Fig. 3.

One-dimensional imaging results of the phantom. (a) Time-reversed direct current (TRDC) image acquired without ultrasound modulation. (b) Time-reversed ultrasonically encoded (TRUE) image acquired using single-transducer (T1) modulation. (c) TRUE image acquired using dual-transducer ($\mathrm{T}1+\mathrm{T}2$) modulation. The experimental data were fitted by the theoretic simulations (solid lines). The incident signal beam and the two ultrasonic transducers were stationary, while the phantom was scanned along the $Z$ axis.