A study of human brain structural connectivity based on diffusion tensor imaging in Alzheimer's disease

Diffusion tensor imaging (DTI) is a magnetic resonance imaging technique that can estimate the directionality of fibers and the microstructural of white matter in human brain. DTI researches have demonstrated that demyelinations existed in white matter of Alzheimer's disease (AD) patients mainly by fractional anisotropy (FA) and apparent diffusion constant (ADC). FA or ADC is usually used to reveal different structural properties at the independent voxel while they cannot tell us the connective relationship among voxels. In this study, we took propagation speed generated by fast marching method (FMM) as connectivity values. The significant differences of connectivity values between AD patients and elderly normal controls (NC) show that the structural connection of some regions has changed in AD patients. DTI data was acquired from 10 NC and 10 AD patients. After preprocessing, we chose the seed points in corpus callosum where FA values evidently changed by group analysis. From the seed point, we tracked all connected voxels using FMM, and then compared connectivity values of these voxels between Ad and NC statistically. The results reveal that AD patients have significant decline of connectivity values in some regions of corpus callosum where we also found significant decline of FA values in. It means that the structural connections of AD patients changed and this phenomenon may help us to explain the decreased functional activity in AD.