Coronary perfusion scanning is a nuclear imaging technique used to evaluate coronary blood flow. Agents containing tracers such thallium-201 or technetium-99m are injected into the blood stream. The material is carried through the coronary arteries and into the capillaries of the myocardium (heart muscle), where it can be absorbed by the myocardial cells. Energy given off by the tracers is detected and processed by special computerized camera systems. Images are produced that show how the tracers were distributed within the heart muscle.
Tissues that are well supplied with blood absorb more tracers, and record as the light areas on scan images. Portions of the heart muscle receiving diminished supplies of blood record proportionately lower levels of tracers, and are imaged with correspondingly less intensity (darker, or black). By comparing scans made while a patient is physically stressed (by exercise or pharmacologicals) with those recorded following a period of rest, diagnostic information regarding the condition of specific portions of the myocardium can be obtained.