Image Processing Algorithms for Digital Mammography: A Pic

Digital mammography systems allow manipulation of fine differences in im- age contrast by means of image processing algorithms. Different display algo- rithms have advantages and disadvantages for the specific tasks required in breast imaging--diagnosis and screening. Manual intensity windowing can produce digital mammograms very similar to standard screen-film mammo- grams but is limited by its operator dependence. Histogram-based intensity windowing improves the conspicuity of the lesion edge, but there is loss of detail outside the dense parts of the image. Mixture-model intensity win- dowing enhances the visibility of lesion borders against the fatty background, but the mixed parenchymal densities abutting the lesion may be lost. Con- trast-limited adaptive histogram equalization can also provide subtle edge in- formation but might degrade performance in the screening setting by en- hancing the visibility of nuisance information. Unsharp masking enhances the sharpness of the borders of mass lesions, but this algorithm may make even an indistinct mass appear more circumscribed. Peripheral equalization displays lesion details well and preserves the peripheral information in the surrounding breast, but there may be flattening of image contrast in the nonperipheral portions of the image. Trex processing allows visualization of both lesion detail and breast edge information but reduces image contrast.