目的：探讨磁共振（magnetic resonance，MR）弥散张量成像（diffusion tensor imaging，DTI）对鉴别诊断 皮肌炎和肌营养不良的价值。方法：纳入经病理证实的皮肌炎患者42例和肌营养不良患者23例。所有患 者均行双侧大腿常规MR及DTI成像，分别比较皮肌炎和肌营养不良患者大腿肌群的信号强度（signal intensity，SI）、表观扩散系数（apparent diffusion coefficient，ADC）、各向异性分数（fractional anisotropy，FA）； 采用独立样本t检验及受试者工作特征曲线（receiver operating characteristic curve，ROC）对所有参数进行 分析。结果：皮肌炎与肌营养不良患者大腿肌群的ADC和FA值差异有统计学意义（P＜0.01、P＜0.05），SI 差异无统计学意义（P＞0.05）。其中DTI的参数ADC对鉴别皮肌炎和肌营养不良具有较高的诊断价值，其 曲线下面积（area under the curve，AUC）、敏感性和特异性分别为 0.723、54.1%和 78.1%。结论：功能序列 DTI作为常规MR的补充技术，有助于鉴别皮肌炎和肌营养不良的鉴别。

To explore the value of magnetic resonance (MR) diffusion tensor imaging (DTI) in the differential diagnosis of dermatomyositis and muscular dystrophy. Methods: A total of 42 patients with pathologically confirmed dermatomyositis and 23 patients with muscular dystrophy were included. All patients underwent routine MR and DTI imaging of both thighs, comparing the signal intensity (SI), apparent diffusion coefficient (ADC), and fractional anisotropy (FA) of the thigh muscle groups between patients with dermatomyositis and muscular dystrophy. Independent samples t-test and receiver operating characteristic curve (ROC) analysis were used for all parameters. Results: There was a significant difference in ADC and FA values of the thigh muscle groups between patients with dermatomyositis and muscular dystrophy (P<0.01, P< 0.05), while there was no significant difference in SI (P>0.05). Among them, the DTI parameter ADC had a high diagnostic value in differentiating dermatomyositis and muscular dystrophy, with an area under the curve (AUC), sensitivity, and specificity of 0.723, 54.1% , and 78.1% , respectively. Conclusion: The functional sequence DTI, as a supplementary technique to conventional MR, helps to distinguish between dermatomyositis and muscular dystrophy.