Composed vibration pulses for ultrasound vibrometry

Composed vibration pulses are developed to generate ultrasound radiationforce for stimulating vibrations in a tissue region with preferred spectraldistributions and increasing specific vibration harmonics when the peakradiation power is limited. The new vibration sequence has multiple pulses inone fundamental period of the vibration. The pulses are sparsely sampled from anorthogonal frequency wave composed of several sinusoidal signals. The phase andamplitude of each sinusoidal signal are adjusted to control the shape of theorthogonal frequency wave. Amplitude of the sinusoidal signal is increased asits frequency increases to compensate for higher loss at higher frequency in thetissue region. The new vibration pulses and detection pulses can be interleavedfor array transducer applications. The new method is evaluated by studying theshear wave propagation in a chicken liver, in vitro. The experimental resultsshow that the new vibration pulses significantly increase induced tissuevibration with the same peak ultrasound intensity, compared with the binaryvibration pulses. The experimental results also show that both pulse amplitudemodulation (PAM) and width modulation (PWM) can be implemented in applications.