A Doppler ultrasound can measure the flow of blood within the heart, veins and arteries, as well as evaluate valve movement, helping to detect blockages. An arterial ultrasound can screen for stroke, peripheral artery disease of the legs, and aortic aneurysm, a common and potentially fatal disease. Venous ultrasound is useful for identifying clots (deep vein thrombosis), varicose veins, and chronic venous insufficiency.