多b值DWI在WHOⅡ～Ⅲ级脑星形细胞瘤IDH基因型的诊断价值

The diagnostic value of multi b-values diffusion weighted imaging in the genotypes of WHO grade Ⅱ—Ⅲ astrocytomas

目的探究多b值扩散加权成像(diffusion weighted imaging,DWI)对WHOⅡ～Ⅲ级脑星形细胞瘤异柠檬酸脱氢酶(isocitrate dehydrogenase,IDH)基因型的诊断价值。材料与方法收集经手术病理确诊为WHOⅡ～Ⅲ级星形细胞瘤、且有IDH基因型的患者资料,术前均行颅脑常规MRI扫描及多b值DWI扫描,测量肿瘤实质区及同一层面对侧正常脑实质区的各参数值:水通道蛋白相关扩散系数(aquaporines related diffusion coefficient,AQP-ADC)、纯扩散系数(true diffusion coefficient,D)、灌注相关扩散系数(perfusion related diffusion coefficient,D*)、灌注分数(perfusion fraction,f),计算校正参数值(瘤体参数值除以对侧正常脑实质参数值):相对AQP-ADC (relative AQPADC)、相对D (relative D)、相对D*(relative D*)、相对f (relative f)等,应用两样本t检验分析IDH突变组与野生组之间的参数值差异,绘制受试者工作特征(receiver operating characteristic,ROC)曲线计算阈值、敏感性及特异性。结果脑星形细胞瘤IDH突变组rD值高于野生组,D*、rD*、rf值低于野生型,差异有统计学意义(P<0.05)。瘤体rD值ROC曲线下面积、阈值、敏感性及特异性分别为0.706、1.839、64.71%、80.00%,D*值分别为0.814、0.00267、88.24%、66.67%;rD*值分别为0.759、0.969、58.82%、93.33%,rf值分别为0.710、1.875、88.24%、53.33%。结论多b值DWI对于诊断WHOⅡ～Ⅲ级脑星形细胞瘤IDH基因型具有一定价值,瘤体D*和rf值诊断IDH基因的敏感性较高,rD*值的特异性较高。

Objective: To investigate the value of multiple b-values diffusion weighted imaging (DWI) in predicting the genotype of isocitrate dehydrogenase1 (IDH) in WHO grade Ⅱ-Ⅲ astrocytomas. Materials and Methods: Patients' data of WHO grade Ⅱ-Ⅲ astrocytomas with IDH genetic information were collected. All routine magnetic resonance imaging (MRI) and multiple b-values DWI were performed before surgery. Measuring the parameters of the astrocytoma's parenchyma and the contralateral normal brain's parenchyma: aquaporines related diffusion coefficient (AQP-ADC), true diffusion coefficient (D), perfusion related diffusion coefficient (D ) and perfusion fraction (f). Then calculate the calibrated parameters (tumor parameters values divided by parameters values measured in the contralateral normal brain's parenchyma): relative AQP-ADC (rAQP-ADC), relative D (rD), relative D (rD ), relative f (rf). A t-test of two samples was used to analyze the difference in parameters between different gene states, and the receiver operating characteristic (ROC) curve was plotted to calculate the threshold, sensitivity and specificity. Results: For astrocytomas, the rD value of IDH mutation group was higher than the IDH wild-type, while the D value, rD value and rf value of the mutation group were lower than the wild type, the difference was statistically significant (P< 0.05). The area under the ROC curve, the threshold, the sensitivity and the specificity of the rD were 0.706, 1.839, 64.71%, 80.00%. The D were 0.814, 0.00267, 88.24%, 66.67%. The rD were 0.759, 0.969, 58.82%, 93.33%. The rf were 0.710, 1.875, 88.24%, 53.33%. Conclusions: Multi b-values DWI has certain application value for diagnosis of IDH genotype in WHO grade Ⅱ-Ⅲ astrocytomas. The values of D and rf are more sensitive to diagnose the genotypes of astrocytoma, while the value of rD has higher specificity.