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 being imaged. Several types of image formats can be displayed. The most familiar one (and the one that creates the actual image of anatomy) is B-mode greyscale scanning. The sound beam is produced by a transducer placed in contact with and acoustically coupled by means of a transmission gel to the animal. Organ structures such as the liver, kidneys, intestines and reproductive tract are visible on the ultrasound when examination takes place.