Simulation-based optimization of the Depth-of-Interaction determination capability of a PET scanner

Cancer encompasses over a hundred diseases characterized by the uncontrolled proliferation of abnormal cells. Proton therapy enables precise tumor targeting while minimizing damage to healthy tissue, yet its effectiveness depends on accurate proton range verification. Among the available methods, Positron Emission Tomography (PET) is preferred for providing real-time, three-dimensional imaging and dosimetric information during treatment. Incorporating depth-of-interaction (DoI) measurement in PET scanners improves spatial resolution and reduces parallax errors, particularly at the periphery of the scanner.

This study aimed to optimize, using simulation-based methods, the DoI determination capability of a dual-ended readout PET detection module. The module was modeled using the ANTS3 simulation toolkit. It consisted of a Lutetium–yttrium oxyorthosilicate (LYSO) scintillator with a 3 × 3 mm² cross-section and 30 mm length, coupled to two Hamamatsu S14161-3050HS-08 Silicon Photomultiplier (SiPM) sensors. The scintillator was encapsulated with an Enhanced Specular Reflector (ESR) film.

The model was validated using available experimental data on the DoI resolution, showing sufficient predictive power. The optimization conducted in this study improved the DoI resolution by about 54% and up to 86% at the center and edges of the scintillator, respectively, compared to the initial configuration. This improvement was achieved by introducing an optical grease coupling between the scintillator and the sensors, implementing scintillator encapsulation with Lambertian scattering, and using a higher-efficiency SiPM sensor. A case study was also conducted to analyze the effect of scintillator size on the module's DoI determination capability. Retro-reflector scintillator encapsulation was identified as a promising option for future investigation.