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Proceedings Paper

Digitally Controlled Beam Attenuator
Author(s): W. W. Peppler; B. Kudva; J. T. Dobbins; C. S. Lee; M. S. Van Lysel; B. H. Hasegawa; C. A. Mistretta
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Paper Abstract

In digital fluorographic techniques the video camera must accommodate a wide dynamic range due to the large variation in the subject thickness within the field of view. Typically exposure factors and the optical aperture are selected such that the maximum video signal is obtained in the most transmissive region of the subject. Consequently, it has been shown that the signal-to-noise ratio is severely reduced in the dark regions. We have developed a prototype digital beam attenuator (DBA) which will alleviate this and some related problems in digital fluorography. The prototype DBA consists of a 6x6 array of pistons which are individually controlled. A membrane containing an attenuating solu-tion of (CeC13) in water and the piston matrix are placed between the x-ray tube and the subject. Under digital control the pistons are moved into the attenuating material in order to adjust the beam intensity over each of the 36 cells. The DBA control unit which digitizes the image during patient positioning will direct the pistons under hydraulic control to produce a uniform x-ray field exiting the subject. The pistons were designed to produce very little structural background in the image. In subtraction studies any structure would be cancelled. For non-subtraction studies such as cine-cardiology we are considering higher cell densities (eg. 64x64). Due to the narrow range of transmission provided by the DBA, in such studies ultra-high contrast films could be used to produce a high resolution quasi-subtraction display. Additional benefits of the DBA are: 1) reduced dose to the bright image areas when the dark areas are properly exposed. 2) improved scatter and glare to primary ratios, leading to improved contrast in the dark areas.

Paper Details

Date Published: 29 December 1982
PDF: 6 pages
Proc. SPIE 0347, Application of Optical Instrumentation in Medicine X, (29 December 1982); doi: 10.1117/12.933815
Show Author Affiliations
W. W. Peppler, University of Wisconsin Center for Health Sciences (United States)
B. Kudva, University of Wisconsin Center for Health Sciences (United States)
J. T. Dobbins, University of Wisconsin Center for Health Sciences (United States)
C. S. Lee, University of Wisconsin Center for Health Sciences (United States)
M. S. Van Lysel, University of Wisconsin Center for Health Sciences (United States)
B. H. Hasegawa, University of Wisconsin Center for Health Sciences (United States)
C. A. Mistretta, University of Wisconsin Center for Health Sciences (United States)


Published in SPIE Proceedings Vol. 0347:
Application of Optical Instrumentation in Medicine X
Gary D. Fullerton; James A. Mulvaney; Arthur G. Haus; William S. Properzio, Editor(s)

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