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Proceedings Paper

X-ray beam equalization for digital fluoroscopy
Author(s): Sabee Y. Molloi; Jerry Tang; Martin R. Marcin; Yifang Zhou; Behzad Anvar
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Paper Abstract

The concept of radiographic equalization has previously been investigated. However, a suitable technique for digital fluoroscopic applications has not been developed. The previously reported scanning equalization techniques cannot be applied to fluoroscopic applications due to their exposure time limitations. On the other hand, area beam equalization techniques are more suited for digital fluoroscopic applications. The purpose of this study is to develop an x- ray beam equalization technique for digital fluoroscopic applications that will produce an equalized radiograph with minimal image artifacts and tube loading. Preliminary unequalized images of a humanoid chest phantom were acquired using a digital fluoroscopic system. Using this preliminary image as a guide, an 8 by 8 array of square pistons were used to generate masks in a mold with CeO2. The CeO2 attenuator thicknesses were calculated using the gray level information from the unequalized image. The generated mask was positioned close to the focal spot (magnification of 8.0) in order to minimize edge artifacts from the mask. The masks were generated manually in order to investigate the piston and matrix size requirements. The development of an automated version of mask generation and positioning is in progress. The results of manual mask generation and positioning show that it is possible to generate equalized radiographs with minimal perceptible artifacts. The equalization of x-ray transmission across the field exiting from the object significantly improved the image quality by preserving local contrast throughout the image. Furthermore, the reduction in dynamic range significantly reduced the effect of x-ray scatter and veiling glare from high transmission to low transmission areas. Also, the x-ray tube loading due to the mask assembly itself was negligible. In conclusion it is possible to produce area beam compensation that will be compatible with digital fluoroscopy with minimal compensation artifacts. The compensation process produces an image with equalized signal to noise ratio in all parts of the image.

Paper Details

Date Published: 11 April 1996
PDF: 12 pages
Proc. SPIE 2708, Medical Imaging 1996: Physics of Medical Imaging, (11 April 1996); doi: 10.1117/12.237780
Show Author Affiliations
Sabee Y. Molloi, Univ. of California/Irvine (United States)
Jerry Tang, Univ. of California/Irvine (United States)
Martin R. Marcin, Univ. of California/Irvine (United States)
Yifang Zhou, Univ. of California/Irvine (United States)
Behzad Anvar, Univ. of California/Irvine (United States)

Published in SPIE Proceedings Vol. 2708:
Medical Imaging 1996: Physics of Medical Imaging
Richard L. Van Metter; Jacob Beutel, Editor(s)

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