Speaker
Description
Prompt-gamma imaging has the potential to reduce range uncertainties in medical proton therapy by detecting prompt-gamma rays emitted during treatment. Within the REALPATH project, we are developing a novel prompt-gamma imaging camera based on an array of 512 LYSO scintillator pixels (6 mm × 6 mm × 30 mm each) coupled to SiPMs and read out by a custom electronics platform incorporating the SITH (Spectroscopy Imaging Timing Hadrontherapy) ASIC. To accommodate the high fluence delivered by modern medical proton accelerators, the detector is designed to cope with rates of up to 1 Mcps per pixel across all 512 pixels. At the same time, good spectroscopic performance at high energies, in the range of 3 MeV to 6 MeV, is important for effective neutron background rejection and prompt-gamma emission analysis. In this contribution, we present the experimental characterization of the first 64-pixel detector module together with the first proton range measurements in a PMMA phantom at CNAO (Centro Nazionale di Adroterapia Oncologica) in Pavia, Italy. Detector characterization was carried out using $^{137}$Cs and $^{241}$Am-Be radioactive sources, enabling performance studies at count rates exceeding 1 Mcps per pixel and at gamma-ray energies up to 4.4 MeV from the $^{241}$Am-Be source. Using these measurements, we investigated the effect of light sharing between neighboring pixels within each 4x4 SiPM array and developed a correction method that significantly improves the detector's spectroscopic performance. The measurements demonstrate a low dead time of 412 ns per event and an excellent energy resolution of 4.8% FWHM at the 4.44 MeV full-energy peak. These characteristics make the detector a promising candidate not only for prompt-gamma imaging but also for other applications requiring position-sensitive, high-rate gamma-ray spectroscopy.