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11 May 1994 Comparison of conventional magnification mammography using film screen mammography and electronic magnification
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The detection of breast microcalcifications is an important finding that can indicate the presence of breast cancer. Once detected, the radiologist attempts to classify the microcalcifications into patterns that are associated with benign or malignant processes. If they cannot be so classified they are considered indeterminate calcifications. Those characteristics of the microcalcifications that are used in this important distinction are the shape and number of calcifications and the presence or absence of any change from a prior mammogram. (1-4) Geometric magnification views are often obtained to provide better visualization of the microcalcifications. Although conventional screen film mammography has sufficient high contrast resolution (20 line pairs per mm (lplmm)) to demonstrate these findings and the type of hand held magnifying lens often used by Radiologists has sufficient power to demonstrate more than 30 lp/mm, in practice, the region containing the microcalcifications is often in a low contrast region of the image and the hand held magnifying lens does not suffice. We produce electronic magnification views of the breast by taking an existing screen film mammogram and digitizing it with a small pixel size. (5) The image is then displayed on a monitor or printed on a laser printer that has a larger pixel size, thereby resulting in magnification. The visibility of the calcifications is enhanced by changing the window level and window width to increase optical density or to decrease luminance and to increase contrast. The effect of these two actions is to correct in part for the low contrast in the original image. Three potential benefits results from electronic magnification: 1. The current film on which calcifications are seen can be magnified and evaluated without the patient having to return for a geometric magnification view. 2. The prior mammogram (if of suboptimal quality) can be digitized and re-displayed to better determine whether the microcalcifications have changed. 3. The digitized image may allow the reclassification of calcifications from benign appearance to a pattern suggestive of cancer, thereby resulting in an earlier decision to biopsy.
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Francine Fields, Matthew T. Freedman M.D., Shih-Chung Benedict Lo, Rebecca A. Zuurbier M.D., and Seong Ki Mun "Comparison of conventional magnification mammography using film screen mammography and electronic magnification", Proc. SPIE 2167, Medical Imaging 1994: Image Processing, (11 May 1994);

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