Alzheimer's Imaging Consortium.

Area of Science:

• Neuroimaging
• Neurology
• Biomarkers

Background:

• Diffusion tensor imaging (DTI) is a valuable biomarker for assessing white matter integrity in neurological conditions.
• Few studies have directly compared white matter microstructure across different neurodegenerative diseases.

Purpose of the Study:

• To characterize and compare white matter tract microstructure in patients with Alzheimer's disease/mild cognitive impairment (ADMCI), Parkinson's disease (PD), and cerebrovascular disease (CVD).
• To utilize DTI data from the Ontario Neurodegenerative Disease Research Initiative (ONDRI) for comparative analysis.

Main Methods:

• Reconstruction of 39 white matter pathways using FreeSurfer's TRACULA.
• Calculation of DTI metrics: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AxD), and radial diffusivity (RD).
• Multivariate general linear models were employed to assess the impact of diagnosis on DTI metrics.

Main Results:

• Diagnosis significantly affected all four DTI metrics (FA, MD, AxD, RD).
• Parkinson's disease (PD) patients exhibited higher FA and lower MD, AxD, and RD compared to ADMCI and CVD patients.
• Minimal significant differences were observed between ADMCI and CVD patient groups.

Conclusions:

• PD patients demonstrated more preserved white matter microstructural integrity than ADMCI or CVD patients.
• ADMCI and CVD patients showed lower FA and higher RD and MD values.
• Advanced diffusion imaging techniques may be required to detect subtle white matter changes in PD.