Application of continuous shear wave elastography method with multiple frequency selection to liver viscoelasticity measurement

In this study, we present a method for evaluating liver viscoelasticity using continuous shear wave elastography with an arbitrary frequency selection. In the Voigt model, viscosity depends on the frequency of shear waves, thus allowing viscosity evaluation by combining measurements at different frequencies. The shear wave frequency must satisfy the continuous shear-wave elastography frequency conditions. Therefore, the shear-wave frequency was selected as an integer fraction of the pulse repetition frequency of the ultrasound device. Low-viscosity phantoms were used in this study. The frequency dependence of shear-wave velocity was confirmed using a viscous phantom. The shear wave velocity dispersion measured using the proposed method was 5.41–8.98 m/s/kHz for four healthy liver volunteers, which are similar to that of a healthy liver reported by magnetic resonance elastography (5.76–7.52 m/s/kHz). It has been demonstrated that the frequency dependence of shear wave propagation can be measured.