A thallium scan is a test that uses a radioactive substance, known as a tracer, to produce images of the heart. This scan allows doctors to determine what part of the heart muscle is not receiving enough blood and might be damaged. The thallium scan is extremely helpful in diagnosing coronary artery disease, which is the presence of blockages in the arteries.
During the scan, a small amount of thallium tracer is injected into the vein. It travels through the bloodstream into the coronary arteries and is picked up by the heart muscle cells. Areas of the heart muscle that receive an adequate amount of blood supply up the tracer immediately. Areas that do not receive the adequate amount of blood pick up the tracer very slowly, or not at all.
Because of the small amount of radiation given off by the tracer, a computer can process the information and produce an image of the radioactivity in various parts of the heart. An area of the heart that receives less blood than the rest of the heart due to a blockage or narrowed artery is called a "defect". A second set of images is taken hours later to determine if the area does not temporarily receive enough blood or if the area is permanently damaged.
Side effects may occur during or after the test, but are usually mild. The necessary information obtained in this test outway the negatives. A thallium scan will help the doctor accurately diagnosis and treat the patient.