Expression of regional brain amyloid-β deposition with [18F]Flutemetamol in Centiloid scale -a multi-site study

Purpose The Centiloid project helps calibrate the quantitative amyloid-beta (A beta) load into a unified Centiloid (CL) scale that allows data comparison across multi-site. How the smaller regional amyloid converted into CL has not been attempted. We first aimed to express regional A beta deposition in CL using ([18F])Flutemetamol and evaluate regional A beta deposition in CL with that in standardized uptake value ratio (SUVr). Second, we aimed to determine the presence or absence of focal A beta deposition by measuring regional CL in equivocal cases showing negative global CL. Methods Following the Centiloid project pipeline, Level-1 replication, Level-2 calibration, and quality control were completed to generate corresponding Centiloid conversion equations to convert SUVr into Centiloid at regional levels. In equivocal cases, the regional CL was compared with visual inspection to evaluate regional A beta positivity. Results 14 out of 16 regional conversions from ([18F])Flutemetamol SUVr to Centiloid successfully passed the quality control, showing good reliability and relative variance, especially precuneus/posterior cingulate and prefrontal regions with good stability for Centiloid scaling. The absence of focal A beta deposition could be detected by measuring regional CL, showing a high agreement rate with visual inspection. The regional A beta positivity in the bilateral anterior cingulate cortex was most prevalent in equivocal cases. Conclusion The expression of regional brain A beta deposition in CL with ([18F])Flutemetamol has been attempted in this study. Equivocal cases had focal A beta deposition that can be detected by measuring regional CL.