Optimal Glass-Forming Solvent Brings Sublimation Dynamic Nuclear Polarization to ¹²⁹Xe Hyperpolarization Biomedical Imaging Standards

In addition to the dedicated spin exchange optical pumping (SEOP) technique, an alternative method to produce hyperpolarized xenon gas using dynamic nuclear polarization (DNP) followed by a sublimation procedure was proposed. The challenge associated with sublimation DNP is to obtain solid-state samples with the required homogeneity following the incorporation of xenon into a glass-forming solvent. We show that the maximum achievable ¹²⁹Xe polarization strongly depends on the xenon concentration dissolved in the solvent and the properties of the solvent itself. Using a 5 T home-built polarizer, the ¹²⁹Xe spins in natural abundance xenon were polarized up to 30% in about 90 min at 1.15 ± 0.05 K. The gas was subsequently extracted to perform ¹²⁹Xe MRI in a distant 9.4 T rodent scanner. We demonstrate that by careful optimization of the sample preparation, sublimation DNP can be used to hyperpolarize ¹²⁹Xe at a polarization level and in quantities that are sufficiently large for biomedical applications