Brain MRI and Automated Image Analysis

All eligible participants had high-resolution brain MRI acquired on a 1.5T Signa TwinSpeed System (General Electric Medical Systems, Waukesha, WI) at both the AGES-I and AGES-II examinations.^{18 (link),22 (link)} Briefly, the core protocol included a T1-weighted 3-dimensional spoiled gradient-echo sequence, a proton density/T2-weighted fast spin-echo sequence, a fluid-attenuated inversion recovery sequence, and a T2*-weighted gradient-recalled echo sequence. MRI scan parameters for all sequences are fully reported elsewhere.^{15 (link),22 (link)} All images were acquired to give full brain coverage, and slices were angled parallel to the anterior commissure-posterior commissure line to give reproducible image views in the oblique-axial plane.
All brain images were analyzed automatically with the AGES/Montreal Neurological Institute image postprocessing pipeline,^{22 (link)} which segments the whole brain into gray matter, normal white matter, WMLs, and CSF. Brain infarcts were defined as defects in the brain parenchyma with a signal intensity that was isointense to that of CSF on all sequences with a diameter ≥4 mm, except for infarcts in the cerebellum, brainstem, and cortex, which had no size criteria.^{21 (link)}