文摘
Despeckling is of great interest for the ultrasound medical images in which various types of noise and artifacts are introduced because of inherent limitations of the acquisition techniques and systems. Among these noise and artifacts, speckle is a main factor, which degrades the quality and most importantly texture information present in the ultrasound images. Due to the speckle, experts may not be able to extract correct and useful information from the images. This paper presents a despeckling method based on a new multiscale geometric representation such as discrete ripplet transform (DRT) and nonlinear bilateral filter (NLBF). The DRT, a new image representation approach with the different features of anisotropy, localization, directionality, and multiscale, is employed to provide effective representation of the noisy coefficients. Bilateral filter is applied to the noisy ripplet coefficient to improve the denoising efficiency and preserve the edge features effectively. The proposed method also helps to improve the visual quality of the ultrasound images. The performance of the proposed method is evaluated on the different ultrasound medical images and results show significant improvement not only in the speckle reduction but also in the edge preservation performance.