Imaging of the larynx--extending the use of stroboscopy-related techniques.

Three methods (I-III) are presented to demonstrate how technical modifications in the use of stroboscopy-related techniques can be applied to further analyze vocal fold vibrations. (I) With double exposure videostroboscopy, dynamic properties of vocal folds can be visualized within one single image. This allows for estimations of horizontal vibratory velocity of the vocal fold margins. (II) Stroboscopic transillumination of the larynx makes it possible to localize initial vocal fold opening in the horizontal glottal plane and to visualize different vibratory opening patterns. Bidirectional color-coded endoscopic imaging of the larynx facilitates a semi-automated, digital measurement of the glottal area. (III) Stroboscopic illumination using four light emitting diodes (LEDs) clipped on a rigid endoscope and triggered by a portable 'pocket-sized', battery-powered electronic control device offers new prospects for performing stroboscopy outside of specialized clinical facilities.