Effect of the phosphor screen optics on the Swank noise performance in indirect-conversion x-ray imaging detectors

C H Lim, S Kam, J C Han, S Yun, H Youn, M -K Moon, H Jeon, H K Kim
2014 Journal of Instrumentation  
The optics between the scintillators and photodiode arrays of indirect-conversion xray imaging systems requires careful design because it can be a cause of secondary quantum sink, which reduces the detective quantum efficiency at high spatial frequencies. The aim of this study was the investigation of the effect of the optical properties of granular phosphor screens -including optical coupling materials and passivation layers in photodiode arrays -on the imaging performance of
more » ... f indirect-conversion x-ray imaging detectors using the Monte Carlo technique. In the Monte Carlo simulations, various design parameters were considered, such as the refractive index of the optical coupler and the passivation layer, the reflection coefficient at the screen backing, and the thickness of the optical coupler. We developed a model that describes the optical pulse-height distributions based on the depth-dependent collection efficiency obtained from the simulations. We used the model to calculate the optical Swank noise. A loss in the number of collected optical photons was inevitable owing to the introduction of intermediate optics and mismatches in the optical design parameters. However, the collection efficiency marginally affected the optical Swank factor performance. The results and methodology of this study will facilitate better designs and optimization of indirect-conversion x-ray detectors. KEYWORDS: Detector design and construction technologies and materials; Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc); X-ray detectors; X-ray radiography and digital radiography (DR)
doi:10.1088/1748-0221/9/05/c05053 fatcat:zd6vv3o4tfdwdl7torfzge6mry