Abstract
This study was aimed for ultrasonographic assessment of the tympanic membrane and the tympanic bulla in five healthy Beagle dogs. To improve an ultrasonographic image, the ear canal was filled with warm saline, and an 11 MHz linear probe and a 6.5 MHz convex probe were used. The structures of ear component such as ear canal, ear cartilage and tympanic membrane were easily identified. Especially, tympanic membrane was presented as a reflaction surface which was resulted from the different acoustic impedence between the fluid-filled anechoic ear canal and the gas-filled hyperechoic tympanic cavity in normal dogs. In five left-side ears, the saline was infused into the external ear canal after the tympanic membrane had been ruptured experimentally. Both anechoic fluid-filled ear canal and tympanic cavity were clearly identified. In five right-side ears, the surgically fluid-filled tympanic cavity was imaged as a hypoechoic oval shaped structure. When tympanic cavity and ear canal have been contained with fluid, it was difficult to identify whether the tympanic membrane was ruptured or not. For assessment of the ear structure with ultrasonography, the 11 MHz linear probe was considered as an optimal equipment for a serial assessment of ear canal, tympanic membrane and tympanic bulla whereas the 6.5 MHz convex probe was suitable to assess the tympanic cavity. The results suggest that ultrasonography with saline infusion into the ear canal can be used to find the intactness of the tympanic membrane and to assess the fluid- filld tympanic bulla.
