Iron-Enhanced MRI in Ischemic Stroke: Intravascular Trapping Versus Cellular Inflammation

To the Editor:With great interest we read the article by Wiart et al on the application of ultrasmall superparamagnetic iron oxide particles (USPIO) as MR contrast medium in experimental stroke.1 Iron particles were administered 5 hours after permanent occlusion of the middle cerebral artery (pMCAO). Subsequent MRI investigations were performed from 6 to 72 hours after pMCAO. Already 6 hours after pMCAO and 1 hour after iron particle injection a hypointense rim surrounding the ischemic lesion was present indicating focal iron deposition. This rim-like signal loss persisted until 72 hours post-pMCAO. Surprisingly, on histology at 24 hours only few F4/80-positive cells …