Pouliquen D, Perroud H, Calza F, Jallet P, Le Jeune J J
Laboratoire de Biophysique, Faculté de Médecine, Angers, France.
Magn Reson Med. 1992 Mar;24(1):75-84. doi: 10.1002/mrm.1910240108.
Superparamagnetic iron oxide particles, a new class of contrast agents for MRI, are extremely good enhancers of proton relaxation. However, the development of such particle systems has resulted in a wide range of preparations whose physico-chemical properties differ greatly. We have conducted a set of physical experiments: X ray diffraction analysis, relaxivity measurements, susceptibility determinations, and thermomagnetic cycling on different preparations of superparamagnetic particles. Our results demonstrate a good correlation between susceptibilities measured in liquid samples at room temperature and the R2/R1 ratio. Susceptibility measurements between liquid nitrogen temperature and room temperature show three different types of behavior dependent on the size of iron oxide crystals. Comparison of heating and cooling curves from strong field thermomagnetic cycles provides information about the maghemite/magnetite crystal content. The information on magnetic properties reported in this study may help to characterize and to select these materials for use as MRI contrast agents.
超顺磁性氧化铁颗粒是一类新型的磁共振成像（MRI）造影剂，是极其优良的质子弛豫增强剂。然而，这类颗粒系统的发展导致了大量制剂的出现，其物理化学性质差异很大。我们进行了一系列物理实验：对不同的超顺磁性颗粒制剂进行X射线衍射分析、弛豫率测量、磁化率测定和热磁循环。我们的结果表明，室温下在液体样品中测得的磁化率与R2/R1比值之间具有良好的相关性。在液氮温度和室温之间进行的磁化率测量显示出三种不同类型的行为，这取决于氧化铁晶体的大小。强场热磁循环的加热和冷却曲线比较提供了有关磁赤铁矿/磁铁矿晶体含量的信息。本研究报告的磁性信息可能有助于表征和选择这些用作MRI造影剂的材料。
