The radial artery is one of two main arteries in the forearm (the other being the ulnar artery), running along the thumb side (lateral aspect) of the forearm from the elbow to the wrist. It is the artery most commonly felt when checking a wrist pulse. On ultrasound, the radial artery appears as a small, pulsatile vessel with a triphasic waveform typical of a high-resistance peripheral artery. Sonography of the radial artery is performed to assess patency before procedures such as arterial line placement or radial artery catheterization, to evaluate for thrombosis or pseudoaneurysm after catheterization, and to perform an Allen test (assessing collateral ulnar artery flow) before radial artery harvesting for coronary bypass grafts.