Ultrasound DMAS beamforming for estimation of tissue speed of sound in multi-angle plane-wave imaging

Abstract

Various methods have been proposed to estimate the tissue speed of sound (SOS) of propagating medium using the curvature of received channel waveform or the analysis of resultant image quality. In our previous study, baseband delay-multiply-and-sum (DMAS) beamforming methods have been developed for multi-angle plane-wave (PW) imaging which relies on signal coherence among transmit events (Tx-DMAS) or receive channel (Rx-DMAS) or both (2D-DMAS) to suppress low-coherence clutters. In this study, we further extend our DMAS beamforming to quantify the level of signal coherence for determining the average SOS in multi-angle PW imaging. The signal coherence in multi-angle PW imaging is represented as the phase coherence factor (PCF) which can be easily estimated from the magnitude ratio of the pixel value of DMAS image to that of DAS image. By searching the beamforming velocity that provides the highest signal coherence of echo matrix, the averaged tissue SOS of the image object can be determined. For the PICMUS experimental dataset, the optimal beamforming velocity $(C_{opt})$ estimated by the proposed PCF method does provide the best image quality. For the Prodigy dataset, the estimated tissue SOS is 1426±6 m/s which is very close to the actual tissue SOS of 1427 m/s and the estimated SOS also corresponds to the $C_{opt}$ with the minimal −6-dB LW and the maximal CR within an error of 10 m/s.