Wavelet-based enhancement of lesion detectability in ultrasound B-scan images

A new technique for enhancing lesion detectability in ultrasound B-scan images is presented. A wavelet based denoising algorithm is proposed. After discussing the mathematical model of the B-scan images, the authors derive the optimal wavelet shrinkage scheme for the model. As such a filter needs exact knowledge of the noise-free signal and the noise statistics, a classical wavelet shrinkage is used for the approximation of the noise-free signal. The performance of this algorithm is compared to the Maximum Likelihood estimator of the B-scan image by using as a figure of merit the area under the ROC curve. The results have shown that the present algorithm is superior in lesion detection, and an improvement in the area under ROC curve of the order of 0.1 is observed.