Feasibility study of a LYSO SiPM based prototype for hybrid Compton and PET imaging

Abstract: We present a prototype for hybrid Compton and positron emission tomography (PET) imaging aimed at enhancing data utilization and enabling concurrent imaging of multiple radiopharmaceuticals. The prototype comprises two detectors that utilize LYSO-SiPM and were available in our laboratory. One detector consists of a 50 × 50 array of LYSO crystals, each measuring 0.9 mm × 0.9 mm × 10 mm with 1 mm pitches, whereas the other detector comprises a 25 × 25 array of LYSO crystals, each measuring 1.9 mm × 1.9 mm × 10 mm with 2 mm pitches. These detectors are mounted on a rotational stage, which enables them to function as either a Compton camera or a PET detector pair. The 64-channel signals from the SiPMs of each detector are processed through a capacitive multiplexing circuit to yield four position-weighted outputs. Distinct energy windows were used to discriminate Compton events from PET events. Energy resolution and energy-channel relationships were calibrated via multiple sources. The measured average energy resolutions (full widths at half maximum, FWHMs) for the detectors at 511 keV were 17.5% and 15.2%, respectively. The initial experimental results indicate an angular resolution (FWHM) of 8.6 ◦ for the system in Compton imaging mode. A V-shaped tube injected with 18F solution was clearly reconstructed, which further verified the imaging capabilities of the system in Compton imaging mode. The results of simulation and experimental imaging studies show that the system can detect tumors as small as 1 mm in diameter when working in PET imaging mode. Mouse bone PET imaging was successfully conducted, with the results matching well with the corresponding CT images. This technology holds great potential for advancing the development of physiological function modalities.