When a patient has a coronary CTA, physician co-investigators, all of whom are certified by the Certification Board of Cardiovascular Computed Tomography and credentialed by Johns Hopkins for CTP, will evaluate the scan for the presence of lesions that would qualify the patient for inclusion. Patients with lesions between 50% and 70% will be approached for participation in the CTP study(37). Those who agree to participate will be scheduled to have the CTP performed within thirty (30) days of the initial Coronary CTA procedure.