Variations of white matter tract length in regions of emotional regulation as assessed in alzheimer diffusion tensor images

Alzheimer´s disease (AD) is a progressive neurodegenerative disorder which affects various regions of brain. The primary damage occurs in white matter (WM) tracts leading to disintegration and death of neurons. Diffusion tensor imaging is one of the most widely used techniques to study the microstructural changes in WM. In this work, variations in length of WM tracts for regions associated with emotional regulation are studied. The images obtained from ADNI database are pre-processed to remove non-brain tissues and non-rigid registration is performed. Deterministic streamline tractography is used to reconstruct the WM tracts for whole brain. Length of each tract is estimated by voxel counting method. Brodmann area maps are superimposed to extract the tracts for areas 11, 38 and 47. Average tract length of each subregion is compared for AD and normal controls. The results show that there is a reduction in average tract length for AD subjects in the three regions studied. Maximum reduction of 27.15% is observed for area 11 followed by 24.43% for area 38 and 16.31% for area 47. No correlation is observed with MMSE score for any of these three sub-regions. This method of quantification of WM degeneration can be used to assess the severity of AD progression.