Effects of image noise in muscle diffusion tensor (DT)‐MRI assessed using numerical simulations

Diffusion tensor (DT)‐MRI studies of skeletal muscle provide information about muscle architecture, microstructure, and damage. However, the effects of noise, the diffusion weighting ( b )‐value, and partial volume artifacts on the estimation of the diffusion tensor (D) are unknown. This study investigated these issues using Monte Carlo simulations of 3 × 9 voxel regions of interest (ROIs) containing muscle, adipose tissue, and intermediate degrees of muscle volume fractions ( f M ). A total of 1000 simulations were performed for each of eight b ‐values and 11 SNR levels. The dependencies of the eigenvalues (λ 1–3 ), mean diffusivity ( λ ), and fractional anisotropy (FA), and the angular deviation of the first eigenvector from its true value (α) were observed. For moderate b ‐values ( b = 435–725 s/mm 2 ) and f M = 1, an accuracy of 5% was obtained for λ 1–3 , λ , and FA with an SNR of 25. An accuracy of 1% was obtained for λ 1–3 , λ , and FA with f M = 1 and SNR = 50. For regions with f M = 8/9, 5% accuracy was obtained with SNR = 40. For α, SNRs of ≥25 and ≥45 were required for ±4.5° uncertainty with f M = 1 and f M = 0.5, respectively; SNR ≥ 60 was required for ±9° uncertainty in single muscle voxels. These findings may influence the design and interpretation of DT‐MRI studies of muscle microstructure, damage, and architecture. Magn Reson Med 60:934–944, 2008. © 2008 Wiley‐Liss, Inc.