 Coronary artery computed tomographic angiography CTA is a widely used, highly accurate technique for the detection of coronary artery disease CAD, with sensitivity and negative predictive values of over 90 1-4. Patients with normal CTA findings have an excellent prognosis and do not require further testing for CAD 5. However, like invasive coronary angiography QCA, CTA is an anatomic test and, unless lesions are very severe 90 stenosis, cannot reliably predict the impairment of flow functional significance of intermediate grade stenoses. 