High performance 3D CZT spectro-imager for BNCT-SPECT: Preliminary characterization

The National Institute of Nuclear Physics (INFN) is supporting the 3CaTS project with the aim of developing a new Single Photon Emission Computed Tomography (SPECT) system for real time 10B therapeutic dose monitoring in the binary experimental hadron therapy called Boron Neutron Capture Therapy (BNCT). BNCT is a highly selective tumour treatment based on the neutron capture reaction 10B(n,α)7Li. The secondary particles have a high LET with ranges in tissues of the order of 10 μm (thus less than the mean cell diameter of few tens μm). Targeting the 10B delivery towards cancer, the released energy lethally damages only the malignant cells sparing the normal tissues, thus enabling a cell-level selective treatment. To properly exploit this selectivity it is mandatory to know the 10B spatial distribution inside patients body during neutron irradiation. This can be achieved by detecting the 478 keV γ ray emitted in the 94% of 10B capture reactions by a SPECT system. A 3D CZT drift strip detector with a sensitive volume of 20x20x5 mm3 was developed, able to perform high-resolution X-ray and γ ray spectroscopic imaging (10-1000 keV). The detector signals are analysed by a custom digital multi-channel electronics, based on two pipelined fast and slow analysis, able to perform multi-parameter analysis and fine temporal coincidences (< 20 ns). Energy resolution of 3.3% (4 keV) and 2% (13 keV) FWHM was measured, with uncollimated sources and no corrections, at 122 keV and 662 keV, respectively.