A simulation model of the counting-rate response of clinical pet systems and it´s application to optimize the injected dose

The design principles of clinical PET data acquisition protocols require images of high statistical quality, while the scanning time remains relatively short and the total amount of radioactive dose does not exceed a level, above which significant count losses are observed. This can be satisfied by determining a range of injected dose levels where the performance parameter of noise equivalent count rate (NECR) is maximized. However certain patient- and scanner-related parameters can shift the range. We propose a methodology to design a model of the NECR response to certain patient-scanner parameters, based on validated simulations of imaging systems and realistic human phantoms. We used Geant4 application for tomography emission and investigated the relationship between the NECR and the patient size, the coincidence time window of the scanner, the dead-time of the system´s electronics and the energy window.