Study of the imaging properties of a SrI2:Eu-based gamma camera

Abstract

International audienceWe will present our study on the detection properties of a SrI2:Eu crystal for possible application in a gamma camera for medical imaging. We tested a disc-shaped SrI2:Eu with dimensions of 38mm in diameter and 5mm thick, coupled to a Hamamatsu 10966 multi anode PMT (MAPMT). At the time, it was the largest size available for a disc-shaped SrI2:Eu crystal. We compared the obtained results to a slightly larger LaBr3:Ce, with the same shape (50 mm diameter x 5 mm thick). Despite its long decay time constant, the SrI2:Eu scintillator has showed remarkable gamma-rays detection properties due to its high light yield (bigger than 80000 photons/keV) and reduced light yield non-proportionality effect, that lead to an energy resolution better than 3% at 662 keV. Anyway the self-absorption effect observed for the SrI2:Eu, represents a serious drawback for the use of large volume optics. As a matter of fact, the self-absorption causes severe energy resolution degradation when the thickness of the crystal increases. For gamma imaging, the use of thin, high light yield scintillator materials is recommended and thus it represent an ideal application for SrI2:Eu.In this communication we will present the complete characterisation of the tested disc-shaped SrI2:Eu prototype scintillator with a standard high quantum efficiency PMT and we will discuss the outcomes of a spot scanning measurement performed on the tested crystal coupled to a MAPMT. The SrI2:Eu mean spatial resolution measured in the central Field of View, obtained with a modified centre of gravity algorithm, will be compared to that of the LaBr3:Ce