Ultrasound speckle reduction using nonlinear Gaussian filters in Laplacian pyramid domain

A new method for reducing the speckle in ultrasound images using non linear Gaussian filters is introduced in this paper. The non linear Gaussian filter is applied in the bandpass images generated by Laplacian pyramid decomposition. In each pyramid layer, the filter is designed to work in the form of a filter chain. The length of the filter chain is determined with a Mean of Squared Absolute Differences estimator. User interaction is facilitated for controlling the amount of noise removal. The overall time required for computations is less and the accuracy and quality of the images is preserved. The algorithm has been tested on phantom data as well as in vivo data. The performance measure is evaluated based on Contrast to Noise ratio(CNR) and an edge preservation parameter. On visually comparing the despeckled images, it can be found that the structure and edge information is preserved while suppressing the speckle. Experimental results prove that this method can be used for removing speckle in medical ultrasound images without compromising the accuracy and quality.