Ultrasmall manganese ferrite nanoparticles as positive contrast agent for magnetic resonance imaging

Magnetic resonance imaging (MRI) has been extensively used as a powerful noninvasive tool in patient healthcare under the assistance of Ti-positive agents or T2-negative agents. The T1-positive agents have distinct signal-enhancing ability to produce higher image contrast and higher spacial resolution in comparison with T2-negative agents which can lower image contrast because their negative signals are often confused with the signals from bleeding, calcification, metal deposits and susceptibility artifacts. The currently clinically used T1-positive agents are dominant with paramagnetic gadolinium (Gd3+) complexes. However the recent discovery of nephrogenic systemic fibrosis (NSF) arisen from Gd-agents in some patients has fostered concerns and restrictions on their clinical use. The pursuit of alternative T1-positive agents has renewed attention given to manganese-based contrast agents