Diffusion tensor MR imaging of the human brain.

TLDR

The study aims to assess intrinsic properties of water diffusion in the normal human brain using quantitative diffusion tensor parameters that are orientation‑insensitive. The authors acquired 31 interleaved echo‑planar diffusion‑weighted images over ~25 min in eight healthy adults and computed maps of principal diffusivities, Trace(D), and anisotropy indices to segment tissues. Trace(D) was uniform across normal brain except for higher values in cortex, while diffusion anisotropy varied markedly, being threefold higher and cylindrically symmetric in corpus callosum and pyramidal tracts but low and asymmetric in regions such as the centrum semiovale, suggesting that diffusion tensor imaging can enhance assessment of gray and white matter disorders.

Abstract

To assess intrinsic properties of water diffusion in normal human brain by using quantitative parameters derived from the diffusion tensor, D, which are insensitive to patient orientation.Maps of the principal diffusivities of D, of Trace(D), and of diffusion anisotropy indices were calculated in eight healthy adults from 31 multisection, interleaved echo-planar diffusion-weighted images acquired in about 25 minutes.No statistically significant differences in Trace(D) (approximately 2,100 x 10(-6) mm2/sec) were found within normal brain parenchyma, except in the cortex, where Trace(D) was higher. Diffusion anisotropy varied widely among different white matter regions, reflecting differences in fiber-tract architecture. In the corpus callosum and pyramidal tracts, the ratio of parallel to perpendicular diffusivities was approximately threefold higher than previously reported, and diffusion appeared cylindrically symmetric. However, in other white matter regions, particularly in the centrum semiovale, diffusion anisotropy was low, and cylindrical symmetry was not observed. Maps of parameters derived from D were also used to segment tissues based on their diffusion properties.A quantitative characterization of water diffusion in anisotropic, heterogeneously oriented tissues is clinically feasible. This should improve the neuroradiologic assessment of a variety of gray and white matter disorders.