Investigating Tissue-Specific Abnormalities in Alzheimer's Disease with Multi-Shell Diffusion MRI.

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Radiology

Background:

• Most Alzheimer's disease (AD) diffusion-weighted MRI (DW-MRI) studies focus on white matter (WM) using tensor models, overlooking gray matter (GM) and cerebrospinal fluid (CSF).
• Existing tensor models have limitations in representing complex fiber structures and partial volume effects with CSF.

Purpose of the Study:

• To present a novel DW-MRI analysis approach for AD that disentangles multiple tissue compartments (WM, GM, CSF).
• To investigate micro- and macroscopic effects and identify differences between AD continuum groups and controls.

Main Methods:

• Utilized multi-tissue constrained spherical deconvolution of multi-shell DW-MRI data.
• Modeled WM fiber orientation distribution, GM, and CSF contributions to the diffusion signal.
• Extracted diffusivity and morphology measures, employing fixel-, voxel-, and tensor-based morphometry with FWE control.

Main Results:

• Detected AD-related abnormalities in WM tracts like the splenium, cingulum, and corticospinal tract.
• Identified changes in tissue composition within the medial temporal lobe and superior longitudinal fasciculus.

Conclusions:

• The developed framework enables simultaneous macro- and microscopic assessment of WM, GM, and CSF.
• This comprehensive approach advances DW-MRI analysis for neurodegenerative diseases.