Royalty free and rights managed images relating to the diagnostic technique of angiography. This medical procedure involves injecting a radio-opaque contrast medium into blood vessels, allowing them to be examined by X-rays (radiography). Cerebral (brain) and heart (coronary) blood vessels are commonly imaged in this way when assessing the risk of strokes or heart attacks. Other examples shown are retinal X-rays, and angiography of varicose veins. Photographs and pictures include surgeons inserting catheters while carrying out angiography procedures on patients. Also shown are molecular models of common contrast agents.