目的 观察核磁共振(MRI)诊 断多发性肌炎(polymyositis,PM)及皮 肌炎(dermatomyositis,DM)的临床价 值。方法 选取拟诊为PM/DM的76例肌 病患者为研究对象，均行MRI、肌电图 (electromyography, EMG)、肌肉活检检 查，测定血清肌酸磷酸激酶(creatinine phosphkinaes,CK)水平，观察皮肤损害 情况；以EMG、肌肉活检、CK、皮肤损 害情况联合检查结果为依据，评估MRI诊 断PM/DM的灵敏度、特异度、准确度、阳 性及阴性预测值，观察PM/DM患者的MRI 表现。结果 76例受试者中，综合诊断呈 阳性者58例，呈阴性者18例；MRI诊断 PM/DM的灵敏度、特异度、准确度、阳 性预测值、阴性预测值分别为81.03%、 94.44%、84.21%、97.92%和60.71%。 肌肉炎性水肿47例(61.84%)、皮下结 缔组织水肿20例(26.32%)、肌筋膜炎 32例(42.11%)、脂肪浸润肌肉萎缩5例 (6.58%)。结论 MRI诊断PM/DM具有较高的 灵敏度、特异度、准确度，图像特点明 显，且为无创检查，重复性好，对及早 检出病变部位、指导后续病理活检有一 定帮助。

Objective To observe the clinical values of magnetic resonance imaging (MRI) in the diagnosis of polymyositis (PM) and dermatomyositis (DM). Methods 76 cases of myopathy patients suspected PM/DM were selected for the study and were given the MRI, electromyography (EMG) and muscle biopsy. Serum creatine phosphokinase (CK) level was measured, and the skin damages were observed. The sensitivity, specificity, accuracy, positive and negative predictive values of MRI in the diagnosis PM/DM were evaluated based on the combined results of EMG, muscle biopsy, CK and skin damages, and the MRI findings of PM/DM patients were observed. Results Among the 76 cases of subjects, 58 cases were positive and 18 cases were negative by comprehensive diagnosis. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of MRI in the diagnosis of PM/DM were 81.03%, 94.44%, 84.21%, 97.92% and 60.71% respectively. There were 47 cases (61.84%) of muscle inflammatory edema, 20 cases (26.32%) of subcutaneous connective tissue edema, 32 cases (42.11%) of myofascitis and 5 cases (6.58%) of fat infiltration atrophy. Conclusion The MRI diagnosis for PM/ DM has high sensitivity, specificity, accuracy and obvious image features, and it is noninvasive examination with good repeatability, and it has some help in the early detection of lesion sites and the guidance of follow-up pathological biopsy.