This examination technique is commonly used to diagnose a variety of blood vessel diseases. You may need to undergo DSA to diagnose obstructive vascular diseases that are caused by blocks or narrowing in the lumen (inner surface) of arteries and veins. Your doctor may also request a DSA to diagnose a brain aneurysm (especially intracranial aneurysm), bleeding vessels, arteriovenous malformations (abnormal connections between arteries and veins), and to study the blood vessel system of cancerous tumours. The angiography also provides a visual guide for interventional procedures needed to re-open blocked arteries such as angioplasty, arterial stent, nephrostomy, and biliary procedures.