The Shear Modulus of the Human Vocal Fold in a Transverse Direction

Department of Computer Science and Engineering, DeMontfort University, Leicester, United Kingdom.
Journal of voice: official journal of the Voice Foundation (Impact Factor: 0.94). 02/2008; 23(2):151-5. DOI: 10.1016/j.jvoice.2007.09.006
Source: PubMed


The aim of this study was to measure the shear modulus of the vocal fold in a human hemilarynx, such that the data can be related to direction of applied stress and anatomical context. Dynamic spring rate data were collected using a modified linear skin rheometer using human hemilarynges, and converted to estimated shear modulus via application of a simple shear model. The measurement probe was attached to the epithelial layer of the vocal fold cover using suction. A sinusoidal force of 3g was applied to the epithelium, and the resultant displacement logged at a rate of 1kHz. Force measurement accuracy was 20microg and position measurement accuracy was 4microm. The force was applied in a transverse direction at the midmembranous point between the vocal process and the anterior commissure. The shear modulus of the three female vocal folds ranged from 814 to 1232Pa. The shear modulus of the three male vocal folds ranged from 1021 to 1796Pa. These data demonstrate that it is possible to obtain estimates for the shear modulus of the vocal fold while preserving anatomical context. The modulus values reported here are higher than those reported using parallel plate rheometry. This is to be expected as the tissue is attached to surrounding structures, and is under natural tension.

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    • "In vitro measurements of the viscoelastic shear properties of human vocal fold tissue have been mostly performed using parallel plate or linear skin rheometry (Chan and Titze, 1999; Goodyer et al., 2003; Chan, 2004; Hess et al., 2006; Chan and Rodriguez, 2008; Dailey et al., 2009; Goodyer et al., 2009). For example, Chan and Rodriguez (2008) designed a custom-built, controlled-strain, linear, simple-shear rheometer for the measurement of the viscoelastic properties at frequencies up to 250 Hz. "
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    • "Another rational supporting this study is given by the vocal folds, which are a typical example of soft tissues vibrating in vivo at frequencies around 100 Hz for male and 1600 Hz for female soprano voices (Švec et al., 2008). The rheology of these tissues, which is well understood at low frequencies but remains unexplored in higher ranges (Chan and Rodriguez, 2008; Goodyer et al., 2009), is a fundamental aspect to consider for developing efficient and functional repair strategies of vocal folds or their replacement by biomaterials (Titze et al., 2004; Duflo et al., 2006; Thibeault et al., 2011). "
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    • "Changes in material properties can lead to behavior such as chaotic vibration or biphonation (Berry et al., 1994; Tao and Jiang, 2006). In the last 30 years, much effort has been undertaken to parameterize the material properties of VF tissue including in vitro measurement of canine larynx and in vivo measurement of human larynges (Perlman et al., 1984; Perlman, 1985; Perlman and Titze, 1985; Perlman and Durham, 1987; Goodyer et al., 2006, 2007a,b, 2009). There have been two comprehensive studies that have examined the effect of material properties on VF eigenstructure (Berry and Titze, 1996; Cook et al., 2009). "
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