Ultrasound images are produced by sound waves.

A scanning probe is passed over the area of the body that is being examined. The probe sends sound waves into the body and then "listens" for echoes reflected back from body structures. An ultrasound image is produced from these detected echoes based upon their intensity and time taken by them to return to the probe.

In order to perform an ultrasound exam, a watery gel must be placed on the skin over the area that is to be examined. This gel is necessary to use in order for the ultrasound signals to pass easily to and from the probe. The gel also assists in allowing the probe to be smoothly passed over the area of interest.