Characterization of the Continuous Elastic Parameters of Porcine Vocal Folds

Publication date: Available online 14 November 2018

Source: Journal of Voice

Author(s): Garret Burks, Raffaella De Vita, Alexander Leonessa

Abstract

This paper presents an evaluation of the elastic properties of porcine vocal folds through uniaxial tensile tests. Inferior vocal fold tissue samples were subjected to tension in the longitudinal direction while digital image correlation techniques were employed to determine strain values throughout the tests. The stress-strain results showed a low-strain linear region, followed by both a nonlinear exponential and then a higher strain linear region. Data from 16 porcine vocal fold samples were analyzed following a similar optimization method as proposed in prior studies [1] to yield continuous model parameters which describe the elastic properties of the tissue. The average low and high strain linear modulus values were found to be 17.86 kPa and 609.27 kPa, respectively. The model also identified the location of two transition points: p₁, describing the transition from the low-strain linear region to an exponential region at 0.122 ± 0.058 mm/mm and p₂, describing the transition from the exponential to the high strain linear region at 0.308 ± 0.069 mm/mm. The exponential region of the averaged data set was found to be described by the relationship σm(ϵxx)=0.083e19.32ϵxx+2.0951 kPa. In addition to locating transition points, the optimization method maintained modulus continuity across all strain values. Averaged elastic modulus values across strain from 0 to 0.40 mm/mm were compared to representative low and high strain linear modulus which were measured at 0.05 and 0.35 mm/mm, respectively. Statistically significant differences were found among all strain intervals between the two transition points and the linear modulus values. These results indicate the need to consider the location of transition points and further highlight the nonlinearity and changes in elastic modulus which are especially important when using excised porcine vocal folds as a model for phonation. The results quantify continuous linear and nonlinear parameters describing the elastic properties which can be used as a framework for future excised larynx tests and while evaluating the dynamics of sound production, which rely heavily on the elastic properties of the tissue.

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