Imaging performance of silicon photomultipliers coupled to BGO and CsI:Na arrays

Abstract

The aim of this study is to investigate the imagingperformance of a silicon photomultiplier array (ArraySL-4) photodetector forpossible PET and potentially SPECT applications using BGO and CsI(Na)pixellated scintillators. Our main objectives are: i) the comparison of theArraySL-4 to the older version SensL's SPMArray4 photo detector in terms ofenergy resolution and peak to valley ratio of a row profile in the floodimage and ii) the study of the effect of different coupling schemes usingultra transmitting glass windows of various thicknesses. We acquired rawimages from two pixellated scintillators (BGO with 2 × 2×5 mm3 and CsI:Na with 1 × 1×5 mm3 pixel sizes) irradiated with 511 keV and1274.5 keV γ-rays from a 22Na source. The SiPM array detectorallowed the clear visualization of the discrete 2 × 2 mm2 pixellated BGOand 1 × 1 mm2 CsI:Na scintillator elements at room temperature (nocooling). The energy resolution of the new SensL ArraySL-4 detector for the2 × 2×5 mm3 BGO pixellated scintillator array is improved for rather 6percentage points (energy resolution improvement equal to 22%) and thepeak to valley ratio is measured higher for both scintillator arrays (forBGO 68% (1.7 × ) and for CsI:Na 154% (2.5 × )) compared with SPMArray4.The clear identification of the 1 × 1 mm2 CsI:Na scintillator elementsprovides evidence that the combination of those SiPMs with even smallerarrays can be used as an efficient imaging detector module. Optical couplingsignificantly improves image uniformity, while the use of BK7 ultratransmitting glass window with 1.35 mm thickness provided the best measureenergy resolution equal to 21.5%.