Radiation force in nonlinear, focused beams

Area of Science:

• Acoustics
• Nonlinear Physics
• Biophysics

Background:

• Focused ultrasonic waves exhibit nonlinear distortions.
• Dissipative radiation force (RF) is a key effect in acoustics.
• Understanding RF is crucial for applications in medical imaging and therapy.

Purpose of the Study:

• To analyze the impact of cumulative nonlinear distortions on dissipative radiation force (RF).
• To investigate RF amplification in focused ultrasonic waves.
• To compare RF behavior in different dissipative media.

Main Methods:

• A simplified analytical model was developed.
• The model separates geometrical focusing and focal diffraction stages.
• Two dissipation models were considered: classical viscous fluid and biological tissue.

Main Results:

• Nonlinear steepening significantly amplifies RF compared to harmonic waves, even without shock formation.
• The study quantifies the enhancement of RF due to nonlinear effects.
• Differences in RF amplification were observed between the two dissipation models.

Conclusions:

• Cumulative nonlinear distortions play a significant role in enhancing the dissipative radiation force.
• The findings are relevant for predicting and controlling acoustic radiation forces in various media.
• The model provides insights into nonlinear acoustics in biological tissues.