The effect of frequency adaptation according to the attenuation coefficient and focus depth on radiation force amplitude and estimated displacements

In remote dynamic elastography, amplitudes of generated displacement fields are directly related to the amplitude of the radiation force. Therefore, displacement improvement for better tissue characterization requires the optimization of the radiation force by increasing the push duration and/or the excitation amplitude of the transducer. The main problem of this approach is that the Food and Drug Administration (FDA) thresholds for medical applications, and transducer limitations may be easily exceeded. In the present study, the effect of the frequency used for the generation of radiation force on the amplitude of the displacement field is investigated. The aim is to apply the adaptive radiation force to increase the displacement amplitude. We found that amplitudes of displacements generated by adapted radiation force sequences are greater than those generated by non-adapted ones. The obtained gains were between 20% and 158% depending on the focus depths and the attenuation of the tested phantom. The signal to noise ratio was also improved by more than four times. We conclude that frequency adaptation is a complementary technique that may be used for the optimization of displacement amplitude. This technique can be used safely to optimize the deposited local acoustic energy, without increasing the risk of damaging tissues and transducers.