Automated Quantification of 18F-Flutemetamol PET Activity for Categorizing Scans as Negative or Positive for Brain Amyloid: Concordance with Visual Image Reads

Clinical trials of the PET amyloid imaging agent 18F-flutemetamol have used visual assessment to classify PET scans as negative or positive for brain amyloid. However, quantification provides addi-tional information about regional and global tracer uptake and may have utility for image assessment over time and across different centers. Using postmortem brain neuritic plaque density data as a truth standard to derive a standardized uptake value ratio (SUVR) threshold, we assessed a fully automated quantification method comparing visual and quantitative scan categorizations. We also compared the histopathology-derived SUVR threshold with one de-rived from healthy controls. Methods: Data from 345 consenting subjects enrolled in 8 prior clinical trials of 18F-flutemetamol injec-tion were used. We grouped subjects into 3 cohorts: an autopsy cohort (n 5 68) comprising terminally ill patients with postmortem confirmation of brain amyloid status; a test cohort (n 5 172) com