Effects of temperature and bias voltage on the properties of a PET detector module based on the individual readout of 1 × 1 mm2 LYSO crystals by monolithic arrays of SiPMs

Abstract

The aim of this work was the development and evaluation of a detector based on SiPMs and fast scintillation crystals feasible for combined PET and MR imaging. Properties of two different 4 × 4 arrays of SiPMs by Hamamatsu — breakdown voltage, pulse height, energy resolution, dark counts and optical crosstalk — were investigated in terms of temperature and voltage dependence. Each channel in such an array consists of either 400 or 1600 cells and has a surface area of 1 × 1 mm2. For the alignment and coupling of individual scintillation crystals (1 × 1 × 20 mm3) to these channels a special holder was designed. The breakdown voltages were at about 70 V for both models. Energy resolutions better than 23 % were observed. A temperature coefficient of the signal amplitude of (-2.7 ± 0.2) %/K and a voltage coefficient of (63 ± 2) %/V were determined for the model with 400 cells, whereas optical crosstalk was found to be an issue that needs further improvement. The dark count rate was below 1 MHz.