Hybrid FEM–CFD Simulation of Acoustic Wave–Fluid Interaction in Biomedical Ultrasound Applications

Biomedical ultrasound systems are based on the accurate wave propagation of acoustic waves in complicated fluid-tissue interfaces. Traditional linearized models do not encompass nonlinear acoustic image, viscous attenuation and tissue heterogeneity which play an essential role in diagnostic imaging and therapeutic ultrasound. In this study, a hybrid simulation model is proposed which combines acoustic solvers writing based on finite element methods (FEM) with file fluid dynamics (CFD) models to satisfactorily estimate wave-fluid interactions. A modified Westervelt equation is used to model nonlinear propagation and tissue-mimicking phantoms are also introduced to model heterogeneous bio-acoustic environments. Parallel computer techniques are used to make sure that simulation is feasible in real-time in clinical scale problems. Harmonic generation and focal spot distortions have both been predicted with high accuracy by the model as is experimentally justified using hydrophone measurements. What is novel is the fact that FEM and CFD are coupled on the interface level, so that the pressure waves are connected to the microfluidic flow fields, and vice versa. This study can enable biomedical engineers to have a tool of prediction to optimise the ultrasound probe design, therapies dosing regimens, and patient-regulated planning of the treatment. The research can be considered as a bridge between the fields of computational acoustics and biomedicine, and one of the steps to safer, more efficient, and customised ultrasound-based medical solutions.