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Proceedings Paper

An Investigation of Digital Mammographic Imaging
Author(s): Robert M. Nishikawa; Martin J. Yaffe
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Paper Abstract

Measurements and theoretical calculations of the limitations of film-screen mammography have been made. The results show that the use of mammographic film-screen systems to image the breast has three major drawbacks: 1) insufficient contrast enhancement for the visualization of subtle tumours and microcalcificatons; 2) limited latitude, i.e. in some patients, structures in thin and thick or dense regions of the breast are not clearly visible on the same film; and 3) dose inefficiency, since most mammograms are not quantum-limited. Digital techniques may overcome these problems by decoupling the image recording and display processes, allowing for contrast enhancement without loss of dynamic range. Using digitized film mammograms and phantom images, we have made a preliminary study of whether image processing can improve visualization of breast lesions. Contrast enhancement by histogram equalization and linear scaling with clipping, and edge enhancement by unsharp masking allowed the extraction of more information than was originally perceived on the film. In these images, however, film grain noise accounts for at least one-third of the total image noise, and thus limits the degree to which the images can be enhanced. To investigate the feasibility of recording digital mammographic images directly, an x-ray image intensifier (XRII) was evaluated. With the use of geometric magnification and small focal spot x-ray tubes, the XRII can produce images with sufficient resolution for mammography. Noise power spectra of both XRII and film-screen images were measured. The XRII was found to have better sensitivity and, if structural mottle can be removed, a higher signal-to-noise ratio than mammographic film-screen systems; however, it is limited by the high attenuation of the front input window at mammographic energies.

Paper Details

Date Published: 13 December 1983
PDF: 9 pages
Proc. SPIE 0419, Application of Optical Instrumentation in Medicine XI, (13 December 1983); doi: 10.1117/12.936024
Show Author Affiliations
Robert M. Nishikawa, University of Toronto (Canada)
Martin J. Yaffe, University of Toronto (Canada)

Published in SPIE Proceedings Vol. 0419:
Application of Optical Instrumentation in Medicine XI
Gary D. Fullerton, Editor(s)

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