Adventitial perfusion and intraplaque hemorrhage: a dynamic contrast-enhanced MRI study in the carotid artery.

BACKGROUND AND PURPOSE Autopsy studies have suggested a relationship between intraplaque hemorrhage (IPH) and vasa vasorum, which arise primarily from the adventitia. Adventitial vasa vasorum can be characterized in the carotid arteries by estimating perfusion parameters via dynamic contrast-enhanced MRI. The purpose of this investigation was to use dynamic contrast-enhanced MRI to test in vivo in a clinical population whether adventitial perfusion, indicative of vasa vasorum microstructure, is associated with IPH. METHODS Symptomatic patients with carotid plaque ipsilateral to the ischemic event underwent bilateral carotid artery MRI examination, which included multicontrast sequences for detecting IPH and a dynamic contrast-enhanced MRI sequence for characterizing adventitial perfusion. Kinetic modeling of the dynamic contrast-enhanced MRI time series was performed to estimate adventitial vp (fractional plasma volume, reflecting local blood supply) and K(trans) (transfer constant, reflecting vessel surface area, and permeability). RESULTS From the 27 patients (22 men; 69 ± 10 years of age) recruited, adventitial perfusion parameters were obtained in 50 arteries. The presence of IPH was associated with a significantly higher value in adventitial K(trans) (0.142 ± 0.042 vs 0.112 ± 0.029 min(-1); P<0.001) but not in vp (0.163 ± 0.064 vs 0.149 ± 0.062; P=0.338). This relationship remained after adjusting for symptomatic status, degree of stenosis, and other confounding factors. CONCLUSIONS This study demonstrated an independent pathophysiological link between the adventitia and IPH and related it to the microstructure of adventitial vasa vasorum. Adventitial perfusion imaging may be useful in studying plaque pathogenesis, but further examination through prospective studies is needed.