Micro-elastography: Toward ultrasonic shear waves in soft solids

Since shear waves in soft human tissues have been used in clinics, little is known about their upper frequency behavior except that they fade out before the ultrasonic regime due to viscoelastic dissipation. Studying this upper bound has become a need in micro-elastography that aims at characterizing a single cell using shear waves. We report through phantom experiments the observation of ultrasonic shear waves at 20.4 kHz. Moreover, it is shown that the Kelvin–Voigt model can predict a frequency upper bound in good agreement with cell experiments. At last, according to this simple rheological model, the maximum error of elasticity estimation when viscosity is neglected (wide spread perfectly elastic assumption) is 40%.