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Proceedings Paper

An iterative method for flat-field correction of digital radiography when detector is at any position
Author(s): Hyoung-Koo Lee; Do-Il Kim; Sung-Hyeon Kim; Dae-Sop Park; Bo-Young Choe; Tae-Suk Suh
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Paper Abstract

For non-uniformity correction a flat field x-ray image is needed, and to obtain it the center of detector is usually aligned with the focal spot of the x-ray tube, which is conserved when examining patients to preserve the flat field. In some of radiographic techniques, however, it is necessary to move the x-ray tube off the center position of detector or tilt the detector. We investigated the effect of X-ray tube positions with respect to detector on the non-uniformity correction, and propose a method to reduce the effect using a new algorithm with computer simulation. Gain images were taken in two SIDs. Pixel values at second SID was calculated using the pixel values at first SID, gain coefficient that represents pixels own unique radiation sensitivity characteristics and the formula based on the solid angle of each detector pixel facing to the x-ray source. Gain coefficient was adjusted using the difference between calculated and real pixel values. Calculation was repeated with new gain coefficient until the gain coefficient was converged into prescribed range. Non-uniformity of blank x-ray images taken with the detector tilted by 0 to 45 degrees was corrected and five ROIs across the image were defined and analyzed. When the proposed algorithm was used for the flat field correction standard deviations of pixel values in the ROIs were reduce to 10% of the cases of usual flat field correction.

Paper Details

Date Published: 20 April 2005
PDF: 5 pages
Proc. SPIE 5745, Medical Imaging 2005: Physics of Medical Imaging, (20 April 2005); doi: 10.1117/12.595394
Show Author Affiliations
Hyoung-Koo Lee, The Catholic Univ. of Korea (South Korea)
Do-Il Kim, The Catholic Univ. of Korea (South Korea)
Sung-Hyeon Kim, The Catholic Univ. of Korea (South Korea)
Dae-Sop Park, The Catholic Univ. of Korea (South Korea)
Bo-Young Choe, The Catholic Univ. of Korea (South Korea)
Tae-Suk Suh, The Catholic Univ. of Korea (South Korea)

Published in SPIE Proceedings Vol. 5745:
Medical Imaging 2005: Physics of Medical Imaging
Michael J. Flynn, Editor(s)

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