Background and Purpose—Inflammation contributes to brain damage caused by ischemic stroke. Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI allows noninvasive monitoring of macrophage recruitment into ischemic brain lesions. In this study, we determined the extent of USPIO enhancement during early stages of ischemic stroke.

Methods—Twelve consecutive patients with typical clinical signs of stroke underwent multimodal stroke imaging at 1.5-T within 24 hours of symptom onset. They received intravenous USPIO (ferumoxtran) infusion at 26 to 96 hours (mean, 44 hours) after stroke. A total of four follow-up MRI scans were performed 24 to 36 hours, 48 to 72 hours, 7 to 8 days, and 10 to 11 days after USPIO infusion.

Results—Nine patients were included in the final analysis. Parenchymal USPIO enhancement occurred in 3 of 9 analyzed patients and was mainly evident on T1-weighted spin-echo images. USPIO-dependent signal changes were spatially heterogeneous, reflecting the distinct patterns of hematogenous macrophage infiltration in different lesion types.

Conclusions—Our findings suggest a variable extent and distribution of macrophage infiltration into early ischemic stroke lesions. USPIO-enhanced MRI may help to more specifically target antiinflammatory therapy in patients with stroke.