Alzheimer's Imaging Consortium

Area of Science:

• Neuroimaging
• Neuropathology
• Biomarker Discovery

Background:

• Alzheimer's disease (AD) staging involves amyloid and tau progression, but their regional impact on neurodegeneration is debated.
• Diffusion MRI detects microstructural changes, aiding in early AD detection and subtype differentiation.
• This study investigates the relationship between regional amyloid and tau deposition and diffusion metrics at the gray/white matter interface.

Purpose of the Study:

• To analyze the impact of regional amyloid and tau burden on diffusion MRI metrics.
• To assess microstructural changes in neuronal health related to protein deposition in Alzheimer's disease.
• To explore the potential of diffusion imaging as an early indicator of neurodegenerative processes.

Main Methods:

• Utilized data from 354 participants from the Knight Alzheimer Disease Research Center.
• Processed T1-weighted, diffusion MRI, and amyloid/tau PET imaging data.
• Employed general linear models to assess regional effects of amyloid and tau Standardized Uptake Value Ratio (SUVR) on Fractional Anisotropy (FA) values.

Main Results:

• Amyloid burden showed broad effects on diffusion, increasing FA in frontal, parietal, and superior temporal cortices, mirroring typical amyloid deposition patterns.
• Tau accumulation demonstrated a focused impact, decreasing FA in medial temporal, occipital, and lateral frontal areas, consistent with tau spread patterns.
• Regionally differential effects of amyloid and tau on FA were observed, highlighting distinct microstructural impacts.

Conclusions:

• Diffusion imaging metrics are strongly associated with the spread of amyloid and tau biomarkers in Alzheimer's disease.
• Observed regional patterns in diffusion metrics correlate with the known spread of amyloid and tau in early AD stages.
• These findings suggest diffusion MRI can serve as an early indicator of myelin integrity or cytoarchitectural changes, improving biomarker specificity for neurodegeneration.