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25 April 2000 Influence of scattered x rays on object sharpness of radiographs
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We investigated the influence of the scattered x-rays on the object sharpness of radiographs for tube voltages of 50 to 100 kV. For the purpose, using a phantom of the polymethyl methacrylate (PMMA) with an aluminum plate of low contrast object, the edge images including the blurs due to the x-ray focal spot, the screen-film system, and the scattered x-rays were produced. However, the shape of the overall modulation transfer function (MTF) derived from the edge image is considered not to be influenced by the scattered x-rays. As a result of comparing the overall MTFs with the product of the MTFs of the x-ray focal spot and the screen-film system, we found that the scattered x-rays gave different influence on the contrast at each spatial frequency for each tube voltage. To investigate the influence of the scattered x-ray on the overall MTF in detail, considering the MTF of the x-ray focal spot, we developed a method for determining the primary and scatter components of the overall MTF, whose components are proportional to the MTFs of the screen-film system and the scattered x-rays, respectively. Using the method, it was found that (1) the overall MTF depends on the MTF of scattered x- rays as well as the MTFs of the focal spot and screen-film system; and (2) at frequencies near 0 mm-1, the influence of the blur due to the scattered x-rays on the object sharpness was greater than that occurred in the intensifying screen and increased with the tube voltage.
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Hidetaka Arimura, Takuji Date, Kaoru Morikawa, Hideaki Kubota, Masao Matsumoto, and Hitoshi Kanamori "Influence of scattered x rays on object sharpness of radiographs", Proc. SPIE 3977, Medical Imaging 2000: Physics of Medical Imaging, (25 April 2000);

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