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

This paper studies the performance of three kinds of rotatory second-order difference filters by theoretical evaluation. The filters calculate, respectively, the minimum, the maximum, and the mean values of their outputs in several directions and have been used for enhancement of shadows in medical images. In this paper, the distribution functions of outputs of three filters are calculated on a model image, and the performance is evaluated. Moreover, applications to real medical images are presented to confirm the obtained results.