In Vitro and In Vivo Comparison Between Intravascular Ultrasound (IVUS) Systems

Inclusion Criteria: * ≥18 years of age * Scheduled for a coronary angiogram at the Royal Adelaide Hospital. * Women must be non-lactating or not of childbearing potential (1 year post menopausal or surgically sterilized \[total hysterectomy, bilateral tubal ligation, bilateral oophorectomy\]). * Target artery must be \>2 mm to accommodate the IVUS catheter. * IVUS must be clinically indicated or indeterminate angiographic lesion in the artery (40%-70% angiographic stenosis) Exclusion Criteria: * Cardiogenic shock * Contraindications to intracoronary nitroglycerin (hypertrophic obstructive cardiomyopathy; cerebral hemorrhage, head trauma; concomitant sildenafil, tadalafil or vardenafil use) * Known coronary artery spasm * Significant bleeding risk (i.e. previous hemorrhagic stroke, active peptic ulcer disease) * Bleeding diathesis * Significant renal impairment (patients will be excluded if their calculated creatinine clearance is \< 30 mL/min)