扩散加权成像中不同扩散敏感系数对乳腺病变的诊断价值

The Study of DWI in Diagnosis of Breast Lesions with Differernt Bvalues

目的研究扩散加权成像(DWI)中不同扩散敏感系数(b值)对乳腺病变的诊断价值及影响因素,并探讨其鉴别良、恶性乳腺肿瘤的最佳界值。资料与方法对155例患者行不同b值的DWI检查,其中136例选取b值(0,500s/mm2),122例选取b值为(0,1000s/mm2)。所有病例结果均经手术病理证实,将DWI表现与组织病理学进行对照。结果两组b值中恶性病变的ADC值均明显低于良性病变,且乳腺良、恶性病变的表观扩散系数(ADC)值均随b值增大而降低。采用非参数法受试者操作特性曲线(ROC)统计学分析方法确定鉴别良、恶性病变的最佳界值,应用此界值对乳腺病变诊断的敏感性和特异性分别为83.3%和56.9%(b=500s/mm2)、73.6%和80.0%(b=1000s/mm2)。结论高b值DWI对乳腺病变诊断的特异性高于低b值DWI,是乳腺动态增强成像检查的一个有益的补充。

Objective To evaluate the diagnostic efficiency of diffusion weighted imaging（DWI） with different b values,and to investigate the best cutoff value for differentiating benign from malignant lesions.Materials and Methods 155 cases with breast lesions underwent MR examinations.136 focal masses with b value of 0 and 500 s/mm2,and 122 with value of 0 and b 1000 s/mm2 by single-shot EPI sequence were performed.The average apparent diffusion coefficient（ADC）,sensitivity,specificity and cutoff ADC value of DWI to distinguish malignant lesions were calculated seprately.Results The average ADC value of malignant lesions was lower than benign lesions,moreover the average ADC value was decreased with increased b value.The ROC curves were generated in order to determine the ADC thresholds that could balance the needs of sensitivity and specificity.We selected the ADC cutoff value of 1.11 × 10-3 mm2 /s mm2 /s for b = 1000 s/mm2 and 1.57 × 10-3 mm2 /s mm2 /s for b = 500 s/mm2.At the cutoff values,the sensitivity and specificity were 73.6% and 80.0% for b = 1000 s/mm2 and 83.3% and 56.9% for b = 500 s/mm2.Conclusion DWI with high bvalue has better spcificity than with low b value and can supplement DCE imaging findings to improve the accuracy of diagnosis.