Composed vibration pulses for ultrasound vibrometry

Composed vibration pulses are developed to generate ultrasound radiation force for stimulating vibrations in a tissue region with preferred spectral distributions and increasing specific vibration harmonics when the peak radiation power is limited. The new vibration sequence has multiple pulses in one fundamental period of the vibration. The pulses are sparsely sampled from an orthogonal frequency wave composed of several sinusoidal signals. The phase and amplitude of each sinusoidal signal are adjusted to control the shape of the orthogonal frequency wave. Amplitude of the sinusoidal signal is increased as its frequency increases to compensate for higher loss at higher frequency in the tissue region. The new vibration pulses and detection pulses can be interleaved for array transducer applications. The new method is evaluated by studying the shear wave propagation in a chicken liver, in vitro. The experimental results show that the new vibration pulses significantly increase induced tissue vibration with the same peak ultrasound intensity, compared with the binary vibration pulses. The experimental results also show that both pulse amplitude modulation (PAM) and width modulation (PWM) can be implemented in applications.