Non-invasive in vivo measurement of the mechanical properties of human vocal fold tissue

Abstract

A non-invasive method was developed and examined to obtain the mechanical properties 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 from the high speed imaging (HSI) and magnetic resonance imaging (MRI) experiments at different phonation pitches, the frequency of the vocal folds vibrations, in the range from 110 to 440 Hz. The MRI images were used to obtain the dimensions of the subjects' vocal folds in the high-speed images. The mucosal wave propagation speed was determined for each subject at different pitches using an automatic image processing algorithm. The shear modulus of the vocal fold mucosa in the transverse direction was then calculated from a surface (Rayleigh) wave propagation dispersion equation using the measured wave speeds. It was shown that the mucosal wave propagation speed and 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.