Combined Application Of¹⁸F-FDG PET/CT And MRI Imaging In Early Diagnosis Of Carotid Atherosclerotic Vulnerable Plaques

Objective: To assess the correlations between plaque characteristics （includingfibrous cap thickness, plaque components and plaque burden） and inflammatoryactivity in carotid atherosclerotic by combined use of two non-invasive imagingmethods-¹⁸F-FDG PET/CT and MRI.Methods: Thirty one carotid atherosclerosis patients were scanned with PET/CTand MRI. These two kinds of images were compared according to anatomylandmarks such as carotid bifurcation. Next we selected the regions of interest（ROI） to calculate the TBR values reflecting the¹⁸F-FDG uptake amounts. Thenthe mean vessel wall thickness, total vessel area, lumen area, vessel wall area andnormalized wall index were calculated and their correlations with TBR wereanalyzed. According to CT, MRI T2W and MRI PDW images, the plaques sliceswere divided into ‘calcification group’,‘collagen group’,‘lipid group’ and‘hemorrhage group’; meanwhile, according to integrity and thickness of fibrouscap, the plaques were divided into ‘ruptured fibrous cap group’,‘thin fibrous capgroup’ and ‘thick fibrous cap group’. The TBR values of the above groups werecomparatively analyzed.Results:（1） The TBR values decreased in order of ‘ruptured fibrous capgroup’>‘thin fibrous cap group’>‘thick fibrous cap group’（p <0.001）.（2） TheTBR values of ‘lipid group’ and ‘hemorrhage group’ were significantly higherthan that of ‘calcification group’ and ‘collagen group’. In addition,‘lipid group’showed no significant difference with ‘hemorrhage group’;‘calcification group’and ‘collagen group’ showed no difference.（3） TBR weakly correlated with themean vessel wall thickness （r=0.231, p <0.001）, vessel wall area （r=0.203, p <0.001）, and normalized wall index （r=0.192, p <0.001）. Conclusion: Combination of non-invasive¹⁸F-FDG PET/CT and MRI methodscould be applied in qualitative and quantitative diagnosis of carotid atheroscleroticplaques, including analyses of plaque size, components, fibrous cap andinflammatory activities. Our data showed that thin or ruptured plaques, lipid-richplaques and hemorrhagic plaques possessed high inflammatory activities.