Validating Stereo-Endoscopy with a Synthetic Vocal Fold Model

Endoscopy has long been an important technique for vocal fold visualization, but it is limited to providing only two-dimensional information. To extend its usage, stereo-endoscopy has been developed to provide two views of the larynx from different angles, enabling three-dimensional viewing of the laryngeal structure. Stereo-matching has recently been applied to reconstruct three-dimensional vocal fold motion from stereo-endoscopic measurement [1, 2]. Further information regarding its accuracy and applicability would make it more clinically relevant. To validate the stereo-endoscopy system, a setup of multiple high-resolution cameras and the stereo-endoscopy system simultaneously recorded the surface of synthetic, self-oscillating vocal fold models. The estimated error in the measurement of the three-dimensional location by the stereo-endoscopy system is low in the transverse plane, whereas the error is relatively large in the inferior-superior direction. Although further improvement is needed to provide reliable information on the inferior-superior movement of the vocal folds, we conclude that the stereo-endoscope is applicable to in vivo measurements of absolute distances of the glottis in the transverse plane such as glottal length, width, and area.