Arterial and Venous Doppler scans of the upper and lower extremities are done using a handheld device (transducer) applied to areas of the arms or legs where the arteries and veins are located. Sound waves are used to produce a visual image of the actual artery or vein, and to measure the blood flow in them. The scans can detect blood clots and problems with valves in the veins. The scan can also detect the severity and location of any blockages in the arteries that supply your legs or arms with blood flow. Your provider uses this information to determine the best course of treatment for you if needed.