3.0 T磁共振灌注加权成像在脑星形细胞瘤分级诊断中的价值

The Value of MR Perfusion Weighted Imaging in Grading Astrocytoma

目的探讨对比剂首过MR灌注加权成像(perfusion weighted imaging,PWI)在脑高、低级别星形细胞瘤鉴别诊断中的价值。资料与方法分析40例经手术病理证实的星形细胞瘤患者的MRI资料,所有患者术前均行常规MRI平扫+增强、PWI,其中低级别组(WHO I、II级)14例,高级别组(WHO III、IV级)26例。结果常规MR平扫+增强扫描诊断高级别星形细胞瘤的敏感性为69.2%,特异性为64.3%,阳性预测值为78.3%,阴性预测值为52.9%,准确性为67.5%。高、低级别星形细胞瘤瘤体实质相对脑血容量(rCBV)值和相对脑血流量(rCBF)值差异均有统计学意义(P<0.05),而相对平均通过时间(rMTT)值差异无统计学意义(P>0.05)。选择Youden指数最大值作为高、低级别星形细胞瘤最佳诊断临界点时,瘤体实质rCBV值受试者工作特征(ROC)曲线下面积(AUC)为0.961,阈值为2.71,敏感性为85.0%,特异性为100%,阳性预测值为100%,阴性预测值为78.0%;瘤体实质rCBF值ROC曲线的AUC为0.877,阈值为1.45,敏感性为85.0%,特异性为71.0%,阳性预测值为85.0%,阴性预测值为71.0%。结论与常规MRI比较,对比剂首过PWI能提高术前星形细胞瘤分级诊断的准确性。瘤体实质rCBV值是星形细胞瘤分级诊断的最特异性指标。

Objective To evaluate the grading value of MR perfusion weighted imaging（PWI）in astrocytoma.Materials and Methods Forty patients with primary cerebral astrocytoma confirmed by pathology underwent conventional MR imaging,dynamic contrast-enhanced T2-weighted perfusion MR imaging on a Siemens 3.0T scanner.Fourteen tumors were low-grade（I-II）and 26 were high-grade（III-IV）.Results Sensitivity,specificity,PPV,NPV and accuracy of conventional MR were 69.2%,64.3%,78.3%,52.9% and 67.5%,respectively,in determining high-grade astrocytoma.Significant statistical differences were found in the rCBV and rCBF about the core of tumor between low and high grade astrocytoma respectively（P0.05）,but the rMTT had no significant statistical differences（P0.05）.The maximum youden index was chosen to determine the optimum thresholds of all the parameters in ROC analyses.At threshold value of 2.71 for rCBV in the core of tumor,the sensitivity,specificity,PPV,and NPV for diagnosing high grade astrocytoma were 85.0%,100%,100%,and 78.0%.In the same way,at threshold value of 1.45,the sensitivity,specificity,PPV,and NPV were 85.0%,71.0%,85.0%,and 71.0%.Conclusion DSC PWI increases the accuracy of pre-operative imaging grading of astrocytoma for the conventional MR imaging.The rCBV in the core of tumor is the most superior diagnostic performance.