0171: Identification of complicated carotid plaques by adding functional fluorodeoxyglucose-positron emission tomographic imaging to morphological characteristics on computed tomographic angiography

Abstract

We developed a simple semi-quantitative score for the analysis of carotid plaques with FDG-PET-CTA imaging and tested whether adding functional imaging criteria extracted from FDG-PET imaging to morphological plaque characteristics identified with CTA might improve the detection of complicated plaques. Twenty-eight patients scheduled for carotid endarterectomy were imaged with PET after injection of FDG followed by CTA of the supra-aortic trunks. Morphological aspects of plaques identified with CTA and metabolic activity quantified with FDG-PET (Tissue to Background ratio, TBR) were measured in the carotid segment with the highest degree of luminal stenosis and graded using semi-quantitative CT and PET scores. Combined score was calculated for each carotid artery by summing CT and PET scores. After carotid endarterectomy, vascular surgeons classified carotid plaques macroscopically as complicated or non-complicated. Twenty-eight carotid arteries were operated in 26 patients (24 symptomatic patients). Sixteen plaques were classified macroscopically as complicated. CTA detected hypodense regions and ulcerations in 81% and 25%, of complicated plaques, and in 33% and 0% of non-complicated plaques, respectively. Hypodense areas on CTA identified complicated plaques with a sensitivity of 87% and a specificity of 67%. Mean TBR with FDG-PET was measured at 2.2±0.4 in complicated plaques and 1.9±0.3 in non-complicated plaques (p<0.05). Values for the semi-quantitative score based on plaques characteristics with CTA and FDG-PET were 5.4±1.7 in complicated plaques and 2.5±2.4 in non-complicated plaques (p<0.05). A combined PET-CT score ≥3 identified complicated plaques with a sensitivity of 100% and a specificity of 67%. Adding FDG-PET imaging criteria to morphological characteristics of plaques on CTA improved the sensitivity of the detection of complicated carotid plaques.