A digital density equalization technique to improve visualization of breast periphery in mammography

In mammographic imaging, the film area corresponding to the breast peripher y is overexposed, resulting in high optical density and degraded contrast i n this region. A digital, model-driven density equalization technique was d esigned and developed to overcome this overexposure problem, taking into ac count the non-linear characteristic curve of the film-digitizer system. The method is based on several image processing and analysis techniques, such as thresholding, which is used to segment the pixels of the mammogram belon ging to the breast region from the background, and wavelet-based fusion, wh ich is used to equalize the pixels of breast periphery selectively while le aving the remaining breast region unaffected. Initial application of the me thod resulted in density-equalized mammographic images, characterized by im proved contrast at the breast periphery.