Figure 1.

Expansion ratio of UCAs within soft tissue (G_L=0.5 MPa) predicted by different models with a PNP of 1.5 MPa and a center frequency of 1.0 MHz. Model I simulates a clean gas bubble oscillating in soft tissue (R₁₀=R₂₀). Model II simulates a shelled gas bubble oscillating in an incompressible liquid (G_L=0.0 MPa, ${\dot{R}}_2∕c=0$). Model III simulates a gas bubble oscillating in a compressible liquid (R₁₀=R₂₀, G_L=0.0 MPa). (a) A lipid-shelled agent; (b) a polymer-shelled agent. UCA parameters are in Table 1 and lower row of Table 2.