Quantification of Fornix Tracts in MCI and AD

Introduction Numerous studies have shown a pattern of progressive hippocampal shrinkage as a result of mild cognitively impairment (MCI) and Alzheimer Disease (AD). One of the major pathways affected by the hippocampus is the fornix, and it has been recently shown that fractional anisotropy (FA) is reduced in normal controls verses AD [DeCarli et al., Alzheimer’s Imaging Consortium IC-P1,July 2008]. The purpose of this study was to (a) objectively define hippocampal ROIs as most previous studies rely on subjectively delineated ROIs to perform DTI analysis, (b) correct for varying subject head sizes using intracranial volume( ICV) of subjects in a novel way to equalize the number of seed points and their anatomical distribution so that total number of tracts becomes independent of the subject's head size, and (c) examine the differences in the equalized streamline fornix tracts.