A compton camera prototype simulation study: Camera performance and first tests of range monitoring capabilities

A Compton Camera (CC) prototype is currently being commissioned at the Ludwig-Maximilians-Universität München. It is planned to be used for studying in-vivo proton or ion beam range monitoring capabilities by means of prompt gamma (PG) rays, exploiting Compton scattering kinematics in order to reconstruct a PG based image correlated to the beam range. The camera consists of a monolithic LaBr
₃
(Ce) scintillation absorber crystal, read out by a 256-fold segmented multi-anode PMT and preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The aim of this study is a comprehensive simulation and reconstruction work in order to assess the design and performance of the constructed prototype under preclinical conditions. The Geant4 [1] toolkit and the MEGAlib [2] software were used to simulate different PG sources coupled with a realistic response of the CC detectors. The image reconstruction is based on the LM-ML-EM (List-Mode Maximum-Likelihood Expectation-Maximization) algorithm. We present the benchmarking of our prototype simulation against experimental data from laboratory mono-energetic photon sources and we demonstrate the range-monitoring capabilities of the prototype in simulated scenarios, based on water phantom targets. Shifts in the proton range as small as 3 mm were detectable using the reconstructed 1D PG profile. Furthermore, we performed a preliminary attempt in small animal irradiation simulations in preparation of future applications to preclinical investigations.