High Frame Rate 3-D Ultrasound Imaging Using Separable Beamforming

Recently, there has been great interest in 3-D ultrasound imaging, but power constraints have precluded practical implementation of high-resolution and high-frame-rate 3-D ultrasound in handheld imaging platforms. In this paper, we propose a separable beamforming procedure for both 3-D synthetic aperture and plane wave systems that drastically reduces computational and hence power requirements. Separable beamforming approximates 2-D array beamforming for 3-D images through a series of beamforming operations on 1-D arrays. Our proposed method is based on a separable delay decomposition method that minimizes phase error. We show that the proposed separable synthetic aperture system achieves 19-fold complexity reduction and the proposed plane wave separable system achieves 12-fold complexity reduction compared to the corresponding non-separable beamforming baseline systems. Furthermore, we verify the performance of the fixed-point-precision separable beamforming and iterative delay calculation through Field II simulations. Our results show that both the synthetic aperture system and the plane wave system can produce images with the same quality as images generated by non-separable beamforming. We also briefly describe how the two types of separable beamformer can be implemented on a modified version of Sonic Millip3De, our recently proposed hardware accelerator for the digital front-end of a 3-D ultrasound system.