The Next Step in Voice Assessment: High-Speed Digital Endoscopy and Objective Evaluation

Michael      Doellinger

Abstract

The data gained by digital high-speed endoscopy and its objective analysis provide many new possibilities to enhance the understanding and investigation of laryngeal dynamics and its pathologies. High-speed imaging overcomes disadvantages of the currently used technique of videostroboscopy. Additionally, objective evaluation of the dynamics finally enables the beginning of evidenced based diagnostics in endoscopic voice diagnostics. Purpose of Review: The purpose of this review is to describe the application and usefulness of endoscopic high-speed digital imaging in combination with objective analysis for clinical diagnostics and for understanding dynamics in the larynx. Recent Findings: High-speed digital endoscopy (2000 – 4000 fps) allows recording the oscillating vocal folds (100Hz – 300Hz) in real time during phonation (i.e. producing a single vowel). Therefore, it is especially useful to visualize and to quantify pathologies, which affect only the dynamic behavior of the vocal folds (i.e. hoarseness) but not the anatomical structure. The basis for objective laryngeal dynamics analysis are the recently developed solid image processing techniques enabling the segmentation of the vocal fold edges within the high-speed movies. For objective evaluation of laryngeal dynamics, several approaches have been suggested. The most common approaches are to evaluate the dynamics of single trajectories or the entire 2D-dynamics (Phonovibrography) directly by linear or non-linear analysis. Also, biomechanical models of the vocal folds are adapted or optimized towards extracted vocal fold movements for classification of voice pathologies. Acoustic recordings in combination with the corresponding high-speed sequences were applied to gain information about occurring dependencies. Using laser projection systems provided the quantification of vocal fold length and vocal fold vibrations in metric units during phonation. Due to high-speed recordings, relations between vocal fold vibrations and associated transglottal airflow could be associated. High-speed imaging was also performed for the investigation of the dynamics of the neoglottis in laryngectomees. It substantially enhanced the understanding of the vibrations of the neoglottis and provided more information than the commonly used videofluoroscopy.

Keywords: Voice, high-speed digital endoscopy, objective analysis, evidence based medicine