The 30 gold standard images used for method development and validation consisted of four or six successive 5‐minute frames beginning at 80 or 90 minutes post‐tracer injection, motion‐corrected and averaged in native space. For quantitative measurement only, the images were smoothed to an approximate uniform resolution based upon the scanner model21 and partial volume correction (PVC, Müller‐Gärtner method)22 was applied to most closely quantify actual binding rather than spill‐in or atrophy; this was because visual reads on uncorrected scans must be able to differentiate between true uptake and off‐target confounds. Regional mean SUVRs were calculated for medial temporal, lateral temporal, medial parietal, and lateral parietal regions measured using PETSurfer in FreeSurfer 6.023, 24 with inferior cerebellar gray matter reference region. SummedSUVR was defined as the summation of each scan's four regional mean SUVRs.
To ensure scans used for further evaluation of the visual read method were consistent with the gold standard scans used to develop the method, for the 131‐scan and full database sets, image frames of similar post‐injection start time and duration were selected from each acquisition protocol (detail in Supplement). Frames were motion‐corrected and averaged, and PET images co‐registered with their respective MRI scans in a common orientation and voxel size without spatial warping. Scans were provided in unsmoothed form; a 4 mm smoothed version was provided for optional comparison. This was consistent with clinical settings in which readers may slightly smooth images, particularly if acquired on scanners with fine pixelation. For report generation for the visual reads and for the supplemental quantitative measurement only, images were warped to a template.