Acoustic modeling of shell-encapsulated gas bubbles

Area of Science:

• Acoustics
• Biomedical Engineering
• Materials Science

Background:

• Current theoretical models fail to accurately capture the acoustic behavior of ultrasound contrast agents like Quantison and Myomap.
• Understanding scatter and attenuation properties is crucial for effective ultrasound imaging and therapeutic applications.

Purpose of the Study:

• To develop and validate an adapted Rayleigh-Plesset model incorporating a viscoelastic shell description for ultrasound contrast agents.
• To accurately predict the acoustic transmission and scattering properties of Quantison, Myomap, and Albunex.

Main Methods:

• Measurements of acoustic transmission and scattering were conducted for contrast agents in the 1-10 MHz frequency band.
• An adapted Rayleigh-Plesset equation with a viscoelastic solid shell model was employed.
• Effective bulk modulus (Keff) and friction parameter (SF) were estimated from transmission data.

Main Results:

• The developed model demonstrated good agreement with experimental data, with scattering differences less than 3 dB.
• For Quantison, the effective bulk modulus was independent of bubble diameter, while for Albunex, it increased with decreasing bubble size.
• Quantison exhibited minimal nonlinear response up to 200 kPa, followed by an abrupt scattering increase above this threshold, not predicted by the model.

Conclusions:

• The proposed viscoelastic model provides an improved description of ultrasound contrast agent acoustic properties compared to existing models.
• The model successfully characterizes the elasticity and viscosity of the agent shells.
• The study highlights limitations of the current model in predicting extreme nonlinear responses of certain agents at high acoustic pressures.