SIMULATION OF THREE-DIMENSIONAL NONLINEAR FIELDS OF ULTRASOUND THERAPEUTIC ARRAYS.

Area of Science:

• Acoustics
• Numerical Modeling
• Ultrasound Physics

Background:

• High Intensity Focused Ultrasound (HIFU) arrays generate complex acoustic fields.
• Nonlinear acoustic effects become significant at higher intensities, altering wave propagation.
• Accurate simulation of these nonlinearities is essential for understanding HIFU applications.

Purpose of the Study:

• To develop a novel numerical model for simulating three-dimensional nonlinear fields from HIFU arrays.
• To investigate the role of nonlinear effects in focused ultrasound beams.
• To analyze the development of shock fronts in HIFU pressure waveforms.

Main Methods:

• Developed a numerical model based on the Westervelt equation.
• Implemented an algorithm to model nonlinear pressure fields with shock fronts.
• Conducted numerical experiments using a 256-element two-dimensional array in water.
• Simulated intensity levels up to 10 W/cm(2).

Main Results:

• The model successfully simulates nonlinear pressure fields and shock front formation.
• Nonlinear effects were found to be significant for modern HIFU array intensities.
• Shock fronts were observed to develop in pressure waveforms at the focus.

Conclusions:

• The developed numerical model provides a valuable tool for studying nonlinear acoustics in HIFU.
• Nonlinear wave propagation and shock formation are critical considerations for HIFU system design and application.
• Simulations confirm the importance of nonlinear effects at characteristic HIFU intensities.