Title: Interscale adaptive threshold wavelet filter for ultrasound image despeckling

Authors: Nirmaladevi Periyasamy; Asokan Ramasamy

Addresses: Department of ECE, Kongu Engineering College, Perundurai, Erode-638060, India ' Kongunadu College of Engineering and Technology, Thottiyam, Trichy, Tamil Nadu, India

Abstract: In this paper, a new wavelet shrinkage algorithm in the undecimated wavelet domain is proposed using an interscale adaptive threshold and an exponential thresholding function for the removal of speckle noise in ultrasound images. An improved spatial adaptive threshold is discussed, exploiting the inter and intrascale dependency of the wavelet coefficients. A new exponential thresholding function is proposed in this paper to overcome the smoothing effect produced by the hard and soft thresholding functions. The reconstructed image exhibits an improved noise removal with preservation of fine details. Performance of the filter is measured using various performance metrics like peak-signal to noise ratio (PSNR), mean square error (MSE), structural similarity index measure (SSIM), equivalent number of looks (ENL) and edge preservation index (EPI). A comparison of the results reveals that the proposed filter shows significant improvement in terms of quantitative measures and in terms of visual quality of the images.

Keywords: undecimated wavelet transform; inter and intrascale dependency; speckle; adaptive threshold; ultrasound images; edge preservation.

DOI: 10.1504/IJBET.2021.116998

International Journal of Biomedical Engineering and Technology, 2021 Vol.36 No.3, pp.293 - 310

Received: 19 May 2018
Accepted: 25 Sep 2018
Published online: 11 Aug 2021 *

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