Möller H E, Chen X J, Chawla M S, Driehuys B, Hedlund L W, Johnson G A
Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina, 27710, USA.
J Magn Reson. 1998 Nov;135(1):133-43. doi: 10.1006/jmre.1998.1563.
The nonequilibrium bulk magnetic moment of hyperpolarized (HP) noble gases generated by optical pumping has unique characteristics. Based on the Bloch equations, a model was developed describing the signal dynamics of HP gases used in magnetic resonance imaging (MRI) of the lung with special consideration to the breathing cycle. Experimental verification included extensive investigations with HP 3He and 129Xe during both inspiration and held breath in live guinea pigs. Radial acquisition was used to investigate the view variations with a temporal resolution of 5 ms. Agreement between theoretical predictions and in vivo results was excellent. Additionally, information about effects from noble gas diffusion and spin-lattice relaxation was obtained. In vivo results for T1 were 28.8 +/- 1.8 s for 3He and 31.3 +/- 1.8 s for 129Xe. Comparison with in vitro data indicated that relaxation in the pulmonary gas space is dominated by dipolar coupling with molecular oxygen. The results provide a quantitative basis for optimizing pulse sequence design in HP gas MRI of the lung.
光泵浦产生的超极化（HP）惰性气体的非平衡体磁矩具有独特的特性。基于布洛赫方程，开发了一个模型来描述肺部磁共振成像（MRI）中使用的HP气体的信号动力学，并特别考虑了呼吸周期。实验验证包括在活体豚鼠吸气和屏气期间对HP 3He和129Xe进行广泛研究。采用径向采集以5毫秒的时间分辨率研究视图变化。理论预测与体内结果之间的一致性非常好。此外，还获得了有关惰性气体扩散和自旋 - 晶格弛豫效应的信息。3He的体内T1结果为28.8±1.8秒，129Xe为31.3±1.8秒。与体外数据的比较表明，肺部气体空间中的弛豫主要由与分子氧的偶极耦合主导。这些结果为优化肺部HP气体MRI中的脉冲序列设计提供了定量基础。
