ROI impact on SUVR quantification in amyloid PET

Abstract

Objectives The imaging of amyloid plaque PET is a promising early marker of Alzheimer's disease. The literature reports different positivity thresholds based on SUVr (Standard Uptake Value ratio) varying the method of quantitation. The choice of the reference atlas has not been studied. The purpose of this study is to compare the effect of two sets of ROI on of amyloid burden quantification, using the same methods of pretreatment and semi-automatic quantification in the same population. Materials and methods A multicenter study from the MAPT acquisitions from 10 to 15 min, 50 min after a bolus injection of 3.7 MBq/ kg of Florebetapir (Amyvid ® ) were performed. The images were visually assessed by three trained observers on a binary scale (+/−) blinded of clinical data. Then a semi-automatic quantification was performed on six cortical regions with two different atlases different set of VOIs (Avid ® and WFU) to obtain two SUVr taking the cerebellum as reference region. The SUVr in each region zone and the cortical average over six regions SUVr means were compared. The positivity thresholds for each method were calculated using visual analysis as a reference. Results 198 subjects (76 ± 4.3 years) were included. On visual analysis 36% of the subjects were amyloid positive (76.6 ± 4.5 years). The average SUVr is greater ROI for WFU ROIs (1.4 ± 0.17 against 1.16 ± 0.19). The SUVr are very different according to the atlas used ( t ± 0.0001), but strongly correlated (q = 0908 pearson, p = 0.001). The semiautomatic quantitative analysis gives 35% (WFU) and 37% (Avid ® ) of amyloid positive subjects with a respective threshold of 1.45 and 1.16. Conclusions SUVr depend on ROI set. However, determining the positivity threshold specific to each of them, we can obtain similar results in terms of diagnostic performance. This variability in ROI set should be taken into account in the analysis of results and especially in meta-analyzes