Evaluation and optimization of geometry parameters of GAGG scintillator-based Compton Camera for medical imaging by Monte Carlo simulation

In nuclear medicine, the development of portable imaging devices that provide high imaging resolution and sensitivity, capable of imaging gamma rays with a wide energy range and multiple radioisotopes tracing capabilities, is so important. These goals have been possible thanks to developing a compact Compton camera, a collimatorless detector coupled to compact silicon photomultiplier(SiPM) array, using scintillator crystal. In this study, the portable segmented GAGG:Ce scintillator-based Compton camera (CC) is optimized with the GATE, a Monte Carlo simulation toolkit based on Geant4, to maximize its performance for a wide range of gamma-ray energy (364–1000 keV). The geometrical parameters are selected as optimization parameters to investigate their effects on CC's performance, including imaging resolution and absolute detection efficiency (DE_a). The geometry parameters of CC include the planner area of scatterer and absorber detectors, their thicknesses, and the distance between them. The results for the energy range of 364–1000 keV show that the most important contributions to the spatial resolution and DE_a of the camera are SAD (scatterer to absorber distance) and the scatterer area while changing absorber area (A_A) showed the most negligible impact. In the short SADs, imaging resolution and DE_a are significantly affected by the detector's size and thickness. On the other hand, in the long SADs (> 4 cm), both spatial resolution and DE_a are significantly affected by the detector's area but less affected by the detector's thickness. Decreasing the scatterer's thickness and the absorber's size or thickness improves imaging resolution without significantly reducing DE_a. The simulation study's findings presented here will provide valuable guidelines for researchers choosing a desired CC's design according to particular objectives, manufacturing limitations in scintillator growth, cost, etc.