Rubidium Rb-82 is a radioactive isotope of rubidium. It is widely used for Positron Emission Tomography (PET) imaging of the myocardium under rest or pharmacologic stress conditions to evaluate regional myocardial perfusion in adult patients with suspected or existing coronary artery disease. Rb-82 decays by positron emission and associated gamma emission with a physical half-life of 75 seconds. In biochemical behavior, it is analogous to potassium ion (K+) and is rapidly extracted by the myocardium proportional to the blood flow. Rb+ participates in the sodium-potassium (Na+/K+) ion exchange pumps that are present in cell membranes. 82 radioactivity in viable myocardium is higher than in infarcted tissue, reflecting intracellular retention. Rubidium 82 chloride was approved by the FDA and is marketed under a trade name Ruby-Fill and Cardiogen-82.