Vascular Inflammation in Subclinical Atherosclerosis Detected by Hybrid PET/MRI

Background: Atherosclerosis is a chronic inflammatory disease, but data on arterial inflammation at early stages is limited. Objectives: The purpose of this study was to characterize vascular inflammation by hybrid ¹⁸ F-fluorodeoxyglucose ( ¹⁸ F-FDG) positron emission tomography/magnetic resonance imaging (PET/MRI). Methods: Carotid, aortic, and ilio-femoral ¹⁸ F-FDG PET/MRI was performed in 755 individuals (age 40 to 54 years; 83.7% men) with known plaques detected by 2-/3-dimensional vascular ultrasound and/or coronary calcification in the PESA (Progression of Early Subclinical Atherosclerosis) study. The authors evaluated the presence, distribution, and number of arterial inflammatory foci (increased ¹⁸ F-FDG uptake) and plaques with or without inflammation (coincident ¹⁸ F-FDG uptake). Results: Arterial inflammation was present in 48.2% of individuals (24.4% femorals, 19.3% aorta, 15.8% carotids, and 9.3% iliacs) and plaques in 90.1% (73.9% femorals, 55.8% iliacs, and 53.1% carotids). ¹⁸ F-FDG arterial uptakes and plaques significantly increased with cardiovascular risk factors (p < 0.01). Coincident ¹⁸ F-FDG uptakes were present in 287 of 2,605 (11%) plaques, and most uptakes were detected in plaque-free arterial segments (459 of 746; 61.5%). Plaque burden, defined by plaque presence, number, and volume, was significantly higher in individuals with arterial inflammation than in those without (p < 0.01). The number of plaques and ¹⁸ F-FDG uptakes showed a positive albeit weak correlation (r = 0.25; p < 0.001). Conclusions: Arterial inflammation is highly prevalent in middle-aged individuals with known subclinical atherosclerosis. Large-scale multiterritorial PET/MRI allows characterization of atherosclerosis-related arterial inflammation and demonstrates ¹⁸ F-FDG uptake in plaque-free arterial segments and, less frequently, within plaques. These findings suggest an arterial inflammatory state at early stages of atherosclerosis.