Fig. 3

Time curves of the ratio of five representative ROIs over the cerebellum. These curves demonstrate that the values reach a plateau after approximately 40 min and become more variable after approximately 70 min of scanning. The optimal scanning time was determined from 40 to 60 min. The values correspond to the mean of the five experiments for five representative ROIs (raphe nuclei, thalamus, basal ganglia, frontal cortex and occipital cortex). Except for the raphe nuclei (in the sagittal plane), the mean values of the right and left sides were taken for the four other regions