CsI(Tl) micropixel scintillation array for ultrahigh resolution gamma-ray imaging

The aim of this paper is to investigate on the spatial resolution limit by coupling a CsI(Tl) micropixel scintillation array to PSPMTs for ultrahigh resolution gamma-ray imaging. To perform this study an array with 0.2 mm pixel size, 0.4 mm pitch, and 1 mm thickness were realized by Spectra Physics (Hilger). The present scintillation arrays technology is suitable to produce large crystal areas. In this paper we present spatial resolution and position results obtained by coupling the micropixel scintillation array to Hamamatsu square PSPMTs: 1" R8520-C12, 1" R5900-L16 and 2" H8500 Flat panel PMT. Preliminary measurements demonstrate that micropixel array shows better performance coupled to H8500 model, in term of the uniformity response. This setup carries out an intrinsic spatial resolution lower limit of about 0.6 mm FWHM at 50% FWHM energy resolution, defining it as minimum scintillation array pitch detectable at 122 keV. Furthermore, from the results obtained by R5900-L16, the position response will be improved reducing the anode size (3 mm size) for a better sampling of the scintillation light.