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In this paper we report an extension to the TACT method for the estimation of sound speed with a single transducer to any depth. This method is based on the hypothesis that the displacement of the tissue caused by transaxial compression follows a theoretical function which we derive analytically. In this method, as in the original TACT, a transducer imparts an accurate transaxial compression to the tissue, and the corresponding change in the arrival time of an echo at a range of interest is measured. This procedure results in a biased speed estimate whose value is range dependent. The theoretical function is fitted to the experimental estimates, from which the unbiased sound speed is then computed.

We describe a new method for the estimation of the speed of sound in soft tissues in the pulse-echo mode. A transducer imparts an accurate transaxial compression to the tissue, and the corresponding change in the arrival time of an echo feature is measured. The ratio between the compressed depth and the difference in arrival time is taken as the estimate of the speed of sound. A second, noncompressing transducer is used to correct for distal tissue movement. We show theoretically and experimentally that accurate speed of sound estimations can be made in overlying and underlying tissue mimicking layers.