The possibility to identify the risk of rupture of a carotid plaque will have tremendous impact in clinical decision making. A vulnerable plaque is considered to have a large lipid rich necrotic core (LRNC), a thin fibrous cap, the presence of inflammatory cells, intraplaque haemorrhage and/or neovascularisation (vasa vasorum). The investigators aim to validate imaging of plaque vulnerability with histology. Previous studies have evaluated the use of imaging to assess carotid plaque vulnerability, mostly showing a good correlation between imaging and histology and/or clinical characteristics. However, they have focused on single modalities, (magnetic resonance imaging [MRI], multidetector-row computed tomography (MDCT), ultrasonography (US) or transcranial Doppler (TCD), and have used relatively small cohorts

The primary goal of this study is to investigate whether there is a correlation between neovascularisation in the carotid atherosclerotic plaque as observed with 3.0 Tesla dynamic contrast-enhanced MRI and histology. Moreover, the investigators aim to investigate the correlation between the volume of the LRNC as determined by dual-energy CT and histology.

Secondly, the investigators will investigate the correlation between the volume of the LRNC, the fibrous cap status and the volume of the calcifications determined by MRI versus histology, the correlation between number of microembolisms and fibrous cap status and the correlation between the deformation pattern seen with ultrasound and the volume of the LRNC.

The imaging parameters showing good correlation with plaque vulnerability characteristics can be used for further analysis in assessing the vulnerable plaque

Inclusion Criteria:

• Patients with a carotid artery stenosis, who are scheduled for carotid endarterectomy

• Age 18 years or older (no maximum age)

• Informed consent by signing informed consent form regarding this study

• Inclusion criteria for carotid endarterectomy

  1. Symptomatic carotid artery stenosis 70-99% within 3 months of neurological symptoms
  2. Symptomatic carotid artery stenosis 50-99% in man within 2 weeks of neurological symptoms
  3. Asymptomatic carotid artery stenosis 70-99% with contralateral occlusion

Exclusion Criteria:

• Severe co-morbidity, dementia or pregnancy
• Standard contra-indications for MRI (ferromagnetic implants like pacemakers or other electronic implants, metallic eye fragments, vascular clips, claustrophobia, etc.)
• Patients who have a documented allergy to MRI or CT contrast media
• Patients with a renal clearance <30 ml/min are not eligible to undergo contrast-enhanced MRI
• Patients with a renal clearance <60 ml/min are not eligible to undergo CT
• Surgery planned within 4 days of inclusion

Patients with a carotid artery stenosis, who are scheduled for carotid endarterectomy, will be included.