Temperature-Ramped ~(129)Xe Spin-Exchange Optical Pumping

摘要

We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode ~(129)Xe hyperpolarizer utilizing three key temperature regimes: (i) "hot"--where the ~(129)Xe hyperpolarization rate is maximal, (ii) "warm"--where the ~(129)Xe hyperpolarization approaches unity, and (iii) "cool"--where hyperpolarized ~(129)Xe gas is transferred into a Tedlar bag with low Rb content (<5 ng per ～1 L dose) suitable for human imaging applications. Unlike with the conventional approach of batch-mode SEOP, here all three temperature regimes may be operated under continuous high-power (170 W) laser irradiation, and hyperpolarized ~(129)Xe gas is delivered without the need for a cryocollection step. The variable-temperature approach increased the SEOP rate by more than 2-fold compared to the constant-temperature polarization rate (e.g., giving effective values for the exponential buildup constant γ_(SEOP) of 62.5 ± 3.7 × 10~(-3) min~(-1) vs 29.9 ± 1.2 × 10~(-3) min~(-1)) while achieving nearly the same maximum %P_(Xe) value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500 Torr (67 kPa) Xe cell loading--corresponding to nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) enhancements of ～3.1 × 10~5 and ～2.32 × 10~8 at the relevant fields for clinical imaging and HP ~(129)Xe production of 3 T and 4 mT, respectively); moreover, the intercycle "dead" time was also significantly decreased. The higher-throughput TR-SEOP approach can be implemented without sacrificing the level of ~(129)Xe hyperpolarization or the experimental stability for automation--making this approach beneficial for improving the overall ~(129)Xe production rate in clinical settings.