Inter-reader agreement of 18F-FDG PET/CT for the quantification of carotid artery plaque inflammation

Abstract

Introduction A significant proportion of ischemic strokes are caused by emboli from unstable atherosclerotic carotid artery plaques. Inflammation is a key feature of plaque instability. Positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-(18F)-fluoro-D-glucose (18F-FDG) is a promising technique to quantify plaque inflammation, but a consensus on the methodology has not been established. High inter-reader agreement is essential if 18F-FDG PET/CT is to be used as a clinical tool for the assessment of unstable plaques and stroke risk. Methods We assessed the inter-reader variability of different methods for quantification of 18F-FDG uptake in 43 patients with carotid artery stenosis ≥70%. Two independent readers delineated the plaque and collected maximum standardized uptake value (SUVmax) from all axial PET slices containing the atherosclerotic plaque. Results Uptake values with and without background correction were calculated and intraclass correlation coefficients were highest for uncorrected uptake values (0.97–0.98) followed by those background corrected by subtraction (0.89–0.94) and lowest for those background corrected by division (0.74–0.79). Conclusion Quantification methods without background correction have the highest inter-reader agreement for 18F-FDG PET of carotid artery plaque inflammation. The use of the single highest uptake value (max SUVmax) from the plaque will facilitate the method’s clinical utility in stroke prevention.