18FDG-PET-CT: an imaging biomarker of high-risk carotid plaques. Correlation to symptoms and microembolic signals.

BACKGROUND AND PURPOSE: We investigated whether uptake of (18)fluoro-2-deoxy-d-glucose (18FDG) positron emission tomography-computed tomography (PET-CT) correlated to clinical symptoms and presence of microembolic signals (MES) detected by transcranial Doppler in patients with carotid stenosis. METHODS: 18FDG-PET-CT and MES detection was performed in consecutive patients with 50% to 99% symptomatic or asymptomatic carotid stenoses. Uptake index was defined by a target to background ratio (TBR) between maximum standardized uptake value of the carotid plaque and the mean standardized uptake value of the jugular veins. End points for analysis were presence of symptoms and presence of MES. RESULTS: We included 123 stenosis derived from 110 patients, 60 symptomatic and 63 asymptomatic. MES positive (+) lesions were found in 16%. TBR values were higher in symptomatic compared with asymptomatic (median 2.07 versus 1.78; P<0.0018) and in MES+ compared with MES- plaques (median 2.14 versus 1.86; P<0.008). TBR values were also higher in asymptomatic MES+ compared with MES- plaques (median 1.97 versus 1.76; P<0.03). The best TBR threshold value for symptomatic versus asymptomatic, for MES+ versus MES-, for symptomatic MES+ versus symptomatic or asymptomatic MES-, and for asymptomatic MES+ versus asymptomatic MES- plaques was 1.9. Sensitivity/specificity were, respectively, 56/77%, 73/63%, 79/64%, and 80/77%. We found a strong correlation between number of MES and TBR values (ρ 0.26; P=0.0043). CONCLUSIONS: 18FDG-PET-CT accurately detected high-risk carotid plaques. Also given its strong correlation to MES, 18FDG-PET-CT may be a useful tool in clinical practice.

Contrast-enhanced ultrasound imaging of carotid plaque neo-vascularization: accuracy of visual analysis.

The aim of our study was to evaluate whether neo-vascularization of the carotid plaque can be accurately assessed by visual analysis of contrast-enhanced ultrasound images and whether these findings correlate with intensity-over-time curve analysis (ITC) and histopathology. Patients with ≥50% symptomatic or ≥60% asymptomatic stenosis according to European Carotid Surgery Trial criteria were included. Four investigators evaluated contrast enhancement visually (three grades), with positive agreement when three or more investigators were unanimous. ITC analysis of contrast enhancement was performed in the plaque and in the lumen. Histopathology (microvessel density with CD34 + staining) was completed when endarterectomy was performed. Visual grading (33 patients, inter-observer agreement = 94%) correlated significantly with ITC analysis (p = 0.03). Histopathology (n = 19) revealed a larger CD34 + area in patients with grade 1/2 versus grade 0 (p = 0.03). Visual analysis of neo-vascularization by means of contrast-enhanced ultrasound imaging is accurate and reproducible, with significant correlations with ITC and histopathology.