Modeling Ultrasound Propagation in the Moving Brain: Applications to Shear Shock Waves and Traumatic Brain Injury

Area of Science:

• Biomedical Engineering
• Computational Physics
• Medical Imaging

Background:

• Studying traumatic brain injury (TBI) in living humans is ethically challenging.
• Brain tissue properties change rapidly postmortem, limiting traditional research.
• Existing simulation methods struggle with subresolution displacements in complex media.

Purpose of the Study:

• To develop and validate a generalized impedance flow method for simulating ultrasound propagation in a moving human brain model.
• To accurately capture shear wave deformation during traumatic impacts using computational modeling.
• To improve in silico reproduction of TBI-related phenomena.

Main Methods:

• Generalized impedance flow method to model continuous subresolution motion in structured acoustical maps.
• Finite difference simulations for ultrasound propagation in human brain tissue.
• Piecewise parabolic method calibrated to ex vivo porcine brain shear shock observations.
• Modeling of L7-4 transducer imaging sequences and beamforming using delay-and-sum and normalized cross-correlation methods.

Main Results:

• The generalized impedance flow method demonstrated small average error (λ/1702) in simulating subresolution displacements.
• The simulation accurately captured shear wave motion, including wave profile, shock front characteristics, and harmonic generation.
• The in silico approach successfully reproduced experimental observations of shear shock waves in porcine brain.

Conclusions:

• The generalized impedance flow method provides an accurate and effective tool for simulating ultrasound propagation in moving brain tissue.
• This approach is expected to enhance the design of imaging sequences and tracking algorithms for TBI research.
• The modeling techniques are applicable to other dynamic phenomena like shear wave elastography and blood flow.