Full‐diffraction and parabolic axisymmetric numerical models to characterize nonlinear ultrasound fields of two‐dimensional therapeutic arrays.

Abstract

Numerical modeling has been shown to be an effective tool to characterize nonlinear pressure fields for single‐element HIFU transducers, but it has not yet been applied for the much more complex three‐dimensional (3‐D) fields generated by therapeutic phased arrays. In this work, two approaches are presented to simulate nonlinear effects in the field of a 256‐element focused array. A new full‐diffraction approach includes rigorous 3‐D simulations of the nonlinear wave equation with a boundary condition given at the elements of the array. A second simpler approach is based on the KZK model and a focused piston source as the boundary condition. The effective aperture and initial pressure of the piston source are set by matching linear simulations of the two models in the focal region. It is shown that as output power is increased, agreement in the focal waveforms of the two simulations, even when shocks were present, is maintained up to very high power outputs of the array. These results demonstrate the feas...