Standardization of amyloid quantitation with florbetapir standardized uptake value ratios to the Centiloid scale

Introduction: Klunk et al. recently proposed a means of standardizing quantitation of amyloid burden from positron emission tomography scans to a common Centiloid scale, and we have applied that method to florbetapir. Methods: Florbetapir and Pittsburgh compound B scans were acquired for 46 mixed clinical presentation subjects within 18 +/- 20 days. Florbetapir and Pittsburgh compound B cortical standardized uptake value ratio (SUVr) values were well correlated for both standard Centiloid (R-2 = 0.894) and Avid (R-2 = 0.901) volume of interests (VOIs). The methods of Klunk et al. were applied to establish a conversion first from florbetapir SUVr values obtained using standard Centiloid VOIs to Centiloids and then from Avid VOIs (Joshi et al.) to Centiloids. Results: The equation for conversion of florbetapir SUVr from Avid VOIs to the Centiloid scale was as follows: Florbetapir Centiloids = 183 X SUVr(Avid) - 177. The threshold that discriminated neuropathologically verified none or sparse versus moderate to frequent plaques in autopsy-confirmed data is 24.1 Centiloids. Discussion: These findings may allow improved tracer-independent amyloid quantitation. (C) 2018 Published by Elsevier Inc. on behalf of the Alzheimer's Association.