Direct Speed of Sound Reconstruction from Full-Synthetic Aperture Data with Dual Regularization

Speed of sound (SoS) reconstruction in pulse-echo ultrasound can reduce aberrations in imaging and provide quantitative biomarkers for diagnostics. State-of-the-art SoS imaging requires beamformed data for time-delay estimation. This translates either into multi-layered models, where absolute delays t(i) at multiple depths are fitted to axial SoS variations, or a perturbation approach, where differential delays between adjacent paths tau(i) are used to map SoS heterogeneities. In this work, we remove the beamforming constraint and propose a dual regularization method to combine absolute and differential delays into a generalized SoS reconstruction. Our approach provides quantitative reconstructions in both layered distributions and focal lesions with bias < 2.3 m/s and rmse < 6 m/s. Moreover, it allows scatterer localization with sub-micron resolution. We show experimental results in SoS reconstruction through heterogeneous aberrating layers.