Measurement of vocal fold depth and thickness in frozen and thawed canine larynges

Abstract

Anatomical data on vocal fold dimensions are necessary for defining the vocal fold boundaries in biomechanical modeling of vocal fold vibration. In the mid-membranous coronal section, vocal fold depth can be defined as the distance from the vocal fold medial surface to the thyroid cartilage, whereas thickness can be defined as the distance from the inferior border of the thyroarytenoid muscle to the vocal fold superior surface. Unfortunately, reliable geometric data from histological sections can be obtained only if the effects of sample preparation are quantified. For instance, tissue deformations are often induced by fixation and dehydration, sometimes producing shrinkages around 30%. In this study, reliable geometric data of the canine vocal fold were obtained by comparing frozen and thawed larynges. Coronal sections of frozen larynges were thawed gradually in saline solution. Images of the mid-membranous coronal sections at various thawing stages were captured by a digital camera. Measurements of vocal fold depth and thickness were made using a graphic software package (NIH image). Results showed that geometric changes of the vocal fold induced by freezing were likely reversed by thawing, such that the vocal fold depth and thickness measured on thawed larynges were representative of the pre-freezing state. [Work supported by NIH Grant No. P60 DC00976.]