In 1969, well before noninvasive myocardial perfusion imaging with thallium-201 and Tc-99m labeled perfusion agents became routine clinical procedures, Dr. Paul J. Cannon and his colleagues at the College of Physicians and Surgeons, Columbia University, applied the inert radioactive gas clearance technique to measure regional myocardial perfusion in patients at the time of invasive coronary arteriography. To make these measurements Dr. Cannon performed an intracoronary injection of a saline solution of the inert radioactive gas xenon-133 (Xe-133) and recorded serial images of the clearance of the radiotracer from the myocardium. The clearance of Xe-133 was recorded with a new multicrystal scintillation camera developed by Drs. Bender and Blau. Injections of the tracer were recorded at rest and following an intervention designed to increase myocardial oxygen consumption and thus, regional perfusion. The slope of the clearance curve of Xe-133 is a direct function of the rate of myocardial capillary blood flow. Cannon validated this technique first in a canine model in 1969 and then applied the technique in patients.1‐3
