Forward propagation of acoustic pressure pulses in 3D soft biological tissue

A simulation method for forward propagation of acoustic pressure pulses in a medium with three-dimensional (3D) spatially-variable acoustic properties is presented. The intended application is to study aspects of ultrasound imaging of soft biological tissue. The forward wave propagation is modelled by a one-way wave equation. The equation describes tissue exhibiting nonlinear elasticity and arbitrary frequency-dependent attenuation. A numerical solution to the equation is found by means of first-order accurate operator splitting and propagation along the spatial depth coordinate. Thus diffraction, nonlinearity and attenuation are solved independently at each propagation step, rendering their relative importance easy to monitor. The method is seen to yield an accurate simulation of the wave propagation when compared to numerical solutions of the full wave equation and experiments in a water tank. By this approach it is possible to simulate wave propagation over relatively large distances-typically several hundred wavelengths-at a modest computational complexity compared to solution of the full wave equation. It furthermore facilitates a high degree of parallelism, thus enabling efficient distribution of the required computations overmultiple processors.