Echo Glottography Ultrasonic Recording of Vocal Fold Vibrations in Preparations of Human Larynges

Abstract

Except for the entirely subjective strobo-scopy there is no generally accepted clinical method for continuous recording of vocal fold vibrations. In laryngology and phoniatrics it is therefore usually difficult to assess vocal fold function objectively. Echoglottography, however, an ultrasonic pulse-echo method for the study of the vibrating vocal folds, meets many of the necessary requirements.

For the recording of vocal fold vibrations a special, highly sensitive ultrasound reflectoscope has been constructed, allowing the use of transducers with different ultrasound frequencies. A pulse repetition frequency of 10 kHz was chosen, sufficient for continuous recording of fast vibratory movements, yet giving an adequate recording depth. In initial experiments an ultrasound frequency of 4 MHz was shown to penetrate even ossified cartilages, this frequency being high enough for high longitudinal and lateral resolution of the ultrasound beam.

As a basis for the development of an echoglotto-graphic method the ultrasound echoes from laryngeal specimens have been recorded. Echoes from the free margin of the vocal folds could be demonstrated and unequivocally identified. Vibrations in these same structures gave rise to characteristic curves, resembling glottograms recorded with other, less convenient methods.