超顺磁性Fe_2O_3用作磁共振胃肠对比剂

Superparamagnetic Fe_2O_3 microparticles as gastrointestinal contrast agent in magnetic resonance imaging

目的制备一种由Fe2O3为主要原料的口服磁共振胃肠造影混悬剂,研究Fe2O3在磁共振磁场中保持超顺磁性和稳定悬浮的临界尺寸。方法根据超顺磁性理论,推导出Fe2O3微粒显示超顺磁现象的临界尺寸理论值和在1.5T磁共振磁场中的临界值;根据磁学理论,分析磁共振对比剂稳定的机制,推导在磁共振磁场中,Fe2O3微粒在对比剂中稳定悬浮的极限尺寸。以小于该尺寸的Fe2O3微粒作主料制备对比剂,并进行磁共振成像对比增强实验研究。结果在1.5T磁共振磁场中,Fe2O3微粒在对比剂中既能稳定悬浮又具有超顺磁性的极限尺寸为11.1nm,Fe3O4为7.1nm。用尺寸为10nm的Fe2O3微粒制备的对比剂,具有稳定、超顺磁性、安全、不沉降、不团聚的特性,且在磁共振成像上呈现明显的阴性对比作用。结论从微粒尺寸角度考虑,用Fe2O3微粒作对比剂中的磁性粒子比Fe3O4更有优势。

Objective To make a kind of oral gastrointestinal contrast agent mainly from Fe2O3, and to study its critical size of suspension stability and superparamagnetism in MR magnetic field. Methods The critical size in 1, 5T magnetic field was deduced according to superparamagnetic theory. The mechanism of suspension stability and the critical size were analyzed based on magnetic theory. Contrast agent was made with Fe2O3 as the major material and MRI relaxation enhancement of the contrast agent was studied. Results The proper limit size for Fe2O3 suspension stability and superparamagnetism in the contrast agent was 11.1 nm, while the proper limit size for Fe3O4 was 7.1 nm. Cnotrast agent made from microparticle with mean diameter of 10 nm had features of stability, settlement and superparamagnetism without obvious toxicity nor agglomeration. Conchtsion Fe2O3 microparticles used as the major materials in magnetic resonance imaging is better than that with Fe3O4 microparticles.