Different variability types. (A) Different types of variability of 18F-FDG brain SUV in male Crl:CD(SD) rats (n = 6). Each data point corresponds to the 18F-FDG brain SUV of one individual animal. Intra-animal variability is the variability between three brain scans of one individual (indicated in red). (B) Column bar representation of the data from (A). Inter-animal variability is the variability between brain SUVs of different individuals acquired on the same test day (represented by the SD, indicated in blue). Inter-study variability is the variability of 18F-FDG brain SUVs between two independent test groups acquired under exactly the same experimental conditions (indicated in green); *P < 0.05.