Development and Preliminary Results of a Large-Pixel Two-Layer LaBr3 Compton Camera Prototype

Objective. Lanthanum bromide (LaBr3) crystal has a high energy resolution and time resolution and has been used in Compton cameras (CCs) over the past few decades. However, LaBr3 crystal arrays are difficult to process because LaBr3 is easy to crack and break; thus, few LaBr3-based CC prototypes have been built. In this study, we designed and fabricated a large-pixel LaBr3 CC prototype and evaluated its performance with regard to position, energy, and angular resolution. Approach. We used two 10 × 10 LaBr3 crystal arrays with a pixel size of 5 mm × 5 mm, silicon photomultipliers (SiPMs), and corresponding decoding circuits to construct our prototype. Additionally, a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition. Monte Carlo (MC) simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype. Main results. The lateral position resolution was 5 mm, and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber, respectively. The corresponding measured energy resolutions were 7.65% and 8.44%, respectively, at 511 keV. The experimental results of 137Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum (FWHMs). The angular resolution of the fabricated prototype was approximately 6° when a point-like 137Cs source was centrally placed at a distance of 5 cm from the scatterer. Signification. We proposed and investigated a large-pixel LaBr3 CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution. The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.