Evaluation of skeletal muscle DTI in patients with duchenne muscular dystrophy

• Published in: NMR in biomedicine Vol. 28; no. 11; pp. 1589 - 1597
• Main Authors: Hooijmans, M. T., Damon, B. M., Froeling, M., Versluis, M. J., Burakiewicz, J., Verschuuren, J. J. G. M., Niks, E. H., Webb, A. G., Kan, H. E.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.11.2015; Wiley Subscription Services, Inc
• Subjects: Adolescent; Child; Child, Preschool; diffusion tensor imaging; Diffusion Tensor Imaging - methods; Duchenne muscular dystrophy; fat fraction; Female; Humans; Leg - pathology; Male; mean water T2; Muscle, Skeletal - pathology; Muscular dystrophy; Muscular Dystrophy, Duchenne - pathology; Musculoskeletal system; Parameter estimation; Reproducibility of Results; Sensitivity and Specificity; Signal-To-Noise Ratio; mean water T2; diffusion tensor imaging; fat fraction; Duchenne muscular dystrophy; signal-to-noise ratio
• DOI: 10.1002/nbm.3427
• ISSN: 0952-3480

Diffusion tensor imaging (DTI) is a popular method to assess differences in fiber organization in diseased and healthy muscle tissue. Previous work has shown that muscle DTI measurements depend on signal‐to‐noise ratio (SNR), %fat, and tissue T2. The goal of this study was to evaluate the potential biasing effects of these factors on skeletal muscle DTI data in patients with Duchenne Muscular Dystrophy (DMD). MR images were obtained of the right lower leg of 21 DMD patients and 12 healthy controls on a Philips 3T system. DTI measurements were combined with quantitative in‐vivo measures of mean water T2, %fat and SNR to evaluate their effect on DTI parameter estimation. All outcome measures were determined within ROIs drawn for six lower leg muscles. Between group analysis, using all ROIs, revealed a significantly elevated FA in the GCL, SOL and PER muscles (p<0.05) and an increased mean diffusivity (p<0.05) and λ3 (p<0.05) in the TA muscle of DMD patients. In‐vivo evaluation of the individual confounders showed behaviour in line with predictions from previous simulation work. To account for these confounders, subsequent analysis used only ROIs with SNR greater than 20. With this criterion we found significantly greater MD in the TA muscle of DMD patient (p<0.009) and λ3 in the TA and GCL muscles (p<0.001) of DMD patients, but no differences in FA. As both increased %fat and lower SNR are expected to reduce the apparent MD and λ3, these between‐group differences are likely due to pathophysiology. However, the increased FA, observed when using all ROIs, likely reflects the effect of low SNR and %fat on the DTI parameter estimation. These findings suggest that measuring mean water T2, %fat and SNR is essential to ascribe changes in DTI measures to intrinsic diffusion changes or to confounding influences. Copyright © 2015 John Wiley & Sons, Ltd. A multi‐parametric MR protocol was used to evaluate the confounding effects of signal‐to‐noise ratio (SNR), fat percentage and changes in mean water T2 on the DTI parameter estimation in patients with Duchenne muscular dystrophy (DMD) and healthy controls. No significant changes in fractional anisotropy (FA) were observed between groups when using only regions of interest (ROIs) with SNR > 20, while an increased FA was detected in the lateral head of the gastrocnemius, the soleus and the peroneus muscles using all ROIs. These findings suggest that external factors have an important effect on the DTI estimation in DMD patients, and that a multi‐parametric MR measurement protocol is essential to distinguish between confounders and pathology.