Abstract
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Objectives: Given the importance of inflammation in atherosclerosis, there is a need for a non-invasive method to assess atherosclerotic plaque inflammation. Prior studies have shown that FDG-PET imaging can be used to assess carotid plaque inflammation in humans. We tested the hypothesis that the addition of CT imaging data to PET can enhance characterization of plaque inflammation (vs. PET alone).
Methods: Seven patients with severe carotid stenosis underwent PET/CT imaging within one month prior to carotid endarterectomy (CEA). PET imaging was performed 3 hours after FDG administration (13 mCi), and the ratio of carotid plaque to jugular vein blood pool FDG uptake was determined (T/B). Shortly after FDG administration, 64-slice MDCT imaging was performed. At CEA, the carotid plaques were removed and plaque inflammation was determined (anti-CD68 antibodies). FDG-PET images were analyzed independently of the CT images, and all image analyses were performed blinded to the histology. Based on the results of this analysis, a PET-CT score was calculated, whereby the value for T/B was added to a value derived from the CT images (+1 for presence of hypodense plaque, +1 for presence of ulceration, +2 for presence of both).
Results: Consistent with prior observations, there was a significant correlation between the inflammation measured histologically, and the FDG signal (T/B), (R=0.88, p<0.01). Further, there was a strong correlation between the presence of either plaque ulceration or hypodense plaque (<40 HU) with plaque inflammation (r=0.94, p<.001, and r=0.84, p<0.02, respectively). Moreover, there was a stronger correlation between the PET-CT score for each patient and the macrophage staining from the corresponding histological sections (R=0.96, P<0.0001).
Conclusions: We establish that PET in combination with CT is superior to PET alone for characterization of plaque inflammation. The validity of this PET-CT score requires prospective assessment.
Research Support (if any): GSK Research Grant (Tawakol)
- Society of Nuclear Medicine, Inc.