Amplitude Modulation Method for Acoustic Radiation Force Impulse Excitation

摘要

Mechanical properties are intrinsic characteristics of biological tissue, which can provide information related to physiological and pathological information. Acoustic radiation force (ARF) is generated by a change of energy density due to the nonlinear ultrasound propagation. Based on ARF excitation, ultrasonic elastography methods had been proved to be able to provide information related to the mechanical properties of tissues. The detection of tissue displacements plays an important role in elastography methods. An amplitude modulation method for ARF impulse (ARFI) excitation has been proposed to increase displacement responses and can further enlarge the difference in displacement responses of media with different stiffness. Two different amplitude-modulated ARF waveforms are employed and compared with traditional ARF waveforms. To understand how these different waveforms may affect displacement responses, the relationship between the ARF and displacement responses has been derived. In the case of different waveforms but with the same impulse and the applying time, the larger the peak-to-peak amplitude of ARF, the greater the displacement response. The influences of the amplitude as well as the applying time of ARF on displacement responses are studied by simulations. Furthermore, a 3.5-MHz focused transducer is excited by different signals in phantom experiments to validate the feasibility of this proposed method. The results demonstrate that displacement responses produced by these amplitude-modulated ARF waveforms can be increased with lower or comparable temperature variation for safety consideration, compared with that of traditional ARF waveforms. Moreover, the displacement sensitivity to distinguish media with different Young & x2019;s modulus can be improved.