CAPITAL: Carotid Artery Plaque Intravascular Ultrasound Evaluation

Inclusion Criteria: >18 years of age Patient must be: Symptomatic with lesions >/= to 50% stenosis, or Asymptomatic with lesions of >/= to 75% stenosis in at least one carotid artery, specific to the internal carotid artery, common carotid artery or bifurcated region; documented through acceptable ultrasound studies, completed within 30 days of recruitment. For patients with bilateral carotid disease- procedures need to be staged greater than 30 days apart. The lesion that has a greater degree of stenosis will be considered as the index procedure. Women of childbearing potential must have a negative pregnancy test within 7 days prior to treatment. The patient is able to give informed consent. Exclusion Criteria: The patient is experiencing a new (acute) neurologic event or has experienced a stroke within the last 30 days prior to enrollment. The patient has intracranial tumors, arterial vascular malformations >5mm, aneurysms or severe intracranial stenosis distal to the target lesion. Presence of thrombus at the target site or loose 'floating' debris as determined by duplex analysis and/or angiography. Existing hemorrhagic disease or coagulation problems creating inability to obtain homeostasis at entry site. The patient has an allergy to, or is unable to tolerate, heparin, concomitant medications (clopidogrel or ticlid, aspirin) or to nitinol metal. The patient has a history of or known reaction to radiocontrast agent (radiopaque dye) and is unable to be premedicated. Coumadin treatment that has continued during the 48 hours prior to enrollment and an INR above hospital normals (i.e. in the event of atrial fibrillation or prosthetic valve replacement). Hemodynamic instability at the time of intervention. Severe chronic renal insufficiency (plasma/ serum creatinine> 2.5 mg/dL) at the time of intervention, except in patients on dialysis.