Food appropriate for evaluation of tongue dynamics during swallowing using ultrasonography

Abstract

Dysphagia is most often diagnosed using video fluorography, video endoscopy, and ultrasonography. Ultrasonography is superior for imaging soft tissue, and enables real-time evaluation of the dynamics of the tongue and pharyngeal region. Since tongue dynamics plays an important role in swallowing in the preparatory and oral stages, the oral cavity function has been evaluated by measuring tongue movement and morphology using the B or M mode of ultrasonography. Evaluation of oral cavity function in D mode using the Doppler method has also recently been reported. However, ultrasonography is not common compared to video fluorography and endoscopy because of a problem with the clarity of the test food images. In this study, we performed basic experiments to investigate appropriate test food for the observation of M-mode images and D-mode flow rate measurement. We also observed images of the oral cavity and measured the speed of food mass transport from the oral cavity to pharynx. Measurements were made using a Prosound SSD-5500 an ultrasonography system, and UST-9126 electronic convex sounding probe (both from Hitachi Aloka Medical, Tokyo, Japan). Five types of test food with different physical properties were prepared in 100cc portions : tap water, carbonated water, and tap water combined with 1, 2 or 3 g of thickener (Toromi Perfect^[○!R], Nisshin Oillio, Tokyo, Japan) (Toromi 1, 2 and 3, respectively). A silicon tube was horizontally fixed in deaerated water and adjusted so that the test food flowed in the tube. Test food flow in the tube was imaged using B-mode echo, and the image clarity was observed. In addition, the test food flow rate in the tube was measured employing the pulse Doppler method and compared with the measured rate calculated from piston movement of the opposite syringe. The subject's oral cavity while swallowing the test food was imaged using the B/D mode, and differences in the image clarity and oral-pharyngeal passage time among the test foods were investigated.
With B-mode imaging thickened water was the most easily observed in the silicon tube. The flow rate spectrum was also clearly displayed in the D mode when the test food was thickened water. However, when the subjects were tested, many light spots were present in the thickened water and there was weakened contrast between the test food and surrounding tissue, making it difficult to observe tongue dynamics and confirm the test food flow. When carbonated water was swallowed, air bubbles were produced and imaged as light spots adhering to the dorsum of the tongue and palate. Echo images concentrated on these regions and made the flow of the test food and the tongue dynamics readily observable. The speed of oral-pharyngeal passage measured in the D mode was fastest for carbonated water, followed by tap water, and Toromi 1, 2 and 3, in that order.