Optimizing Hyperpolarized 129Xe Production under Practical Cryogenic Accumulation Conditions

Following improvements in continuous-flow hyperpolarization technology, ¹²⁹Xe has shown ever-increasing utility as a pulmonary contrast agent. However, polarization remains constrained by conflicting demands of spin-exchange efficiency and T₁ relaxation during cryogenic collection. By collecting ¹²⁹Xe across a range of practical conditions, we developed model to predict conditions for optimal ¹²⁹Xe polarization. In many regimes, the benefits of optimal spin exchange efficiency were outweighed by polarization lost to rapid relaxation in polycrystalline ¹²⁹Xe snow (T₁^snow = 84 minutes). For 1-L, clinical ¹²⁹Xe doses, our model suggests optimal polarizations are obtained using accumulation times <30 minutes and relatively rich (2–2.3%) xenon mixtures.