Accumulating data in the literature suggests that radiolabeled-choline (18F-choline) is a sensitive molecular tracer for PET imaging that is taken up in activated cells and, as such, is able to identify active inflammatory sites. The investigators hypothesize that 18F-choline is also highly taken up in vulnerable plaques in comparison to the stable ones.

Accumulation and subsequent activation of inflammatory cells in the atherosclerotic plaques play an essential role in transforming a stable plaque into a vulnerable plaque at risk to rupture. On this basis, the study aims to evaluate the diagnostic performance of 18F-choline PET in identifying ongoing inflammation within atherosclerotic plaques. The investigators hypothesize that 18F-choline PET is efficient in detecting intraplaque inflammation and identify vulnerable plaques that are prone to rupture in comparison to the stable ones.

It is likely that by correlating the inflammatory status of an atherosclerotic plaque (on 18F-choline PET) with the presence of other vulnerable plaque features (on MR imaging) would be of high clinical relevance for clinical diagnosis of vulnerable plaques.

Inclusion Criteria:

• Patients known with symptomatic carotid artery stenosis (≥2 mm carotid plaque on duplex ultrasound), who are scheduled in the clinical setting to undergo a carotid endarterectomy or who are referred to conservative therapy;
• Age 18 years and older (no maximum age);
• Informed consent by signing informed consent form regarding this study.

Exclusion Criteria:

• Dementia, pregnancy, nursing mothers;
• Serious neurological deficits at symptomatic side (hemi paralysis, complete aphasia);
• Severe heart failure NYHA III-IV and severe pulmonary dysfunction dependent on oxygen supply;
• Patients with contra-indications for MRI (ferromagnetic implants like pacemakers or other electronic implants, metallic splinters in the eyes, vascular clips, claustrophobia, etc.).