LaBr3(Ce) and NaI(Tl) performance comparison for single photon emission imaging

LaBr₃(Ce) crystal showed excellent spectrometric properties mainly due to a very high light output and to an energy resolution slightly affected by the intrinsic factor. Furthermore, the properties of the radiation absorption are very similar to NaI(Tl) ones, hence it offers the potential to replace it in scintillation imaging detectors. Unfortunately, the cost of this crystal is high and it is also affected by a very high hygroscopicity and lower mechanical stability which may compromise its durability. In order to evaluate the real benefits of LaBr₃(Ce), we propose an imaging comparison with a second sample of NaI(Tl) by coupling them to a Hamamatsu H8500C multi-anode PMT. The crystal was produced identical in shape by Saint Gobain. In addition a second high QE MA-PMT was also tested (H8500C-Mod8 series PMT). A Geant4 Monte Carlo simulation was also implemented, where the light transport inside the crystals was taken into account. Very close results were obtained for both crystals when coupled to the new high QE MA-PMT and (0.95±0.05) mm spatial resolution -SR resulted, in spite of simulation where SR of LaBr₃(Ce) was expected to be 22% better than the NaI(Tl) one. This results seems to be related to an unexpected scintillation light background measured only in the LaBr₃(Ce), which limits the advantages would occur due to its highest light yield. Saint-Gobain, the most important manufacturer of LaBr₃(Ce) crystals, has established its own choices in the surface treatment so apparently limiting the intrinsic response of this crystal. In conclusion, these results revisit the use of continuous crystals for small-FoV gamma-camera applications with high spatial and energy resolution tanks to the improvement obtained with the new MA-PMT with high quantum efficiency.