Effects of the Super Bialkali photocathode on the performance characteristics of a position-sensitive depth-of-interaction PET detector module

Super Bialkali (SBA) and Ultra Bialkali (UBA) photocathodes are new technologies that improve the spectral response characteristics of position sensitive PMTs, boosting their quantum efficiency up to 35% and 43% (typ.) respectively [ref Hamamatsu]. Two SBA tubes were introduced into a production line of PET detectors mixed with the regular ones. The detectors were assembled on the same day and by the same operator using the standard factory protocols for detector mounting, calibration and testing. In this work we are reporting our evaluation of the achieved improvement by comparing the spatial and energy resolutions and the depth-of-interaction performance of a PET detector modules with DOI capabilities assembled using the regular and the SBA versions of the same PS-PMT. We conclude that the superior performance of the SBA tube may enable the use of arrays with a larger number of crystals of smaller footprint, thus improving the detector intrinsic spatial resolution without degrading the energy resolution or the phoswich discrimination capability.