Minimum Variance Beamformers for Coherent Plane-Wave Compounding

In this paper we present and analyse a technique for applying minimum variance distortionless response (MVDR) beamforming to a coherent plane-wave compounding (CPWC) acquisition system. In the past, this has been done using a spatial smoothing approach that reduces the effective size of the receive aperture and degrades the image resolution. In this paper, we apply the MVDR algorithms in a novel way to the acquired data from the individual transducer elements, before any summation or other compounding. This enables us to propose a new approach for estimation of the covariance matrix that decorrelates the coherence among the components at all the different acquisition angles. This results in a new approach to receive beamforming for CPWC acquisition. The new beamformer is demonstrated on imaging data acquired with a research scanner. We find the new beamformer offers substantial improvements over the DAS method. It also significantly outperforms the previously published MVDR/CPWC beamformer on phantom studies where the signal from the main target is dominated by noise and interference. These improvements motivate further study in this new approach for enhancing image quality.