扩散敏感因子800时乳腺良恶性病变ADC界值的确定

目的：确定扩散敏感因子为800s/mm^2时乳腺良恶性病变的ADC界值,评价MR扩散加权成像（DWI）对乳腺良恶性病变鉴别诊断的价值。方法：回顾性分析经手术病理证实的70例（78个病灶）乳腺病变的DWI图像,其中良性病变26例（31个病灶）,恶性病变44例（47个病灶）。测量DWI图像上显示的病变表观扩散系数（ADC）值。通过ROC曲线确定ADC值的诊断阈值,并以此值进行鉴别诊断,同时计算ROC曲线下面积。结果：良恶性病变的ADC值均符合正态性分布,良恶性病变的ADC平均值分别为（1.46±0.26）×10^-3mm^2/s和（1.02±0.19）×10^-3mm^2/s,恶性病变的ADC值明显低于良性病变（P〈0.05）。约登指数最大法确定的ADC诊断阈值为1.28×10^-3mm^2/s,以此值进行鉴别诊断时的敏感度、特异度和诊断符合率分别为93.6%,75.9%,86.8%;阳性似然比最大法确定的ADC诊断阈值为1.035×103mm^2/s,以此值进行鉴别诊断时的敏感度、特异度和诊断符合率分别为46.8%,96.6%,65.8%;ROC曲线下面积为0.905（95%可信区间为0.836-0.975）。结论：扩散敏感因子为800s/mm^2时乳腺良恶性病变的ADC界值确定为1.28×10^-3mm^2/s,DWI的ADC值测定有助于乳腺良恶性病变的鉴别诊断。

Value of diffusion weighted MR imaging in the differential diagnosis of benign and malignant breast lesions:affirmation of ADC cut-off value as b value equals to 800s/mm2

Objective：To affirm the cut-off value of apparent diffusion coefficient（ADC） when b value=800s/mm^2 in the differential diagnosis of benign or malignant breast lesions,and to evaluate the diffusion weighted MR imaging（DWI） in the diagnosis of breast diseases.Methods：Bilateral breast axial DWI were performed in seventy female patients（78 lesions） having surgery and histo-pathology proven breast lesions,with benign（26 cases,31 lesions） and malignant（44 cases,47 lesions）.and the imaging materials were retrospectively analyzed.The ADC values of all breast lesions were calculated and its threshold of differentiating benign or malignant lesions was affirmed with receiver operating characteristic curve（ROC）,area under ROC was calculated as well.Results：Twenty-nine benign lesions（29/31） and forty-seven malignant lesions（47/47） were visible on DWI.The ADC values of benign and malignant lesions were（1.46±0.26）×10^-3mm^2/s and（1.02±0.19）×10^-3mm^2/s respectively.The ADC value of malignant lesions were markedly lower than that of benign lesions,with significant statistical difference（P0.05）.The threshold between benign and malignant lesions was 1.28×10^-3mm^2/s by the method of Youden index maximum,with the sensitivity,specificity,and accuracy as 93.6%,75.9%,and 86.8%,respectively.The threshold was 1.035×10^-3mm^2/s by the method of positive likelihood ratio maximum according to ROC,with the sensitivity,specificity,and accuracy as 46.8%,96.6%,and 65.8%,respectively.Area under ROC was 0.905（95% confidence interval was 0.836-0.975）.Conclusion：When b value=800s/mm^2,the cut-off value of ADC in differentiating diagnosis benign or malignant breast lesions was affirmed as 1.28×10^-3mm^2/s.Measurement of ADC value on DWI is an effective parameter in the diagnosis of benign and malignant breast lesions.