Ebert M, Grossmann T, Heil W, Otten W E, Surkau R, Leduc M, Bachert P, Knopp M V, Schad L R, Thelen M
Institut für Physik, Johannes Gutenberg-Universität Mainz, Germany.
Lancet. 1996 May 11;347(9011):1297-9. doi: 10.1016/s0140-6736(96)90940-x.
Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI.
A volunteer inhaled hyperpolarised 3He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10(5) times larger than the polarisation of water protons. This enormous gain in polarisation easily overcomes the loss in signal due to the lower density of the gas.
The in-vivo experiment was done in a whole-body MRI scanner. The 3He image showed clear demarcation of the lung against diaphragm, heart, chest wall, and blood vessels (which gave no signal). The signal intensity within the air spaces was greatest in lung regions that are preferentially ventilated in the supine position; less well ventilated areas, such as the apices, showed a weaker signal.
MRI with hyperpolarised 3He gas could be an alternative to established nuclear medicine methods. The ability to image air spaces offers the possibility of investigating physiological and pathophysiological processes in pulmonary ventilation and differences in its regional distribution.
磁共振成像（MRI）依靠组织中水分子的氢原子核（质子）的磁化作为信号源。这项技术对于研究含有大量水分的组织很有价值，但对于质子含量低的生物组织，尤其是肺部，成像困难。我们报告了使用自旋极化的氦-3进行肺部MRI检查。
一名志愿者吸入超极化的3He以充盈肺部，然后用传统的MRI探测器组件对肺部进行成像。氦以及其他惰性气体的核自旋极化可通过激光光泵极大增强，其极化程度比水质子的极化程度大约大10^5倍。这种极化的巨大增益很容易克服由于气体密度较低导致的信号损失。
在全身MRI扫描仪中进行了体内实验。3He图像清晰显示了肺部与膈肌、心脏、胸壁和血管（无信号）的界限。气腔内的信号强度在仰卧位优先通气的肺部区域最大；通气较差的区域，如肺尖，信号较弱。
超极化3He气体的MRI检查可能是现有核医学方法的一种替代方法。对气腔成像的能力为研究肺通气中的生理和病理生理过程及其区域分布差异提供了可能性。
