Abstract 11326: In vivo Study by Dynamic Contrast-enhanced Magnetic Resonance Imaging Suggests Biological Link between Adventitial Perfusion and Outward Remodeling

Abstract

Background: Current knowledge on the role of adventitia in the atherogenic process is mainly from animal and autopsy studies. Adventitia can be highlighted after contrast injection in ultrasound/MRI. Application of dynamic contrast-enhanced MRI (DCE-MRI) to carotid arteries has been shown to generate perfusion parameters of adventitia. We tested whether adventitial parameters derived from DCE-MRI are associated with subsequent arterial remodeling in subjects with subclinical carotid atherosclerosis.

Methods: 41 subjects with 16-79% asymptomatic carotid stenosis by ultrasound and a lipid core on initial MRI completed a follow-up MRI after 6 months. The MRI protocol included multi-contrast axial imaging on 16 slices to measure changes in lumen and outer wall boundaries over the study period. A DCE-MRI sequence was performed at baseline to obtain a time series of first-pass contrast-enhanced images from a subset (4-8) of slices. Kinetic modeling of the time series was performed to estimate adventitial vp (fractional plasma volume) and Ktrans (transfer constant), which reflect the blood supply and vessel permeability, respectively, of adventitia. Slice-based adventitial vp and Ktrans were averaged per artery for artery-based analyses.

Results: Adventitial vp positively correlated with the expansion rate of the outer wall boundary (rho=0.33, p=0.034) but not the lumen boundary (p=0.328). From regression analysis with baseline value as a covariate, adventitial vp was associated with outer wall expansion in the segment with lipid core (p=0.038). In the remaining segment without lipid core, outer wall change did not appear to be associated with adventitial vp (p=0.542). No association was found between adventitial Ktrans and arterial remodeling.

Conclusion: Our preliminary data in subjects with subclinical atherosclerosis suggest that perfusion parameters of adventitia derived from DCE-MRI may be associated with outward remodeling, supporting an active role of adventitia in plaque progression. DCE-MRI may be useful for characterizing adventitia in vivo and facilitate prospective human studies.