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22 March 2010 Phosphor-filled micro-well arrays for digital x-ray imaging: effects of surface treatments
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We are developing pixel-structured scintillators for the eventual purpose of high-resolution and high-sensitivity x-ray imaging applications. The pixel-structured scintillators were fabricated by filling Gd2O2S:Tb phosphor powder into the silicon micro-well arrays by using a simple sedimentation method. The micro-well arrays having a depth of 180 μm were fabricated by deep reactive ion etching of silicon wafers. To enhance the optical gain and the Swank noise factor, we applied reflectance at the inside wall surfaces. Two different inside-surface treatments were applied; 0.2-μm-thick titanium which has 70% reflectance and 1-μm-thick silicon dioxide which was grown by thermal oxidation. The imaging performance was evaluated in terms of modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). Compared with the commercial phosphor screen as a reference, much enhanced MTF results were measured. However, very low values of the system gain due to trapping of the generated optical photons at the wall surfaces give rise to the poorer DQE performance rather than that of the reference detector. The theoretical cascaded model analysis estimates much improved DQE performances with improved design parameters, such as higher reflectance of 90% at the wall surfaces.
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Seungman Yun, Chang Hwy Lim, Tae Woo Kim, Ian Cunningham, Thorsten Achterkirchen, and Ho Kyung Kim "Phosphor-filled micro-well arrays for digital x-ray imaging: effects of surface treatments", Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76223S (22 March 2010);

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