Viscoelastic characterization of<i>in vitro</i>canine tissue

TLDR

Mechanical properties of biological tissues, especially frequency‑dependent complex, storage, and loss moduli, are essential for evaluating elastographic methods but are often constrained by sample geometry and stress–strain homogeneity. In vitro canine liver specimens were uniaxially compressed over 0.1–400 Hz using an EnduraTEC ELF 3200 with Plexiglas platens, and the resulting moduli spectra were fitted to a Kelvin–Voigt fractional derivative model. The model accurately described the data, revealing a complex modulus contrast between normal tissue and radio‑frequency ablation lesions, a concept with implications for elastography.

Abstract

Mechanical properties of biological tissues are of interest for assessing the performance of elastographic methods that evaluate the stiffness characteristics of tissue. The mechanical properties of interest include the frequency-dependent complex moduli, storage and loss moduli of tissues. Determination of the mechanical properties of biological tissues is often limited by proper geometry of the sample, as well as homogeneity of the stress–strain relationship. Measurements were performed on in vitro canine liver tissue specimens, over a frequency range from 0.1 to 400 Hz. Tests were conducted using an EnduraTEC ELF 3200, a dynamic testing system for determining the mechanical properties of materials. Both normal tissues and thermal lesions prepared by radio frequency ablation were tested. Experiments were conducted by uniaxially compressing tissue samples using Plexiglas platens larger than the specimens and measuring the load response. The resulting moduli spectra were then fit to a modified Kelvin–Voigt model, called the Kelvin–Voigt fractional derivative model. The data agree well with the model and in comparing the results from the normal tissue with that of the thermal lesions, the concept of a complex modulus contrast is introduced and its applications to elastography are discussed.