Investigation of solid-state photomultipliers for positron emission tomography scanners

Solid-state devices to detect photons are under active research and development because they, unlike photomultiplier tubes (PMT), can be used under high-magnetic-field and radio-frequency environments, such as in magnetic resonance imaging (MRI) scanners. In addition, some of the solid-state devices have a higher particle detection efficiency and only a slightly less gain than PMTs, currently the first choice to detect photons in positron emission tomography (PET) scanners. We have tested solid-state photomultipliers (SSPM) among several different solid-state devices in the market. This paper describes the test methods and the characteristics of SSPMs with an emphasis on use in PET scanners. We obtained a 25 % energy resolution and a 4.5-ns time resolution with ²²Na and lutetium yttrium oxyorthosilicate (LYSO), both full-width at half maximum (FWHM). The number of fired mini-cells and the amplification factor were, respectively, estimated to be 154 ± 37 for ²²Na and (3.8 ± 0.9) × 10⁵. Even though SSPM-LYSO couplings resulted in worse performances than PMT-LYSO couplings, the solid-state devices have good potential for use in the PET scanners, especially in combined PET/MRI scanners because the new solid-state devices appear to have better characteristics, such as a higher quantum efficiency and a larger number of mini-cells, than the tested SSPMs.