The FeraSpin Series comprises six superparamagnetic iron oxide (SPIO) and undltrasmall (USPIO) particles specifically formulated for pre-clinical magnetic resonance imaging (MRI): FeraSpin XS, FeraSpin S, FeraSpin M, FeraSpin L, FeraSpin XL, and FeraSpin XXL. Their well-defined sizes allow for MRI studies that rely on specific particle sizes.
FeraSpin XS to XXL are agents of high relaxivity and enhance the contrast in T1- as well as T2- and T2*-weighted MRI. The T2 effect increases with increasing particle size whereas the T1 effect increases with decreasing particle size. Upon accumulation in cells, the T1 effect diminishes and the T2 effect increases.
Upon intravenous injection, all agents of this series circulate in the bloodstream and are taken up by macrophages. They accumulate in the liver and spleen and are degraded within a few days. The iron is transferred into the physiological iron stores.
Uptake by macrophages depends on the particle size. Uptake by the Kupffer cells (macrophages of the liver) increases with particle size, thus leading to rapid accumulation in the liver and spleen and a short blood circulation time. With decreasing particle size, the uptake by the Kupffer cells is reduced, leading to a prolonged circulation time and increased uptake by other macrophages.
FeraSpin XS shows the longest blood circulation time among the FeraSpin products and therefore is particularly suited for vascular studies. This USPIO particle has the highest T1 effect and is specifically formulated for magnetic resonance angiography (MRA).