Any test that relies on the use of radioactive tracers to diagnose disease. Radioactive isotopes are either injected into the body or inhaled, the dose of radiation is minimal, and the substances used either lose their radioactivity in a short time or are excreted. Nuclear medicine scans may be used to diagnose tumors, biliary disease, gastrointestinal emptying or bleeding, coronary artery disease, valvular heart disease, red blood cell survival time, renal dysfunction, deep vein thrombosis, pulmonary embolus, thyroid function, osteomyelitis (or other infections), fractures, and cardiac ejection fraction. Isotopes of thallium, iodine, or other metals are used. In 2005, nearly 20 million nuclear medicine examinations were performed in the U.S. alone, most for obtaining images of the heart and coronary arteries.