Matching breast lesions in multiple mammographic views

By combining information from multiple mammographic views (temporal, mediolateral oblique (MLO) and cranio-caudal (CC), or bilateral) it should be possible to improve the accuracy of computer-aided diagnosis (CAD) methods. In literature various approaches have been described to establish correspondence between multiple views. Highnam et al. [1] used a model-based method to find a curve in the MLO view which corresponds to the potential positions of a point in the CC view. Kok-Wiles et al. [2] used a representation of the nested structure of ?salient? bright regions to match mammogram pairs. Karssemeijer et al. [3] and Lau et al. [4] both used a set of landmarks and applied a nonlinear interpolation to align the skin line of two breast images. Almost all matching approaches are based on acquiring a set of landmarks. In a mammogram the nipple is the most obvious landmark. Radiologists use the distance to the nipple to correlate a lesion in MLO and CC view. It is generally believed that this distance remains fairly constant. The goal of this paper is twofold: first, to investigate to what extent this distance remains constant in multiple views, and second, to investigate if the accuracy of automated detection of the nipple is sufficient to use the distance to the nipple as a reliable measure for matching. For this purpose we used an annotated database which contained 327 corresponding mammogram pairs from the Dutch breast cancer screening program.