多b值DWI对术前幕上胶质瘤分级的应用研究

目的：探讨何种 b 值扩散加权成像(DWI)对胶质瘤术前分级更有价值。方法回顾性分析经手术病理证实的38例胶质瘤(高级别24例、低级别14例)患者的 MRI 资料,均行常规 MRI 检查和3种 b 值的 DWI 检查(b=1000 s/mm2、2000 s/mm2、3000 s/mm2),分析 DWI 上肿瘤的信号特征,测量肿瘤最小表观扩散系数(ADC)值。对不同 b 值的肿瘤最小 ADC 值绘制受试者工作特征曲线(ROC),选取最佳诊断阈值,采用χ2检验分析不同序列的敏感性、特异性的差异。结果 b= 3000 s/mm2 DWI 图像上,91.6%(22/24)高级别胶质瘤呈高信号,85.7%(12/14)低级别胶质瘤呈低信号,以高信号作为诊断高级别胶质瘤的标准,诊断高级别和低级别胶质瘤的敏感性及特异性最高(91.6%和100%)。在 b 值相同时高级别胶质瘤的最小 ADC 值低于低级别胶质瘤,差异有统计学意义(P<0.05)；3种 b 值鉴别高级别和低级别胶质瘤敏感性的差异有统计学意义(P<0.05),当以 ADC 3000<0.74×10-3 mm2/s 作为鉴别高级别胶质瘤的敏感性和特异性最高,分别为100%和87.3%。结论高 b 值 DWI 比常规 b 值 DWI 更能准确反映胶质瘤分级,应用 b=3000 s/mm2 DWI 肿瘤最小 ADC 值为胶质瘤术前更准确分级提供量化指标。

The application study of multi-b value diffusion weighted imaging in preoperative histological grading of supratentorial glioma

Objective To investigate the optimal b value of diffusion-weighted imaging (DWI)in predicting the grade of cerebral gliomas.Methods 38 patients with pathologically-proved brain gliomas (24 high-grade gliomas and 14 low-grade ones)were studied retrospectively.All patients received conventional MRI and DWI examination with three different b values (1 000 s/mm2 ,2 000 s/mm2 and 3 000 s /mm2 ).The signal features of the tumor on DWI with three different b values were evaluated and compared.The minimum ADC values of the tumors were calculated and compared between each other.Through drawing the ROC curve of different b values, the best diagnostic threshold was found.The sensitivity and specificity in predicting the grade of brain gliomas were assessed using Chi-square test.Results On DWI with b value of 3 000 s/mm2 ,91.6% (22/24)of high-grade tumors showed hyper-intensity, while 85.7%(12/14)of low-grade tumors presented hypo-intensity signals.Regarding hyper-intensity signals as diagnostic criterion for high-grade tumors,the sensitivity and specificity were 91.6% and 100% respectively.When the b value was similar,the minimum ADC value of high-grade glioma was significantly lower than that of low-grade glioma,and statistically significant differences in differentiating high-grade glioma from low-grade glioma existed among three b values (P <0.05).When the ADC 3 000 value<0.74×10 -3 mm2/s was regarded as a standard for the identification of high-grade and low-grade glioma,the sensitivity and specificity were 100% and 87.3%respectively.Conclusion DWI with high b value is more useful than standard moderate b value in preoperative grading the gliomas.When DWI with b value of 3 000 s/mm2 is used,the minimum ADC value will provide quantitative indicators in preoperatively precisely predicting grading glioma.