We propose an automatic contour extraction scheme based on an active contour model (Snake). In this technique, after first determining the central point of a mass, an initial contour is arranged, and a control point's direction of movement is limited to directions radiating from the central point. Moreover, it became possible to increase extraction accuracy by choosing the pixel used for processing and using two images, an edge intensity image and a degree of separation image defined based on the concentration histogram, for the calculation of the image forces of a snake. The accuracy of the placement of the central point and the automated extraction method were investigated using 53 digitized mammograms having many difficult contours. The results were quantitatively compared with correct segmentation described by doctor's sketches. The number of cases in which the extracted region corresponded with the correct one at 81 to 100% and 61 to 80% were 25 and 12, respectively. The initial results of the application of this technique show that it may be effective in improving the performance of our CAD system.
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