Diffusion Tensor Imaging in Alzheimer's Disease

Diffusion tensor imaging (DTI) provides information on tissue microstructure that is different from conventional T1 and T2-weighted MRI. Although, the value of DTI is likely to be greatest for assessing white matter degeneration in Alzheimer's disease (AD), cross-sectional DTI studies consistently show increased diffusivity in gray matter regions that are typically involved with the neurodegenerative pathology in AD such as the medial temporal lobes and temporoparietal association cortices. The white matter tracts that connect these gray matter regions such as the limbic pathways, long association fibers of inferior and superior longitudinal fasciculi also show elevated diffusivity and decreased directionality of diffusivity. Although the pathological underpinnings of DTI abnormalities in AD are yet unclear, DTI changes in AD are thought to represent disruption of myelin and axons in the white matter and neuronal cell bodies in the gray matter.