Reliability evaluation of average sound speed estimation using backscattered waves of ultrasound

Abstract

Speed of sound (SOS) of ultrasound is useful for diagnosis. The average SOS estimation based on the phase aberration correction is practical and provides a reasonable estimation for a perfectly homogeneous medium. However, the estimation error in an inhomogeneous medium has not been clarified yet. Therefore, the impact of the inhomogeneity of SOS distribution on the average SOS estimation was investigated in this study.

In a simulation, assuming the liver parenchyma, the SOS distribution was provided using Gaussian random numbers with a mean of 1530 m/s and a standard deviation (σ; inhomogeneity) of 0 to 20 m/s. As the result that focusing and coherence methods were applied to the calculated backscattered waves, the variance of estimated SOS increased as σ increased. The tendency was also reproduced in a phantom experiment. Consequently, the σ that guarantees the reliability of average SOS estimation was suggested to be around 5 m/s.