Ultrasonography - In House

Ultrasonography is the second most commonly used imaging format in veterinary practice. It uses ultrasonic sound waves in the frequency range of 1.5-15 megahertz (MHz) to create images of body structures based on the pattern of echoes reflected from the tissues and organs. Several different types of image formats can be displayed.

The most familiar one (and the one that creates the actual image of anatomy) is B-mode, or gray-scale scanning. The sound beam is produced by a transducer placed in contact with the animal. An ultra short pulse of sound is directed into the animal, after which the transducer switches to the receive mode. Echoes occur as the sound beam changes velocity while passing through tissues of varying density. The greater the change in velocity, the greater the strength of the echo. The transducer then reconverts the echoes to electrical impulses recorded by the computer in the ultrasound machine. The strength of the echo, the time required for the echo to return after the pulse, and the direction the sound beam was sent is recorded.

Using the information from multiple echoes, the machine creates an image that represents the appearance of the tissues when cut in that same plane on an anatomic specimen. In modern scanning systems, the sound beam is swept through the body many times per second, producing a dynamic, real time image that changes as the transducer is moved across the body. This real-time image is easier to interpret and allows the examiner to scan continuously until a satisfactory image is obtained.