Angiography is a procedure in which specialized imaging techniques help to analyze the flow of blood through blood vessels. A dye that is visible by x-ray, called contrast dye, is injected into the catheter, and x-rays are used to visualize blood flow through a particular vessel. Digital subtraction angiography is used to "subtract" out the x-ray signal from tissues and bones, so the doctor can focus on the blood vessels, according to MedlinePlus. There are several different types of angiography, which are named, based on the blood vessel analyzed.
Cerebral Angiography
Cerebral angiography is a procedure in which contrast dye is used to image the flow of blood through blood vessels of the brain. In cerebral angiography, a catheter is inserted into a blood vessel, often in the groin, and pushed through the blood vessels until it reaches the carotid artery, the artery in the neck, according to MedlinePlus. The contrast dye is then administered through the catheter, and the doctor visualizes the flow of blood through the brain blood vessels by X-ray imaging that depicts moving X-ray images on a monitor. Cerebral angiography can identify potentially serious cerebral blood vessel abnormalities. These abnormalities include blockages; aneurysms, which occur when a weakened portion of the blood vessel wall bulges outward; abnormal narrowing of a blood vessel; and inflammation of the blood vessels, called vasculitis.
Pulmonary Angiography
Pulmonary angiography is used to diagnose problems with blood vessels in the lungs. Harvard Health Publications reports that, in pulmonary angiography, the contrast dye is injected into a catheter that is placed in the pulmonary artery, which supplies the blood vessels of the lungs with blood. This type of angiography is often performed to identify possible pulmonary emboli, which are blood clots that commonly originate in the blood vessels of the legs, and can travel to and block the smaller blood vessels of the lungs.
Coronary Angiography
This type of angiography is used to examine the blood vessels that supply the heart with blood. According to the American Heart Association, contrast dye is injected into a catheter that has been placed into the aorta, the large coronary artery, and then x-ray imaging aids in the blood flow analysis. Coronary angiography is used to determine if there are blockages in the coronary arteries, or vessel damage that may potentially cause future heart attacks. Coronary angiography can also be used to determine the functional causes of heart valve defects. Valves help to let blood into and out of the heart at regulated intervals. If there are structural problems with the valves, blood flow throughout the whole body can be affected.
Fluroescein Angiography
Another type of angiography is fluorescein angiography, which is used to analyze the blood flow through the blood vessels of the eyes. During this procedure, a dye that is fluorescent, rather than a dye visible by x-ray, is injected into a vein in the arm, according to the University of Michigan Kellogg Eye Center. As the fluorescent dye travels through the blood vessels in the retina, the light-sensing structure located at the back of the eye, a specialized camera takes a series of pictures. Due to leaking, or abnormal location of the fluorescent dye, retinal blood vessel damage can be diagnosed through this procedure.
