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A nonlinear ultrasound propagation simulator using the Slowly Varying Envelope Approximation

Traditional ultrasound imaging takes into account linear propagation only. However, new methods seek to exploit the nonlinear properties of tissues, which create a specific contrast source. Optimizing these methods require simulating the pressure field in the media at a reasonable computational cost. This paper details how using the Slowly Varying Envelope Approximation (SVEA), a method coming from nonlinear optics, enables to compute several harmonics generated by nonlinearity. This simulator is suited to media with a nonlinearity coefficient varying in all 3 spatial dimensions. SVEA one-way field predictions are compared with those of three other simulators up to the fifth harmonic, showing a good agreement up to 1.1 dB depending on the simulator. This method runs on desktop computers in less than 8 minutes for a 128×128×512×400 discretization grid.