GEANT4/GATE Simulation Studies in the Emission Tomography

Abstract

Radiotracer imaging studies for a small field, high resolution ∞-Camera system and a clinical system for Positron Emission Tomography (PET) by means of GATE (GEANT4 Application for Tomographic Emission) simulations are presented in this work. In a validation phase, which preceded the main study, experimentally obtained results for planar images with the existing ∞-Camera system were directly compared to simulated data. A simple phantom structure, consisting of four parallel capillaries filled with 99mTc water solution, was imaged by the γ-Camera system for several phantom-collimator distances and the measured and Monte-Carlo calculated spatial projections were compared. The major objective of this validation study was the optimal description of the most important components, the hexagonal, parallel-hole Pb-collimator and the pixelated CsI scintillation crystal of the γ-imaging system in terms of GATE components. In the main study, a GATE simulation setup for this ∞-Camera detector is used and Monte-Carlo data are accumulated for simple geometrical phantoms with different monophotonic radiotracer energies and relative intensities. In parallel, a commercially available cylindrical shaped PET scanner ring, consisting of 32 sectors with 4 x 6 x 6 LSO scintillation crystals, has been constructed in the GATE environment. Simulation data are obtained for the most usual positron emitters (18F, 11C and 15O) and for several phantom geometries. The spatial resolution of both systems and their overall performance is presented and discussed in this study.