Low-frequency surface wave propagation and the viscoelastic behavior of porcine skin

Abstract

A physical model describing the propagation of low frequency surface waves in relation to the viscoelastic behavior of porcine skin is presented along with a series of empirical studies testing the performance of the model. The model assumes that the skin behaves as a semi-infinite, locally isotropic, viscoelastic half-space. While the assumption of a semi-infinite body is violated, this violation does not appear to have a significant impact on the performance of the model based upon the empirical studies. One Hertz surface waves in the skin propagate primarily as Rayleigh waves with a wavelength and velocity of approximately 3 m and 3.0 m/s, respectively. The amplitude of the acoustic wave as measured by tracking the acoustic stress wave - induced shift in a backscattered laser speckle pattern, decreased exponentially with lateral distance from the acoustic source. Using this model of surface wave propagation, the mechanical loss factor or tan δ of the skin was measured to be on the order of 0.14±0.07. The results presented herein are consistent with earlier works on the propagation of low frequency acoustic waves in biological tissues and should serve as a theoretical and empirical basis for using the wave characteristics of propagating surface waves in combination with the mechanical behavior of the tissue for biomechanical studies and for potential diagnostic applications.