Contourlet transform and iterative noise free filtering based bilayer filter for enhancing echocardiogram

Commonly used filters for removing impulse noises tend to remove fine details and edges while denoising. Thus, these filters cannot be used for images such as echocardiogram (ECHO) where we need to preserve the edges. In this paper, a novel bilayer filter, consisting of a contourlet transform based filter in the primary layer and iterative noise free filter in the secondary layer is proposed. Form study is performed on Lena image, corrupted by varying amounts of impulse noises (speckle noise and salt & pepper noise). Both the analytical and perceptual quality results show that the proposed method is superior to existing techniques used for denoising echocardiogram, viz., median filter and contourlet transform filter. And finally, the technique was applied on a 57 frame echocardiogram and the results were analyzed by a doctor and according to his opinion, the proposed method achieves better denoising with negligible loss of fine details, than the methods adopted earlier.