Characteristics of rotatory second order difference filter for computer aided diagnosis of medical images

This paper studies performance of three kinds of rotatory second order difference filters by evaluating it theoretically. These three filters respectively calculate the minimum, the maximum and the mean values of the outputs of the second order difference filters in several directions and have been used for enhancement of shadows in medical images. In this paper, we calculate distribution functions of outputs of three filters on a model image and evaluate the performance. Moreover, we present applications to real medical images to confirm the obtained results. (author)