Molecular Magnetic Resonance Imaging of Vascular Inflammation After Recanalization in a Rat Ischemic Stroke Model

Abstract

BACKGROUND AND PURPOSE: Brain imaging has become central in the management of acute ischemic stroke. Detection of parenchymal injury and perfusion enables characterization of the extent of ischemic damage, which guides treatment decision-making. Additional assessment of secondary events, such as inflammation, which may particularly arise after recanalization, may improve diagnosis and (supplementary) treatment selection. Therefore, we developed and tested a molecular magnetic resonance imaging (MRI) approach for in vivo detection of vascular inflammation after transient middle cerebral artery occlusion in rats. METHODS: Molecular MRI of VCAM-1 (vascular cell adhesion molecule-1) expression was performed with a targeted contrast agent, in addition to MR angiography, and diffusion-, T2- and perfusion-weighted MRI, from 1 hour until 96 hours after transient middle cerebral artery occlusion in rats. RESULTS: VCAM-1 expression, detected with susceptibility-weighted MRI, was significantly enhanced at 6 hours after recanalization as compared with 1-hour postrecanalization, coinciding with a transient decline in perfusion after initial hyperperfusion. VCAM-1 levels declined after 24 hours, but remained elevated, particularly in lesion borderzones. CONCLUSIONS: The implementation of molecular MRI of vascular inflammation into imaging protocols after acute ischemic stroke could provide complementary information that may guide treatment decision-making before and after recanalization therapy.