Size analysis of carboxydextran coated superparamagnetic iron oxide particles used as contrast agents of magnetic resonance imaging

Abstract

Superparamagnetic iron oxide particles in commercial products Resovist and SH U555C, used as magnetic resonance imaging contrast agents, are polydispersed and covered with a thick organic coating so that the average particle sizes were reported between 3 and 62nm with different definitions. It is unclear which size determines the transverse relaxation rate 1∕T2 of water suspensions of such particles. Comparing the measured 1∕T2 and average sizes of different definitions determined from magnetization curve, transmission electron microscopy image, x-ray diffraction, and dynamic light scattering, it is found that the 1∕T2 behavior is basically determined by the diameter of bare single-crystal magnetic particles having the particle-volume-weighted average volume (about 14 or 9nm for Resovist or SH U555C) and is slightly influenced by their thick organic coating. This is explained by the low partial density of the coating substance and the overwhelming water occupation adjacent to magnetic particles.

Experimental study on T2 relaxation time of protons in water suspensions of iron-oxide nanoparticles: Effects of polymer coating thickness and over-low

“…This is contradicted to the good agreement between experimental 1=T 2 and Eq. (6) in this regime for water suspensions of iron-oxide nanoparticles [14]. Such a discrepancy may be resolved by noticing that 1=T 2 given by Eq.…”

“…For comparing the measured 1=T 2 of water suspensions of SH U555C and Resovist particles with the modeling 1=T 2 vs. t D curves, the relevant average particle size was chosen in [14] as the average diameter corresponding to the particle-volume-weighted average volume…”

“…This difficulty has been overcome in [13], where a technique of particle size determination from magnetization measurements is proposed. Using a certain average particle size determined by this technique, the measured 1=T 2 of water suspensions of superparamagnetic iron-oxide particles of commercial products Resovist and SH U555C has been compared with its theoretical values [14]. It is found that the theoretical 1=T 2 is larger than the experimental one by about 20% for both cases, and the difference may be reasonably attributed to the effect of organic coating.…”

Synthesis and properties of magnetite/hydroxyapatite/doxorubicin nanocomposites and magnetic liquids based on them

“…We note that analysis of the sizes of superparamagnetic iron oxide nanoparticles coated with a layer of carboxydextran, which are applied as contrast agents in magnetic resonance imaging (a commercial product Resovist and SH U555C) using a magnetization curve and images of ensembles of particles, obtained by transmission electron microscopy, has been performed in [38].…”

Magnetic Particle Imaging: Kinetics of the intravascular signal in vivo

“…6 It is important to note that the physical mean iron core diameter as measured by, eg, transmission electron microscopy and vibrating sample magnetometry, is between 5 nm and 15 nm, as described by many working groups, and the clusters contributing most of Resovist's MPI-signal as described in Eberbeck et al 6 contain these smaller particles, as can also be shown by transmission electron microscopy. 6,[15][16][17][18][19] These clusters may also account for a fraction with a larger hydrodynamic diameter than the other particle fractions in Resovist. These would be cleared more rapidly from the blood by the reticuloendothelial system and the MPI signal would decrease more rapidly than the actual concentration of the tracer measured, eg, on MRI.…”