Optical simulation environment with accurate gamma photon penetration model for PET detector blocks

Positron Emission Tomography (PET) is a widely used nuclear medical imaging technique that provides functional information of human organs. In the PET device the detector plays an important role. It stops the gamma photons and generates an electronic signal which is processed by the detector system electronics. The geometrical and optical properties of the detector block have fundamental influence on the basic characteristics of a given PET device. Accurate detector block design is required to achieve appropriate system sensitivity and detector crystal needle identifiability. In our previous work we have created and validated a DETECT2000 based modelling environment, called PetDetSim, able to simulate and analyze different PET detector block geometries. PetDetSim models the gamma photon penetration in a simplified way. This simplification significantly reduced the simulation time but sometimes leaded to inaccurate result. Consequently, a better gamma photon penetration technique should be adopted in order to provide a more precise/realistic detector response as inter-crystal scattering can lead to mispositioning detected events and can complicate calibration of PET detectors. In this work we have extended our environment with a precise gamma photon penetration model using the Geant4 based GATE simulation toolkit. The result of extending the simulation environment with GATE simulation resulted in “noise” in the detector response originating from inter-crystal scattering. The result is a more realistic PET detector response that can be simulated with our environment in order to support the development of novel detector block designs and energy- and position-discrimination algorithms.