The primary aim of this project is to assess if advanced ultrasound methods such as SMI (Superb microvascular Imaging) and SWE (Shear Wave Elastography) can identify intraplaque neovascularization and plaque tissue stiffness in carotid artery plaques and relate these results to ipsilateral cerebrovascular symptoms.

The secondary aim of this project is to assess the level of agreement between the structural plaque characteristics assessed by advanced ultrasound examinations such as SMI, SWE, CEUS (Contrast enhanced ultrasound), GSM (Plaque gray-scale-median) and carotid MRI, metabolic activity of plaque assessed by 18F-FDG PET/CT with histology as the gold standard. Findings from the methods mentioned above will be related to cerebrovascular symptoms, blood tests (cholesterol-tot, LDL, HDL, CRP, leukocytes, glucose, HbA1c) and other cardiovascular risk factors at inclusion and upon 1 year follow up.

The project will include 3 studies:

Study 1:

Analyse the correlation between SMI assessed neovascularization and degree of stenosis in symptomatic patients with high-grade (>50%) carotid stenosis versus asymptomatic patients with high-grade (>50%) carotid stenosis.

All patients upon inclusion will undergo:

• Clinical, neurological evaluation
• Blood tests
• SMI, CEUS and SWE ultrasound
• Carotid MRI
• PET (subgroup)
• DW-MRI
• Histological assessments after the removal of plaque at carotid endarterectomy (CEA).

Study 2:

SMI and vascular events. Asymptomatic patient's follow-up at 12 months:

• Clinical neurological evaluation
• Blood test
• SMI, CEUS, SWE ultrasound
• Carotid MRI
• PET (subgroup)

Study 3:

This study will use the same patient pool described in study 1 undergoing the previously described procedural examinations upon inclusion and at one year follow up. Quantification of stiffness/elasticity in the artery wall will be performed and compared to plaque echogenicity measured as GSM . These results will be correlated to histology of the carotid plaque after trombendarterectomy, risk markers in blood (lipids, HbA1c, CRP, leukocytes), other cardiovascular risk markers (hypertension, diabetes, nicotine) and cerebrovascular symptoms.

Inclusion Criteria:

• Atherosclerotic carotid stenosis >50% with or without cerebrovascular symptoms.

Exclusion Criteria:

• Malignancies
• Inflammatory disease

• All patients with an atherosclerotic carotid stenosis >50% admitting department of neurology, Oslo University Hospital, Rikshospitalet as an in-patient or an out-patient will be considered for inclusion