Albert M S, Cates G D, Driehuys B, Happer W, Saam B, Springer C S, Wishnia A
Department of Chemistry, State University of New York, Stony Brook 11794-3400.
Nature. 1994 Jul 21;370(6486):199-201. doi: 10.1038/370199a0.
As currently implemented, magnetic resonance imaging (MRI) relies on the protons of water molecules in tissue to provide the NMR signal. Protons are, however, notoriously difficult to image in some biological environments of interest, notably the lungs and lipid bilayer membranes such as those in the brain. Here we show that 129Xe gas can be used for high-resolution MRI when the nuclear-spin polarization of the atoms is increased by laser optical pumping and spin exchange. This process produces hyperpolarized 129Xe, in which the magnetization is enhanced by a factor of about 10(5). By introducing hyperpolarized 129Xe into mouse lungs we have obtained images of the lung gas space with a speed and a resolution better than those available from proton MRI or emission tomography. As xenon (a safe general anaesthetic) is rapidly and safely transferred from the lungs to blood and thence to other tissues, where it is concentrated in lipid and protein components, images of the circulatory system, the brain and other vital organs can also be obtained. Because the magnetic behaviour of 129Xe is very sensitive to its environment, and is different from that of 1H2O, MRI using hyperpolarized 129Xe should involve distinct and sensitive mechanisms for tissue contrast.
按照目前的实施方式，磁共振成像（MRI）依靠组织中水分子的质子来提供核磁共振信号。然而，在某些感兴趣的生物环境中，尤其是肺部以及诸如大脑中的脂质双分子膜，质子的成像非常困难。在此我们表明，当通过激光光泵浦和自旋交换增加原子的核自旋极化时，129Xe气体可用于高分辨率MRI。此过程产生超极化的129Xe，其磁化强度增强了约10(5)倍。通过将超极化的129Xe引入小鼠肺部，我们获得了肺部气体空间的图像，其速度和分辨率优于质子MRI或发射断层扫描。由于氙气（一种安全的全身麻醉剂）能迅速且安全地从肺部转移到血液，进而转移到其他组织，并在脂质和蛋白质成分中富集，因此也能获得循环系统、大脑和其他重要器官的图像。由于129Xe的磁行为对其环境非常敏感，且与1H2O不同，使用超极化129Xe的MRI应该涉及独特且灵敏的组织对比机制。
