An overview of despeckle-filtering techniques

Abstract

This chapter provides an introduction and a brief overview of selected despeckle-filtering techniques for ultrasound imaging and video expanded from [1]. A despeckle-filtering evaluation protocol is proposed, a brief literature review, as well as an image despeckle-filtering (IDF) toolbox [3] and a video despeckle filtering (VDF) [4] software toolbox are presented. Moreover, selected applications for ultrasound image and VDF techniques are illustrated. Speckle is a multiplicative noise [1-4], which degrades ultrasound images and videos and negatively influences the image and video interpretation, diagnosis and visual appearance [5]. Noise speckle reduction is therefore essential for improving the visual observation quality or as a preprocessing step for further automated analysis, such as image/ video segmentation, texture analysis and encoding in ultrasound image and video. On the other hand, speckle can also be used as an information carrier on the underlying tissue properties. As illustrated in the previous chapters in Part I (see also Part IV), this implies it can be used, for example, for tissue classification. Alternatively, assuming that speckle moves in the image in the same way as the underlying tissue, it allows for tissue motion estimation using one of the many speckle tracking approaches presented in literature. A large number of despeckle-filtering techniques have been proposed in the past years for ultrasound images and very few for videos, which is usually applied for improving their visualization and interpretation or as a preprocessing step for further image/video analysis. This analysis includes segmentation, feature extraction, image and video compression, data transfer and registration. The present review study discusses, compares and evaluates ultrasound image and VDF techniques for the common carotid artery (CCA) introduced so far in the literature. Applications of the techniques are presented on simulated and real ultrasound images and videos (see also Chapters 7-10) of the CCA.