Angina pectoris. Coloured Gamma Camera Scan (scintigram) of the human heart, showing angina at full stress. At left and upper right are regions of the heart (yellow, orange); between these areas there is a low blood supply (blue). This poor supply of blood to a region of the heart results in angina pectoris, an intense chest pain. It is caused by obstruction of the coronary arteries, usually due to the formation of atheroma plaques (atherosclerosis). Drugs or surgery may relieve the symptoms of angina. Gamma scanning uses a radioactive tracer (Thallium-201, here) injected into the blood, and detected with a gamma camera.