[Imaging of the myocardium with thallium-201].

Myocardial imaging after the intravenous injection of radionuclides offers a non-invasive, highly sensitive and reliable method for the detection of myocardial infarction and regional myocardial ischaemia. Considerable attention has been given to various isotopes as a means of independent assessment of regional blood flow distribution in the normal, ischaemic or infarcted myocardium. The clinical use of cationic tracers such as potassium-43 and rubidium-81 is based upon the principle that tracer uptake is proportional to regional myocardial blood flow. A region of absent tracer uptake suggests the presence of previous infarction or fibrosis, while a new perfusion defect appearing after stress suggests transient ischaemia. These isotopes, however, have significant physical limitations as imaging agents. The physical and biological properties of thallium-201, however, make it ideally suited for imaging of the myocardium with currently available imaging equipment.