Denoise and contrast enhancement of ultrasound speckle image based on wavelet

This paper presents a nonlinear algorithm for speckle reduction and contrast enhancement of ultrasound image. Speckle is multiplicative noise and is mainly responsible to make ultrasonic images degenerate. We adopt Jain´s speckle noise model to carry out our scheme. Shrinkage of wavelet coefficients via soft thresholding within finer levels of scale is carried out on coefficients of logarithmically transformed ultrasonic image. Enhancement of image features is accomplished via nonlinear stretching followed by hard thresholding of wavelet coefficients within midrange spatial frequency levels of analysis. A spatially weighted averaging operation is done to smooth wavelet coefficient at first level in order to avoid effect of pulse energy. We show experimentally that this technique produced superior results when compared to results obtained from existing denoising methods alone. A study suggests that such denoising and enhancement. may improve the overall consistency of expert.