18F-FDG PET/CT for the quantification of inflammation in large carotid artery plaques

There is currently no consensus on the methodology for quantification of 18 F-FDG uptake in inflammation in atherosclerosis. In this study, we explore different methods for quantification of 18 F-FDG uptake in carotid atherosclerotic plaques and correlate the uptake values to histological assessments of inflammation. Forty-four patients with atherosclerotic stenosis ≥70% of the internal carotid artery underwent 18 F-FDG PET/CT. Maximum standardized uptake values (SUV max ) from all plaque-containing slices were collected. SUV max for the single highest and the mean of multiple slices with and without blood background correction (by subtraction (cSUV) or by division (target-to-background ratio (TBR)) were calculated. Following endarterectomy 30 plaques were assessed histologically. The length of the plaques at CT was 6-32 mm. The 18 F-FDG uptake in the plaques was 1.15-2.66 for uncorrected SUVs, 1.16-3.19 for TBRs, and 0.20-1.79 for cSUVs. There were significant correlations between the different uptake values ( r = 0.57-0.99, P < 0.001). Methods with and without blood background correction showed similar, moderate correlations to the amount of inflammation assessed at histology ( r = 0.44-0.59, P < 0.02). In large stenotic carotid plaques, 18 F-FDG uptake reflects the inflammatory status as assessed at histology. Increasing number of PET slices or background correction did not change the correlation.