Speckle Reduction of Echocardiograms via Wavelet Shrinkage of Ultrasonic RF Signals

We propose a new speckle reduction algorithm for clinical echocardiograms. The proposed method employs Wavelet Shrinkage to reduce the noise on an ultrasonic signal. In the wavelet shrinkage, at first, original ultrasonic signal is decomposed into wavelet coefficients by multiresolution decomposition using orthogonal wavelet. A threshold of which objective is suppression of noise component is estimated on the resultant complex wavelet coefficient. Wavelet coefficients corresponding to noise are eliminated by soft-thresholding. The noise reduction by the wavelet shrinkage can remove specific frequency components. In this study, we employed the RI-Spline wavelet that was proposed as a shift-invariant mother wavelet. We conducted experiments using clinical ultrasonic signals to evaluate the noise reduction performance of the proposed method. Ten clinical subjects were used in the experiments. The experimental results show that the algorithm provides superior performance on speckle and noise reduction compared to that of existing speckle reduction method.