It is imaging of vascular system of body using X-rays. Vessels are not visible normally hence special dye (contrast agent) is injected in to blood). In this process dye is injected inside body through small injection in groin with help of wire and plastic tube (guidewire and catheter). This dye flows through blood vessels and same time X-rays are taken to delineate blood vessels. DSA is similar to coronary angiography (CAG) performed for knowing obstruction in blood vessels of heart.