The term "angiogram" refers to any imaging study that is used to evaluate the arteries of the body. An angiogram is typically completed if there is concern that arteries are becoming narrowed and decreasing the flow of blood to the body. Narrowing in the arteries is often due to atherosclerosis and diabetes, although there are other disease processes that can lead to narrowing of the arteries.
There are two main classes of angiograms, including "catheter" angiograms and CT or MRI angiograms. The main difference from the patient perspective is that catheter angiograms are more invasive. In a catheter based angiogram, contrast is injected into the bloodstream through a vein or artery using a catheter. A catheter is a device that is inserted into an artery or vein and extended to the organ being studied. Contrast (a dye that enhances the outline of the artery) is then delivered directly into the artery being studied. The catheter is introduced into a vein or artery thorugh a small incision, and is moved forward into the artery being studied by the physician. A physician will then capture x-ray images of the artery being studied, which can be played in real time like a movie. These images provide a highly detailed outline of the artery or vein being studied. The primary advantages of a catheter angiogram are enhanced outline of the artery being studied. In addition, the physician has the ability to inflate a balloon (angioplasty) or insert a device (a stent) that will improve blood flow to the artery. The disadvantage of a catheter angiogram is that it is an invasive procedure for the patient with a risk of perforating the artery or leading to infection. These risks are generally small but carry significant adverse effects.
CT angiograms are completed using computed tomography technology. (MRI may be used and is referred to as "MR" angiography, please see CT vs. MRI). Recent advances in computed tomography technology provide for highly detailed images, and CT angiograms are becoming more widespread as this new technology has made it possible to accurately evaluate small structures. This is especially true in the small coronary arteries of the heart, which were almost always performed with catheter angiograms in the past.
The primary advantage of using CT angiography instead of catheter angiography is that the physician does not need to insert a catheter directly into a vein or artery to inject dye. The physician will instead administer a contrast agent into an a peripheral vein (usually in the arm) using a small needle. This contrast agent highlights blood flow throughout the body. A CT angiogram does not carry the risk of perforating an artery or infection as seen with catheter angiography. In addition, CT angiography images can be "processed" by a computer to recreate three dimensional images of the organs being studied. This provides your physician with additional information that is not available on a catheter angiogram. For example, a cardiac CT angiogram also gives information on the size of the heart ventricles, the health of the heart (as infarct areas can be visualized), and the amount of calcium in the arteries. The primary risks of CT angiography include radiation exposure and reaction to contrast agents.
