USPIO作为T1-T2双增强对比剂的初步动物成像研究

A pilot imaging study of ultra-small superparamagnetic iron oxide serving as a T1-T2 double contrast enhancer in rats

摘要:

目的：研究粒径对超顺磁性氧化铁（superparamagnetic iron oxide，SPIO）纳米颗粒T1和T2弛豫效能的影响，并选取超小粒径SPIO（ultra-small SPIO，USPIO）探究其作为磁共振T1-T2双增强对比剂在体内成像应用中的特点。方法：采用共沉淀法制备3种不同粒径的SPIO。测定样本基本理化性能和磁学特性，采用临床3.0T MRI成像仪，研究不同MRI序列下USPIO大鼠体内对比增强成像特点。结果：成功制备3种不同粒径的SPIO：[A：（14.14±4.94） nm；B：（28.30±7.65） nm；C：（93.81±33.01） nm]，测得在不同磁场强度下的T1、T2弛豫效能。小粒径的SPIO纳米颗粒具有更低的r2/r1（0.5 T：2.14），是潜在的T1、T2双增强对比剂，且低磁场下具有更低的r2/r1，有利于T1增强显影。大鼠成像显示，USPIO在T2加权成像序列下能明显降低肝脏T2成像信号，在短TE的T1加权序列下能明显提高肝脏、心血管T1信号，具有较小分子对比剂更长的成像时间窗。结论：粒径是影响SPIO弛豫效能的重要参数，USPIO具有更低的r2/r1比，是潜在的T1、T2双增强对比剂。

Abstract:

Objective：To investigate the influence of particle size of superparamagnetic iron oxide（SPIO） nanoparticles on T1-T2 re－laxation efficiency，as well as the features of ultra-small SPIO（USPIO） as the T1-T2 double contrast enhancer in in vivo imaging. Methods：The coprecipitation method was used to prepare three types of SPIO nanoparticles with different particle sizes. The basic physical-chemical and magnetic properties of the samples were measured，and a 3.0 T MRI imager was used to investigate the imaging properties of USPIO as the T1-T2 double contrast agent in rats under different MRI sequences. Results：Three types of SPIO nanopar－ticles （A：14.14±4.94 nm；B：28.30±7.65 nm；C：93.81±33.01 nm） were successfully prepared and the relaxation properties of T1 and T2 at different magnetic field intensities were measured. SPIO nanoparticles with a smaller particle size had a lower r2/r1 ratio（0.5 T：2.14） and were the potential T1-T2 double contrast enhancers；such nanoparticles had a significantly lower r2/r1 ratio in low mag－netic field and might help with T1 contrast-enhanced imaging. The imaging of the rats showed that USPIO significantly reduced the T2 signal intensity of the liver on T2WI and increased the T1 signal intensity of the liver and the cardiovascular system on short-TE T1WI，with a longer time window for imaging than small-molecule contrast agents. Conclusion：Particle size is one of the important parameters affecting the relaxation efficiency of SPIO. USPIO has a lower r2/r1 ratio and can be used as the potential T1-T2 double contrast enhancer.