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

Abstract

Background. 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.Methods and Results. 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 5 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 5 0.44-0.59, P < 0.02).Conclusions. 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. (J Nucl Cardiol 2017)

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

“…Our interpretation of this finding is that the plaque inflammation we can detect with 18 F-FDG PET is homogeneously spread out, and also present in the extreme tails of the plaque. This was also one of our main findings when we explored associations between different 18 F-FDG uptake parameters and plaque inflammation at histopathology [17]. Furthermore, this is in accordance with the study results from Kwee et al [12] who found a strong correlation between TBRs of ipsilateral symptomatic plaques and contralateral asymptomatic plaques and supports the hypothesis that plaque inflammation is systemic to some extent.…”

“…A strength of our study is a relatively large patient population with a wide range of uptake values (max SUV max from 1.18 to 2.66) representing low to high plaque inflammatory activity confirmed by histology [17].…”

“…The background was calculated as the mean of the SUV mean in these four ROIs. Different measures of 18 F-FDG uptake were calculated (Table 2) as previously described in detail [17]. Blood background corrected values were calculated as the 18 F-FDG uptake values divided by the mean blood pool activity (TBR) and subtraction of the blood pool activity from the 18 F-FDG uptake values (corrected SUV (cSUV)).…”

Technical considerations for quantification of 18F-FDG uptake in carotid atherosclerosis

“…Johnsrud et al 1 recruited 44 patients with carotid artery atherosclerosis associated with[70% stenosis for 18 F-FDG PET/CT. Of these patients, 30 underwent endarterectomy and histological assessment of inflammation to evaluate the correlation between different 18 F-FDG uptake quantification methods and histological indices of inflammation.…”

“…In this issue of the Journal of Nuclear Cardiology, Johnsrud et al 1 have explored the correlation between different quantification methods of 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake and plaque inflammation in endarterectomy specimens of patients with severe carotid stenosis. It has been over a decade since the initial reports of 18 F-FDG accumulation in unstable carotid plaques and its correlation with indices of plaque vulnerability.…”