The significant effect of size and concentrations of iron oxide nanoparticles on magnetic resonance imaging contrast enhancement

In this study, iron oxide (γ-Fe₂O₃) nanoparticles (IONs) were successfully synthesized using sol-gel method, and characterized by XRD and VSM. The potential application of the differently sized IONs (22 nm and 30 nm) as magnetic resonance imaging (MRI) contrast agents was investigated. The relaxation time (T2) of the IONs was measured at room temperature and concentration range of 9–84 µg/ml using fast spin echo sequence with six echoes. The size was found to affect the contrast enhancement of the MRI image, with the T2 for 22 nm sized γ-Fe₂O₃ nanoparticles exhibiting a shorter dephasing compared to the 30 nm sized γ-Fe₂O₃ nanoparticles. The T2 relaxivity also decreased with increasing concentration (9–84 µg/ml) of the γ-Fe₂O₃ nanoparticles. Based on the T2-weighted analysis, a better signal (i.e. brighter image) was achieved for the 30 nm sized γ-Fe₂O₃ nanoparticles. Thus, the use of IONs to enhance MR image contrast is dependent on the nanoparticle size and concentration of the IONs. In general, the results indicate that the synthesized γ-Fe₂O₃ nanoparticles are promising materials for use as MRI contrast agents.