Combined positron emission tomography (PET) and computed tomography (CT) can assess both anatomy and biology of carotid atherosclerosis. We sought to assess whether 18F-fluoride or 18F-fluorodeoxyglucose can identify culprit and high-risk carotid plaque.
Methods and Results
We performed 18F-fluoride and 18F-fluorodeoxygluose PET/CT in 26 patients following recent TIA or minor ischemic stroke: 18 patients with culprit carotid stenosis awaiting carotid endarterectomy and 8 controls without culprit carotid atheroma. We compared standardized uptake values (SUVs) in the clinically adjudicated culprit to the contralateral asymptomatic artery, and assessed the relationship between radiotracer uptake and plaque phenotype or predicted cardiovascular risk (ASSIGN score). We also performed micro PET/CT and histological analysis of excised plaque.
On histological and microPET/CT analysis, 18F-fluoride selectively highlighted micro-calcification. Carotid 18F-fluoride uptake was increased in clinically adjudicated culprit plaques compared to asymptomatic contralateral plaques (log10SUVmean 0.29±0.10 versus 0.23±0.11, p=0.001) and compared to control patients (log10SUVmean 0.29±0.10 versus 0.12±0.11, p=0.001). 18F-Fluoride uptake correlated with high-risk plaque features (remodeling index [r=0.53, p=0.003]; plaque burden [r=0.51, p=0.004]) and predicted cardiovascular risk [r=0.65, p=0.002]). Carotid 18F-FDG uptake appeared to be increased in 7/16 culprit plaques but no overall differences in uptake were observed in culprit versus contralateral plaques or control patients. However, 18F-FDG did correlate with predicted cardiovascular risk (r=0.53, p=0.019) but not with plaque phenotype.
18F-Fluoride PET/CT highlights culprit and phenotypically high-risk carotid plaque. This has the potential to improve risk-stratification and selection of patients who may benefit from intervention.