Vascular ultrasound is performed by placing the patient in a supine position, exposing the part of the vessel to be examined, while applying a coupling agent to the ultrasound probe and sweeping it along the course of the vessel, at which point it is possible to see whether there is a thrombus or blockage in the vessel, whether there is plaque, and the flow rate of the blood. For veins, it is also possible to observe whether there is regurgitation in the valves within the veins, the location of the regurgitation and the extent of it. Vascular ultrasound is a non-invasive vascular test and is used routinely by physicians to screen patients because it can identify lesions within the vessels in most cases. Often, if a lesion is found on ultrasound, angiography is also an option if further testing is needed.