Measuring Strain in Porcine Vocal Folds with DIC

Figure 1

Porcine vocal folds with a layer of speckle pattern with the contour of depth position on the superior surface of vocal fold. (Z-axis is directed vertically upward, and Z ¼ 0 is the image plane).

Cameras: Two high-speed black and white Photron Fastcam MC2—Model 10 K

Lenses: Canon Zoom EF-S17-85 mm; Canon, which allowed for increased optical resolution.

Light: fiber optic (Model 21-AC) with two semirigid probes was located approximately 8–10 cm away from the vocal fold surface to produce sufficient light. The light beam was oriented at an angle of approximately 30_ with respect to the horizontal axis to minimize glare.

Frame Rate: 3000 fps (higher frame rates decreased the field of view, and 3000 frames per second was the highest rate at which the region of interest was completely captured by cameras.)

Field of View: 40 cm between the vocal folds and the cameras was found to provide an optimum field of view.

To better understand the mechanics of phonation and, as a result, vocal fold maladies including nodules, cysts, and polyps, researchers at McGill University used a VIC-3D digital image correlation system from Correlated Solutions to quantify the mechanical strain and stress in excised porcine larynges during self-oscillation. The stresses that occur in this process include shear, aerodynamic, tensile, compressive, and inertial stresses - all of which cause 3D deformations during vocal fold vibration. These mechanical stresses are thought to be a strong contributor to voice trauma. This study aimed to develop an accurate, easy-to-use, and noninvasive method for the measurement of the displacement field over the superior surface of porcine vocal fold tissue.

Figure 2

Contours of normal strain εxx on deformed superior surface of vocal fold for A. open state and B. close state of vocal folds.

Figure 3

A. Excised larynx setup. B. Larynx holder.