Stability and sensitivity of water T 2 obtained with IDEAL-CPMG in healthy and fat-infiltrated skeletal muscle

• Published in: NMR in biomedicine 2016-12, Vol.29 (12), p.1800-1812
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Adipose Tissue - diagnostic imaging; Adult; Algorithms; Body Water - diagnostic imaging; Feasibility Studies; Female; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Magnetic Resonance Imaging - methods; Male; Middle Aged; Muscle Weakness - diagnostic imaging; Muscle, Skeletal - diagnostic imaging; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3654

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