3.0 tesla mr750

All participants were scanned on a GE 3.0 Tesla MR750 (Waukesha, WI) using an 8 channel head coil. A T1-weighted brain volume was acquired in the axial plane with a 3D inversion recovery prepared fast spoiled gradient-echo (3D SPGR) sequence using the following parameters: TI = 450 ms; TR = 8.1 ms; TE = 3.2 ms; flip angle = 12°; acquisition matrix = 256 × 256 ×156 mm, FOV = 256 mm; slice thickness = 1.0 mm. Voxels were 1 mm isotropic. The image acquisition protocol also included T2 weighted and FLAIR anatomical scans, which were reviewed by a neuroradiologist (H.A.R.) for exclusionary abnormalities. The T1-weighted volume was segmented into tissue classes using the updated segmentation feature in SPM12 (www.fil.ion.ucl.ac.uk/spm).

Detailed methods for [C-11] PiB radiochemical synthesis, PiB-PET scanning with a 70 minute dynamic acquisition, and distribution volume ratio map generation using the Logan method and the cerebellum as a reference region have been described previously [36 ]. PiB-PET images were registered to a T1-weighted anatomical scan collected on a GE 3.0 Tesla MR750 (Waukesha, WI) using an 8 channel head coil [36 , 37 (link)]. A composite measurement of global amyloid derived from eight bilateral ROIs (angular gyrus, anterior cingulate gyrus, posterior cingulate gyrus, frontal medial orbital gyrus, precuneus, supramarginal gyrus, middle temporal gyrus, and superior temporal gyrus) was calculated as described previously [38 (link), 39 (link)]. N=91 participants underwent PiB-PET imaging approximately 4.1 years (SD 0.66, range 2.0–5.3) prior to CAB testing.