Identification of the breast edge using areas enclosed by iso-intensity contours

The segmentation of a mammogram into background and breast is a crucial first step in the computer aided diagnosis of mammograms that has the advantage of simplifying further processing of the image (by eliminating the background) and also provides a reference for the alignment of views when two views are being compared. A novel method of segmenting the breast from the background by analysing the area enclosed by iso-intensity contours is presented. Results are evaluated by comparison with manual borders drawn by three radiologists for a set of 25 mammograms. The effect of different pre-processing methods, on the accuracy of automated borders, is investigated. The best methods yielded average root-mean-square differences between the manual and automated iso-intensity borders of 3.0+/-0.3 mm for the image set containing clear breast edges and 4.8+/-0.5 mm for the image set containing indistinct breast edges compared to 5.1+/-0.8 and 7.9+/-0.9 mm for the two data sets with no pre-processing. Results are also compared to those obtained from global thresholding.