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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 investigate the value of perfusion weighted imaging (PWI) with contrast-first MR in the differential diagnosis of high and low grade astrocytomas. Materials and Methods MRI data of 40 patients with astrocytoma confirmed by surgery and pathology were analyzed. All patients underwent MRI plain imaging and enhanced PWI before operation. Among them, 14 patients in the low-grade group (WHO I and II) had high Grade group (WHO III, IV level) in 26 cases. Results The sensitivity and accuracy of MR plain scan and enhanced scan in diagnosing high - grade astrocytomas were 69.2%, 64.3%, 78.3%, 52.9% and 67.5% respectively. There were significant differences in rCBV and rCBF between high and low grade astrocytomas (P <0.05), while the difference of relative mean transit time (rMTT) No statistical significance (P> 0.05). When the maximum Youden index was selected as the best diagnostic threshold for high and low grade astrocytomas, the area under the curve of ROC curve (AUC) was 0.961 and the threshold value was 2.71, with a sensitivity of 85.0%, specificity was 100%, positive predictive value was 100%, negative predictive value was 78.0%; AUC of ROC curve of real rCBF value of tumor was 0.877, threshold was 1.45, sensitivity was 85.0%, specificity was 71.0% , Positive predictive value was 85.0%, negative predictive value was 71.0%. Conclusion Compared with conventional MRI, contrast agent first pass PWI can improve the accuracy of preoperative astrocytoma grading diagnosis. The rCBV value of the tumor is the most specific index for the differential diagnosis of astrocytoma.