Abstract #1826

Irkens M, Oros-Peusquens A, Jander S, Shah N, Saleh A, Schroeter M

We investigate the field inhomogeneities generated by ultrasmall superparamagnetic iron oxide particles (USPIO) accumulation in the rat brain following stroke. Two stroke models are used, one induced by photothrombosis (PT), the other by main cerebral arterial occlusion (MCAO). The inflamation produced by stroke is followed by aninflux of macrophages at the site of the lesion. The time scale of this process depends on the stroke pathophysiology. Macrophages can be visualised in MRI by their strong uptake of USPIO from the vasculature. The effect of USPIO accumulation on the local R2* relaxation properties isinvestigated using a gradient echo sequence with multiple echoes. Strong non-exponential decay of the FID is observed frequently. Correspondingly, the Fourier transform of the FID shows lineshapes with forms significantly deviating from a Lorentzian shape. These lineshapes, intensities and widths aremonitored and mapped in several exemplars, at 2 as well as 7 days following in