title: Non-invasive in vivo measurement of the shear modulus of human vocal fold tissue.
abstract: Voice is the essential part of singing and speech communication. Voice disorders significantly affect the quality of life. The viscoelastic mechanical properties of the vocal fold mucosa determine the characteristics of the vocal folds oscillations, and thereby voice quality. In the present study, a non-invasive method was developed to determine the shear modulus of human vocal fold tissue in vivo via measurements of the mucosal wave propagation speed during phonation. Images of four human subjects' vocal folds were captured using high speed digital imaging (HSDI) and magnetic resonance imaging (MRI) for different phonation pitches, specifically fundamental frequencies between 110 and 440 Hz. The MRI images were used to obtain the morphometric dimensions of each subject's vocal folds in order to determine the pixel size in the high-speed images. The mucosal wave propagation speed was determined for each subject and at each pitch value using an automated image processing algorithm. The transverse shear modulus of the vocal fold mucosa was then calculated from a surface (Rayleigh) wave propagation dispersion equation using the measured wave speeds. It was found that the mucosal wave propagation speed and therefore the shear modulus of the vocal fold tissue were generally greater at higher pitches. The results were in good agreement with those from other studies obtained via in vitro measurements, thereby supporting the validity of the proposed measurement method. This method offers the potential for in vivo clinical assessments of vocal folds viscoelasticity from HSDI.
authors.affiliation: Biomechanics Research Laboratory, Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada H3A 0C3. Electronic address: siavash.kazemirad@mail.mcgill.ca.
authors.forename: Siavash
authors.initials: S
authors.lastname: Kazemirad
authors.affiliation: Biomechanics Research Laboratory, Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada H3A 0C3.
authors.forename: Hani
authors.initials: H
authors.lastname: Bakhshaee
authors.affiliation: Biomechanics Research Laboratory, Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada H3A 0C3.
authors.forename: Luc
authors.initials: L
authors.lastname: Mongeau
authors.affiliation: Department of Laryngology, McGill University, Montreal, Quebec, Canada H3A 1A1.
authors.forename: Karen
authors.initials: K
authors.lastname: Kost
mesh_terms: D000328:Adult; D000465:Algorithms; D004548:Elasticity; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010699:Phonation; D014827:Vocal Cords / Q000502:physiology*; D055815:Young Adult
keywords: High-speed imaging; Mucosal wave propagation; Non-invasive measurement; Shear modulus