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

•22 nm and 30 nm γ-Fe2O3 nanoparticles were synthesized using sol-gel method.•The size was found to affect the contrast enhancement of the MRI image.•T2 for 22 nm sized γ-Fe2O3 nanoparticles exhibited a shorter dephasing compared to the 30 nm nanoparticles.•T2 relaxivity also decreased with increasing concentration (9–84 µg/ml) of the γ-Fe2O3.•γ-Fe2O3 nanoparticles are promising materials for use as MRI contrast agents. 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.