Modeling nonlinear ultrasound propagation in tissue from array transducers and application to tissue harmonic imaging

A computational model is presented to simulate nonlinear propagation of ultrasound in tissue from array transducers. The model is based on an operator splitting approach with a fractional step marching scheme, whereby the effects of diffraction, attenuation and nonlinearity can be considered independent over small steps. This algorithm avoids the use of the parabolic approximation used by the KZK model, and may be more accurate for focused sources. Simulated transmitted pressure profiles and pulse-echo second-harmonic point spread functions are presented as examples of the capabilities of the algorithm for design and optimization of tissue harmonic imaging systems. Dynamic focusing and pulse inversion are shown to be advantageous for increasing second harmonic levels, and for improving spatial resolution.