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 = 0.894) and Avid (R = 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 × SUVr - 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.