Theoretical model for the threshold onset of contrast microbubble oscillations

Area of Science:

• Biophysics
• Acoustic Science

Background:

• High-speed optical observations reveal a threshold acoustic pressure amplitude for microbubble radial oscillation.
• Phospholipid-coated contrast microbubbles exhibit non-linear behavior under acoustic stimulation.

Purpose of the Study:

• To propose a theoretical model explaining the observed threshold behavior in microbubble oscillation.
• To elucidate the role of the phospholipid layer's mechanical properties in initiating microbubble oscillation.

Main Methods:

• Theoretical modeling of microbubble dynamics.
• Analysis of phospholipid layer's limiting shear stress.

Main Results:

• A threshold acoustic pressure amplitude exists below which microbubble oscillation does not initiate.
• The phospholipid layer's limiting shear stress is identified as the cause of this threshold behavior.
• The proposed model accurately predicts the dependence of oscillation onset on initial bubble radius.

Conclusions:

• The mechanical properties of the phospholipid shell, specifically its limiting shear stress, govern the initiation of microbubble oscillation.
• This finding provides a physical explanation for the experimentally observed acoustic threshold in contrast microbubbles.