Matching Regions for Mammographic Views: Comparison and Compensation for Deformations

Matching features on MLO and CC mammograms has shown to improve performance of computer aided detection systems. False positive rates can be lowered by reducing the search space during matching. Various methods have been proposed to de ne the search space. These do either not explicitly compensate for the breast deformation or simulate the whole process. In this study, we investigated the benefit of extending the common approaches by some basic compensations for breast deformations and compare several methods. Performance was tested on 50 pairs of mammograms with corresponding masses annotated by a radiologist. No clear advantage of straight strips or annular bands was observed for the common methods. Extensions to remove the pectoral muscle by shearing, compensating for gravity on MLO views by shearing and a volume-preserving transformation to get similar breast shapes in both views worked well when breast shapes were elliptical (mean (maximum) error of 5.3 (18.6) mm for 25 pairs). Using this strategy for elliptical breast shapes and straight strips after pectoral shearing for the rest resulted in lowest mean errors (6.7 mm) for the whole dataset.