Modeling Scintillation Kinetics and Coincidence Time Resolution in Heterostructured Scintillators

In the search for new materials and technologies to push the timing performances of time-of-flight positron emission tomography (TOF-PET) detectors, it is important to have a model capable of predicting the coincidence time resolution (CTR) of the system to be implemented. While for bulk standard scintillators, a model that takes into account the intrinsic properties of the material (and the characteristics of the photodetector) is already well established, it has never been experimentally validated for composite structures. As heterostructured scintillators–i.e., the combination of two or more materials with complementary properties–are emerging as a possible solution to the conflict between fast timing and high detection efficiency for TOF-PET detectors, such validation becomes necessary. In this work, by using a time-correlated single photon counting (TCSPC) setup capable of simultaneously recording the TCSPC signal and the scintillation pulse on an event-by-event basis, we experimentally demonstrate that the scintillation kinetics of heterostructures can be modeled as a linear combination of the scintillation kinetics of the materials that constitute the heterostructure itself. Based on these results, we develop an extension of well-established CTR analytical model which can be applied to heterostructured scintillators.