High resolution and efficiency annihilation photon detection with a multi-element BGO converter and two-dimensional optical readout

An annihilation photon detection technique using an array of small, optically decoupled BGO crystals as converter and a two dimensional optical readout has been investigated. The readout comprised a microchannel plate image intensifier coupled to a Reticon RA-100 photodiode array. Tests on a target of 25 2 mm square, 1 cm long elements, packed in a 5 by 5 array, have shown that scintillation light from 0.66 MeV photons is localized in individual elements. Spatial resolution is thus, on the millimetre scale, limited by element dimensions. Compton scattering in the converter degrades spatial resolution and/or detection efficiency. Simulations show that an efficiency >40% may be expected for unambiguous reconstruction of photon interaction coordinates in an array of 2 mm square, 2 cm long crystals. (orig.)