Figure 2.

Bubble dynamics of two microbubbles (R₁ and R₂) in the viscoelastic tissue predicted by different models (I–IV) at different values of initial surface tension σ₀ (p_A = 100 kPa). (a–c) Normalized radii of a small bubble (R₁) with an initial radius of R₁₀ = 1 μm and (d–f) a large bubble (R₂) with R₂₀ = 5 μm as a function of time. Model I and model II represent uncoated and lipid-coated microbubbles without considering bubble–bubble interactions, respectively, whereas model III and model IV represent the corresponding cases with considering bubble–bubble interactions at d_i,j = 20 μm.