¹⁸F-Florbetaben PET beta-amyloid binding expressed in Centiloids

The Centiloid (CL) method enables quantitative values from Aβ-amyloid (Aβ) imaging to be expressed in a universal unit providing pathological, diagnostic and prognostic thresholds in clinical practice and research and allowing integration of multiple tracers and methods. The method was developed for ¹¹C-PiB scans with zero CL set as the average in young normal subjects and 100 CL the average in subjects with mild Alzheimer's disease (AD). The method allows derivation of equations to convert the uptake value of any tracer into the same standard CL units but first requires head-to-head comparison with ¹¹C-PiB results. We derived the equation to express ¹⁸F-florbetaben (FBB) binding in CL units.

Paired PiB and FBB PET scans were obtained in 35 subjects. including ten young normal subjects aged under 45 years (33 ± 8 years). FBB images were acquired from 90 to 110 min after injection. Spatially normalized images were analysed using the standard CL method (SPM8 coregistration of PET data to MRI data and the MNI-152 atlas) and standard CL regions (cortex and whole cerebellum downloaded from http://www.gaain.org ).

FBB binding was strongly correlated with PiB binding (R ² = 0.96, SUVR_FBB = 0.61 × SUVR_PiB + 0.39). The equation to derive CL values from FBB SUVR was CL units = 153.4 × SUVR_FBB - 154.9. The CL value in the young normal subjects was -1.08 ± 6.81 for FBB scans compared to -0.32 ± 3.48 for PiB scans, giving a variance ratio of 1.96 (SD_{FBB CL}/SD_{PiB CL}).

¹⁸F-FBB binding is strongly correlated with PiB binding and FBB results can now be expressed in CL units.