Reverberation suppression and enhanced sensitivity by coherence-based beamforming

Abstract

Diffuse acoustic reverberation is often present in poor quality ultrasound images and can mask organs and anatomical structure. In addition, imaging methods such as blood flow and targeted microbubble imaging can be problematic in the presence of reverberation and thermal noise. We present a beamforming method that is based on the spatial coherence of backscattered ultrasound waves. The method differentiates signal from noise based on the spatial coherence of the signal and small spatial differences (or lags), and is therefore called the Short-Lag Spatial Coherence (SLSC) beamformer. Because diffuse reverberation and thermal noise are spatially incoherent, they can easily be distinguished from tissue, blood, and other signals of interest. We present SLSC beamforming and its applications to cardiac and other imaging targets, tissue harmonic imaging, flow imaging, and molecular imaging. We show that the technique improves the visibility of organ structures and the sensitivity of flow and molecular imaging targets by suppression of noise signals. We demonstrate a real-time SLSC beamforming prototype system that achieves upwards of 35 fps in cardiac imaging and 50 fps in molecular imaging. The system demonstrates high-quality, stable images of in vivo organs and targets using the SLSC beamformer.