Design and Validation of a SPECT Prototype for Treatment Monitoring in BNCT and First Experimental Tomographic Results

Boron Neutron Capture Therapy (BNCT) is an advanced cancer treatment that combines radiation therapy with targeted drug delivery. Patients are administered a boron compound that accumulates in tumour cells and are then irradiated with thermal neutrons that induce 10B(n,α )7Li reactions, whose high-LET products locally deposit a high dose to tumour cells. The additional 478 keV gamma ray generated by the de-excitation of 7Li can be detected outside the patientfs body and can be used for dose localization and monitoring using the SPECT technique. In this study, we show the first experimental tomographic results obtained with a prototype BNCT-SPECT system at the LENA neutron facility in Pavia, Italy. Measurements are acquired with the BeNEdiCTE detection module, based on a 5 cm 5 cm 2 cm LaBr3(Ce+Sr) monolithic scintillator crystal coupled to an 8 8 matrix of Near Ultraviolet High-Density silicon photomultipliers (SiPMs). The system shows good performance in detecting the incoming radiation of interest and in reconstructing 2-D planar images of boron samples irradiated with thermal neutrons. Thanks to the aid of STIR (Software for Tomographic Image Reconstruction), we show a successful 3-D reconstruction of 2 vials containing 7371 ppm of 10B placed at 1.4 cm distance, starting from four partial projections and using 10 iterations of the Maximum Likelihood Expectation Maximization (MLEM) algorithm.