Comparative Study of Scintillators for PET/CT Detectors

A growing interest in the development of dual modality PET/CT scanners prompts the comparative study of numerous scintillators to select the best one, which could be used simultaneously in PET detectors working in the pulsing mode and in the CT detectors working in the current mode. In the comparative measurements, done in the same experimental conditions, various samples of BGO, GSO, GSO:Ce, Zr, LGSO, LSO, LYSO, MLS, ${\rm LaCl}_{3}$, ${\rm LaBr}_{3}$ and CWO scintillators were tested. The measurements covered a determination of the light output, energy resolution, non-proportionality of the light yield, decay times of the light pulses and for the selected crystals their time resolution for 511 keV annihilation quanta. Moreover, a comparative study of afterglow, induced by 60 keV $\gamma$ -rays from a strong $^{241}{\rm Am}$ source (13.9 GBq), was done in the second range of time. The LSO-like crystals are the best in the PET scanners application. However, they do not fit to the CT requirements, due to a high afterglow. The studies conclude that besides of the well known BGO, only GSO:Ce and most likely ${\rm LaBr}_{3}$ might be considered for the simultaneous PET/CT detector.