Three dimensional (3D) display of the pharyngeal air space change by a compensation posture for dysphagia using cone-beam CT

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Change postures in swallowing changes the shape of oropharyngeal space. The purpose of first research was to analyze this change using 3 dimensional data from cone-beam CT.To see the effect of gravity, 10 volunteers were taken in sitting position with cone-beam CT (CBCT) and in supine position Multislice CT (MSCT) asking saliva swallow to anticipate rest position. Unfortunately, only 3 volunteers became rest position after swallow. From these 7 cases' data, soft palate was a little affected by the gravity. Further, hyoid bone, epiglottis and esophageal entrance were more affected by the gravity and have a tendency of aging.To analyze the effect of head rotation to one side to the shape of pharyngeal space, we took CBCT with head-on and rotated to the right side. Videoendoscopy was taken in 2 volunteers. It was said that the piriform sinus in the rotated side will disappear because of the pressure to this area, but another side will be enlarged. From our CT data, we reconstructed 3 D images. The piriform sinus was not shrunk completely in the rotated side but rather enlarged. The opposite side of piriform sinus also enlarged. But in the level of the upper piriform sinus, the shape of the pharynx changed to a tear-drop shape from the oval one. The opposite side was enlarged and rotated side was shrank. Most of the researches to analyze this they use endoscopy and it does not allow the direct observation of the piriform sinus when rotated.