BackgroundFinding sensitive clinical outcome measures has become crucial in natural history studies and therapeutic trials of neuromuscular disorders. Here, we focus on 1‐year longitudinal data from quantitative magnetic resonance imaging (MRI) and phosphorus magnetic resonance spectroscopy (31P MRS) in a placebo‐controlled study of sirolimus for inclusion body myositis (IBM), also examining their links to functional, strength, and clinical parameters in lower limb muscles.MethodsQuantitative MRI and 31P MRS data were collected at 3 T from a single site, involving 44 patients (22 on placebo, 22 on sirolimus) at baseline and year‐1, and 21 healthy controls. Assessments included fat fraction (FF), contractile cross‐sectional area (cCSA), and water T2 in global leg and thigh segments, muscle groups, individual muscles, as well as 31P MRS indices in quadriceps or triceps surae. Analyses covered patient‐control comparisons, annual change assessments via standard t‐tests and linear mixed models, calculation of standardized response means (SRM), and exploration of correlations between MRI, 31P MRS, functional, strength, and clinical parameters.ResultsThe quadriceps and gastrocnemius medialis muscles had the highest FF values, displaying notable heterogeneity and asymmetry, particularly in the quadriceps. In the placebo group, the median 1‐year FF increase in the quadriceps was 3.2% (P < 0.001), whereas in the sirolimus group, it was 0.7% (P = 0.033). Both groups experienced a significant decrease in cCSA in the quadriceps after 1 year (P < 0.001), with median changes of 12.6% for the placebo group and 5.5% for the sirolimus group. Differences in FF and cCSA changes between the two groups were significant (P < 0.001). SRM values for FF and cCSA were 1.3 and 1.4 in the placebo group and 0.5 and 0.8 in the sirolimus group, respectively. Water T2 values were highest in the quadriceps muscles of both groups, significantly exceeding control values in both groups (P < 0.001) and were higher in the placebo group than in the sirolimus group. After treatment, water T2 increased significantly only in the sirolimus group's quadriceps (P < 0.01). Multiple 31P MRS indices were abnormal in patients compared to controls and remained unchanged after treatment. Significant correlations were identified between baseline water T2 and FF at baseline and the change in FF (P < 0.001). Additionally, significant correlations were observed between FF, cCSA, water T2, and functional and strength outcome measures.ConclusionsThis study has demonstrated that quantitative MRI/31P MRS can discern measurable differences between placebo and sirolimus‐treated IBM patients, offering promise for future therapeutic trials in idiopathic inflammatory myopathies such as IBM.

中文翻译：

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磁共振成像和波谱观察西罗莫司对包涵体肌炎肌肉的影响

背景寻找敏感的临床结果测量在神经肌肉疾病的自然史研究和治疗试验中变得至关重要。在这里，我们重点关注定量磁共振成像（MRI）和磷磁共振波谱的一年纵向数据（31P MRS）在西罗莫司治疗包涵体肌炎（IBM）的安慰剂对照研究中，还检查了它们与下肢肌肉功能、力量和临床参数的联系。方法定量 MRI 和31P MRS 数据是在 3 T 时从单个地点收集的，涉及基线和第 1 年的 44 名患者（22 名服用安慰剂，22 名服用西罗莫司）和 21 名健康对照。评估包括脂肪分数 (FF)、收缩横截面积 (cCSA) 和水 T2在整体腿部和大腿节段、肌肉群、个体肌肉以及31P MRS 指数股四头肌或者小腿三头肌。分析涵盖患者对照比较、通过标准进行的年度变化评估t‐测试和线性混合模型，标准化响应平均值（SRM）的计算，以及 MRI 之间的相关性探索，31P MRS、功能、强度和临床参数。结果股四头肌和腓肠肌内侧肌肌肉具有最高的 FF 值，表现出显着的异质性和不对称性，特别是在股四头肌。在安慰剂组中，股四头肌的 1 年 FF 中位数增加为 3.2%（磷< 0.001)，而西罗莫司组为 0.7% (磷= 0.033）。两组患者的 cCSA 均显着下降股四头肌1年后（磷< 0.001），安慰剂组的中位变化为 12.6%，西罗莫司组的中位变化为 5.5%。两组之间的 FF 和 cCSA 变化差异显着（磷< 0.001）。安慰剂组中 FF 和 cCSA 的 SRM 值分别为 1.3 和 1.4，西罗莫司组中分别为 0.5 和 0.8。水T2值最高的是股四头肌两组的肌肉均显着超过对照值（磷< 0.001），并且安慰剂组高于西罗莫司组。处理后，水T2仅西罗莫司组显着增加股四头肌（磷< 0.01）。多种的31与对照组相比，患者 P MRS 指数异常，且治疗后保持不变。基线水 T 之间存在显着相关性2和 FF 基线以及 FF 的变化（磷< 0.001）。此外，在 FF、cCSA、水 T 之间观察到显着相关性2，以及功能和力量结果测量。结论这项研究表明，定量 MRI/31P MRS 可以辨别安慰剂和西罗莫司治疗的 IBM 患者之间的可测量差异，为未来特发性炎症性肌病（如 IBM）的治疗试验带来希望。