Simulation and experimental characterization of in-beam PETITION PET scanner for proton therapy

An in-beam PET scanner has been developed within the PETITION (PET for InTensive care units and Innovative protON therapy) collaboration to exploit the full potential of proton therapy by enabling either real-time range verification of proton beams or daily biological adaptation of treatment plans based on PET imaging acquired in treatment position before delivery. To optimize the design, the performance of various scanner geometries was first investigated using Monte Carlo simulations in GATE (v8.2), assessing sensitivity and spatial resolution with a 1 MBq ²²Na point source and evaluating image reconstruction using a uniform 1 MBq activity-filled water cylinder and a proton-irradiated head phantom. Based on these studies, a novel C-shaped scanner was developed and simulations were compared with the experimental performance. The prototype achieved a peak simulated sensitivity of 2.9%, with measured sensitivity of 2.1%. Spatial resolution was 2.0 mm FWHM tangentially and axially, and 3.5–4.0 mm radially, showing good agreement between simulations and measurements. Multi-angle acquisition and reconstruction improved image quality, reducing artefacts and enhancing similarity to reference scans in the water cylinder study. Activity distributions from the proton-irradiated head phantom showed alignment with expected activation profiles, demonstrating reliable reconstruction of clinically relevant signals. These findings confirm the feasibility of an open-ring PET scanner for proton therapy with performance comparable to clinical PET systems while uniquely enabling in-treatment position imaging and online beam range verification. Therefore, it supports novel approaches for adaptive and biologically guided proton therapy.