A spectroscopic and imaging gamma-detector prototype towards dose monitoring in BNCT

We report the performances of a compact gamma-ray detection prototype, based on a 2” LaBr3 scintillator crystal coupled to a matrix of 64 SiPMs, designed as a single unit for a future SPECT system for dose monitoring in BNCT. The aim of the module is to detect the 478 keV gamma rays emitted by the boron neutron capture reactions, in order to map the 10B distribution in the patient. The spectroscopic capabilities of the module have been validated by irradiating borated vials with thermal neutrons fluxes in the order of 1 × 105 n/cm2/s. The good energy resolution of the detector (2.7% at 662 keV) has allowed to resolve the boron neutron capture photopeak, achieving excellent linear correlation between the number of detected events at 478 keV and the boron concentration in the vials irradiated. Preliminary imaging results based on a Convolutional Neural Network and obtained by irradiating a 5 cm × 5 cm × 2 cm square crystal with a 1 mm collimated 137Cs source (662 keV) are also reported.