Effects of b-value and echo time on magnetic resonance diffusion tensor imaging-derived parameters at 1.5 t: A voxel-wise study

The diffusion weighting factor (b-value) and echo time (TE) are two important parameters that influence quantitative measurements of diffusion tensor imaging (DTI). The present study employs a voxel-wise post-processing scheme to investigate the effects of b-value and TE on the reproducibility and accuracy of DTI-derived indices based on actual human brain data with commonly used imaging parameters. Five repeated DTI datasets of six b-values and five TE values were acquired from a healthy subject. The reproducibility and accuracy of axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), fractional anisotropy (FA), and the principal eigenvector (PEV) are assessed by calculating the voxel-wise standard deviation, coefficient of variance, and difference of mean values from the reference DTI dataset acquired with number of excitations (NEX) = 15. The results show that the reproducibility and accuracy of AD, RD, MD, FA, and PEV are significantly impacted by b-value and TE, and that there is a significant difference between gray and white matter tissues. Therefore, the reproducibility and accuracy of DTI-derived indices depends on the b-value and TE for both gray and white matter.