R2* Mapping in a Primate Model of CAA Shows Aging-Related Increases in GM and Reversal in WM with Transient Edema

Motivation: Amyloid-related imaging abnormalities (ARIA), seen in Alzheimer's patients (AD) undergoing anti-amyloid immunotherapy, are partly caused by cerebral amyloid angiopathy (CAA). Squirrel monkeys (SQMs) offer a unique model for studying ARIA Goal(s): Characterize MR imaging biomarkers in aging SQMs using conventional MRI for edema and quantitative R2* for iron-related pathology. Approach: R2* map enables co-registration between animals allowing quantitative assessment via atlas-based analysis Results: Whole brain R2* increase is mirrored in gray matter (GM) but not in white matter (WM). WM R2* reversal is likely due to edema, predominantly in the occipital and prefrontal cortex. Longitudinal monitoring revealed that WM hyperintensities can be transient. Impact: ARIA is a condition seen during the pharmaceutical treatment of AD. Studying SQM can offer valuable insights into the disease mechanisms.