ABSTRACT
Objective Amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD)used to be evaluated by an-alyzing the characteristics of the brain gray matter via diffuse tensor imaging (DTI).This study was to characterize the damage to the mi-crostructural integrity of the brain gray matter in aMCI and AD patients using the mean diffusivity ( MD) of DTI and to investigateits transformation rules. Methods This retrospective study included 30 cases ofaMCI, 30 cases of AD, and another 30 normal controls. We measured the MD values of the whole brain gray matter , established the MD network of the water molecules in the gray matter , char-acterized the small-world network, and performed correlation analysis by neuropsychological assessment . Results Compared with the normal controls, the MDnetworks of the aMCI and AD groupsexhibited abnormal small world characteristics , namely, a higher clustering coefficient and a longer path , which reflected the damage to themicrostructure of the gray matter , and theaverage connectivity in the aMCI patients was lowerthan that in thenormal controls but higher than that in the AD group ( P<0.05) .The MD values of the gray matter were negatively correlated with the Montreal Cognitive Assessment Scale scores in the 11 hub regions of the brain , including the bilateral hippo-campus and the limbic system ( P<0.05) . Conclusion The diffusion feature of the water molecules in the brain gray matter of the aMCIpatient may help to detect early ADand reflect the damage to the brain microstructure in patients with neurodegenerative diseases .