Rate-dependence of the key performance parameters in an Anger logic based PET detector

The image quality of a PET scanner depends strongly on the spatial, energy, and time resolution of the detector. These parameters are usually specified for the case of low count rates. At higher rates, signals from subsequent events can overlap, and this pile-up deteriorates the resolution. In an Anger based detector, the high encoding ratio of scintillator pixels to photo multiplier tubes (PMTs) facilitates pile-up. The probability of pile-up depends on the detector geometry, the scintillator material, and the trigger scheme, and it increases with the count rate. In this paper, the key performance parameters of a whole-body PET detector are investigated as a function of the rate. Experimentally, we use scintillator arrays which can be coupled to PMT arrays with PMTs of different size, but otherwise similar characteristics. First results are presented which show-that signal pile-up leads to only small performance deterioration in typical /sup 18/F oncology studies, but has to be considered when using short lived tracers, e.g. based on /sup 11/C or /sup 15/O.