儿童幕下非典型畸胎样/横纹肌样瘤与髓母细胞瘤的MRI对比研究

Diffusion-weighted imaging diagnosis of infratentorial atypical teratoid tumor/rhabdoid tumor and medulloblastoma in children

目的探讨联合应用磁共振成像(MRI)及磁共振扩散加权成像(DWI)的表观扩散系数(ADC)值在幕下非典型畸胎样/横纹肌样瘤(AT/RT)与髓母细胞瘤的鉴别诊断价值。方法回顾性分析经手术病理证实的71例髓母细胞瘤及21例幕下AT/RT患者,本组中所有患者均在术前行MRI、DWI检查,比较分析这两种肿瘤实质的平均ADC值(ADC_(mean))、最小ADC值(ADC_(min))、rADC。结果在71例髓母细胞瘤及21例幕下AT/RT中,常规MRI征象包括T_1WI、T_2WI、瘤周水肿、出血改变、播散的差异无统计学意义(P均>0.05),强化方式、囊变的差异具有统计学意义(P均<0.05),且AT/RT具有较特征性的环带状强化、偏心性大囊变。AT/RT的ADC_(mean)、ADC_(min)、rADC均低于髓母细胞瘤(P均<0.05);经受试者工作特征(ROC)曲线分析发现ADC_(min)鉴别AT/RT与髓母细胞瘤的曲线下面积(0.929)大于ADC_(mean)(0.820)或rADC的曲线下面积(0.916);ADC_(mean)以0.613×10^(-3) mm^2/s为阈值时,诊断两种肿瘤的敏感度和特异度分别达78.9%、81.0%;ADC_(min)以0.507×10^(-3)mm^2/s为阈值时,诊断两种肿瘤的敏感度和特异度分别达81.7%、90.5%;rADC以0.790为阈值时,诊断两种肿瘤的敏感度和特异度分别达90.1%、85.7%。结论联合分析常规MRI特征和DWI参数(ADC_(mean)、ADC_(min)、rADC)是鉴别诊断幕下AT/RT与髓母细胞瘤较可靠的检查方法 ,且肿瘤实质区rADC、ADC_(min)具有较高的敏感度及特异度,可为临床治疗方案的制定及评估预后提供帮助。

Objective To investigate the value of diffusion-weighted imaging （DWI） and apparent diffusion coefficient （ADC）for diagnosing infratentorial atypical teratoid tumor/rhabdoid tumor （AT/RT） and medulloblastoma.Methods Pre-operative MRI including DWI of 92 children with pathologically confirmed medulloblastoma （71） and infratentorial AT/RT （21） was retrospectively analyzed.The mean and minimum ADC values as well as tumor/normal brain ADC ratios （rADC） were compared between AT/RT and medulloblastoma.Results In the 92 patients,conventional MRI manifestations including T1 and T2 signal intensities,peritumoral edema,hemorrhage and dissemination were not significantly different between the two tumors （all P〉0.05）.The degree of contrast enhancement and cyst/necrosis were significantly different （all P〈0.05）.The pattern of band-like enhancement surrounding cystic or necrotic areas was typical in AT/RT.The mean and minimum ADCs,and rADC of AT/RT were significantly lower than that of medulloblastoma （all P〈0.05）.The ROC analysis showed that the area under the curve of minimum ADC （0.929） was greater than that of mean ADC （0.820） and rADC （0.916） for differentiating the two tumors.Using cutoff mean ADC value of 0.613×10-3 mm2/s,DWI was 78.9% sensitive and 81.0% specific for differential diagnosis.At cutoff minimum ADC of 0.507×10-3 mm2/s,DWI was 81.7% sensitive and 90.5% specific.The cutoff rADC of 0.790 was 90.1% sensitive and 85.7% specific.Conclusion DWI using mean and minimum ADC and rADC is reliable for differential diagnosis of infratentorial AT/RT and medulloblastoma.rADC and minimum ADC have higher sensitivity and specificity than mean ADC.