Superparamagnetic iron oxide: Enhanced detection of splenic VX2 tumor with magnetic resonance imaging in rats / 中国组织工程研究

ABSTRACT

BACKGROUND:Sensitivity of diagnoses differentiating smaller nodes of splenic metastasis (＜ 1 cm) from CT and MRI is poor. So whether superparamagnetic iron oxide can enhance magnetic resonance imaging (MRI) of splenic VX2 tumor in rats need to be further studied.OBJECTTVE To establish splenic VX2 tumor models, investigate MRI scanning combining with superparamagnetic iron oxide of specific reticuloendothelial system, and study the diagnostic significance of superparamagnetic iron oxide-enhanced MR images on splenic metastases.DESIGN: Duplicated-measured animal study.SETTING: Medical Imaging Center, Nanfang Hospital of the Southern Medical University.MATERIALS The experiment was carried out in the Medical Imaging Center (Military Key Laboratory), Nanfang Hospital of the Southern Medical University from May 2005 to March 2006. A total of 25 adult SD rats, of either gender, weighing 200-300 g, were selected in this study. The animal experiment had got confirmed consent from local ethic committee. All rats were randomly divided into tumor group (n =20) and blank control group (n =5).METHODS: Models of VX2 tumor in spleen were established successfully. The images obtained before and after administration of superparamagnetic iron oxide. T1-weighted image(T1WI) (450/12 ms) and T2-weighted image(T2WI)(4 000/128 ms) were used to scan sequences. The imaging parameters of various tissues were analyzed before and after superparamagnetic iron oxide-enhanced MRI scanning. Rats in the blank control group were not used to establish models and the sequences were scanned as the same as those in the experimental group.MAIN OUTCOME MEASURES: Signal characteristics of various tissues before and after before and after superparamagnetic iron oxide-enhanced MRI scanning.RESULTS: Eight out of 20 rats died in the tumor group and other 12 and 5 rats in the control group were involved in the final analysis. MR scanning indicated that 8 rats in the tumor group had splenic VX2 tumor. ① On plain MR scanning T1-weighted splenic VX2 tumor showed hypointensity or isointensity which approximated to the signal intensity (SI) of splenic parenchyma. All lesions had been not displayed well. ② On superparamagnetic iron oxide enhancement T2WI sequence the SI of splenic parachyma decreased obviously with percentage of signal intensity loss (PSIL) was 56.11%,But the SI of tumor was not evidently change with PSlL was 1.90%. Nevertheless the signal-to-noise ratio (SNR) of normal splenic parenchyma around the lesions had obviously difference (P ＜ 0.001) comparatively. So the contrast between tumor and spleen increased, and tumor displayed more clear. Moreover the contrast-to-noise (CNR) between VX2 tumor and splenic parenchyma had an evidently difference with 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.So it is not good to characterize the lesions in spleen. On superparamagnetic iron oxide enhanced T2WI the contrast degree of lesions increased obviously. Consequently, superparamagnetic iron oxide-enhanced T2WI MRI scanning can improve the rate of detection and characterization in lesions of spleen.