Abstract 518: Characterization of Carotid Atherosclerosis: A Comparison Between PET Activity, Plaque Morphology and Histopathology
Background: While vascular FDG uptake correlates with inflammation, its relationship to plaque morphology remains unclear. Accordingly, we tested the hypothesis that FDG uptake is higher in segments with plaques that have high-risk morphological features (HRM).
Methods: PET (3 hrs after 13 mCi FDG) and contrast-enhanced MDCT imaging were performed on 10 patients with carotid stenosis, within 1 month before carotid endarterectomy (CEA). FDG uptake was reported as target-to-blood background ratio (TBR). HRM features were determined by CT, as presence of: positive remodeling, luminal irregularities/ulceration, or plaque hypodensity (HU<40). Inflammation was measured (CD68 staining) in plaques removed at CEA. Analysis of the PET, CT, and histological data was performed at pre-specified intervals relative to the bifurcation by three independent, blinded investigators.
Results: 19 of the 42 plaques demonstrated at least 1 HRM feature. FDG uptake (TBR) was greater in plaques with (vs. without) at least 1 HRM (2.41±1.11 vs. 1.55±0.42, p<0.005). Specifically, TBR was higher in plaques with (vs. without): positive remodeling (2.90±1.17 vs 1.60±0.46, p<0.001) and hypodensity (2.64±1.34 vs 1.59±0.23, p=0.001), but not luminal irregularities (2.64±1.41 vs 1.80±0.52, p=0.23). CD68 staining was greater in plaques with (vs. without) at least 1 HRM (9.1±10.9 vs. 2.7±5.1, p=0.025).
Conclusions: FDG uptake is greatest in plaques containing high-risk morphological features. While FDG uptake has been loosely described as a vessel-wall phenomenon, these data demonstrate that underlying plaque characteristics are important determinant of FDG uptake.