Abstract: Light diffusion in radiographic detection systems plays a major role in image quality and, consequently, in the radiation dose received by the patient. This study aims to examine the impact of X-ray penetration depth on the light emission performance of the gold-standard Gd₂O₂S:Tb powder phosphor, commonly used in radiographic cassettes and flat-panel digital medical imagers. Our investigation was carried out using LIGHTAWE, which relies on Monte Carlo techniques to extract light emission performance. The program takes as input the optical features of the beam and the structural properties of the phosphor material, and produces output related to light transmission (both amount and distribution).Results are presented based on the depth of interaction, considering different X-ray energy beams (20–80 keV) and various material thicknesses (100–250 μm). Three different particle sizes were examined: nano (50 nm), submicron (500 nm), and micro (7 μm) scale. It was observed that as energy increases, the percentage of transmission also increases by 18.12% and 96.15% at 100 μm and 250 μm, respectively. Moreover, as material thickness increases, resolution decreases by 53.04% and 22.03% for 20 keV and 80 keV, correspondingly. In conclusion, the highest percentage variations in transmission are found at 250μm, while spatial resolution is favored at 80keV.

Keywords: Radiographic detectors, granular phosphors, light diffusion, Mie Scattering, Monte Carlo, medical imaging

Pages: 43-52

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