Simultaneous Coded Plane-Wave Imaging Using an Advanced Ultrasound Forward Model

Abstract

In the quest for higher acquisition rates of ultrasound images, the simultaneous emission of encoded waves has the potential to overcome the trade-off between acquisition time and image quality. However, the lack of fully orthogonal codes has led to the use of forward models and inverse problem approaches to estimate the imaged medium. Nonetheless, due to some simplifying assumptions on which these models rely, the previously stated trade-off still appears in these acquisition/reconstruction schemes. In this paper, a forward model for ultrasound wave propagation inside a scattering medium is developed for the simultaneous coded emission of plane waves. The tissue reflectivity function of the imaged medium is estimated by solving an ℓ1-regularized version of the corresponding inverse problem. The proposed method is evaluated in silico and in vitro. We demonstrate that this method outperforms the conventional technique that consists of successive emissions of plane waves, reconstruction using delay and sum (DAS), and coherent compounding. In silico, the ability to separate close scatterers is improved by a factor of four in the axial direction and by a factor of 2.5 in the lateral direction. In vitro, the spatial resolution at −6 dB is decreased by a factor of seven. These results suggest that the proposed method could be a valuable tool, particularly for ultrasound imaging of sparse mediums such as in ultrasound localization microscopy.