Supplementary Material for: Imaging of Carotid Plaque Neovascularization by Contrast-Enhanced Ultrasound and Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Background: Carotid plaque neovascularization (vasa vasorum [VV]) may be useful for detecting high-risk atherosclerotic plaques. Contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are 2 commonly used techniques for imaging VV of the carotid plaque, yet the relationship between their measurements remains unknown. Objectives: We aimed to blindly evaluate the correlation between CEUS and DCE-MRI in measuring carotid plaque VV. Methods: We recruited subjects with asymptomatic carotid stenosis (≥50%). VV was graded by CEUS, based on richness of contrast signal, according to 3 different methods named CEUS_A, CEUS_B and CEUS_C on different point scales (the higher the values, the higher the estimated VV). A 3.0 T MRI scanner was used for VV quantification by DCE-MRI using gadolinium contrast kinetic modelling for computing the fractional plasma volume (vp) and transfer constant (K^trans). Results: The analysis included 30 patients. A significant correlation between CEUS and DCE-MRI findings was observed when CEUS_C was used for neovessel grading and DCE-MRI was used to determine adventitial (r = 0.460, p = 0.010) and plaque (r = 0.374, p = 0.042) Ktrans values. CEUS_B (r = 0.416, p = 0.022) and CEUS_C (r = 0.443, p = 0.014) grading showed a significant correlation with regard to the maximal K^trans. Conclusions: We found a positive but weak correlation and a moderate diagnostic agreement between neovessels as visually graded by CEUS and adventitial neovessels assessed by DCE-MRI K^trans in carotid atherosclerosis. These findings may help in understanding how VV density, flow, and permeability influence in vivo measurements by CEUS and DCE-MRI as well as in selecting the most appropriate variables and imaging method in future research and potentially in clinical settings. Further confirmative studies are necessary to confirm our results.