Fourier Domain Beamforming and Structure-Based Reconstruction for Plane-Wave Imaging.

Ultrafast imaging based on coherent plane-wave compounding is one of the most important recent developments in medical ultrasound. It significantly improves image quality and allows for much faster image acquisition. This technique, however, requires large computational loads motivating methods for sampling and processing rate reduction. In this work we extend the recently proposed frequency domain beamforming (FDBF) framework to plane-wave imaging. Beamforming in frequency yields the same image quality while using fewer samples. It achieves at least 4 fold sampling and processing rate reduction by avoiding oversampling required by standard processing. To further reduce the rate we exploit the structure of the beamformed signal and use compressed sensing methods to recover the beamformed signal from its partial frequency data obtained at a sub-Nyquist rate. Our approach obtains 10 fold rate reduction compared to standard time domain processing. We verify performance in terms of spatial resolution and contrast based on scans of a tissue mimicking phantom obtained by a commercial Aixplorer system. In addition, in vivo carotid and thyroid scans processed using standard beamforming and FDBF are presented for qualitative evaluation and visual comparison. Finally, we demonstrate the use of FDBF for shearwave elastography by generating velocity maps from beamformed data processed at sub-Nyquist rates.