Effects of Echo Time on Diffusion Quantification of Brain White Matter at 1.5T and 3.0T

The aim was to investigate the effects of echo time (TE) on diffusion quantification of brain white matter. Seven rhesus monkeys (all males; age, 4-6 years; weight, 5-7 kg) underwent diffusion tensor imaging (DTI) with a series of TEs in 1.5T and 3.0T MR scanners. The mean diffusivity (MD), fractional anisotropy (FA), primary (lambda(1)), and transverse eigenvalues (lambda(23)) were measured in a region of interest at the bilateral internal capsule. Pearson correlation showed that the FA and lambda(1) increased and lambda(23) decreased with TE both at 1.5T and 3.0T except for the MD. Repeated measurement analysis of variance (ANOVA) also showed significantly higher FA and lower MD and lambda(23) at 3.0T than those at 1.5T (P < 0.01), but no statistical differences were found in lambda(1) between these two field strengths (P = 0.709). These findings implied that TE and field strength might influence diffusion quantification in brain white matter. Magn Reson Med 61:755-760, 2009. (C) 2009 Wiley-Liss, Inc.