Concordance in Detecting Amyloid Positivity Between 18F-florbetaben and 18F-flutemetamol Amyloid PET Using Quantitative and Qualitative Assessments

Abstract

Background In the present study, the discrepancy in detecting amyloid beta (Aβ) positivity between 18F-florbetaben (FBB) and 18F-flutemetamol (FMM) positron emission tomography (PET) was quantitatively and qualitatively assessed.Methods Paired FBB and FMM PET images were obtained on separate days from 107 participants. Three experts visually quantified the scans as positive or negative for Aβ deposition. Quantitative assessment was performed using global cortical standardized uptake value ratio (SUVR) with the whole cerebellum (WC) as a reference region.Results Inter-rater agreement was excellent for FBB (Fleiss k = 0.86) and FMM (Fleiss k = 0.78). The concordance rates between FBB and FMM were 94.4% (101/107) for visual assessment and 98.1% (105/107) for SUVR cut-off categorisation. Both FBB and FMM showed high agreement rates between visual assessment and SUVR positive or negative categorisation (93.5% in FBB and 91.2% in FMM). When the two ligands were compared based on SUVR cut-off categorisation as standard of truth, although not statistically significant, the false-positive rate (visual assessment-positive, SUVR-negative) was higher in FMM (9.1%) than in FBB (1.8%) (P = 0.13). In those cases, assessing uptakes in the lateral temporal cortex was often more problematic than in other regions in visual analysis, especially near the border with the occipital lobe.Conclusion Our findings suggested that both FBB and FMM had excellent agreement when used to quantitatively and qualitatively evaluate Aβ deposits, thus, combining amyloid PET data associated with the use of different ligands from multi-centers can be useful in future research.