Initial characterization of a benchtop microPET system based on LYSO crystal arrays and Hamamatsu H8500 PS-PMTs

A microPET system for small animal studies is currently being developed at Instituto de Física, UNAM. The main goal of this project is to build a cost-effective benchtop system that could be suitable for research purposes. The basic design uses off-the-shelf components and is being assembled using nuclear instrumentation modules and in-house built readout circuits. The detection modules are based on pixelated scintillator LYSO crystal arrays coupled to Hamamatsu H8500 position-sensitive photomultiplier tubes with a resistive chain readout system. Pulse digitization is performed with a commercial fast analogue-to-digital data acquisition board. The uniformity, cross-talk and aperture function of the photomultipliers have been measured. The modules are able to identify individual crystals (out of 400) with a 4-to-1 peak-to-valley ratio. The measured energy resolution of 22Na spectra in individual crystals ranges from 7% to 15%; the dead time of the system is between 17 and 42 μs depending on the source volume, and the resolving time is 1.16±0.01 ns. The design and characterization of the system includes Monte Carlo simulations of the detectors.