Natural History of Atherosclerosis

Inclusion Criteria: * stable carotid artery disease not requiring revascularization * asymptomatic carotid artery stenosis \< 80% or symptomatic patients with stenosis \< 60 % * prophylactic therapy with aspirin (\> 100mg/day, statin, blood pressure therapy if indicated (goal \< 130/80 mmHg)) * informed consent Exclusion Criteria: * non atherosclerotic occlusive disease (Bürgers disease) * uncontrolled BP (DBP \> 110 mmHg and/or SBP \> 200 mmHg) * hemorrhagic disease or platelet count \< 100'000 mm\^3 * Known active liver disease (elevations of GPT GOT or increased ammonia) * impaired renal function (crea \> 180 mmol/l) * pregnancy * severe claustrophobic reactions * short - term life - threatening pathology * physically unable to participate in the study * compliance not guaranteed