Feature extraction for detection and classification of the clustered microcalcifications in digitized mammograms

Abstract

Breast cancer is one of the major causes of mortality increase to middle aged women, especially in developed countries. Mammography associated with clinical breast examination is the most effective method for early detection of breast cancer. Clustered microcalcifications on mammograms are an important sign in the detection of breast cancer. Mammogram interpretation has been performed by radiologists by visual examination of the films for the presence of abnormalities that can be interpreted as cancerous changes. The computer-aided diagnosis (CAD) will be useful to increase the diagnosis sensitivity of radiologists. The CAD can be categorized into three groups, such as the image enhancement, the detection of suspicious lesions, and the classification of suspicious lesions as benign or malignant. This thesis proposes three effective CAD methods; one is for the adaptive enhancement of mammographic images, another is for the detection of clustered microcalcifications, and the other is for the classification of clustered microcalcifications. The proposed adaptive enhancement is based on the first derivative and the local statistics. The adaptive enhancement method consists of three processing steps. The first step is to remove the film artifacts which may be misread as microcalcifications. The second step is to compute the gradient images by using the first derivative operators. The third step is to enhance the important features of the mammographic image by adding the adaptively weighted gradient images. Local statistics of the image are utilized for adaptive realization of the enhancement, so that image details can be enhanced and image noise can be suppressed. The objective performances of the proposed method were compared with those by the conventional image enhancement methods for a simulated image and the seven mammographic images containing real microcalcifications. The performance of the proposed method is also evaluated by means of the receiver operating-...