Reproducibility of Non-Invasive A 1 Adenosine Receptor Quantification in the Rat Brain Using [ 18 F]CPFPX and Positron Emission Tomography

Purpose The A 1 AR antagonist 8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([ 18 F]CPFPX) has recently been shown to be a suitable radiotracer for quantitative in vivo imaging of the A 1 adenosine receptor (A 1 AR) in rats. The present study evaluates the reproducibility of non-invasive longitudinal A 1 AR studies with [ 18 F]CPFPX and a dedicated small animal positron emission tomography (PET) scanner. Procedures Twelve male Sprague Dawley rats underwent four repeated dynamic PET scans with a bolus injection of [ 18 F]CPFPX. A 1 AR availability was determined by different non-invasive approaches including simplified and multilinear reference tissue (olfactory bulb)-based models and graphical methods. The outcome parameter binding potential ( BP ) was evaluated in terms of variability and reproducibility. Results Repeated estimations of [ 18 F]CPFPX BP ND gave reliable results with acceptable variability (mean 12 %) and reproducibility (intraclass correlation coefficients raging from 0.57 to 0.68) in cortical and subcortical regions of the rat brain. With regard to kinetic models, test-retest stability of the simplified reference-tissue model (SRTM) was superior to multilinear and graphical approaches. Conclusions Non-invasive quantification of A 1 AR density in the rat brain is reproducible and reliable with [ 18 F]CPFPX PET and allows longitudinal designs of in vivo imaging studies in rodents.