Inclusion Criteria1. Patients above 40 years of age with carotid artery stenosis that do not achieve criteria for CEA (<50% for men, <70% for women, by NASCET criteria) or the patient has declined CEA.
2. Patients above 40 years of age with atherosclerotic disease of aortic arch and its branches.
Exclusion Criteria1. Patients with new stroke and a modified Rankin score >3
2. Chronic kidney disease with an estimated Glomerular Filtration Rate (eGFR) of <30 ml/min/1.73 m2
3. Atrial fibrillation
4. Pregnant women
5. Prior ipsilateral carotid intervention
6. Prior neck radiotherapy
7. Inability to tolerate the supine position
8. Participation in the study would result in delay to surgery
9. Psychiatric illness/social situations that would limit compliance with study requirements
10. History of allergic reaction attributed to 18F-Fluoride
11. History of allergic reaction to gadolinium contrast media
12. Metal implants or devices including pacemakers and defibrillators