2 March 2006 Substrate effect on indirect digital radiography system performance
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In a typical indirect flat-panel digital radiography detector, a phosphor screen is coupled to an a-Si:H imaging array, whose pixels comprise an a-Si:H photodiode and an a-Si:H TFT switch. This two-dimensional array is fabricated on a thin glass substrate that usually contains a rather high concentration of heavy elements such as barium. In previous system performance analyses, only the effect of K-fluorescence reabsorption in the phosphor screen was included. The effect of K-fluorescence from heavy elements in the glass substrate of the array was not taken into account. This K-fluorescence may be excited directly by primary x-rays that penetrate the overlying phosphor and interact in the glass, or by K-fluorescence x-rays that escape from the phosphor into the glass. In this paper, we extend the parallel-cascaded linear systems model to include the effect of K-fluorescence from heavy elements in the glass substrate. As an example, the MTF, NPS, and DQE of an indirect flat-panel imager consisting of a Gd2O2S:Tb phosphor screen and an a-Si:H photodiode/TFT array fabricated on a glass substrate containing barium, are calculated. Degradations in MTF and DQE as a result of the K-fluorescence from the substrate are presented and discussed.
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A. R. Lubinsky, A. R. Lubinsky, Kwok L. Yip, Kwok L. Yip, David P. Trauernicht, David P. Trauernicht, John Yorkston, John Yorkston, } "Substrate effect on indirect digital radiography system performance", Proc. SPIE 6142, Medical Imaging 2006: Physics of Medical Imaging, 61423J (2 March 2006); doi: 10.1117/12.655564; https://doi.org/10.1117/12.655564

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