Dynamic measurements of soft tissue viscoelastic properties with a torsional resonator device

Abstract

A new method for measuring the mechanical properties of soft biological tissues is presented. Dynamic testing is performed by using a torsional resonator, whose free extremity is in contact with a material sample. An analytical model of a semi-infinite, homogenous, isotropic medium is used to model the shear wave propagation in the material sample and allows determining the complex shear modulus of the soft tissue. By controlling the vibration amplitude, shear strains of less than 0.2% are induced in the tissue so that the material response can be assumed to be linear viscoelastic. Experiments are performed at different eigenfrequencies of the torsional oscillator and the complex shear modulus is characterized in the range 1-10 kHz. First in vitro experiments on bovine liver confirmed the sensitivity of the proposed technique. The experiment does not damage the soft tissue and allows a fast and local measurement, these being prerequisites for future applications in-vivo during open surgery. © Springer-Verlag Berlin Heidelberg 2004.