The Centiloid Project aims to standardize quantitative amyloid plaque estimation by PET imaging. The project addresses the variability in reported tracer retention numbers, which can be attributed to different units, scanner dependencies, and tracers. The authors propose a standardized method for analyzing PiB PET data and scaling any non-standard method to a 0-100 scale, anchored by young controls (≤45 years) and typical Alzheimer's disease (AD) patients. This scale, named "Centiloids," is designed to facilitate direct numeric comparisons across different measures. The project outlines a three-level process: Level 1 sets the anchor points for the scale, Level 2 calibrates new methods to the Centiloid scale, and Level 3 ensures reproducibility. The approach is based on the most widely used method, [C-11]Pittsburgh Compound-B (PiB) tissue ratios, but also includes methods for scaling using fluorine-18 tracers when necessary. The data and reference volumes used in the Centiloid process are publicly available to promote transparency and reproducibility.The Centiloid Project aims to standardize quantitative amyloid plaque estimation by PET imaging. The project addresses the variability in reported tracer retention numbers, which can be attributed to different units, scanner dependencies, and tracers. The authors propose a standardized method for analyzing PiB PET data and scaling any non-standard method to a 0-100 scale, anchored by young controls (≤45 years) and typical Alzheimer's disease (AD) patients. This scale, named "Centiloids," is designed to facilitate direct numeric comparisons across different measures. The project outlines a three-level process: Level 1 sets the anchor points for the scale, Level 2 calibrates new methods to the Centiloid scale, and Level 3 ensures reproducibility. The approach is based on the most widely used method, [C-11]Pittsburgh Compound-B (PiB) tissue ratios, but also includes methods for scaling using fluorine-18 tracers when necessary. The data and reference volumes used in the Centiloid process are publicly available to promote transparency and reproducibility.