Evaluation and Validation of a Sensitivity Model for a Three-layer LaBr3 Compton Telescope

A three-layer Compton Telescope, capable of measuring two and three-interaction events, is being developed at IRIS group (Image Reconstruction, Instrumentation and Simulations for medical imaging applications) of IFIC-Valencia. It is based on continuous LaBr ₃ crystals coupled to SiPMs; consequently, a large number of projections can be obtained (high granularity). In order to achieve an accurate reconstruction process, precise estimations of the System Matrix and the Sensitivity Matrix are needed. Given that Monte-Carlo calculations of the aforementioned quantities are computationally expensive due to the high granularity of the imaging device, an analytical model would be advisable. The group has already proposed and assessed a model for two-interaction events. In the present work we propose a similar model for three-interaction events. Whereas three-interaction events allow to obtain the energy of incident gamma-rays without full-absorption requirement, efficiency loss and richer diversity of signal/background events must be handled. In this work we present a preliminary validation of the proposed model, by comparing its performance and predictions with Monte-Carlo simulations. Images of simulated point-like monochromatic sources, as well as a preliminary background study, are also reported.