Evaluation of light collection in digital indirect detection x-ray imagers: Monte Carlo simulations with a more realistic phosphor screen model

Abstract

We are performing simulation studies to investigate whether a microlens layer sandwiched between a phosphor screen and a photodetector will improve light collection in indirect-detection x-ray imagers. In this study, we examined the light collection efficiency after incorporating the spatial and angular spread of photons due to the phosphor screen in the model. Monte Carlo simulations of a uniform, planar x-ray source were conducted and the light collection efficiencies of two imager configurations were compared. Imager 1 had the screen in direct contact with the photodetector while Imager 2 had a microlens array sandwiched between the screen and the photodetector. A total of 72% of the scintillation light (31% in the “central” pixel directly below the x-ray interaction point and 41% in the 8 nearest neighbor pixels) was collected by the photodetector for Imager 2 compared with only 56% (28% in the central pixel and 28% by the nearest neighbor pixels) for Imager 1.