Assessing tissue motions induced by orthogonal-frequency pulses and binary pulses using a laser vibrometer

Laser vibrometry is used to assess tissue motions induced by orthogonal-frequency pulses and binary pulses. The tissue motions in a swine liver is induced by ultrasound radiation force and measured by a laser vibrometry. The displacements of tissue motion induced by the orthogonal frequency pulses are higher than that of binary pulses from 3 dB to about 10 dB from 700 Hz to 900 Hz with a reduced excitation intensity that is only 17% of that of the binary pulses. The study finds that the peak displacement of the motion is proportional to the excitation energy and the spectrum of the motion velocity is strongly correlated to the spectrum of the excitation PWM pulses. Thus, the excitation pulses of ultrasound vibrometry should be carefully designed according to the prescribed spectral distribution that is preferred for applications.