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Axial asymmetry of water diffusion in brain white matter
Author(s) -
Lazar Mariana,
Lee Jong Hoon,
Alexander Andrew L.
Publication year - 2005
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20653
Subject(s) - asymmetry , white matter , nuclear magnetic resonance , diffusion mri , diffusion , brain asymmetry , physics , magnetic resonance imaging , medicine , neuroscience , psychology , lateralization of brain function , radiology , thermodynamics , quantum mechanics
The diffusion tensor (DT) is a three‐dimensional (3D) model of diffusivity in biological tissues. In white matter (WM), the major eigenvector, which is the direction of greatest diffusivity, is generally assumed to align with the direction of the fiber bundles. The distribution of major eigenvectors in WM has been investigated using color‐based maps and WM tractography (WMT). However, anatomical patterns in the medium and minor eigenvector directions have largely been ignored in DTI studies of the human brain. In this study, the patterns of medium and minor eigenvectors in the brain were investigated using both color‐based maps and WMT. Specific WM structures, such as the corona radiata, internal and external capsules, sagittal stratum, cingulum, and superior longitudinal fasciculus, demonstrated coherent patterns in the medium and minor eigenvector directions. These patterns were consistent across subjects. The orthogonal or axial diffusion asymmetry may be explained by merging, diverging, or crossing fiber geometries. The effects of orthogonal diffusion asymmetry on WMT were also investigated. This study shows that WM axial asymmetry causes anisotropic dispersion patterns in the estimated tract trajectories. The medium and minor eigenvector patterns may be useful for elucidating the local dispersion distributions of WM tracts. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.