Multimodal Brain Imaging of Aging and Amyloid Burden

All participants were scanned on the same MRI scanner (Philips Achieva; 3.0 T) and PET camera (Discovery RX VCT 64 PET-CT; General Electric Healthcare) at the Cyceron Center (Caen, France). High-resolution T1-weighted structural imaging were acquired to measure GM volume and an echo-planar imaging/spin echo diffusion weighted sequence (DKI) was performed to obtain white matter (WM) microstructural integrity measurements. Mean kurtosis parameter maps reflected WM microstructural integrity based on the number, density, orientation, and degree of organization of WM microstructures [39 (link)]. Myelin and axonal integrity was also estimated from the radial and axial parameters of DKI, respectively [40 (link)]. Fluorine 18-labeled (¹⁸F) florbetapir-PET scans were obtained with a 10-min acquisition beginning 50 min after the intravenous injection reflecting amyloid burden. ¹⁸F-fluorodeoxyglucose (FDG)-PET scans were acquired on a subset of participants (n = 92) to measure brain glucose metabolism. The detailed acquisition and preprocessing procedures [27 ] are available in Supplementary Material 1. The sample size for each imaging modality is reported in Supplementary Table 1.