NEW METHOD OF EVALUATING MUSCLE FUNCTION WITH MAGNETIC RESONANCE IMAGER

目的：确定T2松弛时间能否检测出与激素性肌病相关的肌纤维萎缩。材料和方法：动物和人类研究由伦理委员会批准。获得知情同意。12只大白兔随机分为两组，每组6只，每天皮下注射曲安奈德3 mg/kg，连续10天，对照组注射生理盐水。治疗前后进行磁共振(MR)检查。用双向重复方差分析和Bonferroni后处理方法比较激素治疗前后比目鱼肌和腓肠肌的T2和脂肪沉积率(FDR)，以及对照组和激素治疗组的脂肪沉积率(FDR)。成像后处死动物。检测细胞外间隙比(ECSR)和纤维直径。用皮尔逊相关…分析T2、ECSR和2型肌纤维直径之间的相关性对腓肠肌进行更多的Bonferroni矫正试验，以确定影响T2的因素。采用非配对t检验，比较两组受试者的T2松弛时间和双侧双侧肌肉的FDR。结果：兔腓肠肌T2值在激素治疗后较激素治疗前显著延长(P<0.01)，较生理盐水治疗后显著延长(P<0.01)。生理盐水给药前后正常兔腓肠肌T2值无明显差异，与激素治疗前比较也无显著差异。比目鱼肌的T2和两肌的FDR差异无统计学意义。腓肠肌T2、ECSR与2型肌纤维直径呈显著正相关(P_.01)。在人类中，患者的腓肠肌T2显著长于志愿者(P_.01)。结论：激素性肌病伴肌纤维萎缩表现为腓肠肌T2松弛时间延长，作者认为T2松弛时间延长主要是由于反映2型肌纤维萎缩的ECSR增加所致。较少

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