Imaging intraplaque inflammation in carotid atherosclerosis with 18F-fluorocholine positron emission tomography-computed tomography

Abstract

Background - 18 F-fluorocholine (18 F-FCH) uptake is associated with cell proliferation and activity in tumor patients. We hypothesized that 18 F-FCH could similarly be a valuable imaging tool to identify vulnerable plaques and associated intraplaque inflammation and atheroma cell proliferation. Methods and Results - Ten consecutive stroke patients (90% men, median age 66.5 years, range, 59.4-69.7) with ipsilateral >70% carotid artery stenosis and who underwent carotid endarterectomy were included in the study. Before carotid endarterectomy, all patients underwent positron emission tomography to assess maximum 18 F-FCH uptake in ipsilateral symptomatic carotid plaques and contralateral asymptomatic carotid arteries, which was corrected for background activity, resulting in a maximum target-to-background ratio (TBRmax). Macrophage content was assessed in all carotid endarterectomy specimens as a percentage of CD68 + -staining per whole plaque area (plaqueCD68 +) and as a maximum CD68 + percentage (maxCD68 +) in the most inflamed section/plaque. Dynamic positron emission tomography imaging demonstrated that an interval of 10 minutes between 18 F-FCH injection and positron emission tomography acquisition is appropriate for carotid plaque imaging. TBRmax in ipsilateral symptomatic carotid plaques correlated significantly with plaqueCD68 + (Spearman's ρ=0.648, P=0.043) and maxCD68 + (ρ=0.721, P=0.019) in the 10 corresponding carotid endarterectomy specimens. TBRmax was significantly higher (P=0.047) in ipsilateral symptomatic carotid plaques (median: 2.0; interquartile range [Q1-Q3], 1.5-2.5) compared with the contralateral asymptomatic carotid arteries (median: 1.4; Q1-Q3, 1.3-1.6). TBRmax was not significantly correlated to carotid artery stenosis (ρ=0.506, P=0.135). Conclusions - In vivo uptake of 18 F-FCH in human carotid atherosclerotic plaques correlated strongly with degree of macrophage infiltration and recent symptoms, thus 18 F-FCH positron emission tomography is a promising tool for the evaluation of vulnerable plaques.