Objective:To establish a rodent model of VX2 tumor of the spleen,to analyze relationship between the change of the signal intensity on superparamagnetic iron oxide enhanced magnetic resonance image(MRI)and pathologic change to evaluate the ability of superparamagnetic iron oxide enhanced MRI for detection of splenic metastases.Methods:8 rodent models of VX2 tumor of spleen were established successfully.The images were obtained before and after administration of superparamagnetic iron oxide.T1-weighted spin-echo(SE)pulse sequence with a repetition time(TR)of 450 msec,and echo time(TE)of 12 msec(TR/TE=450/12)was used.The imaging parameters Of T2-weighted SE pulse sequence were as follows:TR/TE=4000/128. Results:On plain MR scanning T1-weighted splenic VX2 tumor showed hypointensity or isointensity which approximated to the SI of splenic parenchyma.Therefore all lesions were not displayed clearly.On superparamagnetic iron oxide enhancement T2WI sequence the SI of splenic parenchyma decreased obviously with percentage of signal intensity loss(PSIL)of 55.04%,But the SI of tumor was not evidently changed with PSIL of 0.87%. Nevertheless the SNR of normal splenic parenchyma around the lesions had obvious difference(P＜0.001)comparatively.Therefore the contrast between tumor and spleen increased.and tumor displayed more clearly.Moreover the contrast-to-noise(CNR)between VX2 tumor and splenic parenchyma had an evident difference before and after admininstration of superparamagnetic iron oxide(P＜0.001).Conclusion:On superparamagnetic iron oxide enhancement T1WI sequence the contrast of tumor-to-spleen is poor.Therefore it is not sensitive to characterize the lesions in spleen.On superparamagnetie iron oxide enhanced T2WI the contrast degree of lesions increases obviously.Consequently, superparamagnetic iron oxide-enhanced T2WI MRI scanning can improve the rate of detection and characterization for lesions of spleen.