Ultrasonic transmission mode imaging of the nonlinear parameter B/A: a simulation study

The simulation of a system designed to image the nonlinearity parameter B/A is discussed. The algorithm entails the interaction of a pump and probe pulse, taking into account nonlinear distortion and absorption of the acoustic energy. Simulations are performed for both waterlike and highly attenuative media. Different pump and probe waveforms are studied. It is shown that broadband impulsive pump waveforms in general lead to the best estimates of the nonlinearity parameter. Another alternative providing good resolution was a broadband chirp pump of considerably longer duration. The resolution of the simulated images obtained from the coherent probe waveform was directly proportional to the probe frequency. The highly attenuative media altered the shape of the pump substantially, but in the case of the chirp pump the reconstructed images were not significantly degraded.