MR imaging of adventitial vasa vasorum in carotid atherosclerosis

Vasa vasorum in the adventitia of atherosclerotic arteries may play a role in plaque progression. In this investigation, a method for characterizing vasa vasorum in the carotid artery is proposed, in which the perfusion properties of the adventitia are probed via dynamic contrast‐enhanced (DCE) MRI. A parametric “vasa vasorum image” is automatically generated that depicts the plasma volume ( v p ) and transfer constant ( K trans ). The average K trans within the adventitia is proposed as a quantitative measurement related to the extent of the vasa vasorum. In 25 subjects with lesions meeting the requirements for carotid endarterectomy (CEA) significantly higher adventitial K trans of 0.155 ± 0.045 min –1 was observed, compared to 0.122 ± 0.029 min –1 in the remaining 20 subjects with moderate disease ( P < 0.01). In the 25 subjects with endarterectomy specimens, histological evaluation showed that adventitial K trans was significantly correlated with the amount of neovasculature ( R = 0.41; P = 0.04) and macrophages ( R = 0.49; P = 0.01) in the excised plaque. In the remaining 20 subjects without histology, elevated adventitial K trans was significantly correlated with the log of C‐reactive protein (CRP) levels ( R = 0.57; P = 0.01) and was elevated in active smokers compared to nonsmokers (0.141 ± 0.036 vs. 0.111 ± 0.017 min –1 ; P = 0.02). Because these factors are all associated with higher risk of atherosclerotic complications, these results suggest that adventitial K trans may be a marker of risk as well. Magn Reson Med 59:507–514, 2008. © 2008 Wiley‐Liss, Inc.