Temperature-Ramped 129Xe Spin-ExchangeOptical Pumping

摘要

We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode ¹²⁹Xe hyperpolarizer utilizing three key temperature regimes: (i) “hot”—where the ¹²⁹Xe hyperpolarization rate is maximal, (ii) “warm”—where the ¹²⁹Xe hyperpolarization approaches unity, and (iii) “cool”—where hyperpolarized ¹²⁹Xe 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 ¹²⁹Xe 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 γSEOP of 62.5 ± 3.7 × 10^–3 min^–1 vs29.9 ± 1.2 × 10^–3 min^–1) while achieving nearly the same maximum %PXe value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500Torr (67 kPa) Xe cell loading—corresponding to nuclear magneticresonance/magnetic resonance imaging (NMR/MRI) enhancements of ∼3.1× 10⁵ and ∼2.32 × 10⁸ at therelevant fields for clinical imaging and HP ¹²⁹Xe productionof 3 T and 4 mT, respectively); moreover, the intercycle “dead”time was also significantly decreased. The higher-throughput TR-SEOPapproach can be implemented without sacrificing the level of ¹²⁹Xe hyperpolarization or the experimentalstability for automation—making this approach beneficial forimproving the overall ¹²⁹Xe production rate in clinicalsettings.