Optimising scintillator-based X-ray detectors for fast imaging systems

Scintillator-based X-ray detectors are essential in modern technology, finding applications in medical imaging and security screening. The demand for ultra-fast scintillators has driven rapid advancements in related materials and technologies, particularly in applications where fast timing is critical, such as TOF-PET and next-generation colliders. This thesis explores state-of-the-art fast inorganic scintillators and their application in X-ray detectors for rapid X-ray Computed Tomography (CT) systems. Experimental characterisations of state-of-the-art fast inorganic scintillators available on the market reveal that gadolinium garnets, specifically Ce:GAGG and Ce:GGAG, exhibit high potential for implementation in fast X-ray detectors, effectively competing with the widely-used Ce:LYSO. Monte-Carlo simulations and dedicated measurements confirm this potential by analysing these characterised scintillators within energy-integrating detectors for X-ray CT. Gadolinium garnets, thanks to their exceptional light yield, show the potential to significantly enhance the quality of reconstructed images. Additionally, using a simulation framework that I developed, the feasibility of implementing SiPM-based scintillator detectors, particularly in photon-counting CT, is explored. Ce:GAGG, Ce:GGAG, and particularly Ce:LYSO, emerge as leading choices for photon-counting detectors, showcasing superior count-rate and energy discrimination capabilities, assessed by introducing in the field an alternative quality parameter. This research paves the way for future projects in the field of scintillator-based energy-integrating and photon-counting X-ray detectors, including prototype production and commercial considerations. In photon-counting applications, scintillators in synergy with SiPM technology represent, in particular, an exciting research direction as an alternative to direct conversion detectors.