磁共振弥散加权成像表观弥散系数值对小儿后颅窝肿瘤的诊断价值

Value of apparent diffusion coefficient of magnetic resonance diffusion-weighted imaging for diagnosis of children′s posterior fossa tumors

目的分析磁共振弥散加权成像(DWI)表观弥散系数(ADC)值对诊断小儿后颅窝肿瘤的作用。方法收集25例后颅窝肿瘤患儿的临床资料,分析常规磁共振成像(MRI)及DWI图像特征,测量肿瘤的最低ADC值并进行对比。结果 25例均为单发肿块,位于四脑室、小脑蚓及小脑半球,平扫以T1WI等或低、T2WI高信号为主。髓母细胞瘤(MB)11例,DWI呈高信号,增强后明显强化。室管膜瘤7例,DWI呈等高信号,具有侵袭性生长特点,增强后不均匀中等强化。毛细胞星形细胞瘤(PA)5例,DWI呈等低信号,均伴大小不等囊变,增强后呈"蜂窝状""环形"及壁结节强化。非典型畸胎样/横纹肌样瘤(AT/RT)2例,呈DWI高等低混杂信号,增强后明显不均匀强化。最低ADC值MB<AT/RT<室管膜瘤<PA。结论 MB与AT/RT的最低ADC值有重叠之处,鉴别诊断需结合常规MRI图像。室管膜瘤生长方式具有特征性,PA具有典型强化方式,结合ADC值可为术前诊断提供可靠影像学依据。

Objective To analyze the effect of the apparent diffusion coefficient(ADC)value of magnetic resonance diffusion weighted imaging(DWI)in the diagnosis of children′s posterior fossa tumors.Methods The clinical data of 25 patients with posterior fossa tumor were collected,the features of conventional MRI and DWI images were analyzed,and the lowest ADC values of tumors were measured and compared.Results All 25 cases had single tumor,which located in the tetraventricular,cerebellar worm and cerebellar hemisphere.In 11 cases with myeloblastoma(MB),DWI showed high signal and obvious enhancement after enhancement.In 7 cases with ependymoma,DWI showed equi-high signal,with invasive growth characteristics,and non-uniform and moderate enhancement after enhancement.In 5 cases with hair cell astrocytoma(PA),DWI showed equal low signal,all of which were accompanied by different size cystic changes.After enhancement,there were"honeycomb""ring"and wall nodule enhancement.Two cases with atypical teratoid/rhabdomytoma(AT/RT)presented high and low DWI mixed signal,and the enhancement was obviously uneven.Minimum ADC value MB<AT/RT<ependymoma<PA.Conclusion The minimum ADC values of MB,AT/RT overlap,and conventional MRI images should be combined for differential diagnosis.The growth pattern of ependymoma is characteristic,and PA has typical enhancement pattern.Combined with ADC value,it can provide reliable imaging basis for preoperative diagnosis.