Sinclair Christopher D J, Morrow Jasper M, Janiczek Robert L, Evans Matthew R B, Rawah Elham, Shah Sachit, Hanna Michael G, Reilly Mary M, Yousry Tarek A, Thornton John S
UCL Institute of Neurology, MRC Centre for Neuromuscular Diseases, London, WC1N 3BG, UK.
UCL Institute of Neurology, Neuroradiological Academic Unit, London, WC1N 3BG, UK.
NMR Biomed. 2016 Dec;29(12):1800-1812. doi: 10.1002/nbm.3654. Epub 2016 Nov 3.
Quantifying muscle water T (T -water) independently of intramuscular fat content is essential in establishing T -water as an outcome measure for imminent new therapy trials in neuromuscular diseases. IDEAL-CPMG combines chemical shift fat-water separation with T relaxometry to obtain such a measure. Here we evaluate the reproducibility and B sensitivity of IDEAL-CPMG T -water and fat fraction (f.f.) values in healthy subjects, and demonstrate the potential of the method to quantify T -water variation in diseased muscle displaying varying degrees of fatty infiltration. The calf muscles of 11 healthy individuals (40.5 ± 10.2 years) were scanned twice at 3 T with an inter-scan interval of 4 weeks using IDEAL-CPMG, and 12 patients with hypokalemic periodic paralysis (HypoPP) (42.3 ± 11.5 years) were also imaged. An exponential was fitted to the signal decay of the separated water and fat components to determine T -water and the fat signal amplitude muscle regions manually segmented. Overall mean calf-level muscle T -water in healthy subjects was 31.2 ± 2.0 ms, without significant inter-muscle differences (p = 0.37). Inter-subject and inter-scan coefficients of variation were 5.7% and 3.2% respectively for T -water and 41.1% and 15.4% for f.f. Bland-Altman mean bias and ±95% coefficients of repeatability were for T -water (0.15, -2.65, 2.95) ms and f.f. (-0.02, -1.99, 2.03)%. There was no relationship between T -water (ρ = 0.16, p = 0.07) or f.f. (ρ = 0.03, p = 0.7761) and B error or any correlation between T -water and f.f. in the healthy subjects (ρ = 0.07, p = 0.40). In HypoPP there was a measurable relationship between T -water and f.f. (ρ = 0.59, p < 0.001). IDEAL-CPMG provides a feasible way to quantify T -water in muscle that is reproducible and sensitive to meaningful physiological changes without post hoc modeling of the fat contribution. In patients, IDEAL-CPMG measured elevations in T -water and f.f. while showing a weak relationship between these parameters, thus showing promise as a practical means of quantifying muscle water in patient populations.
独立于肌肉内脂肪含量来量化肌肉水T（T-水），对于将T-水确立为神经肌肉疾病即将开展的新治疗试验的一项结果指标至关重要。IDEAL-CPMG将化学位移脂肪-水分离与T弛豫测量法相结合以获得这样一种测量指标。在此，我们评估了IDEAL-CPMG的T-水和脂肪分数（f.f.）值在健康受试者中的可重复性和B敏感性，并证明了该方法在量化显示不同程度脂肪浸润的患病肌肉中T-水变化方面的潜力。使用IDEAL-CPMG对11名健康个体（40.5±10.2岁）的小腿肌肉在3T下进行了两次扫描，扫描间隔为4周，同时也对12名低钾性周期性麻痹（HypoPP）患者（42.3±11.5岁）进行了成像。对分离出的水和脂肪成分的信号衰减拟合一条指数曲线，以确定T-水，并手动分割肌肉区域的脂肪信号幅度。健康受试者小腿水平肌肉的总体平均T-水为31.2±2.0毫秒，肌肉间无显著差异（p = 0.37）。T-水的受试者间和扫描间变异系数分别为5.7%和3.2%，f.f.分别为41.1%和15.4%。Bland-Altman平均偏差和±95%重复性系数对于T-水为（0.15，-2.65，2.95）毫秒，对于f.f.为（-0.02，-1.99，2.03）%。在健康受试者中，T-水（ρ = 0.16，p = 0.07）或f.f.（ρ = 0.03，p = 0.7761）与B误差之间没有关系，T-水和f.f.之间也没有任何相关性（ρ = 0.07，p = 0.40）。在HypoPP患者中，T-水和f.f.之间存在可测量的关系（ρ = 0.59，p < 0.001）。IDEAL-CPMG提供了一种可行的方法来量化肌肉中的T-水，该方法具有可重复性，并且对有意义的生理变化敏感，无需对脂肪贡献进行事后建模。在患者中，IDEAL-CPMG测量到T-水和f.f.升高，同时这些参数之间显示出较弱的关系，因此显示出作为量化患者群体肌肉水的一种实用手段的前景。
