The application of magnetic resonance ultrasmall magnetic Fe3O4 nano bimodal contrast agent in rabbit orthotopic liver tumors

To investigate the diagnostic value of ultra-small superparamagnetic Fe3O4 nanoparticles as dual modal contrast agent in rabbit orthotopic liver tumor. Twenty-four New Zealand rabbits with orthotopic liver tumor were randomly divided into experimental group and control group. The experimental group contained 12 rabbits which intravenously injected with Fe3O4 nanoparticles and the control group contained 12 rabbits which intravenously injected with Gd-DTPA. After injection, the cross-sectional T1 and T2-weighted scan images of experimental group and cross-sectional T1-weighted scan images of control group were obtained at the different timepoints (including 0, 5, 15, 20, 30, 45, 60, 75, 90, 120, 180, and 240 min) with a clinical 3.0 T MRI scanner. The SNR value of the tumor site and the normal liver site at different time points were calculated, respectively, and then the signal change value (CNR) of the tumor relative to the normal liver tissue was obtained. The r1 value of Fe3O4 nanoparticles was significantly higher than Gd-DTPA (6.97 mM(-1) s(-1) for Fe3O4 nanoparticles and 4.75 mM(-1) s(-1) for Gd-DTPA and only Fe3O4 nanoparticles exhibited the r2 relaxation rate which was 22.53 mM(-1) s(-1)). In addition, the r2/r1 ratio of Fe3O4 was 3.23 which also demonstrated the strong MR relaxation characteristics of Fe3O4 nanoparticles. Compare with clinical used MRI contrast agent (Gd-DTPA), the ultra-small magnetic Fe3O4 nanoparticles not only showed the better T1 contrast enhancement but also exhibited the T1/T2 dual-modal enhanced contrast ability, which could improve the accuracy and sensitivity of MRI diagnosis and realize the early diagnosis of diseases in prospect.