Digital mammography systems allow manipulation of fine differences in image contrast by means of image processing algorithms. Different display algorithms 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 mammograms 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 windowing enhances the visibility of lesion borders against the fatty background, but the mixed parenchymal densities abutting the lesion may be lost. Contrast-limited adaptive histogram equalization can also provide subtle edge information but might degrade performance in the screening setting by enhancing 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. Abbreviations: CLAHE = contrast-limited adaptive histogram equalization, HIW = histogram-based intensity windowing, MIW = manual intensity windowing, MMIW = mixture-model intensity windowing
Pisano et al. REF tested different image enhancement techniques: Manual Intensity Windowing, Histogram-based Intensity Windowing, Mixture-Model Intensity Windowing, Contrast-Limited Adaptive Histogram Equalization (CLAHE), unsharp masking, peripheral equalization, and Trex processing for digital mammography to check how these algorithms may affect the ability of radiologists to interpret the images.
Image Processing Algorithms for Digital Mammography: A Pictorial Essay
Radiographics : a review publication of the Radiological Society of North America, Inc
Radiographics : a review publication of the Radiological Society of North America, Inc
Medicine