Comparison between two different full-wave methods for the computation of nonlinear ultrasound fields in inhomogeneous and attenuating tissue

Nonlinear propagation is important in many diagnostic and therapeutic applications of medical ultrasound. The design of equipment and protocols for nonlinear modalities is facilitated by the simulation of the nonlinear ultrasound field. However, many existing simulation tools have difficulties of dealing with realistic features like tissue inhomogeneity, power law losses, or steered beams. Recently, two full-wave simulation methods for nonlinear ultrasound have been developed that are able to deal with these features. Those methods are known as the Iterative Nonlinear Contrast Source method (INCS; an integral equation method) and k-Wave (a pseudospectral time domain method). This paper assesses the accuracy of both methods by comparing their spatial and spectral results for two test configurations. In both configurations, a square piston excites a three-cycle Gaussian-modulated tone burst with a center frequency of 1 MHz and a source pressure of 750 kPa. The medium in the first configu...