A Multi Directional Perfect Reconstruction Filter Bank Designed with 2-D Eigenfilter Approach: Application to Ultrasound Speckle Reduction

Abstract

B-Mode ultrasound images are degraded by inherent noise called Speckle, which creates a considerable impact on image quality. This noise reduces the accuracy of image analysis and interpretation. Therefore, reduction of speckle noise is an essential task which improves the accuracy of the clinical diagnostics. In this paper, a Multi-directional perfect-reconstruction (PR) filter bank is proposed based on 2-D eigenfilter approach. The proposed method used for the design of two-dimensional (2-D) two-channel linear-phase FIR perfect-reconstruction filter bank. In this method, the fan shaped, diamond shaped and checkerboard shaped filters are designed. The quadratic measure of the error function between the passband and stopband of the filter has been used an objective function. First, the low-pass analysis filter is designed and then the PR condition has been expressed as a set of linear constraints on the corresponding synthesis low-pass filter. Subsequently, the corresponding synthesis filter is designed using the eigenfilter design method with linear constraints. The newly designed 2-D filters are used in translation invariant pyramidal directional filter bank (TIPDFB) for reduction of speckle noise in ultrasound images. The proposed 2-D filters give better symmetry, regularity and frequency selectivity of the filters in comparison to existing design methods. The proposed method is validated on synthetic and real ultrasound data which ensures improvement in the quality of ultrasound images and efficiently suppresses the speckle noise compared to existing methods.

Fully Automatic Measurement of Intima-Media Thickness in Ultrasound Images of the Common Carotid Artery Based on Improved Otsu’s Method and Adaptive Wind Driven Optimization

“…14,27 Speckle reduction is an important step in the preprocessing of the ultrasound carotid images. In this study, the Nagare's filter 30,31 is used for speckle noise reduction. This filter is a multi-directional perfect reconstruction filter bank designed with 2-D eigenfilter method, it can suppress the speckle noise via the effective utilization of the good frequency selectivity of the filters.…”

“…Accordingly, this study proposes an improved Otsu-AWDO method for improving the robustness to speckle noise. First, a Nagare's filter 30,31 is used for reducing the speckle noise in the carotid ultrasound images. Next, an IFC method 32 is used for enhancing the blurred edges in the filtered images.…”

Design of two-dimensional PR quincunx filter banks with Euler–Frobenius polynomial and lifting scheme

“…The directional information is an important feature of 2-D signals. To overcome these issues, many researchers have proposed 2-D nonseparable FBs design techniques, such as, directional FBs [1], contourlets [2], TIDFB [4] and 2-D quincunx FBs [5,6]. These FBs extract the directional information of the natural images more efficiently.…”