Shear wave propagation in an elastic tissue mimicking phantom with different acoustic radiation force beams. The top row uses an unfocused beam, and the bottom row uses a focused beam. (a) Acoustic intensity for unfocused beam with 16 elements. (b)–(d) Snapshots of shear waves produced by an unfocused beam at 1.275, 2.550, and 3.825 ms, respectively. (e) Acoustic intensity for a focused beam with 64 elements focused at 20 mm. (f)–(d) Snapshots of shear waves produced by a focused beam at 1.275, 2.550, and 3.825 ms, respectively.