Ultrasonography

Ultrasonography for veterinary diagnosis was first employed in the late 1960s. The technique had already been used for examination of slaughter animal tissues. The first clinical application began with pregnancy diagnoses in sheep and then dogs.

Figure 18.6 Dorsal MRI (T2W) of the pelvis of a dog.

G = urethra; H = bulb of urethra.

Currently the technique is used mainly in farm animals, although there are applications in ophthalmology and pregnancy diagnosis in small animals. In recent years ultrasonog­raphy of the abdomen has almost become part of the routine diagnostic procedure.

The sound frequency employed in ultrasonography is higher than the range of human hearing. Dogs and cats can perceive ultrasound well in excess of human ability, although they do not show any disturbance at the frequencies used clinically.

The ultrasound transducer converts electrical energy to ultrasound and a computer develops images that are displayed on a computer screen. The high-frequency sound is inaudible to human ears and apparently causes no disturbance to animals. The sound waves promote echoes that bounce back from the targets, giving information on the size, shape and consistency of the soft tissues and organs. Ultrasonography is particu­larly useful for examinations of the abdomen from which a picture of the organs or the pregnant uterus can be prepared by the computer.

18.6