Evaluation of a double layer 2×2cm thick pixellated NaI(Tl) array for application in positron imagers

Results are presented on the preliminary evaluation of the specially designed double NaI(Tl) pixel arrays for application in economical small field of view positron imagers, primarily intended for cardiac imaging. The high performing LSO or GSO scintillator based positron imagers suffer from high cost, while current NaI(Tl) based positron imagers have comparatively low efficiency, partially due to lower stopping power of NaI(Tl). To remedy this last limitation, in collaboration with Saint Gobain Crystals and Detectors a double 3×3×20mm pixellated crystal array was designed with a total thickness of 40mm, by optically coupling two identical pixel arrays. One-sided and double-sided optical readout was tested to provide depth of interaction and/or to improve the 511 keV photopeak energy resolution. Very encouraging results were obtained and a follow-up study will focus on an implementation of the concept in a practical cardiac imager.