Department of Chemistry, Integrative Biosciences (Ibio), Wayne State University, Karmanos Cancer Institute (KCI), 5101 Cass Ave, Detroit, MI 48202, United States.
XeUS Technologies, G. Karaiskaki 2A, P. Lakatamia, Nicosia 2312, Cyprus.
J Magn Reson. 2020 Jun;315:106739. doi: 10.1016/j.jmr.2020.106739. Epub 2020 Apr 30.
We present studies of spin-exchange optical pumping (SEOP) using ternary xenon-nitrogen-helium gas mixtures at high xenon partial pressures (up to 1330 Torr partial pressure at loading, out of 2660 Torr total pressure) in a 500-mL volume SEOP cell, using two automated batch-mode clinical-scale Xe hyperpolarizers operating under continuous high-power (~170 W) pump laser irradiation. In this pilot study, we explore SEOP in gas mixtures with up to 45% He content under a wide range of experimental conditions. When an aluminum jacket cooling/heating design was employed (GEN-3 hyperpolarizer), Xe polarization (%P) of 55.9 ± 0.9% was observed with mono-exponential build-up rate γ of 0.049 ± 0.001 min for the He-rich mixture (1000 Torr Xe/900 Torr He, 100 Torr N), compared to %P of 49.3 ± 3.3% at γ of 0.035 ± 0.004 min for the N-rich gas mixture (1000 Torr Xe/100 Torr He, 900 Torr N). When forced-air cooling/heating was used (GEN-2 hyperpolarizer), %P of 83.9 ± 2.7% was observed at γ of 0.045 ± 0.005 min for the He-rich mixture (1000 Torr Xe/900 Torr He, 100 Torr N), compared to %P of 73.5 ± 1.3% at γ of 0.028 ± 0.001 min for the N-rich gas mixture (1000 Torr Xe and 1000 Torr N). Additionally, %P of 72.6 ± 1.4% was observed at a build-up rate γ of 0.041 ± 0.003 min for a super-high-density He-rich mixture (1330 Torr Xe/1200 Torr He/130 Torr N), compared to %P = 56.6 ± 1.3% at a build-up rate of γ of 0.034 ± 0.002 min for an N-rich mixture (1330 Torr Xe/1330 Torr N) using forced air cooling/heating. The observed SEOP hyperpolarization performance under these conditions corresponds to %P improvement by a factor of 1.14 ± 0.04 at 1000 Torr Xe density and by up to a factor of 1.28 ± 0.04 at 1330 Torr Xe density at improved SEOP build-up rates by factors of 1.61 ± 0.18 and 1.21 ± 0.11 respectively. Record %P levels have been obtained here: 83.9 ± 2.7% at 1000 Torr Xe partial pressure and 72.6 ± 1.4% at 1330 Torr Xe partial pressure. In addition to improved thermal stability for SEOP, the use of He-rich gas mixtures also reduces the overall density of produced inhalable HP contrast agents; this property may be desirable for HP Xe inhalation by human subjects in clinical settings-especially in populations with heavily impaired lung function. The described approach should enjoy ready application in the production of inhalable Xe contrast agent with near-unity Xe nuclear spin polarization.
我们展示了在高氙分压（加载时高达 1330 托，总压为 2660 托）下使用三元氙-氮-氦气体混合物进行自旋交换光学泵浦（SEOP）的研究，在 500 毫升 SEOP 细胞中使用两种自动化批量临床规模的 Xe 超极化器，在连续高功率（约 170 W）泵浦激光照射下运行。在这项初步研究中，我们在广泛的实验条件下探索了含高达 45%氦的气体混合物中的 SEOP。当采用铝套冷却/加热设计（GEN-3 超极化器）时，与富含氮的气体混合物（1000 托 Xe/100 托 He，900 托 N）中γ为 0.035±0.004 min 的 49.3±3.3%相比，富含氦的混合物（1000 托 Xe/900 托 He，100 托 N）中观察到 Xe 极化率（%P）为 55.9±0.9%，γ为 0.049±0.001 min。当使用强制风冷/加热时（GEN-2 超极化器），与富含氮的气体混合物（1000 托 Xe/1000 托 N）中γ为 0.028±0.001 min 的 73.5±1.3%相比，富含氦的混合物（1000 托 Xe/900 托 He，100 托 N）中观察到 83.9±2.7%的%P，γ为 0.045±0.005 min。此外，对于超高密度富含氦的混合物（1330 托 Xe/1200 托 He/130 托 N），在γ为 0.041±0.003 min 的建立率下观察到 72.6±1.4%的%P，与在γ为 0.034±0.002 min 的富含氮的混合物（1330 托 Xe/1330 托 N）相比，%P=56.6±1.3%，使用强制风冷/加热。在这些条件下观察到的 SEOP 超极化性能对应于在 1000 托 Xe 密度下的 1.14±0.04%的%P 提高，并且在 1330 托 Xe 密度下的 1.28±0.04%的%P 提高，通过分别为 1.61±0.18 和 1.21±0.11 的改进 SEOP 建立率因子提高。在此获得了创纪录的%P 水平：在 1000 托 Xe 分压下为 83.9±2.7%，在 1330 托 Xe 分压下为 72.6±1.4%。除了 SEOP 的热稳定性提高外，富含氦的气体混合物的使用还降低了产生的可吸入 HP 对比剂的整体密度；在临床环境中，尤其是在肺部功能严重受损的人群中，对人类受试者吸入 HP Xe 而言，这一特性可能是可取的。所描述的方法应可轻松应用于生产近全 Xe 核自旋极化的可吸入 Xe 造影剂。
