Ultrasound is a painless, non-invasive test that uses sound waves to examine soft internal organs and structures. This technique has many medical applications, including the evaluation of leg veins. Such tests are known as vascular ultrasound or vascular sonography (suh-NAWG-ruh-fee). Generally, ultrasound testing is conducted by a technician or radiologist. Before the procedure begins, the skin is prepped with a gel. A device called a transducer (tranz-DOO-suhr) is passed over the skin, sending high-frequency waves through the body. These waves bounce off of internal structures much like an echo, creating images which are displayed on a video monitor. Typically, a radiologist writes a report for the doctor based on his or her interpretation of these images. Vascular ultrasound may reveal problems such as blood clots, varicose veins, the location of failed valves, and the backward flow of blood, a condition called reflux. It can be especially helpful in diagnosing diseased saphenous (suh-FEE-nuhs) veins, as these veins are too deep in the leg to be examined visually or manually. Ultrasound may also be utilized to assist in the sclerotherapy (sklehr-oh-THEHR-uh-pee), or injection, of these deeper veins.