Renal perfusion assessment using magnetic nanoparticles with 7T dynamic susceptibility contrast MRI in rats

Magnetic nanoparticles (MNPs) can be used as magnetic resonance imaging (MRI) contrast agent with dynamic susceptibility contrast (DSC) MRI, which is an important in vivo method to assess organ perfusion with multiple clinical applications. Since variations in particle size and PEGylation of MNPs may potentially influence particle-tissue interactions in the microcirculation, we evaluate their effects on rat kidneys with DSC MRI. Anesthetized Sprague Dawley rats were cannulated for intravenous injection of dextran-coated MNPs (50 nm and 250 nm; 5 mg/kg) with or without PEGylation during acquirement of DSC MRI images. The results demonstrate that both particle size and PEGylation may alter perfusion parameters. Relative mean transit time (rMTT) of 50 nm particles is 1.8 fold of that of 250 nm particles with or without PEGylation. In MNPs of 50 nm, PEGylation is associated with 38% and 25% shorter time-to-peak (TTP) and time from onset to 50% drop from peak (T50), respectively; however, PEGylation exerts no effect on these parameters of 250 nm particles. Nevertheless, particle size or PEGylation exert no influence on the prediction of relative blood flow or relative blood volume of the kidney. In conclusion, DSC MRI is a feasible method to evaluate renal perfusion and properties of MNPs in circulation.