A comparison of the imaging performance of different PSPMTs for PET applications

Three different types of Position Sensitive PhotoMultiplier tube have been studied and compared in terms of their imaging performance when coupled to scintillator arrays. Such position sensitive tubes often form the basis for the coincident detection of the 511 keV gamma-rays produced as a result of positron annihilation in PET. The three tubes studied here are the R2486, the R8520 and the H8500 all from Hamamatsu and span a number of years of technological development. The R2486 is a circular tube that has a photocathode of diameter 50 mm and a body diameter of 76 mm. The R8520 is a compact 25.7×25.7 mm2 square detector with a 22×22 mm2 active area. The H8500, also called the flat panel tube, is a large area square detector of 52×52 mm2 with an active area of 49×49 mm2. A 40×40 mm2 YAP:Ce matrix composed of 2×2×25 mm3 pixels is used in order to assess the imaging performance of each tube at 511 keV. This imaging performance is characterised here in terms of the image pixel FWHM and the peak-to-valley ratio. After the presentation of these results a discussion is given of the relative merits of each tube and its suitability for future PET applications.