Changes in imaging technique (e.g., film/screen combination, processing conditions, kVp, and exposure time) can alter the mammographic appearance of breast tissue. The effect of changes in mammographic technique on the measured value of the regional skewness and fractal dimension were evaluated for 30 digitized mammographic cases through simulated changes in the shape of the characteristic (H & D) curve . It was found that both the regional histogram skewness and the fractal measure are quite robust with respect to change in the sensitometric curve of the film used to produce the mammogram. With moderate increases or decreases in the film gradient, there was little variation in the values obtained. This is to be expected, as the dominant effect of small changes in technique would be a shift in the histogram (i.e., a change in mean). Because the shape of the histogram would be largely unaffected, characterization through the higher order moments of the distribution is relatively insensitive to variations in sensitometry.
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