Cortical diffusion MRI microstructure associations with amyloid PET in cognitively normal people

Brisbane Convention & Exhibition Centre 

Diffusion MRI (dMRI) is sensitive to small changes in brain microstructure and may offer sensitivity to early Alzheimer's disease (AD) neuropathology that precedes macrostructural brain changes. Subtle pathology associated with early amyloid (Aβ) deposition may be better captured by dMRI measures in cortical gray matter (GM), where the earliest AD histopathological changes occur, compared to GM volume or thickness, the most commonly used MRI biomarkers. Recently, single-shell adaptations of multi-shell NODDI [1] and mean apparent propagator (MAP)-MRI [2] dMRI models have been proposed: NODDI-DTI [3] and MAP-AMURA [4], respectively. These models may mimic the sensitivity of multi-shell models to sources of non-Gaussianity in the GM, including dispersion and restriction, and may help to identify early correlates of Aβ accumulation before neurodegeneration and cognitive impairment occur. Here, we evaluated relationships between Aβ PET and advanced single-shell cortical microstructural measures in cognitively normal (CN) individuals from 3 AD studies. For comparison, more conventional DTI and cortical thickness (CTh) measures were also evaluated.