Iron oxide particle-enhanced MRI suggests variability of brain inflammation at early stages after ischemic stroke

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.