Fast simulation of non-linear pulsed ultrasound fields using an angular spectrum approach

Area of Science:

• Acoustics
• Medical Imaging
• Computational Physics

Background:

• Non-linear ultrasound propagation is crucial for advanced imaging techniques.
• Existing numerical methods for simulating non-linear ultrasound fields are computationally intensive.
• Accurate simulation of pulsed non-linear ultrasound is essential for transducer design and performance evaluation.

Purpose of the Study:

• To develop and validate a fast, non-linear pulsed ultrasound field simulation method.
• To enhance the computational efficiency of non-linear ultrasound simulations.
• To enable accurate modeling of complex array transducer behavior in non-linear regimes.

Main Methods:

• Implementation of a non-linear wave equation solver based on the angular spectrum approach (ASA).
• Analytical derivation of the ASA solution to the Westervelt equation for non-linear acoustics.
• Integration of the ASA with Field II software for simulating arbitrary array transducers and excitation signals.
• Comparison of ASA simulation results against a numerical operator splitting method (OSM) based program (Abersim).

Main Results:

• The ASA method achieved a speed increase of approximately 140 times compared to numerical methods.
• Simulation of a 5MHz, 2-cycle pulsed ultrasound field at the focal point took only 12 minutes on a standard PC.
• The non-linear ASA demonstrated high accuracy, with a full width error of 1.5% at -6dB and 6.4% at -12dB for the second harmonic point spread function compared to Abersim.
• The simulation accurately modeled pulsed non-linear ultrasound fields for complex transducer geometries.

Conclusions:

• The developed non-linear ASA provides a significantly faster and accurate alternative for simulating pulsed ultrasound fields.
• This method can accelerate the design and optimization of ultrasound systems, particularly for non-linear imaging applications.
• The ASA's efficiency and accuracy make it a valuable tool for research in medical ultrasound and acoustics.