Background and Purpose—Inflammation is a major risk factor for atherosclerotic plaque rupture and clinical events. Previous studies have shown that plaque [¹⁸F]fluorodeoxyglucose (FDG) uptake correlates with macrophage content. In this study we examined the reproducibility of 3 methods of quantifying plaque FDG uptake in the carotid arteries using positron emission tomography (PET). The correlation between 2 simplified uptake parameters (standardized uptake value [SUV], vessel wall-to-blood ratio [VBR]) and a gold standard technique (influx rate [K_i]) was also determined. We used MRI to correct carotid plaque FDG uptake for partial volume error.

Methods—Seven patients with a recent carotid territory transient ischemic attack underwent imaging twice within 8 days using MR and FDG-PET. MR coregistered to PET was used to delineate regions of interest, and to facilitate partial volume correction (PVC).

Results—SUV was the most reproducible parameter irrespective of whether it was normalized by body surface area (BSA), lean body mass, or weight (intraclass correlation coefficient=0.85, 0.88, and 0.90, respectively). VBR correlated better to K_i than SUV (r=0.58 VBR, r=0.46 SUV^BSA). PVC improved these correlations to r=0.81 VBR and r=0.76 SUV^BSA, and only slightly degraded the reproducibility of SUV (intraclass correlation coefficient=0.83–0.85).

Conclusions—MR-guided FDG-PET is a highly reproducible technique in the carotid artery and the excellent anatomic detail provided by MR facilitates PVC. Of the methods examined, SUV^BSA_PVC appears to represent the best compromise between reproducible and accurate determination of FDG metabolism in carotid artery vessel wall.