目的 探讨3.0T磁共振扩散加权成像鉴别诊断乳腺良恶性病变的价值，并对b值进行优化。方法 b值分别取0、400、 700、850、1000s/mm2，对55例乳腺病变进行3.0T MRI-DWI扫描。分析各b值DWI图像质量评分差异，比较乳腺病 灶、病灶周围乳腺腺体、同侧乳腺病灶远离部位正常腺体ADC值的差异。结果 b值分别为400、700、850s/mm2时， DWI图像质量逐渐清晰，评分差异有统计学意义(p<0.01)，b=850s/mm2与b=1000s/mm2图像质量评分差异无统计学意 义(p>0.05)。取各b值时，良性病变与恶性病变、良恶性病变周围腺体组织间ADC值差异均有统计学意义(p<0.01)， 同侧乳腺远离病灶的正常腺体ADC值差异无统计学意义(p>0.05)。b=850s/mm2时，ADC阈值为1.24×10-3mm2/s，乳腺 恶性病变的敏感度、特异度、阴性预测值、阳性预测值和诊断正确率较高。结论 3.0T MR乳腺DWI成像最适宜b值为 850s/mm2。ADC值有助于鉴别乳腺良恶性病变，病变周围腺体ADC值可能具有重要的鉴别诊断价值。

Objective To analyze the diagnostic value of diffusion weighted imaging (DWI) to differentiate the benign and malignant breast lesions, and optimize the b-value at 3.0T-MR. Methods MRI-DWI examination with different b values of 0, 400, 700, 850 and 1000 s/mm2 were applied to fifty-five cases of breast lesions which proved by biopsy or surgical pathology. Image quality score and apparent diffusion coefficient(ADC) values were compared among benign lesions, malignant lesions, normal glandular tissue and glandular tissue around the lesions using different b values. Results The difference of the image quality score was statistically significant(p<0.01) among the b-value 400, 700, 850 s/mm2 , but not between 850 and 1000 s/mm2(p>0.05). ADC values showed significant difference between breast benign lesions and malignant lesions, and among the glandular tissues around the lesions in different b value (P<0.01), but ADC values demonstrated no difference in the normal glandular tissue far away from the lesions (P>0.05). The diagnostic sensitivity, specificity, positive predictive value, negative predictive value and accuracy were higher than others when ADC was 1.24×10-3mm2/s following b value 0, 850s/mm2. Conclusion The best b-value may be 0,850s/ mm2 in breast DWI at 3.0T. ADC value will contribute to distinguishing benign and malignant breast lesions. The ADC value of the glandular tissue around lesion may be very important in differentiating benign and malignant breast lesions.