Duplex ultrasound incorporates B-mode, Pulsed-Doppler and color-Doppler to determine hemodynamics within the blood vessels of the body. Vascular Ultrasound is the main branch of radiology that uses Duplex. Vascular Ultrasound, a subspeciality within Ultrasound, helps determine multiple factors within the circulatory system. It can evaluate central (abdominal) and peripheral arteries and veins, it helps determine the amount of stenosis (narrowing) or occlusion (complete blockage) within an artery, it assists in ruling out aneurysmal disease as well as being the main aid to rule out thrombotic events. Duplex is an inexpensive, non-invasive way to determine pathology. Duplex evaluation is usually done prior to any invasive testing or surgical intervention.