X-RAY STUDY OF VOCAL FOLD LENGTH

Lateral radiography was used to study vocal fold length and laryngeal tilt as a function of changes in fundamental frequency of phonation. Ten male subjects sustained phonation, at a predetermined vocal intensity, at 98, 131, 196 and 262 Hz while four lateral X-rays of the larynx were taken. The X-rays provided six laryngeal indices: four measures of vocal fold length; one of the ventral cricoid-to-thyroid cartilage distance; and one of the A-P distance of the laryngeal tract at the ventricle. All measures were corrected for enlargement using a formula accounting for the object-to-casette and X-ray source-to-casette distance. From the data obtained, the following conclusions may be drawn: (a) lateral radiography provides a means of observing and measuring the changes in vocal fold length and cricoid-thyroid tilt; (b) as the fundamental frequency of phonation is increased (in the modal register), the vocal folds become longer, the increase becoming less at the extremely high frequencies; (c) the distance between the thyroid and cricoid cartilages tends to be reduced as the fundamental frequency of phonation increases. © 1968 S. Karger AG, Basel.