Added value of morphological features to breast lesion diagnosis in ultrasound

Ultrasound imaging plays an important role in breast lesion differentiation. However, diagnostic accuracy depends on ultrasonographer experience. Various computer aided diagnosis systems has been developed to improve breast cancer detection and reduce the number of unnecessary biopsies. In this study, our aim was to improve breast lesion classification based on the BI-RADS (Breast Imaging - Reporting and Data System). This was accomplished by combining the BI-RADS with morphological features which assess lesion boundary. A dataset of 214 lesion images was used for analysis. 30 morphological features were extracted and feature selection scheme was applied to find features which improve the BI-RADS classification performance. Additionally, the best performing morphological feature subset was indicated. We obtained a better classification by combining the BI-RADS with six morphological features. These features were the extent, overlap ratio, NRL entropy, circularity, elliptic-normalized circumference and the normalized residual value. The area under the receiver operating curve calculated with the use of the combined classifier was 0.986. The best performing morphological feature subset contained six features: the DWR, NRL entropy, normalized residual value, overlap ratio, extent and the morphological closing ratio. For this set, the area under the curve was 0.901. The combination of the radiologist's experience related to the BI-RADS and the morphological features leads to a more effective breast lesion classification.