A new method for radiographically locating upper respiratory and upper digestive tract structures in rats

A new procedure is described for radiographically locating structures of the upper respiratory and upper digestive tracts. These structures are difficult to visualize in small laboratory animals. In this method, a barium paste and tantalum dust mixture is specifically applied to the epiglottis, valleculae, soft palate and tongue in anesthetized rats to identify their positions. The mixture is easily visualized in radiograms and offers many advantages over traditional techniques, such as liquid barium swallows, insufflated tantalum powder or solid metallic implants. This enhanced visibility is due to the mixture's viscosity, which allows it to remain on the structures longer despite copious salivary flow. In addition, the thick consistency allows the radiopaque marker to adhere only where placed initially, and thus enables more precise measurements of the shape and position of upper respiratory and upper digestive tract structures.