不同扩散梯度因子值的乳腺MR扩散加权成像对比研究

目的 确定一个最佳的用于乳腺MR DWI的b值.方法 按照前瞻性设计,选取怀疑乳腺癌的乳腺可触性包块患者40例,术前行双侧乳腺MR和DWI扫描,b值分别取1000、800和600 s/mm2,肉眼判断DWI图像等级,采用单因素方差分析比较3组b值的DWI像信噪比和病灶ADC值,采用ROC曲线评价ADC值诊断价值.结果40例患者中乳腺癌26例,良性肿块14例,DWI显示36例,共42个病灶.3组b值下的DWI图像质量均较好,加例中视觉分级达A级的分别占75.0%(30例)、77.5%(31例)和77.5%(31例).3组b值DWI图像对病灶的检出能力相同.b=1000、800和600 s/mm2的信噪比平均值分别为63±22、82±27和96±29,3组间比较差异具有统计学意义(P<0.01).良性病变平均ADC值分别为(1.44±0.28)× 10-3、(1.50±0.32)×10-3和(1.52±0.29)×10-3mm2/s,3组间比较差异无统计学意义(P=0.725).恶性病变平均ADC值分别为(1.00±0.25)×10-3、(0.98±0.19)×10-3和(1.07±0.22)×10-3mm2/s,3组间比较差异也无统计学意义(P=0.358).3组b值的ADC值诊断乳腺良恶性病变的ROC曲线下面积分别为0.879、0.885和0.865;诊断良恶性病变的阈值分别为1.295×10-3、1.435×10-3和1.335×10-3mm2/s;诊断乳腺癌的敏感性分别为80.0%、92.0%和84.0%,特异性均为90.0%;阳性预测值分别为95.2%,95.8%和95.5%.结论综合图像信噪比和ADC值诊断价值,认为在乳腺DWI中,b=800 s/mm2是乳腺DWI成像的最佳b值.

Comparative study of MR diffusion weighted imaging for breast with different b values

Objective To explore the optimal b value in MR DWI for breast.Methods Forty patients with palpable masses of breasts underwent MR and DWI at b = 1000, 800 and 600 s/mm2 before surgery according prospective planning. Visual assessment, signal to noise ratio (SNR) of DWI and the ADC values of benign and malignant lesions were compared among three b values using one-way ANOVA test.The diagnostic value of ADC were analyzed by ROC curves.Results Of the 40 patients, there were 26 patients with malignant lesions and 14 patients with benign lesions verified by histopathology.36 patients with 42 lesions were examined by DWI, and detectabilities at three b values were alike.Most DWI at b = 1000, 800 and 600 s/mm2 were of high quality, and images of grade A were 75.0% (30/40), 77.5% (31/40) and 77.5% (31/40), respectively.Mean SNR at b = 1000, 800 and 600 s/mm2 were 63 ± 22,82 ± 27 and 96 ± 29 respectively.Compared with one another, there was statistically significant difference (P <0.01).Mean ADC of benign lesions at different b values were (1.44 ± 0.28) × 10-3, (1.50 ± 0.32) × 10-3 and (1.52±0.29) × 10-3 mm2/s respectively. Compared with one another, there was no statistically significant difference (P = 0.725).Mean ADC of malignant lesions were (1.00 ± 0.25) × 10-3, (0.98 ± 0.19) × 10-3 and (1.07 ± 0.22) × 10-3 mm2/s respectively.Compared with one another, there was also no statistically significant difference (P = 0.358).The area under the ROC curves at b = 1000,800 and 600 s/mm2 were 0.879,0.885 and 0.865 respectively.Threshold value to distinguish benign and malignant lesions were 1.295 × 10-3,1.435×10-3 and 1.335×10-3 mm2/s respectively.Sensitivity of diagnosing breast cancer were 80.0%, 92.0% and 84.0%, and specificity were all 90.0% . Positive predictive values were 95.2%, 95.8% and 95.5% at b = 1000, 800 and 600 s/mm2.Conclusion Combining SNR and the value of ADC in diagnosing benign and malignant breast lesions, the study indicated that b = 800 s/mm2 was the optimal b value in breast DWI.