PiB PET Imaging for Amyloid-Beta Quantification

Participants received a single intravenous bolus injection of ¹¹[C] PiB (between 4.7 and 19.0 mCi). PET imaging [24 (link)] was conducted with a Siemens 962 HR+ ECAT PET or Biograph 40 scanner (Siemens/CTI, Knoxville KY), and magnetic resonance imaging (MRI) using MPRAGE T1-weighted images (1 mm×1 mm×1.25 mm) was obtained for anatomic reference as described previously [25, 26 (link)]. Participants underwent a 60-min dynamic scan with ¹¹[C] PiB, and PET data was processed using regions of interest (ROIs) derived from structural MRIs using Freesurfer [25, 26 (link)]. Regional time-activity curves were extracted for each ROI, and binding potentials were calculated using Logan graphical analysis [27 (link)] with cerebellar gray matter as the reference region. The mean cortical binding potential (MCBP) was calculated based on a set of selected cortical regions known to have high levels of deposition in AD [28 (link)], including precuneus, rostral middle frontal cortex, superior frontal cortex, superior temporal cortex, middle temporal cortex, lateral orbitofrontal cortex, and medial orbitofrontal cortex [25 (link)]. A MCBP cutoff of >0.18 for positivity was chosen to be consistent with prior studies [9, 28–30 (link)].