Stephen E. Rose, and Jonathan B. Chalk
Centre for Magnetic Resonance
University of Queensland
Brisbane, QLD, 4072, Australia
Diffusion tensor imaging (DTI) based tractography enables selective reconstruction of specific white matter (WM) pathways. The cingulum tracts, connecting hippocampal, thalamic and association cortices, are suspected to be involved in the episodic memory impairment in mild cognitive impairment (MCI). We investigate the local micro structural WM changes along the cingulum paths that could not be studied effectively due to its curvilinear feature in the posterior and anterior regions, which causes significant difficulty in defining the regions of interest and in comparing diffusion properties across individual subjects in three dimensional (3D) brain images. We develop a new analysis technique to define the complex 3D regions of interest, reconstruct the entire cingulum tracts, and measure the regional micro structural WM alternations along the major fiber bundles. Our approach is based on DTI tractography and geodesic path mapping, which allows cross-subject evaluation of diffusion properties along the cingulum by parameterizing the space of reconstructed pathways as a function of geodesic distance. Assessment of the technique by comparing 17 MCI participants and 17 controls reveals specific anatomical locations along the left cingulum paths with significantly reduced fractional anisotropy value in the MCI subjects. The results show that this analysis technique is promising and may provide a sensitive approach to determining the integrity of WM tracts for complex regions of interest in the brain.
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