Flat Panel PMT for photon emission imaging

Over the last 15 years Hamamatsu has been developed two generations of Position Sensitive Photomultipliers (PSPMTs). The first and the second generation were based on mesh dynode and metal channel dynode respectively. In this paper, we present the first results obtained from the last generation: Hamamatsu H8500 Flat Panel PSPMT. The active area is increased to 2 in. with minimum peripheral dead zone and thickness down to 12.5 mm. Measurements were addressed to nuclear medicine for single photon imaging. To this aim, we have taken into account two different electronic readout: resistive chain and multi-anode readout (64 channels). To evaluate the imaging performance, the Flat Panel PSPMT was coupled to CsI(Tl) and NaI(Tl) scintillation arrays with pixel size of 3 and 2 mm, respectively. Images of CsI(Tl) array, obtained by multi-anode readout, showed an improvement of spatial resolution, from 1.2 to 0.8 mm, and of position linearity response. On the contrary for NaI(Tl) array, no relevant image differences between two system readout were obtained.