Identification of Plaque Vulnerability Wit PET/MRI: a Feasibility Study of 18F-Flutemetamol in Atherosclerosis

Rationale: Amyloid beta (Ab) is mainly known for its role in Alzheimer's disease (AD) pathology. However, Ab seems not only to be involved in AD pathology, but also in atherosclerosis, which might explain the remarkable similarities in risk factors between these two pathologies. In vitro studies suggest that a major part of this association is based on the ability of amyloid to lead to macrophage activation and thus inflammation. These data lead to the hypothesis that Ab is associated with plaque vulnerability.

18F-Flutemetamol is a PET tracer with high affinity for Ab. This has been extensively studied in AD patients.

Objective: To validate 18F-Flutemetamol PET in the evaluation of plaque vulnerability.

Study design: A cross-sectional validation study. Study population: 25 adults, who have recently (<14days) experienced a transient ischemic attack (TIA) or stroke with a carotid artery plaque of ≥30% and without evidence of another etiology than carotid atherosclerosis (i.e. cardiac or small vessel).

Of these 25 patients, 10 patients will be included who have been scheduled for carotid endarterectomy (CEA). The other 15 will be selected of patients who are not scheduled to undergo CEA.

Intervention: All patients will undergo a PET/MRI scan with 18F-Flutemetamol, either before the scheduled CEA or within the first 30 days following the cerebrovascular event. Imaging will include the carotid and coronary arteries as well as the brain.

Main study parameters/endpoints: Tracer uptake in the carotid artery will be correlated to vulnerable plaque characteristics as assessed by MRI. In the 10 CEA patients, tracer uptake and MR imaging of different plaque characteristics will be validated with plaque histology of the surgically removed specimen.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: There is no additional benefit for study subjects. Study subjects will receive the same treatment as non-participating patients. Patients will be screened for in- and exclusion criteria to minimize risks.

For optimal MR imaging patients will be injected with a Gadolinium based contrast agent, which is a common procedure and associated with very low risk of complications. The PET tracer 18F-flutemetamol has been studied extensively and is currently used in patients with AD. Adverse events were not frequent and mainly mild. The radioactivity dose will be around 6.8 mSv.