Fluoroscopy and angiography are special applications of X-ray imaging. A fluorescent screen and image intensifier tube are connected to a closed-circuit television system. This allows real-time imaging of structures in motion which can be augmented with a radio-opaque contrast agent. Radio-opaque contrast agents are usually administered by swallowing or injecting dye into the patient’s body to delineate the anatomy and functioning of the blood vessels, the genitourinary system or the gastrointestinal tract. Two radio-opaque contrast agents are presently in everyday use. Barium sulfate is given orally or rectally for evaluation of the GI tract. In multiple proprietary forms, iodine is given by oral, rectal, intra arterial or intravenous routes. These radio-opaque contrast agents strongly absorb or scatter X-rays and, in conjunction with real-time imaging, demonstrates dynamic processes, such as peristalsis in the digestive tract or blood flow in arteries and veins. Iodine contrast may also be concentrated in abnormal areas more or less than normal tissues and make abnormalities like tumours, cysts and inflammation more conspicuous.