Potential of magnetic resonance plaque imaging using superparamagnetic particles of iron oxide for the detection of carotid plaque

Macrophages and by-products are important in plaque destabilization in atherosclerosis. Ultra-small superparamagnetic particles of iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging may be suitable for the detection of macrophages in atherosclerotic plaques. The present study investigated the potential of MR plaque imaging using SPIO in 10 patients scheduled for carotid endarterectomy before and 24-43 hours after administration of SPIO (fercarbotran, 0.016 ml/kg). Three-dimensional gradient recalled acquisition in the steady state (3D-GRASS) was used for detecting macrophages within plaques. Signal loss on the post-contrast 3D-GRASS images was found in 5 of 10 cases, and accumulation of SPIO particles in the vessel wall was confirmed in 4 of these 5 cases. Intracytoplasmic localization of SPIO particles within recruited macrophages was verified by double staining analysis. A correlation between MR plaque imaging using SPIO and localization of macrophages was demonstrated in 6 of 10 patients. This study indicates that MR plaque imaging using SPIO is a potential functional imaging tool to detect infiltration of macrophages in human atherosclerotic carotid plaque.