Abstract
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. We performed 18F-fluoride and 18F-fluorodeoxyglucose PET/CT in 26 patients after recent transient ischemic attack 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 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 [Assessing Cardiovascular Risk Using SIGN Guidelines to Assign Preventive Treatment]). We also performed micro PET/CT and histological analysis of excised plaque. On histological and micro PET/CT analysis, 18F-fluoride selectively highlighted microcalcification. Carotid 18F-fluoride uptake was increased in clinically adjudicated culprit plaques compared with asymptomatic contralateral plaques (log10standardized uptake valuemean 0.29±0.10 versus 0.23±0.11, P=0.001) and compared with control patients (log10standardized uptake valuemean 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-fluorodeoxyglucose uptake appeared to be increased in 7 of 16 culprit plaques, but no overall differences in uptake were observed in culprit versus contralateral plaques or control patients. However, 18F-fluorodeoxyglucose 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.
Highlights
Combined positron emission tomography (PET) and computed tomography (CT) can assess both anatomy and biology of carotid atherosclerosis
Carotid 18F-fluoride uptake was increased in clinically adjudicated culprit plaques compared with asymptomatic contralateral plaques and compared with control patients. 18F-Fluoride uptake correlated with high-risk plaque features, and predicted cardiovascular risk [r=0.65, P=0.002])
18F-Fluoride positron emission tomography and computed tomography (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
Summary
Two cohorts of people with a recent transient ischemic attack (TIA) or minor ischemic stroke were recruited: a case cohort with a high-grade internal carotid artery stenosis (≥50% by North American Symptomatic Carotid Endarterectomy Trial[25] criteria for men, ≥70% for women) scheduled to undergo carotid endarterectomy and a control cohort in whom the cause of stroke was not attributed to carotid atheroma. Example of 18F-fluoride (A, B, C) and 18F-FDG (D, E, F) positron emission tomography (PET)/computed tomography (CT) of 1 patient before surgery for symptomatic carotid stenosis. Static analysis of 18F-FDG and 18F-fluoride uptake was performed on an OsiriX workstation (OsiriX version 3.5.1 64-bit; OsiriX Imaging Software, Geneva, Switzerland). Inter- and intraobserver reproducibility of 18F-fluoride uptake measurements were determined using a random selection of 12 patients (24 carotids) by 2 experienced observers (A.T.V., G.S.) who were blinded to the clinical data during analysis. Statistical Analysis Radiotracer uptake, expressed as mean and maximum SUV, was compared between the clinically adjudicated culprit carotid plaque and the contralateral side. Areas of macrocalcification showing comparatively little uptake (A, C, F) These examples show that 18F-fluoride provides information of the presence of microcalcification and does not highlight all calcification. Statistical significance was defined as a 2-sided P
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