A Spectroscopic and Imaging Scintillator-Based Detector for Dose Monitoring in BNCT

We report on the experimental characterization of a detection module based on a 2" cylindrical LaBr
3
(Ce+Sr) scintillator crystal, coupled to a matrix of 64 Silicon Photo-multipliers (SiPMs), developed as a basic element for a SPECT system for dose monitoring in Boron Neutron Capture Therapy (BNCT). The module is developed to detect the 478 keV gamma rays emitted by the excited
⁷
Li produced in the
¹⁰
B(n, α)
⁷
Li reaction, in order to have real-time monitoring of the dose released locally. Thanks to the good energy resolution of the detector (2.7% at 662 keV), the photopeak at 478 keV is well separated from the adjacent e
⁺
-annihilation photopeak at 511 keV, mainly originated from the pair production process due to the 2.2 MeV gamma rays created by the hydrogen-neutron capture. In this work, we present the results obtained by irradiating
¹⁰
B-loaded samples, with concentration as low as 62 ppm, with a neutron flux of approximately 1×10
⁵
n/cm
²
/s. Good linearity between the number of events detected at 478 keV and the boron concentration of the samples has been obtained. The first imaging results have been obtained with a 5cm×5cm×2cm square crystal and a Convolutional Neural Network for data elaboration.