NEW METHOD OF EVALUATING MUSCLE FUNCTION WITH MAGNETIC RESONANCE IMAGER

目的：探讨T2舒张时间是否能检测类固醇肌病相关肌纤维萎缩。材料和方法：动物和人体研究经伦理委员会批准。获得知情同意。将12只家兔分为连续10天每天皮下注射3 mg/kg曲安奈德酮组（n_6）和对照组（n_6）。治疗前后分别行磁共振（MR）成像。采用双向重复方差分析和Bonferroni事后检验评价类固醇治疗效果，比较治疗前后及对照兔与类固醇治疗兔比目鱼、腓肠肌T2和脂肪沉积比（FDR）。成像后处死家兔。检测细胞外间隙比（ECSR）和纤维直径。采用Pearson相关分析T2、ECSR和2型肌纤维直径之间的相关性，采用腓肠肌Bonferroni校正法进行More检验以确定影响T2的因素。在人类中，通过使用非配对t检验来评估类固醇的效果，比较了未接受类固醇治疗的志愿者和接受类固醇治疗的患者的T2松弛时间和两种肌肉的FDR。结果：家兔经类固醇治疗后腓肠肌T2明显长于类固醇治疗前（p < 0.01），明显长于生理盐水治疗后（p < 0.01）。生理盐水给药前后对照家兔腓肠肌T2、类固醇给药前对照家兔腓肠肌T2无明显差异。比目鱼肌T2和FDR均无显著性差异。T2、ECSR与腓肠肌2型肌纤维直径有显著相关（p < 0.01）。在人类中，患者的腓肠肌T2明显长于志愿者（p < 0.01）。比目鱼肌T2和FDR无显著性差异。结论：腓肠肌T2松弛时间延长可检测到与类固醇肌病相关的肌纤维萎缩；作者认为T2松弛时间延长主要是由于ECSR增加，反映2型肌纤维萎缩。少

Purpose :To determine whether muscle fiber atrophy associated with steroid myopathy can be detected with T2 relaxation time.Materials and Methods:Animal and human studies were approved by the ethics committee. Informed consent was obtained. Twelve rabbits were divided into a group that received 3 mg/kg of triamcinolone subcutaneously each day for 10 consecutive days (n_6) and a control group that received saline (n_6). Magnetic resonance (MR) imaging was performed before and after treatment. T2 and fat deposition ratio (FDR) of soleus and gastrocnemius muscles before and after treatment and between control rabbits and rabbits treated with steroids were compared by using two-way repeated analysis of variance and Bonferroni post hoc test to evaluate effects of steroid treatment. After imaging, rabbits were sacrificed. Extracellular space ratio (ECSR) and fiber diameter were examined. Correlation among T2, ECSR, and diameter of type 2 muscle fibers was analyzed with a Pearson correlation … More test with Bonferroni correction in gastrocnemius to determine factors affecting T2. In humans, T2 relaxation time and FDR of both muscles were compared between volunteers not treated with steroids and patients treated with steroids by using an unpaired t test to evaluate the effects of steroids.Results :In rabbits, T2 of gastrocnemius muscle was significantly (P_.01) longer after steroid treatment than before steroid treatment and was also significantly (P_.01) longer than after saline administration. T2 of the gastrocnemius showed no significant difference in control rabbits before or after saline administration or in control rabbits and rabbits before steroid administration. T2 of the soleus muscle or FDR of either muscle showed no significant difference. There was a significant correlation (P_.01) among T2, ECSR, and diameter of type 2 muscle fibers in the gastrocnemius. In humans, T2 of the gastrocnemius was significantly (P_.01) longer in patients than in volunteers. T2 of the soleus or FDR of eithermuscle showed no significant difference.Conclusion :Muscle fiber atrophy associated with steroid myopathy is detectable as prolongation of T2 relaxation time in the gastrocnemius muscle ; the authors believe prolongation of T2 relaxation time is mainly due to increased ECSR reflecting type 2 muscle fiber atrophy. Less