Assessment of the spatial resolution of PET scanners using a Geant4-based Monte Carlo tool

In this paper, the spatial resolution of PET scanners is assessed by means of a Geant4-based Monte Carlo tool. To obtain a high level of accuracy, all relevant contributions like β⁺ range and gamma noncollinearity, crystal size and material, intercrystal scatter, and scanner geometry are implemented in detail. For a system based on Anger logic, the scintillator light yield, the photon statistics and the PMT characteristics are also taken into account. In the simulation, Monte Carlo and analytical algorithms share a common setup, which allows for the necessary computation speed to generate clinical count statistics without compromising accuracy. In the first part, the major contributions to the spatial resolution are analyzed separately. The impact on the total system resolution is then illustrated by investigating three scanner designs with different gantry sizes, crystal sizes, crystal materials and β⁺ tracers.