Performance Analysis of In-Beam PET Range Verification System for Carbon Ion Beams

The superconducting ion gantry (SIG) project aims to develop a reliable in vivo range verification system (RVS) for integration into a multi-ion gantry. The project includes researching, designing, and testing the system’s fundamental components. Based on RVS element performance, the ultimate goal is to design a full system that meets clinical requirements. Therefore, in this study, we present the performance evaluation of a small in-beam positron emission tomography (PET) prototype for carbon ion irradiations. The experimental setup consists of six-PET modules arranged in hexagonal geometry (3 versus 3 partial ring configuration), with a radius of 98 mm. Each detector block features 16×16 pixels, 3.2 mm pitch of segmented lutetium fine silicate (LFS) scintillator crystals, coupled one-to-one to silicon photomultiplier (SiPM) matrices. Homogeneous phantoms were irradiated with two monoenergetic beams at different energies at CNAO (Italian National Center of Oncological Hadron Therapy). Data were acquired online during the irradiation. For this study, images are reconstructed from the irradiation in the pauses between beam spills (interspill). The performance analysis was focused on evaluating the stability of range difference estimation considering different subsets of coincidence events along the beam irradiation.