Nonlinear propagation in Doppler ultrasound.

The nonlinear propagation of ultrasound was demonstrated using Doppler transducers on two commercial duplex machines. The influence of nonlinear propagation on Doppler measurements was studied on both a flow phantom and a string phantom. It was found that although the pulse waveforms showed clearly different degrees of nonlinear distortion, no effect due to the nonlinearity could be detected on the received Doppler spectrum both in terms of the maximum frequency or underlying Doppler spectral profile.