Videokymography: a New High-Speed Method for the Examination of Vocal-Fold Vibrations

Videokymography is a new optical high-speed method for investigation of vibrations which was developed especially for examination of vocal-fold vibrations. Videokymography is based on a modified CCD video camera, which is able to work in two different modes: standard and high-speed. In the standard mode the camera works as a normal commercial video camera providing 25 images (50 interlaced fields) per second. In the high-speed mode the camera delivers images from a single selected line with a frequency of almost 8000 line images/s. The successive line images are put below each other, creating a new videokymographic image monitoring vibration of the selected part of the vocal folds in time. A foot switch makes it possible to change instantaneously between the standard and high-speed modes. Ordinary videolaryngoscopic equipment with a powerful endoscopic continuous-light source can be used for the videokymographic examination of the vocal folds. Both the standard as well as high-speed images can be recorded by means of a normal video recorder, which makes the technique cost-friendly. The method is able to objectively evaluate important parameters of the vocal-fold vibration, such as the open, opening, closing and closed phases of the vibratory cycle, propagation of mucosal waves, left-right differences in phase or amplitude, etc. Videokymography provides more detailed information on voice disorders and considerably enriches laryngostroboscopy. There is no problem for videokymography to evaluate hoarse or unstable voices in which laryngostroboscopy fails. Also, the method is able to reveal structural irregularities on the medial surface of the vocal fold (e.g., sulcus glottidis) which can easily be overlooked in laryngostroboscopy. It is demonstrated how combination of a few laryngostroboscopic and videokymographic images can shortly and efficiently summarize important anatomical, physiological/pathological and vibrational properties of the laryngeal tissues in various patients.