Kinetic Properties of 99mTc.Q12

Background I'Tc-Q12 is a new Tc(III) perfusion imaging agent that permits prompt myocardial visualization in humans. We postulated that 9'Tc-Q12 myocardial activity is related to actual myocardial blood flow during conditions of myocardial ischemia and pharmacological coronary artery vasodilation and that 99'Tc-Q12 shows little or no myocardial redistribution as long as 4 hours after intravenous injection. Methods and Results In seven anesthetized, open chest dogs, the left circumflex coronary artery was occluded, and dipyridamole (0.32 or 0.56 mg/kg) was infused into the right atrium, followed by 10 mCi of 'Tc-Q12. Myocardial blood flow was measured by radiolabeled microspheres. The animals were euthanized, and a total of 315 myocardial samples were assayed in a well counter for 9'Tc activity. One week later, radiolabeled microsphere activity was determined, and myo