The CTP procedure involves infusion of a stress agent and a contrast bolus prior to image acquisition. The CTP examination will be graded using the standard 17-segment myocardial model recommended by the ACCF/AHA for nuclear myocardial perfusion and stress echocardiography, in comparison to the myocardial appearance from the baseline coronary CTA. Areas of myocardial hypo-enhancement (decreased CT signal) under hyperemic conditions (coronary vasodilation during the regadenoson infusion) indicate possible ischemia.