Objective  To analyze the MRI signaling characteristics of ultra-small superparamagnetic iron oxide (USPIO) and GoldMag-Coreshell (GoldMag) at different concentrations and to study the appropriate MR imaging methods.   Methods  USPIO and GoldMag were diluted with phosphate-buffed solution (PBS) into 47 samples at the concentration

s of 0.5 μg/ml～1 000 μg/ml. MRI was performed at FSE T

1

WI

FSE T

2

WI

and GRE T

2

*WI. Rules of changes in signal intensity of GoldMag and USPIO at different concentrations were observed. The signal intensity change ratio was calculated and concentration-signal intensity curves were plotted.   Results  The MRI signal intensity of USPIO and GoldMag was almost identical. The MRI signal intensity increased at FSE T

1

WI with the increased concentration

decreased slightly at FSE T

2

WI and significantly at GRE T

2

*WI. A significant difference was found in the MRI signal intensity of the two contrast media (＞30 μg/ml

40-90 μg/ml）at FSE T

1

WI and FSE T

2

WI (P＜0.05) but not at GRE T

2

*WI (P＞0.05).   Conclusion  The MRI signal intensity of USPIO and GoldMag is almost identical. GoldMag is a rather ideal nanoparticle contrast agent for MRI molecular imaging

and GRE T

2

*WI is the best imaging sequence for USPIO and GoldMag.