Quantitative diffusion-tenser anisotropy brain MR imaging: Normative humandata and anatomic analysis

PURPOSE: To obtain normative human cerebral data and evaluate the anatomtom ic information in quantitative diffusion anisotropy magnetic resonance (MR) imaging. MATERIALS AND METHODS: Quantitative diffusion anisotropy MR images were obt ained in 13 healthy adults by using single-shot echo-planar MR imaging and a combination of tetrahedral and orthogonal gradient encoding (whole-brain coverage in about 1 minute). White matter (WM) anatomy was assessed at visu al inspection, and values were measured in various brain regions. Different anisotropy measures, including total anisotropy (A(sigma)), were compared on the basis of information content rotational invariance and susceptibilit y to noise. Partial volume and noise effects were simulated. RESULTS: Anisotropy MR images depicted WM features not typically seen on co nventional MR images (eg, external capsule, thalamic substructures, basal g anglia, occipital WM, thickness of the internal capsule). Statistically sig nificant anisotropy differences occurred across brain regions, which were r eproducible within and across subjects. A, was highest in commissural WM an d progressively lower in projection and association WM. This order parallel ed that of known resistance to spread of vasogenic edema, which suggested t hat anisotropy may be sensitive to WM histologic structure. Gray matter (CM ) A(sigma), data were consistent with zero anisotropy, and partial volume W M-GM effects were approximately linear. A(sigma) image quality could be eff ectively improved by means of averaging. CONCLUSION: Quantitative diffusion anisotropy images can be obtained rapidl y and demonstrate subtle WM anatomy. Different histologic types of WM have significant and reproducible anisotropy differences.