STATISTICAL-BASED SUB-BAND FILTERING TECHNIQUE FOR DIGITAL MAMMOGRAM ENHANCEMENT

摘要

Early detection and diagnosis of breast cancer markedly increases survival rate. Digital mammography is believed to help breast image experts to detect breast cancer early. Accurate diagnosis also depends on the quality of the image presented to the experts. This study addresses the quality improvement of the image. A statistically based sub-band filtering method is applied to enhance the mass and calcification shown in the digital mammograms by inhibiting noise. The method is based on sub-band transformation due to its decomposition characteristic and includes two steps: noise inhibition and boundary enhancement. Contrast ratios and frequency responses are measured to evaluate the enhancement performance and the distortion affect, respectively, to validate the effectiveness of the proposed technique. By comparing the enhancement performance of proposed and conventional methods, a phantom mammogram image that consists of similar mammographic microcalcifications, breast gland and well-circumscribed mass is designed for simulation experiment. Moreover, the real mammograms with microcalcifications are also applied on representing the efficient enhancement ability by the proposed method in this paper. Results in this study demonstrate that the proposed method improves the quality of the image more than other enhancement methods, according to these two criteria. The comparison results show that not only the image quality is improved but also within less image distortion,