An Algorithm for Circle Filter Based Multi Scale Application for Enhancement of Pulmonary Nodules

The detection of lung nodules is a difficult problem in the field of medical aided diagnosis, due to the noise and the disturbance of blood vessels and tracheas. According to this problem, this paper brings forward a Circle filter algorithm based on the anisotropy smoothing equations. Firstly, a circle smoothing equation is deduced by means of the anisotropy smoothing equations and Hessian matrix of the circle in the Gaussian model. Secondly, analyzing the characters of eigenvalues of the Hessian matrix, we present a function for the circle enhancement filtering. Finally, the circle enhancement filter is then used to enhance the nodule image, which is smoothed in different scales. The experiment result shows that this algorithm has effectively suppressed the non-circle disturbance; hence enhanced images are obtained, which will be beneficial for the feature extraction and classification of nodules.