A combination of pixel-based beamforming and Wiener filter to improve ultrasound image quality

We previously developed coherent pixel-based beamforming to generate two-way focused ultrasound images, where the transmit focusing is achieved by accumulating data from multiple transmits. Most of the impact of this, however, is on the lateral resolution which directly benefits from the large “effective” aperture. In this study we extend the field pattern analysis and form a new Wiener filter that can be combined with coherent pixel-based processing to enhance the axial resolution. The Wiener filter is applied to the received waveform before performing the spatiotemporal mapping. The proposed combination is evaluated through simulation and on data obtained in a phantom study. The imaging results show that the new combination improves on the axial resolution of the coherent pixel-based approach while still maintaining its good performance in lateral resolution and imaging contrast.

I. Introduction

Advances in high performance computing and hardware flexibility have enabled the implementation of complex ultrasound beamformers as alternatives to conventional dynamic focusing. Prominent among them is the synthetic aperture (SA) beamformer [1], which generates an image focused in both transmit and receive (i.e. two-way focusing). The transmit focusing is achieved by accumulating data among multiple transmits acquired using a diverging wave, where the waveshape is usually assumed as a spherical pulse propagating from a single or multiple active elements.