Imaging detector designs based on flat panel PMT

Over the last 10 years, because of close proximity positioning, small field of view imagers have demonstrated superior spatial resolution and sensitivity at multiple orientations compared to the conventional nuclear camera. Design favoring high spatial resolution at a reasonable cost is the main goal and to this aim a number of photodetector designs have been proposed. The recent availability of Hamamatsu Flat Panel photomultiplier (PMT) makes it a promising and realistic candidate by significant improving compactness, packing fraction of PSPMT designs and lowering costs. In this paper we analyze the spatial resolution potential of a small gamma imager based on Hamamatsu H8500 PMT coupled to different scintillation material arrays like CsI(Tl) and NaI(Tl), with crystal pixel size ranging between 0.2 and 1.8 mm. The imaging performances and limitations for application in scintimammography, linphoscintigraphy and small animal imaging are critically explored. The results show very good position linearity, spatial resolution and gain. Furthermore the array structure of anodes favours the exploiting of new methods of charge analysis for a precise calculation of gamma ray interaction position. Unfortunately the light sampling is still limited by too big anode size that impairs photodetector performances for ultra high spatial resolution applications.