Image acquisition & preprocessing
Participants underwent baseline PET scanning sessions for tau ([ Structural MRI (MPRAGE) scans were acquired for each POINTER participant using identical parameters to the ADNI3 protocol: TR=2300ms, TE=min full echo, voxel size=1mm isotropic, FOV=256mm. For all participants, sMRI data were segmented into cortical and subcortical regions based on anatomical landmarks using FreeSurfer v7.1 (To acquire tau-PET images, participants were injected with 5 mCi of the MK6240 tracer and scanned from 90-110 minutes post-injection (4 × 5 minute frames). To acquire A Tracer-specific PET ROIs were sampled using MRI-based native space FreeSurfer parcellations (