Fractional Flow Reserve and Intravascular Ultrasound RelationShip STudy

Inclusion Criteria: * Sign written informed consent to participate in the study. * Clinical indication for coronary angiography for stable or unstable angina Specific Angiographic Inclusion Criteria: * Patients required to have an intermediate coronary lesion (stenosis 40-80% by visual estimate) in one or more native, major epicardial coronary artery with reference diameter ≥2.5mm (visual estimate) * The vessel(s) with the intermediate lesion must have no flow limiting lesions and must be available for imaging and must be considered safe for imaging evaluation. Exclusion Criteria: * Patient has had a documented acute ST-segment elevation myocardial infarction within the past 24 hours * Decompensated heart failure or hypotension requiring intubation, inotropes, intravenous diuretics or intraaortic balloon counterpulsation. * Renal dysfunction (creatinine clearance \< 60 mL/min/1.73m2) * Pregnancy or breast-feeding * Standard contra-indications to MRI for implanted ferro-magnetic devices - i.e.: pacemakers, defibrillator (AICD), and aneurysm clips * Body weight \> 400lbs * Left ventricular hypertrophy \>1.5cm by by echocardiogram * History of bronchospasm or asthma * ECG evidence of conduction defect, including 2nd or 3rd degree AVB * Patient has a known hypersensitivity, allergy or contraindication to gadolinium-based contrast agents. * Prior participation in this study or patient is currently enrolled in another investigational use device or drug study that has not reached its primary endpoint. If the patient is enrolled in another study that is not investigational, required visits for that trial must not interfere with the conduct of this trial. Angiographic Exclusion Criteria: * Unprotected left main lesion location. * Ostial lesion * Angiographic evidence of severe calcification or marked tortuosity of the target vessel that would preclude safe imaging * Lesion is located within or distal to an arterial or saphenous vein graft. * Angiographic presence of thrombus in the lesion or vessel studied. * Lesion in a vessel with \<2.5 mm reference diameter or with more than one lesion in the vessel