A time efficient optical model for GATE simulation of a LYSO scintillation matrix used in PET applications

The dual planar head DoPET (Dosimetry with a Positron Emission Tomograph) tomograph was simulated using GATE (Geant4 Application for Emission Tomography) to evaluate the DoPET performance and its agreement with simulation results including all the relevant physical aspects. An optical model was proposed to predict with accuracy the asymmetrical deterioration of the energy resolution of the detector and at the same time to avoid a too long computation time when activating the optical processes in GATE. The proposed optical model was shown to be around three orders of magnitude faster than a DoPET simulation with GATE optical processes enabled. A good agreement was found between experimental and simulated data using the optical model. This points out that optical interactions inside the crystal elements induce a predictable degradation of the spectra information as acquired by DoPET. Finally, our proposed optical model could be useful to simulate a scintillation matrix and its read out by a position sensitive photomultiplier commonly employed in PET detectors.