Low frequency elastic wave imaging by adaptive combination of fundamental and tissue harmonic ultrasonic waves

When low frequency sinusoidal vibration of frequency under several hundred Hz is applied from the surface of the sample, the resulting movement inside the sample is measured from the Doppler frequency shift of the transmitted probing ultrasonic waves. Two-dimensional Fourier transform is applied in order to estimate the internal vibration wave fronts both for the fundamental and the second harmonic ultrasonic wave frequencies. An adaptive combination is used to reconstruct of the final wave front. Two-dimensional motion maps which show the elastic wave propagation inside the medium are shown for several phantoms.