灌注成像在髓母细胞瘤诊断中的价值

摘要

Objective To explore the value of diffusion-weighted imaging (DWI), 1H-magnetic resonance spectroscopy (1H-MRS) and 3D whole-brain arterial spin labeling (3D ASL) in the diagnosis of medulloblastoma in the posterior cranial fossa. Methods The magnetic resonance imaging (MRI) findings of 16 patients with pathologically confirmed medulloblastoma in the posterior cranial fossa were analyzed retrospectively. All the patients were examined with plane and enhanced brain MRI scans;5 patients also underwent examinations with DWI, 12 with MRS, and 5 with 3D ASL. Results Medulloblastomas were found in the vermis and the fourth ventricle in 9 cases, in the cerebellar hemisphere in 5 cases, and in the cerebellopontine angle in 1 case; in 1 case multiple lesions were detected. The tumors showed iso-intense or slightly hypo-intense signals on T1WI, and iso-intense or hyper-intense signals on T2WI and FLAIR. The lesions showed high signals in DWI and low signals in ADC. Intra-lesion cysts were common (n=12), and calcification and bleeding were rarely seen. Mild patchy enhancement (n=6) or significant enhancement (n=10) was seen after contrast agent administration. Obstructive hydrocephalus was found in 12 cases and the subarachnoid space was involved in 3 cases. In all the 12 patients receiving MRS examination, high Cho and low NAA were found with significantly increased Cho/Cr (≥3.5) and Cho/NAA (≥4.0) ratios;Tau peak was seen in 8 cases, and Lip peak was found in 4 cases. All the 5 patients receiving 3D ASL examination showed decreased cerebral blood flow (CBF). Conclusion The characteristic features of medulloblastomas in DWI, MRS and 3D ASL offer assistance to the diagnosis of atypical medulloblastoma.%目的：探讨弥散加权成像（DWI）、氢质子波谱成像（1H-MRS）、三维动脉自旋标记（3D ASL）灌注成像在后颅窝髓母细胞瘤诊断中的价值。方法回顾性分析经手术病理证实的16例髓母细胞瘤MRI表现。所有病例均行常规MRI平扫及增强扫描，5例行DWI检查，12例行MRS检查，5例行3D ASL检查。结果9例位于蚓部-四脑室，5例位于小脑半球，1例位于桥小脑角区，1例多发。MRI表现T1WI呈等或稍低信号，T2WI、FLAIR序列呈等或稍高信号，实性成分DWI均为高信号，ADC图为低信号。肿瘤囊变、坏死多见（n=12），钙化少见（n=1），无明显出血。增强扫描呈轻度斑片状（n=6）或明显强化（n=10）。12例可见梗阻性脑积水，3例并发脑脊液种植转移。MRS上Cho峰明显升高，NAA峰明显降低，Cho/Cr（≥3.5）和Cho/NAA（≥4.0）比率明显增高。此外，8例可见Tau峰，4例可见Lip峰。5例ASL均呈低灌注。结论髓母细胞瘤的DWI、MRS及ASL灌注表现具有特征性，有助于对不典型髓母细胞瘤明确诊断。