Hyperpolarized ¹²⁹Xe MRI Using Dissolution DNP on a Commercial Polarizer: From Solid-State Optimization to In Vivo Lung Imaging

Hyperpolarized ¹²⁹Xe MRI Using Dissolution DNP on a Commercial Polarizer: From Solid-State Optimization to In Vivo Lung Imaging | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hyperpolarized ¹²⁹Xe MRI Using Dissolution DNP on a Commercial Polarizer: From Solid-State Optimization to In Vivo Lung Imaging Emma Wiström, Jean-Noël Hyacinthe, Esben Søvsø Szocska Hanssen, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9236425/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Hyperpolarized ¹²⁹Xe gas is a powerful diagnostic tool in pulmonary MRI, uniquely enabling imaging of ventilation and gas exchange through its dissolved-phase signal. While xenon is conventionally hyperpolarized using spin-exchange optical pumping (SEOP), an alternative approach based on dynamic nuclear polarization (DNP) followed by sublimation has emerged. However, xenon DNP has so far been restricted to custom-built hardware and primarily explored for solid-state physics applications. In this work, we establish optimized conditions for solid-state polarization of xenon using a commercial DNP polarizer. The resulting robust and reproducible protocol enables in vivo imaging in porcine lungs, providing sufficient signal to extract biologically relevant information comparable to that obtained with SEOP. This work bridges a critical gap in xenon DNP, advancing it from proof-of-principle demonstrations on specialized systems to implementation on standardized instrumentation suitable for in vivo applications. Biological sciences/Biological techniques Physical sciences/Engineering Physical sciences/Optics and photonics Xenon (129Xe) dissolution DNP SEOP Hyperpolarization Hyperpolarized gas MRI lung MRI Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Hyperpolarized (HP) ¹²⁹Xe MRI is an excellent diagnostic tool for diseases related to the alteration of human lungs’ function and structure. 1 – 3 To this end, ventilation imaging has been the subject of many preclinical and clinical studies for more than two decades, 4–7 and in 2022 its related clinical product, Polarean’s XENONVIEW ™ , received FDA approval as an ionizing radiation-free alternative to 133 Xe scintigraphy for adults and pediatric patients aged 12 years and older. 8 Moreover, xenon is lipophilic. Therefore, it dissolves in tissue, blood, and can cross the blood-brain barrier. This peculiar feature, together with 129 Xe broad chemical shift dispersion as a function of the molecular environment, makes it an ideal tracer for perfusion MRI of organs such as the brain, 9 the kidneys, 10 and the lungs. Remarkably, it was recently demonstrated that HP 129 Xe lung perfusion could detect lower gas transfer to the red blood cells in patients with long-COVID, despite having normal CT findings. 11 , 12 Spin Exchange Optical Pumping (SEOP) is the gold-standard method to hyperpolarize 129 Xe. 13 – 15 This technique is limited to noble gases, with polarization transfer occurring directly in the gas phase. In SEOP, a gas mixture containing the noble gas (for example, 129 Xe), a buffer gas (such as 4 He), a radiation-trapping suppression gas (typically N 2 ), and trace amounts of alkali-metal vapor (for example, Rb) is loaded into a so-called pumping cell. The cell is maintained in a magnetic field of a few mT and heated to approximately 100–200°C. The Rb atoms are optically pumped with circularly polarized laser light at 795 nm, and subsequently transfer polarization to the 129 Xe nuclei through collisions and angular-momentum exchange. The He and N 2 gases serve to broaden the Rb absorption line and to quench radiative de-excitation, respectively. The Rb atoms are optically pumped with circularly polarized laser light at 795 nm, and subsequently transfer polarization to the 129 Xe nuclei through collisions and angular-momentum exchange. The He and N 2 gases serve to broaden the Rb absorption line and to quench radiative de-excitation, respectively. While generally leading to lower polarizations than stopped-flow systems, continuous-flow systems with cryogenic accumulation yield higher Xe production rates and are more adapted for clinical use. For instance, the SEOP system used in this study (POLARIS Technology, University of Sheffield) can produce up to 300 cm 3 of 129 Xe with a nuclear spin polarization ( P Xe ) of approximately 30% in 5 min (i.e. throughput of 3.6 L/h). 16 An alternative way to generate HP 129 Xe gas is using dissolution Dynamic Nuclear Polarization (dDNP), followed by a sublimation step to separate the gas from the liquid phase of the dissolved sample. 17 – 19 Unlike SEOP, in dDNP, the polarization transfer to the nuclei happens in the solid state at low temperature (0.8–1.4 K) and at much higher magnetic fields (3.35–7 T). 19 The source of polarization is represented by unpaired electron spins, in form of organic free radicals, mixed with the target molecules in a ratio of 1 to 1000. Unless the substrate of interest spontaneously solidifies into an amorphous solid at low temperature (e.g. pyruvic acid), to avoid crystallization of the sample that would hinder a random orientation distribution of the electron spins, common practice is to dissolve the substrate and the radical into a glassing agent such as water:glycerol or DMSO. Excitation slightly off-resonance of the electrons’ Zeeman transition by using microwave irradiation triggers the polarization transfer to the nuclei. 20 Once hyperpolarized, the solid sample is transformed into an injectable solution through a sudden temperature jump and dilution procedure, the so-called dissolution step. 21 One of the strengths of dDNP is to be compound-agnostic: in principle, any NMR active nucleus can be hyperpolarized in the solid-state and, provided that its liquid-state relaxation time ( \(\:{T}_{1}\) ) is long enough (i.e. tens of seconds), a hyperpolarized solution containing that nucleus can be obtained. Hence, dDNP offers the chance to enhance the liquid-state NMR signal of various nuclei such as 13 C, 1 H, 31 P, and 6 Li by several orders of magnitude while using a single polarizing apparatus. 18 , 22 – 25 Nevertheless, when dDNP is used to hyperpolarize 129 Xe, some extra elements must be considered already before the dissolution/sublimation step: 18 Xe is in the gas state at standard temperature and pressure conditions. A host glassing solvent with melting temperature close to the Xe triple-point (i.e. 161.4 K) is needed to dissolve the radical. Xe and the radical-doped glassing solvent must be mixed while coexisting in the liquid state. Xe is lipophilic, and the glassing solvent polarity determines the gas solubility threshold above which the liquified gas and solvent will form a heterogeneous mixture. We recently demonstrated that sample preparation at controlled temperature (i.e. 160 K) together with ultrasonication of the liquid Xe and radical doped solvent mixture yielded improved and consistent DNP results. 29 Moreover, microwave frequency modulation led to solid-state 129 Xe polarization levels comparable to what can be achieved with 13 C samples at 5 T. 29,30 In the present study, we focus on establishing a robust polarization and gas extraction protocol applicable to a commercial dDNP polarizer installed in a clinical setting at Aarhus University Hospital. Hyperpolarized gas acquisitions were performed on a clinical scanner, and the results were compared to those obtained using a gold-standard SEOP polarizer, routinely used for clinical HP 129 Xe MRI. Experimental methods Xenon dDNP hardware The dDNP system used in this study was a SpinAligner polarizer (Polarize, Denmark) operating at 6.7 T and 1.3 K. We used a sample vial larger and with thicker walls compared to the standard SpinAligner vial to increase sample volume and improve sample’s thermal insulation during loading (Fig. 1 ). To prevent the sample from melting during loading, pump/flush of the airlock prior to sample insertion was reduced from three cycles to one and descending speed increased from 15 mm/s to 150 mm/s. To acquire the 129 Xe signal during DNP experiments, the SpinAligner probe was tuned and matched remotely to 78.5 MHz and 50 Ohm, respectively. Xenon dDNP sample preparation All dDNP samples in this work consist of 30 mM trityl radical (Finland acid), isobutanol and 1.0 x 10 − 3 mole of either natural abundant xenon gas (26% 129 Xe) or isotopically enriched xenon gas (86% 129 Xe, Cortecnet, France). This amount is equivalent to 25 mL xenon gas (at atmospheric pressure). The gas was dissolved either in 300 µL of radical-doped solvent (3.3 M of Xe concentration), or in 500 µL of radical-doped solvent (2.0 M of Xe concentration). Solvent and gas mixing was performed at -100°C using ultrasonication (Fig. 2 A), as previously described. 29 Once fully mixed, the sample was flash frozen by immersing the sample cup in liquid nitrogen, where it was kept until loading into the polarizer. The Xe DNP sample preparation method was developed and described in detail earlier. For further information refer to our previous works. 18 , 29 , 31 Xenon dDNP solid-state measurements The ideal microwave frequency for the specific sample composition was determined by frequency sweeps, with and without frequency modulation (sinusoidal output with ± 20 MHz peak-to-peak modulation amplitude at 10 kHz modulation rate), from 187.8 GHz to 188.4 GHz in 10 MHz-steps (Fig. 3 C /D ). At each frequency step, the sample was polarized with 12 mW microwave power for 5 minutes, and the NMR signal was acquired with a 25° hard pulse and averaged 16 times. Between microwave frequency steps, the residual signal after readout was destroyed by a pulse saturation block (2000 x 25°). 31 Microwave power at best irradiation frequency was optimized by sweeping the output value from 3 mW to 30 mW with increments of 3 mW ( Figure S2 ). The sample polarization buildup was measured at optimal microwave irradiation conditions acquiring the 129 Xe NMR signal every 3 minutes (5° hard pulse, averaged 16 times). All DNP data were acquired in SPINit 2021.01 (RS2D, Mundolsheim, France), exported as JCAMP-DX files, processed first in MNova (MestreLab Research, Santiago, Spain), then in MATLAB R2024b. Xenon Sublimation Dissolution of the frozen and hyperpolarized sample was performed using the standard hardware and procedure of the SpinAligner polarizer but, instead of dissolving into an open receiver, we used a purposed built phase separator (Fig. 2 C /D ). The phase separator ( Figure S3 ), made of Polychlorotrifluoroethylene (PTCFE) and Polyether ether ketone (PEEK) is hermetically sealed using a NBR o-ring at the lid connection and Flangeless Fittings (IDEX P-335, BGB Analytik AG, USA) around the 1/8” outer diameter Polytetrafluoroethylene (PTFE) tubing, for inlet of the liquid/gases mixture and outlet of the gases only. Xe and He gases are finally collected in a 0.6 L Tedlar bag (Sigma-Aldrich, Switzerland) connected at the end of the gas extraction line via a PEEK Luer Lock (IDEX-P-683, BGB Analytik AG, USA) a 3-way stopcock (Fig. 2 D). The buffer volume (8 mL D 2 O) and He gas push time (2 s) were optimized to obtain at the same time complete dissolution of the frozen sample and no liquid contamination of the Tedlar bag. Prior to dissolution, the extraction system (Fig. 2 B-D) was evacuated using a vacuum pump. After extraction of the gas, the Tedlar bag was closed and transported to the 3T MRI scanner (Fig. 2 E). The full procedure from dissolution to the onset of MR acquisition took approximately 60 s. In a separate set of experiments, cryocollection was used to estimate the extracted volume amount of Xe gas from the dDNP polarizer. In this case, the Tedlar bag was replaced by a high-pressure NMR tube. After dissolution and liqui/gas phase separation, the Xe/He gas mixture was pushed into the NMR tube and the inlet closed at the end of the push time. The NMR tube was then plunged in liquid nitrogen to freeze the Xe, and a vacuum pump connected to the inlet to remove the He. Afterwards, the pump was replaced by an empty syringe, the Xe ice warmed up, and the syringe piston pulled until possible. SEOP hyperpolarization 129 Xe Gas Preparation In all SEOP experiments, the 129 Xe gas was polarized to about 30% using a spin exchange optical pumping (SEOP) polarizer (POLARIS, University of Sheffield, Sheffield, UK). 7 The gas mixture was 3% isotopically enriched xenon (86% 129 Xe), 10% N 2 , and 87% He flowed through a glass cell (volume = 3534 cm 3 , temperature = 130°C; total gas pressure = 2 bars) at a flow rate of 2000 standard cubic centimeters per minute (sccm). After polarization the 3% xenon gas mixture was collected without cryogenic separation, dispensing 600 mL directly into a 1 L Tedlar bag, yielding a 129 Xe dose of ~ 15 mL per bag. The polarization of this single batch took approximately 10 min. The elapsed time from gas collection to onset of MR acquisition was approximately 90 s. Animal Model and Xenon Gas Administration The study examined female Danish Landrace pigs, weighing approximately 40 kg. The pig was anesthetized through an ear vein catheter (fentanyl and propofol, doses 8 and 18 mL/h, respectively), intubated and attached to a mechanical ventilator at fractional inspired oxygen levels (FiO2) of 21% with a continuous flow of 5400 mL/min in pressure-controlled ventilation-volume guaranteed mode (PCV-VG). This study complied with institutional and national guidelines and was approved by the Animal Experiment Council, governed under the Danish Animal Inspectorate, before initiation under license 2023-15-0201-01553. Xenon gas was administered by unplugging the mechanical ventilation system from the tracheal tube and switching to the Tedlar bag. Functional residual capacity was achieved by waiting approximately 2 s before connecting the bag to the tracheal tube. Xenon gas was administered to the lungs in a steady flow with a gentle pressure on the bag, emptying it in 3 s to avoid damaging the lungs with excessive pressure. At the end of the experiment the animal was euthanized under anesthesia by an injection of pentobarbital. MRI acquisition and data processing All HP 129 Xe MRI and MRS experiments were performed on a 3 T MRI scanner (MR750, GE HealthCare, Waukesha, WI, USA) using a 129 Xe transmit-receive quadrature vest coil (Clinical MR Solutions, Brookfield, WI, USA) tuned to 35.3 MHz. Tedlar bag acquisition We first compared the performance of xenon dDNP to SEOP in clinically relevant experimental conditions, by measuring Tedlar bags with non-localized MRS acquired with 10 consegutive 30° hard pulses with repetition time TR = 2 s. \(\:{T}_{1}\) relaxation times for DNP and SEOP samples were obtained by fitting a mono-exponential curve to the data (n = 3). All magnetization and \(\:{T}_{1}\) data were processed in MATLAB R2024b. We also acquired ventilation images of the Tedlar bags prior to the in vivo experiment ( Figure S5 / S6 ). In vivo acquisition As anatomical reference, coronal 3D \(\:{T}_{1}\) -weighted ( \(\:{T}_{1w}\) ) proton images were acquired from the same volume as xenon MRSI using a 3D SSFP imaging sequence with FOV = 40 × 40 × 20 cm3, matrix = 256 × 256 × 128, FA = 3°, TR = 3.4 ms, and TE = 2.1 ms, on the scanner's body coil within a breath-hold after administrating a 600 mL Tedlar bag of ambient air corresponding to the volume of administrated xenon gas. Both in vivo experiments of xenon imaging hyperpolarized with SEOP and dDNP were acquired with the same 3D Cartesian MRSI trajectory with a Hamming weighted random k-space sampling designed with a matrix size of 10 × 10 × 3 covering a field-of-view (FOV) of 30 × 30 × 30 cm 3 with a total of 824 excitations. A spectrally tailored RF pulse with a duration of 0.6 ms and partial self-refocusing was designed to excite the dissolved and gas phases with FAs of 10 ° and 0.1 ° and passbands of 500 and 200 Hz. The repetition time was 25.2 ms, resulting in a total acquisition time of 21 s, suitable for a single breath-hold in pigs. Data was acquired with 300 samples at a bandwidth of 20 kHz, corresponding to a spectral resolution of 67 Hz (1.91 ppm). Results Solid-state Xenon DNP In the initial development, we used a sample volume of 300 µL to obtain a dissolved gas concentration of 3.3 M as it was close to our previous work. However, DNP performance using Finland trityl benefitted from lower Xe concentration in the solid sample. Increasing the sample volume to 500 µL while keeping the total amount of dissolved Xe constant (2 M Xe concentration) doubled the solid-state signal (Fig. 3 A), while keeping the buildup times constant almost unchanged (T 300 = 1120 s, T 500 = 1117 s). Using enriched Xe further increased (times 3) the solid-state signal. Surprisingly, the buildup time constant increased (T enriched = 1262 s). Applying frequency modulation improved the polarization by 1.5 times and reduced the buildup time by 60% (Fig. 3 B). The improvement from frequency modulation is also visible in the relative magnitudes of the frequency sweeps (Fig. 3 C /D ). Sublimation of xenon Using croycollection, we were able to recover approximately 20 mL of Xe gas inside the syringe, in good agreement with the theoretical 25 mL dissolved into the radical doped isobutanol during sample preparation. Assuming that the direct extraction of the hyperpolarized gas inside the 600 mL Tedlar bag had the same efficiency, dDNP polarized gas mixture had a final xenon concentration around 3%, similar to that of SEOP without cryocollection and accumulation of the gas. As a first feasibility and repeatability assessment of the Xenon dDNP method in a clinical setting, the two Tedlar bags filled one with SEOP polarized gas and the other with DNP polarized gas were inserted in the MRI scanner and 129 Xe signal acquired with a train of 30° hard pulses every 2 s. The apparent \(\:{T}_{1}\) measured 17.4 ± 1.2 s and 20.1 ± 3.1 s for SEOP polarized gas and DNP polarized gas, respectively (Fig. 4 ). The SNR of the of the SEOP prolarized gas was approximately 3 times higher (see Figure S6 for a detailed discussion about the SNR of the two Tedlar bags). In vivo xenon Finally, in vivo 129 Xe MRSI of porcine lungs was overlaid onto anatomical images (Fig. 5 ) for both hyperpolarization methods, dDNP and SEOP. The SEOP-derived signal spans a slightly larger spatial extent, likely reflecting its higher signal-to-noise ratio (see Figure S7 ). Discussion As demonstrated in our previous work on solid-state xenon DNP, the properties of the radical are strongly influenced by the microscopic environment, ultimately determining the maximum achievable polarization. 23 In the present study, trityl radicals were selected over TEMPO due to the higher operating magnetic field (6.7 T) of the commercially available SpinAligner system. At 5 T, the electron relaxation time \(\:{T}_{1e}\) of TEMPO was previously measured in the range of 11–40 ms, 29 and is expected to decrease further at higher magnetic fields ( Figure S1 ). Such shortening of \(\:{T}_{1e}\) can limit polarization transfer efficiency, as excessively fast electron relaxation reduces the effectiveness of dynamic nuclear polarization. In contrast, trityl radicals, with their narrower ESR linewidth and longer relaxation times, are better suited for high-field DNP conditions. 33 , 34 The observed increase in polarization with larger sample volumes (Fig. 3 A) is likely related to improved gas dispersion within the sample matrix, resulting in greater xenon homogeneity. This effect led to the identification of 500 µL as an optimal sample volume under the current experimental constraints, including the Tedlar bag concentration and sublimation workflow. Under these conditions, the larger sample vials enabled xenon concentrations comparable to those obtained from SEOP without cryocollection when using a 600 mL Tedlar bag. However, this optimization is closely tied to the specific hardware configuration and may not directly translate to other systems. Microwave frequency modulation was found to enhance polarization, consistent with previous findings. 29 By effectively broadening the excitation bandwidth, frequency modulation allows a larger fraction of the EPR spectrum to contribute to the DNP process. This is reflected in the increased separation between positive and negative extrema in the frequency sweeps (Fig. 3 C /D ). Additionally, the observed shift of the zero-crossing point and the overall spectrum toward lower frequencies suggests increased electron saturation, leading to a reduction in the local magnetic field, analogous to a Knight shift–like effect. 32 Although the relative improvement in polarization is less pronounced for trityl than for TEMPO, due to the intrinsically narrower EPR spectrum and longer relaxation time of trityl radicals, 33,34 frequency modulation remains a beneficial strategy for maximizing solid-state polarization. 29 , 33 , 34 Optimization of the sublimation process represents an important step toward establishing dDNP as a viable hyperpolarization method for 129 Xe in biomedical applications. A further increase in achievable magnetization was obtained through the use of isotopically enriched xenon. The signal enhancement we obtained (i.e. threefold) was in good agreement with the 129 Xe isotopic fraction increase from natural abundance (26%) to enriched (86%). Differently, while higher target nuclei concentration would normally induce a shorting of the time constant because of faster spin diffusion, 35 we observed a mild increase from 1117 s to 1262 s. Probably, the increased nuclear heat capacity due to 3-fold more concentrated 129 Xe nuclei counterbalanced faster spin-diffusion and led to slower build-up of the polarization. 36 The apparent \(\:{T}_{1}\) relaxation of 129 Xe gas from the two Tedlar bags is, within experimental errors, very similar and close to 20 s. Being the real \(\:{T}_{1}\) of 129 Xe in a Tedlar bag 38 min and 6 h at 1.5 mT and 3 T, respectively, we can infer that: the transport (60–90 s) from polarizer (DNP or SEOP) to MRI scanner has relevant contribution to polarization losses; the decay in Fig. 4 is predominantly due to rf pulsing. Indeed, an apparent relaxation time of 17.4 s and 20.1 s due to rf pulsing every 2 s, is the result of a flip angle of 27° and 25°, respectively. This is in good agreement with the 30° nominal flip-angle used for these acquisitions. Notably, this study represents the first direct comparison of dDNP- and SEOP-derived xenon under identical isotopic enrichment conditions (86% 129 Xe). In vivo experiments (Fig. 5 ) revealed practical limitations associated with the delivered gas volume. The use of 600 mL, compared to the standard 800 mL for porcine studies, resulted in reduced lung inflation, which may have influenced the observed signal distribution. Moreover, at a xenon concentration of 3%, such volumes are unlikely to be sufficient for adult human imaging, although they may be appropriate for preclinical studies in smaller animal models. Indeed, the signal distribution in the lower lung regions is comparable between the two methods, indicating that dDNP-derived xenon provides consistent regional ventilation contrast. Remarkably, both MRSI datasets demonstrate the presence of gaseous 129 Xe as well as dissolved-phase xenon resonances around 200 ppm ( Figure S7 ). Nonetheless, SEOP provides broader spatial coverage, likely reflecting its superior polarization and delivery efficiency. Overall, Fig. 5 demonstrates that, despite reduced sensitivity, dDNP enables spatially resolved lung imaging with signal localization comparable to the established SEOP approach, when very large volumes are not required. Conclusion In this work, we demonstrate the feasibility of hyperpolarizing 129 Xe using dissolution dynamic nuclear polarization in a commercially available high-field polarizer. By adapting the experimental setup—including radical selection, sample geometry, microwave frequency modulation, and sublimation conditions—we achieved solid-state polarization levels sufficient for downstream gas-phase delivery and in vivo imaging. The use of trityl radicals proved advantageous at 6.7 T, while frequency modulation and increased sample volume contributed to improved polarization efficiency. The implementation of isotopically enriched xenon further enhanced the achievable magnetization, yielding near-proportional gains in solid-state polarization. Combined with an optimized sublimation workflow, these developments enabled the production of hyperpolarized xenon suitable for preclinical imaging experiments. In vivo MRSI demonstrated that dDNP-derived xenon can capture both gaseous and dissolved-phase signals and reproduce key features of regional ventilation. Compared to the established SEOP approach, dDNP remains limited by reduced signal-to-noise ratio, spatial coverage, and overall robustness. Additional constraints arise from gas delivery volume and concentration, which currently restrict translation to larger animal models or clinical applications. Nevertheless, the possibility to perform multi-nuclear hyperpolarized MR with the same polarizer has great potential and can represent a cost-attractive option for pre-clinical applications. 38 Declarations Data availability The author declares that all data supporting the findings of this study are available within the paper and its supplementary information files. Raw data are available from the corresponding author ( [email protected] ) on reasonable request. Acknowledgments We thank Dr Thanh Lê from EPFL and M. Duy Anh Dang from Aarhus University Hospital for their constant help with experiments. Research funding This work was supported by the SNSF SPARK grant (501100001711_190547, assigned to Capozzi), the SNSF Ambizione grant (501100001711_193276, assigned to Capozzi). The SNSF Project grant (310030_170155 assigned to Hyacinthe). Karen Elise Jensens Foundation, Lundbeck and Novonordisk foundation (Assigned to Laustsen). Contributions A.C., J.N.H. and C.L. designed and supervised the study. E.W., E.H. and M.V. acquired and processed data. A.C., E.W., J.N.H., M.V. analyzed the data. A.C. and E.W. wrote the manuscript. All authors discussed the results and reviewed the manuscript. Competing Interest A.C. works for Polarize ApS. Polarize is a tech company that builds and commercializes dDNP equipment. All the other authors declare no conflict of interest. Ethics statement This study complied with institutional and national guidelines and was approved by the Animal Experiment Council, governed under the Danish Animal Inspectorate, before initiation under license 2023-15-0201-01553. References Mugler, J. P. & Altes, T. A. Hyperpolarized 129Xe MRI of the human lung. J. Magn. Reson. Imaging . 37 , 313–331 (2013). Wild, J. M. et al. Review of Hyperpolarized Pulmonary Functional 129Xe MR for Long-COVID. J. Magn. Reson. Imaging . 59 , 1120–1134 (2024). Qing, K. et al. 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Hyacinthe, J. N., Capozzi, A. & Comment, A. Beyond Spin Exchange Optical Pumping: Hyperpolarization of 129 Xe via Sublimation Dynamic Nuclear Polarization. in Hyperpolarized Xenon-129 Magnetic Resonance: Concepts, Production, Techniques and Applications (eds. Meersmann, T. & Brunner, E.) 442–452The Royal Society of Chemistry, (2015). 10.1039/9781782628378-00442 Mariager, C., Ringgaard, S., Ardenkjaer-Larsen, J. H. & Laustsen, C. Hyperpolarized xenon by d-DNP using the clinical GE SpinLab polarizer system. in ISMRM ISMRM, (2017). Wiström, E., Hyacinthe, J. N., Lê, T. P., Gruetter, R. & Capozzi, A. 129Xe Dynamic Nuclear Polarization Demystified: The Influence of the Glassing Matrix on the Radical Properties. J. Phys. Chem. Lett. 15 , 2957–2965 (2024). Lê, T. P., Hyacinthe, J. N. & Capozzi, A. Multi-sample/multi-nucleus parallel polarization and monitoring enabled by a fluid path technology compatible cryogenic probe for dissolution dynamic nuclear polarization. Scientific Reports 2023 13:1 13, 1–14 (2023). Capozzi, A., Ardenkjear-Larsen, J. H. & Hyacinthe, J. N. 129Xe gas hyperpolarized via sublimation DNP at 6.7 T and 1.1 K using a reusable purpose-built fluid path. in P063 273EuroIsmar, (2019). Slichter, C. P. Principles of Magnetic Resonance (Springer-, 1996). Jan Henrik Ardenkjær-Larsen. Hyperpolarization by Dissolution Dynamic Nuclear Polarization. in Dynamic Hyperpolarized Nuclear Magnetic Resonance (eds. Jue, T. & Mayer, D.) vol. 6 1–21 (Springer International Publishing, Cham, (2021). Hu, K. N., Bajaj, V. S., Rosay, M. & Griffin, R. G. High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. J. Chem. Phys. 126 , 44512 (2007). Lumata, L. et al. Effect of 13C enrichment in the glassing matrix on dynamic nuclear polarization. J. Magn. Reson. 209 , 179–186 (2011). Wenckebach, W. T. Dynamic nuclear polarization via thermal mixing: beyond the high temperature approximation. J. Magn. Reson. 277 , 68–78 (2017). Nikolaou, P. et al. Near-unity nuclear polarization with an open-source 129Xe hyperpolarizer for NMR and MRI. Proc. Natl. Acad. Sci. U.S.A. 110, 14150–14155 (2013). Lê, T. P., Hyacinthe, J. N. & Capozzi, A. Multi-sample/multi-nucleus parallel polarization and monitoring enabled by a fluid path technology compatible cryogenic probe for dissolution dynamic nuclear polarization. Sci. Rep. 13 , 7962 (2023). Additional Declarations Competing interest reported. A.C. works for Polarize ApS. Polarize is a tech company that builds and commercializes dDNP equipment. All the other authors declare no conflict of interest. Supplementary Files 20260325SIfinal.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 04 May, 2026 Reviewers agreed at journal 04 May, 2026 Reviewers invited by journal 21 Apr, 2026 Editor assigned by journal 21 Apr, 2026 Editor invited by journal 21 Apr, 2026 Submission checks completed at journal 17 Apr, 2026 First submitted to journal 17 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9236425","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":628248328,"identity":"029c9e71-ecd6-48f6-9528-3fedebd9e2f7","order_by":0,"name":"Emma Wiström","email":"","orcid":"","institution":"EPFL, Station 6 (Bâtiment CH)","correspondingAuthor":false,"prefix":"","firstName":"Emma","middleName":"","lastName":"Wiström","suffix":""},{"id":628248329,"identity":"1a552832-76ff-4926-bae9-d2669afff085","order_by":1,"name":"Jean-Noël Hyacinthe","email":"","orcid":"","institution":"EPFL, Station 6 (Bâtiment CH)","correspondingAuthor":false,"prefix":"","firstName":"Jean-Noël","middleName":"","lastName":"Hyacinthe","suffix":""},{"id":628248330,"identity":"f46359d7-220e-4f10-bd00-1d95ec379d4c","order_by":2,"name":"Esben Søvsø Szocska Hanssen","email":"","orcid":"","institution":"Aarhus University","correspondingAuthor":false,"prefix":"","firstName":"Esben","middleName":"Søvsø Szocska","lastName":"Hanssen","suffix":""},{"id":628248331,"identity":"5c6e6894-4b0e-40ff-8707-cb2dca5d4f3a","order_by":3,"name":"Michael Vaeggemose","email":"","orcid":"","institution":"Aarhus University","correspondingAuthor":false,"prefix":"","firstName":"Michael","middleName":"","lastName":"Vaeggemose","suffix":""},{"id":628248332,"identity":"f832ba7e-e31f-49d5-b717-d113ba05e116","order_by":4,"name":"Christoffer Laustsen","email":"","orcid":"","institution":"Aarhus University","correspondingAuthor":false,"prefix":"","firstName":"Christoffer","middleName":"","lastName":"Laustsen","suffix":""},{"id":628248333,"identity":"77d1ed2a-570e-4f75-9e4b-a7fd5728bb2b","order_by":5,"name":"Andrea Capozzi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIiWNgGAWjYHACA2S2DQMD8+EGBsYG4rWkMTCwJZKkheEwYS38s5u3ffhQwyAPZBz++KPgvJw5G1D9zx24tUjcOVY8c8YxBsMZd44lGEgY3Da2bGNsYOw9g8dZN3KMmXnYGBKADIMEA4PbiRvuNzYwM7bh1iEP0vLnH0MCkGFwIMHgXP2GY4z4tRiAtAAVJAAZhg0HQLoIaTG8kVbM2NsnYbjxzrFkxgaDZMOdQL8c7MWjRe5G8maGH99s5OVug0Lsj528ORvzwQc/8WiBAgkwgjgViA8Q1ADTBdcyCkbBKBgFowAZAAADrVNU1VWfvgAAAABJRU5ErkJggg==","orcid":"","institution":"EPFL, Station 6 (Bâtiment CH)","correspondingAuthor":true,"prefix":"","firstName":"Andrea","middleName":"","lastName":"Capozzi","suffix":""}],"badges":[],"createdAt":"2026-03-26 16:23:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9236425/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9236425/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108097621,"identity":"cf3e1f88-8645-4533-ac34-ed7dc675c3e4","added_by":"auto","created_at":"2026-04-29 10:15:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":17602,"visible":true,"origin":"","legend":"\u003cp\u003eTechnical drawings of sample vials used in the polarizer SpinAligner (Polarize, Denmark): standard vial in use, and the larger, thicker-walled vial used in xenon dDNP.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/e6c52cee8f7fdfb58f18fd38.png"},{"id":108182591,"identity":"f36d866d-3790-4d19-9c76-34bf73246d6c","added_by":"auto","created_at":"2026-04-30 08:59:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":199334,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental setup of xenon DNP and the time estimates\u003cstrong\u003e:\u003c/strong\u003e sample preparation \u003cstrong\u003e(A)\u003c/strong\u003e, DNP hyperpolarization in a SpinAligner \u003cstrong\u003e(B)\u003c/strong\u003e, sublimation with a cryogenic-free phase separator (more detailed in S3) \u003cstrong\u003e(C)\u003c/strong\u003e, gas collection of xenon and helium in a Tedlar bag \u003cstrong\u003e(D)\u003c/strong\u003e, MRI acquisition of a Tedlar bag or in vivo, either with a ventilation or spectroscopy sequence \u003cstrong\u003e(E)\u003c/strong\u003e.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/8531a25a3471fedb0ef6fde2.png"},{"id":108097623,"identity":"b1596cd6-205b-40f0-b332-174def9dd767","added_by":"auto","created_at":"2026-04-29 10:15:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":692062,"visible":true,"origin":"","legend":"\u003cp\u003eDNP buildup of solid-state xenon hyperpolarization in samples with 30 mM radical, and 25 mL natural abundant xenon in volumes of 300 and 500 µL, as well as enriched xenon gas in a 500 µL sample volume \u003cstrong\u003e(A)\u003c/strong\u003e. DNP buildup of natural abundant xenon in a sample volume of 500 µL with and without frequency modulation \u003cstrong\u003e(B)\u003c/strong\u003e. Microwave frequency sweeps with and without frequency modulation of sample volume 300 µL \u003cstrong\u003e(C)\u003c/strong\u003e and 500 µL \u003cstrong\u003e(D)\u003c/strong\u003e.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/d38ff4eaf7dbedc4a4804a92.png"},{"id":108181823,"identity":"58292123-efb7-4171-b1b2-2ef4d5846727","added_by":"auto","created_at":"2026-04-30 08:58:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":284543,"visible":true,"origin":"","legend":"\u003cp\u003eNormalized signal decay of \u003csup\u003e129\u003c/sup\u003eXe in Tedlar bags, hyperpolarized via SEOP and DNP. Acquired with a non-localized MRS, 10 repeated 30° hard pulses, TR = 2 s. T\u003csub\u003e1 \u003c/sub\u003evalues ascertained by mono-exponential fitting (n=3).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/e58b9af8d96094156de2228d.png"},{"id":108097625,"identity":"4413b3a4-fea6-483b-a39c-f4440008b718","added_by":"auto","created_at":"2026-04-29 10:15:07","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":616540,"visible":true,"origin":"","legend":"\u003cp\u003eIn vivo MRSI images with hyperpolarized \u003csup\u003e129\u003c/sup\u003eXe produced by DNP and SEOP, overlayed anatomical images of porcine lungs. Both methods delivered 600 mL of xenon gas, isotopically enriched at 86% \u003csup\u003e129\u003c/sup\u003eXe. The field-of-view (FOV) is 30 × 30 × 30 cm\u003csup\u003e3\u003c/sup\u003e, exciting the dissolved and gas phases with FAs of 10 ° and 0.1 °.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/792ce03167ba63903bef34de.png"},{"id":108184231,"identity":"99005eeb-d316-4aa4-9769-7ecb5e8971ae","added_by":"auto","created_at":"2026-04-30 09:03:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2122832,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/adfab8f6-936e-4754-8cff-bade815e05db.pdf"},{"id":108097627,"identity":"46572be2-41e8-4137-a927-0ba364fa3ca8","added_by":"auto","created_at":"2026-04-29 10:15:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1434972,"visible":true,"origin":"","legend":"","description":"","filename":"20260325SIfinal.docx","url":"https://assets-eu.researchsquare.com/files/rs-9236425/v1/e38a6884efe86b26e68fa821.docx"}],"financialInterests":"Competing interest reported. A.C. works for Polarize ApS. Polarize is a tech company that builds and commercializes dDNP equipment. All the other authors declare no conflict of interest.","formattedTitle":"Hyperpolarized ¹²⁹Xe MRI Using Dissolution DNP on a Commercial Polarizer: From Solid-State Optimization to In Vivo Lung Imaging","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHyperpolarized (HP) \u0026sup1;\u0026sup2;⁹Xe MRI is an excellent diagnostic tool for diseases related to the alteration of human lungs\u0026rsquo; function and structure.\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e To this end, ventilation imaging has been the subject of many preclinical and clinical studies for more than two decades,\u003csup\u003e4\u0026ndash;7\u003c/sup\u003e and in 2022 its related clinical product, Polarean\u0026rsquo;s XENONVIEW\u003csup\u003e\u0026trade;\u003c/sup\u003e, received FDA approval as an ionizing radiation-free alternative to \u003csup\u003e133\u003c/sup\u003eXe scintigraphy for adults and pediatric patients aged 12 years and older.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e Moreover, xenon is lipophilic. Therefore, it dissolves in tissue, blood, and can cross the blood-brain barrier. This peculiar feature, together with \u003csup\u003e129\u003c/sup\u003eXe broad chemical shift dispersion as a function of the molecular environment, makes it an ideal tracer for perfusion MRI of organs such as the brain,\u003csup\u003e9\u003c/sup\u003e the kidneys,\u003csup\u003e10\u003c/sup\u003e and the lungs. Remarkably, it was recently demonstrated that HP \u003csup\u003e129\u003c/sup\u003eXe lung perfusion could detect lower gas transfer to the red blood cells in patients with long-COVID, despite having normal CT findings.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eSpin Exchange Optical Pumping (SEOP) is the gold-standard method to hyperpolarize \u003csup\u003e129\u003c/sup\u003eXe.\u003csup\u003e\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e This technique is limited to noble gases, with polarization transfer occurring directly in the gas phase. In SEOP, a gas mixture containing the noble gas (for example, \u003csup\u003e129\u003c/sup\u003eXe), a buffer gas (such as \u003csup\u003e4\u003c/sup\u003eHe), a radiation-trapping suppression gas (typically N\u003csub\u003e2\u003c/sub\u003e), and trace amounts of alkali-metal vapor (for example, Rb) is loaded into a so-called pumping cell. The cell is maintained in a magnetic field of a few mT and heated to approximately 100\u0026ndash;200\u0026deg;C. The Rb atoms are optically pumped with circularly polarized laser light at 795 nm, and subsequently transfer polarization to the \u003csup\u003e129\u003c/sup\u003eXe nuclei through collisions and angular-momentum exchange. The He and N\u003csub\u003e2\u003c/sub\u003e gases serve to broaden the Rb absorption line and to quench radiative de-excitation, respectively.\u003c/p\u003e \u003cp\u003eThe Rb atoms are optically pumped with circularly polarized laser light at 795 nm, and subsequently transfer polarization to the \u003csup\u003e129\u003c/sup\u003eXe nuclei through collisions and angular-momentum exchange. The He and N\u003csub\u003e2\u003c/sub\u003e gases serve to broaden the Rb absorption line and to quench radiative de-excitation, respectively.\u003c/p\u003e \u003cp\u003eWhile generally leading to lower polarizations than stopped-flow systems, continuous-flow systems with cryogenic accumulation yield higher Xe production rates and are more adapted for clinical use. For instance, the SEOP system used in this study (POLARIS Technology, University of Sheffield) can produce up to 300 cm\u003csup\u003e3\u003c/sup\u003e of \u003csup\u003e129\u003c/sup\u003eXe with a nuclear spin polarization (\u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003eXe\u003c/em\u003e\u003c/sub\u003e) of approximately 30% in 5 min (i.e. throughput of 3.6 L/h).\u003csup\u003e16\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eAn alternative way to generate HP \u003csup\u003e129\u003c/sup\u003eXe gas is using dissolution Dynamic Nuclear Polarization (dDNP), followed by a sublimation step to separate the gas from the liquid phase of the dissolved sample.\u003csup\u003e\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e Unlike SEOP, in dDNP, the polarization transfer to the nuclei happens in the solid state at low temperature (0.8\u0026ndash;1.4 K) and at much higher magnetic fields (3.35\u0026ndash;7 T).\u003csup\u003e19\u003c/sup\u003e The source of polarization is represented by unpaired electron spins, in form of organic free radicals, mixed with the target molecules in a ratio of 1 to 1000. Unless the substrate of interest spontaneously solidifies into an amorphous solid at low temperature (e.g. pyruvic acid), to avoid crystallization of the sample that would hinder a random orientation distribution of the electron spins, common practice is to dissolve the substrate and the radical into a glassing agent such as water:glycerol or DMSO. Excitation slightly off-resonance of the electrons\u0026rsquo; Zeeman transition by using microwave irradiation triggers the polarization transfer to the nuclei.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Once hyperpolarized, the solid sample is transformed into an injectable solution through a sudden temperature jump and dilution procedure, the so-called dissolution step.\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eOne of the strengths of dDNP is to be compound-agnostic: in principle, any NMR active nucleus can be hyperpolarized in the solid-state and, provided that its liquid-state relaxation time (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e) is long enough (i.e. tens of seconds), a hyperpolarized solution containing that nucleus can be obtained. Hence, dDNP offers the chance to enhance the liquid-state NMR signal of various nuclei such as \u003csup\u003e13\u003c/sup\u003eC, \u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e31\u003c/sup\u003eP, and \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003eLi by several orders of magnitude while using a single polarizing apparatus.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan additionalcitationids=\"CR23 CR24\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e Nevertheless, when dDNP is used to hyperpolarize \u003csup\u003e129\u003c/sup\u003eXe, some extra elements must be considered already before the dissolution/sublimation step:\u003csup\u003e18\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eXe is in the gas state at standard temperature and pressure conditions.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eA host glassing solvent with melting temperature close to the Xe triple-point (i.e. 161.4 K) is needed to dissolve the radical.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eXe and the radical-doped glassing solvent must be mixed while coexisting in the liquid state.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eXe is lipophilic, and the glassing solvent polarity determines the gas solubility threshold above which the liquified gas and solvent will form a heterogeneous mixture.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eWe recently demonstrated that sample preparation at controlled temperature (i.e. 160 K) together with ultrasonication of the liquid Xe and radical doped solvent mixture yielded improved and consistent DNP results.\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e Moreover, microwave frequency modulation led to solid-state \u003csup\u003e129\u003c/sup\u003eXe polarization levels comparable to what can be achieved with \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC samples at 5 T.\u003csup\u003e29,30\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn the present study, we focus on establishing a robust polarization and gas extraction protocol applicable to a commercial dDNP polarizer installed in a clinical setting at Aarhus University Hospital. Hyperpolarized gas acquisitions were performed on a clinical scanner, and the results were compared to those obtained using a gold-standard SEOP polarizer, routinely used for clinical HP \u003csup\u003e129\u003c/sup\u003eXe MRI.\u003c/p\u003e"},{"header":"Experimental methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eXenon dDNP hardware\u003c/h2\u003e\n \u003cp\u003eThe dDNP system used in this study was a SpinAligner polarizer (Polarize, Denmark) operating at 6.7 T and 1.3 K.\u003c/p\u003e\n \u003cp\u003eWe used a sample vial larger and with thicker walls compared to the standard SpinAligner vial to increase sample volume and improve sample\u0026rsquo;s thermal insulation during loading (Fig. \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eTo prevent the sample from melting during loading, pump/flush of the airlock prior to sample insertion was reduced from three cycles to one and descending speed increased from 15 mm/s to 150 mm/s.\u003c/p\u003e\n \u003cp\u003eTo acquire the \u003csup\u003e129\u003c/sup\u003eXe signal during DNP experiments, the SpinAligner probe was tuned and matched remotely to 78.5 MHz and 50 Ohm, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eXenon dDNP sample preparation\u003c/h3\u003e\n\u003cp\u003eAll dDNP samples in this work consist of 30 mM trityl radical (Finland acid), isobutanol and 1.0 x 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e mole of either natural abundant xenon gas (26% \u003csup\u003e129\u003c/sup\u003eXe) or isotopically enriched xenon gas (86% \u003csup\u003e129\u003c/sup\u003eXe, Cortecnet, France). This amount is equivalent to 25 mL xenon gas (at atmospheric pressure). The gas was dissolved either in 300 \u0026micro;L of radical-doped solvent (3.3 M of Xe concentration), or in 500 \u0026micro;L of radical-doped solvent (2.0 M of Xe concentration).\u003c/p\u003e\n\u003cp\u003eSolvent and gas mixing was performed at -100\u0026deg;C using ultrasonication (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), as previously described.\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e Once fully mixed, the sample was flash frozen by immersing the sample cup in liquid nitrogen, where it was kept until loading into the polarizer. The Xe DNP sample preparation method was developed and described in detail earlier. For further information refer to our previous works.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003ch3\u003eXenon dDNP solid-state measurements\u003c/h3\u003e\n\u003cp\u003eThe ideal microwave frequency for the specific sample composition was determined by frequency sweeps, with and without frequency modulation (sinusoidal output with \u0026plusmn;\u0026thinsp;20 MHz peak-to-peak modulation amplitude at 10 kHz modulation rate), from 187.8 GHz to 188.4 GHz in 10 MHz-steps (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC\u003cstrong\u003e/D\u003c/strong\u003e). At each frequency step, the sample was polarized with 12 mW microwave power for 5 minutes, and the NMR signal was acquired with a 25\u0026deg; hard pulse and averaged 16 times. Between microwave frequency steps, the residual signal after readout was destroyed by a pulse saturation block (2000 x 25\u0026deg;). \u003csup\u003e31\u003c/sup\u003e Microwave power at best irradiation frequency was optimized by sweeping the output value from 3 mW to 30 mW with increments of 3 mW (\u003cstrong\u003eFigure S2\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eThe sample polarization buildup was measured at optimal microwave irradiation conditions acquiring the \u003csup\u003e129\u003c/sup\u003eXe NMR signal every 3 minutes (5\u0026deg; hard pulse, averaged 16 times).\u003c/p\u003e\n\u003cp\u003eAll DNP data were acquired in SPINit 2021.01 (RS2D, Mundolsheim, France), exported as JCAMP-DX files, processed first in MNova (MestreLab Research, Santiago, Spain), then in MATLAB R2024b.\u003c/p\u003e\n\u003ch3\u003eXenon Sublimation\u003c/h3\u003e\n\u003cp\u003eDissolution of the frozen and hyperpolarized sample was performed using the standard hardware and procedure of the SpinAligner polarizer but, instead of dissolving into an open receiver, we used a purposed built phase separator (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC\u003cstrong\u003e/D\u003c/strong\u003e). The phase separator (\u003cstrong\u003eFigure S3\u003c/strong\u003e), made of Polychlorotrifluoroethylene (PTCFE) and Polyether ether ketone (PEEK) is hermetically sealed using a NBR o-ring at the lid connection and Flangeless Fittings (IDEX P-335, BGB Analytik AG, USA) around the 1/8\u0026rdquo; outer diameter Polytetrafluoroethylene (PTFE) tubing, for inlet of the liquid/gases mixture and outlet of the gases only. Xe and He gases are finally collected in a 0.6 L Tedlar bag (Sigma-Aldrich, Switzerland) connected at the end of the gas extraction line via a PEEK Luer Lock (IDEX-P-683, BGB Analytik AG, USA) a 3-way stopcock (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). The buffer volume (8 mL D\u003csub\u003e2\u003c/sub\u003eO) and He gas push time (2 s) were optimized to obtain at the same time complete dissolution of the frozen sample and no liquid contamination of the Tedlar bag. Prior to dissolution, the extraction system (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB-D) was evacuated using a vacuum pump. After extraction of the gas, the Tedlar bag was closed and transported to the 3T MRI scanner (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE). The full procedure from dissolution to the onset of MR acquisition took approximately 60 s.\u003c/p\u003e\n\u003cp\u003eIn a separate set of experiments, cryocollection was used to estimate the extracted volume amount of Xe gas from the dDNP polarizer. In this case, the Tedlar bag was replaced by a high-pressure NMR tube. After dissolution and liqui/gas phase separation, the Xe/He gas mixture was pushed into the NMR tube and the inlet closed at the end of the push time. The NMR tube was then plunged in liquid nitrogen to freeze the Xe, and a vacuum pump connected to the inlet to remove the He. Afterwards, the pump was replaced by an empty syringe, the Xe ice warmed up, and the syringe piston pulled until possible.\u003c/p\u003e\n\u003ch3\u003eSEOP hyperpolarization \u003csup\u003e129\u003c/sup\u003eXe Gas Preparation\u003c/h3\u003e\n\u003cp\u003eIn all SEOP experiments, the \u003csup\u003e129\u003c/sup\u003eXe gas was polarized to about 30% using a spin exchange optical pumping (SEOP) polarizer (POLARIS, University of Sheffield, Sheffield, UK).\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e The gas mixture was 3% isotopically enriched xenon (86% \u003csup\u003e129\u003c/sup\u003eXe), 10% N\u003csub\u003e2\u003c/sub\u003e, and 87% He flowed through a glass cell (volume\u0026thinsp;=\u0026thinsp;3534 cm\u003csup\u003e3\u003c/sup\u003e, temperature\u0026thinsp;=\u0026thinsp;130\u0026deg;C; total gas pressure\u0026thinsp;=\u0026thinsp;2 bars) at a flow rate of 2000 standard cubic centimeters per minute (sccm). After polarization the 3% xenon gas mixture was collected without cryogenic separation, dispensing 600 mL directly into a 1 L Tedlar bag, yielding a \u003csup\u003e129\u003c/sup\u003eXe dose of ~\u0026thinsp;15 mL per bag. The polarization of this single batch took approximately 10 min. The elapsed time from gas collection to onset of MR acquisition was approximately 90 s.\u003c/p\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eAnimal Model and Xenon Gas Administration\u003c/h2\u003e\n \u003cp\u003eThe study examined female Danish Landrace pigs, weighing approximately 40 kg. The pig was anesthetized through an ear vein catheter (fentanyl and propofol, doses 8 and 18 mL/h, respectively), intubated and attached to a mechanical ventilator at fractional inspired oxygen levels (FiO2) of 21% with a continuous flow of 5400 mL/min in pressure-controlled ventilation-volume guaranteed mode (PCV-VG). This study complied with institutional and national guidelines and was approved by the Animal Experiment Council, governed under the Danish Animal Inspectorate, before initiation under license 2023-15-0201-01553. Xenon gas was administered by unplugging the mechanical ventilation system from the tracheal tube and switching to the Tedlar bag. Functional residual capacity was achieved by waiting approximately 2 s before connecting the bag to the tracheal tube. Xenon gas was administered to the lungs in a steady flow with a gentle pressure on the bag, emptying it in 3 s to avoid damaging the lungs with excessive pressure. At the end of the experiment the animal was euthanized under anesthesia by an injection of pentobarbital.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eMRI acquisition and data processing\u003c/h3\u003e\n\u003cp\u003eAll HP \u003csup\u003e129\u003c/sup\u003eXe MRI and MRS experiments were performed on a 3 T MRI scanner (MR750, GE HealthCare, Waukesha, WI, USA) using a \u003csup\u003e129\u003c/sup\u003eXe transmit-receive quadrature vest coil (Clinical MR Solutions, Brookfield, WI, USA) tuned to 35.3 MHz.\u003c/p\u003e\n\u003ch3\u003eTedlar bag acquisition\u003c/h3\u003e\n\u003cp\u003eWe first compared the performance of xenon dDNP to SEOP in clinically relevant experimental conditions, by measuring Tedlar bags with non-localized MRS acquired with 10 consegutive 30\u0026deg; hard pulses with repetition time TR\u0026thinsp;=\u0026thinsp;2 s. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e relaxation times for DNP and SEOP samples were obtained by fitting a mono-exponential curve to the data (n\u0026thinsp;=\u0026thinsp;3). All magnetization and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e data were processed in MATLAB R2024b.\u003c/p\u003e\n\u003cp\u003eWe also acquired ventilation images of the Tedlar bags prior to the \u003cem\u003ein vivo\u003c/em\u003e experiment (\u003cstrong\u003eFigure S5\u003c/strong\u003e/\u003cstrong\u003eS6\u003c/strong\u003e).\u003c/p\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eIn vivo acquisition\u003c/h2\u003e\n \u003cp\u003eAs anatomical reference, coronal 3D \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e-weighted (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1w}\\)\u003c/span\u003e\u003c/span\u003e) proton images were acquired from the same volume as xenon MRSI using a 3D SSFP imaging sequence with FOV\u0026thinsp;=\u0026thinsp;40 \u0026times; 40 \u0026times; 20 cm3, matrix\u0026thinsp;=\u0026thinsp;256 \u0026times; 256 \u0026times; 128, FA\u0026thinsp;=\u0026thinsp;3\u0026deg;, TR\u0026thinsp;=\u0026thinsp;3.4 ms, and TE\u0026thinsp;=\u0026thinsp;2.1 ms, on the scanner\u0026apos;s body coil within a breath-hold after administrating a 600 mL Tedlar bag of ambient air corresponding to the volume of administrated xenon gas.\u003c/p\u003e\n \u003cp\u003eBoth \u003cem\u003ein vivo\u003c/em\u003e experiments of xenon imaging hyperpolarized with SEOP and dDNP were acquired with the same 3D Cartesian MRSI trajectory with a Hamming weighted random k-space sampling designed with a matrix size of 10 \u0026times; 10 \u0026times; 3 covering a field-of-view (FOV) of 30 \u0026times; 30 \u0026times; 30 cm\u003csup\u003e3\u003c/sup\u003e with a total of 824 excitations. A spectrally tailored RF pulse with a duration of 0.6 ms and partial self-refocusing was designed to excite the dissolved and gas phases with FAs of 10 \u0026deg; and 0.1 \u0026deg; and passbands of 500 and 200 Hz. The repetition time was 25.2 ms, resulting in a total acquisition time of 21 s, suitable for a single breath-hold in pigs. Data was acquired with 300 samples at a bandwidth of 20 kHz, corresponding to a spectral resolution of 67 Hz (1.91 ppm).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eSolid-state Xenon DNP\u003c/h2\u003e \u003cp\u003eIn the initial development, we used a sample volume of 300 \u0026micro;L to obtain a dissolved gas concentration of 3.3 M as it was close to our previous work. However, DNP performance using Finland trityl benefitted from lower Xe concentration in the solid sample. Increasing the sample volume to 500 \u0026micro;L while keeping the total amount of dissolved Xe constant (2 M Xe concentration) doubled the solid-state signal (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), while keeping the buildup times constant almost unchanged (T\u003csub\u003e300\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1120 s, T\u003csub\u003e500\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1117 s). Using enriched Xe further increased (times 3) the solid-state signal. Surprisingly, the buildup time constant increased (T\u003csub\u003eenriched\u003c/sub\u003e = 1262 s). Applying frequency modulation improved the polarization by 1.5 times and reduced the buildup time by 60% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The improvement from frequency modulation is also visible in the relative magnitudes of the frequency sweeps (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC\u003cb\u003e/D\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eSublimation of xenon\u003c/h2\u003e \u003cp\u003eUsing croycollection, we were able to recover approximately 20 mL of Xe gas inside the syringe, in good agreement with the theoretical 25 mL dissolved into the radical doped isobutanol during sample preparation. Assuming that the direct extraction of the hyperpolarized gas inside the 600 mL Tedlar bag had the same efficiency, dDNP polarized gas mixture had a final xenon concentration around 3%, similar to that of SEOP without cryocollection and accumulation of the gas. As a first feasibility and repeatability assessment of the Xenon dDNP method in a clinical setting, the two Tedlar bags filled one with SEOP polarized gas and the other with DNP polarized gas were inserted in the MRI scanner and \u003csup\u003e129\u003c/sup\u003eXe signal acquired with a train of 30\u0026deg; hard pulses every 2 s. The apparent \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e measured 17.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 s and 20.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 s for SEOP polarized gas and DNP polarized gas, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The SNR of the of the SEOP prolarized gas was approximately 3 times higher (see Figure S6 for a detailed discussion about the SNR of the two Tedlar bags).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eIn vivo xenon\u003c/h2\u003e \u003cp\u003eFinally, in vivo \u003csup\u003e129\u003c/sup\u003eXe MRSI of porcine lungs was overlaid onto anatomical images (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) for both hyperpolarization methods, dDNP and SEOP. The SEOP-derived signal spans a slightly larger spatial extent, likely reflecting its higher signal-to-noise ratio (see \u003cb\u003eFigure S7\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eAs demonstrated in our previous work on solid-state xenon DNP, the properties of the radical are strongly influenced by the microscopic environment, ultimately determining the maximum achievable polarization.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e In the present study, trityl radicals were selected over TEMPO due to the higher operating magnetic field (6.7 T) of the commercially available SpinAligner system. At 5 T, the electron relaxation time \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1e}\\)\u003c/span\u003e\u003c/span\u003e of TEMPO was previously measured in the range of 11\u0026ndash;40 ms,\u003csup\u003e29\u003c/sup\u003e and is expected to decrease further at higher magnetic fields (\u003cb\u003eFigure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e). Such shortening of \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1e}\\)\u003c/span\u003e\u003c/span\u003e can limit polarization transfer efficiency, as excessively fast electron relaxation reduces the effectiveness of dynamic nuclear polarization. In contrast, trityl radicals, with their narrower ESR linewidth and longer relaxation times, are better suited for high-field DNP conditions.\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e The observed increase in polarization with larger sample volumes (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA) is likely related to improved gas dispersion within the sample matrix, resulting in greater xenon homogeneity. This effect led to the identification of 500 \u0026micro;L as an optimal sample volume under the current experimental constraints, including the Tedlar bag concentration and sublimation workflow. Under these conditions, the larger sample vials enabled xenon concentrations comparable to those obtained from SEOP without cryocollection when using a 600 mL Tedlar bag. However, this optimization is closely tied to the specific hardware configuration and may not directly translate to other systems.\u003c/p\u003e \u003cp\u003eMicrowave frequency modulation was found to enhance polarization, consistent with previous findings.\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e By effectively broadening the excitation bandwidth, frequency modulation allows a larger fraction of the EPR spectrum to contribute to the DNP process. This is reflected in the increased separation between positive and negative extrema in the frequency sweeps (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC\u003cb\u003e/D\u003c/b\u003e). Additionally, the observed shift of the zero-crossing point and the overall spectrum toward lower frequencies suggests increased electron saturation, leading to a reduction in the local magnetic field, analogous to a Knight shift\u0026ndash;like effect.\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e Although the relative improvement in polarization is less pronounced for trityl than for TEMPO, due to the intrinsically narrower EPR spectrum and longer relaxation time of trityl radicals, \u003csup\u003e33,34\u003c/sup\u003e frequency modulation remains a beneficial strategy for maximizing solid-state polarization.\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eOptimization of the sublimation process represents an important step toward establishing dDNP as a viable hyperpolarization method for \u003csup\u003e129\u003c/sup\u003eXe in biomedical applications. A further increase in achievable magnetization was obtained through the use of isotopically enriched xenon. The signal enhancement we obtained (i.e. threefold) was in good agreement with the \u003csup\u003e129\u003c/sup\u003eXe isotopic fraction increase from natural abundance (26%) to enriched (86%). Differently, while higher target nuclei concentration would normally induce a shorting of the time constant because of faster spin diffusion, \u003csup\u003e35\u003c/sup\u003e we observed a mild increase from 1117 s to 1262 s. Probably, the increased nuclear heat capacity due to 3-fold more concentrated \u003csup\u003e129\u003c/sup\u003eXe nuclei counterbalanced faster spin-diffusion and led to slower build-up of the polarization. \u003csup\u003e36\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe apparent \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e relaxation of \u003csup\u003e129\u003c/sup\u003eXe gas from the two Tedlar bags is, within experimental errors, very similar and close to 20 s. Being the real \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{1}\\)\u003c/span\u003e\u003c/span\u003e of \u003csup\u003e129\u003c/sup\u003eXe in a Tedlar bag 38 min and 6 h at 1.5 mT and 3 T, respectively, we can infer that: the transport (60\u0026ndash;90 s) from polarizer (DNP or SEOP) to MRI scanner has relevant contribution to polarization losses; the decay in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e is predominantly due to rf pulsing. Indeed, an apparent relaxation time of 17.4 s and 20.1 s due to rf pulsing every 2 s, is the result of a flip angle of 27\u0026deg; and 25\u0026deg;, respectively. This is in good agreement with the 30\u0026deg; nominal flip-angle used for these acquisitions.\u003c/p\u003e \u003cp\u003eNotably, this study represents the first direct comparison of dDNP- and SEOP-derived xenon under identical isotopic enrichment conditions (86% \u003csup\u003e129\u003c/sup\u003eXe). \u003cem\u003eIn vivo\u003c/em\u003e experiments (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) revealed practical limitations associated with the delivered gas volume. The use of 600 mL, compared to the standard 800 mL for porcine studies, resulted in reduced lung inflation, which may have influenced the observed signal distribution. Moreover, at a xenon concentration of 3%, such volumes are unlikely to be sufficient for adult human imaging, although they may be appropriate for preclinical studies in smaller animal models. Indeed, the signal distribution in the lower lung regions is comparable between the two methods, indicating that dDNP-derived xenon provides consistent regional ventilation contrast. Remarkably, both MRSI datasets demonstrate the presence of gaseous \u003csup\u003e129\u003c/sup\u003eXe as well as dissolved-phase xenon resonances around 200 ppm (\u003cb\u003eFigure S7\u003c/b\u003e). Nonetheless, SEOP provides broader spatial coverage, likely reflecting its superior polarization and delivery efficiency.\u003c/p\u003e \u003cp\u003eOverall, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e demonstrates that, despite reduced sensitivity, dDNP enables spatially resolved lung imaging with signal localization comparable to the established SEOP approach, when very large volumes are not required.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this work, we demonstrate the feasibility of hyperpolarizing \u003csup\u003e129\u003c/sup\u003eXe using dissolution dynamic nuclear polarization in a commercially available high-field polarizer. By adapting the experimental setup\u0026mdash;including radical selection, sample geometry, microwave frequency modulation, and sublimation conditions\u0026mdash;we achieved solid-state polarization levels sufficient for downstream gas-phase delivery and in vivo imaging. The use of trityl radicals proved advantageous at 6.7 T, while frequency modulation and increased sample volume contributed to improved polarization efficiency.\u003c/p\u003e \u003cp\u003eThe implementation of isotopically enriched xenon further enhanced the achievable magnetization, yielding near-proportional gains in solid-state polarization. Combined with an optimized sublimation workflow, these developments enabled the production of hyperpolarized xenon suitable for preclinical imaging experiments. \u003cem\u003eIn vivo\u003c/em\u003e MRSI demonstrated that dDNP-derived xenon can capture both gaseous and dissolved-phase signals and reproduce key features of regional ventilation.\u003c/p\u003e \u003cp\u003eCompared to the established SEOP approach, dDNP remains limited by reduced signal-to-noise ratio, spatial coverage, and overall robustness. Additional constraints arise from gas delivery volume and concentration, which currently restrict translation to larger animal models or clinical applications. Nevertheless, the possibility to perform multi-nuclear hyperpolarized MR with the same polarizer has great potential and can represent a cost-attractive option for pre-clinical applications. \u003csup\u003e38\u003c/sup\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author declares that all data supporting the findings of this study are\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eavailable within the paper and its supplementary information files. Raw data are available from the corresponding author ([email protected]) on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Dr Thanh L\u0026ecirc; from EPFL and M. Duy Anh Dang from Aarhus University Hospital for their constant help with experiments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch funding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the SNSF SPARK grant (501100001711_190547, assigned to Capozzi), the SNSF Ambizione grant (501100001711_193276, assigned to Capozzi). The SNSF Project grant (310030_170155 assigned to Hyacinthe). Karen Elise Jensens Foundation, Lundbeck and Novonordisk foundation (Assigned to Laustsen).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA.C., J.N.H. and C.L. designed and supervised the study. E.W., E.H. and M.V. acquired and processed data. A.C., E.W., J.N.H., M.V. analyzed the data. A.C. and E.W. wrote the manuscript. All authors discussed the results and reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA.C. works for Polarize ApS. Polarize is a tech company that builds and commercializes dDNP equipment. All the other authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study complied with institutional and national guidelines and was approved by the Animal Experiment Council, governed under the Danish Animal Inspectorate, before initiation under license 2023-15-0201-01553.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMugler, J. P. \u0026amp; Altes, T. A. Hyperpolarized 129Xe MRI of the human lung. \u003cem\u003eJ. Magn. Reson. 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Multi-sample/multi-nucleus parallel polarization and monitoring enabled by a fluid path technology compatible cryogenic probe for dissolution dynamic nuclear polarization. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cb\u003e13\u003c/b\u003e, 7962 (2023).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Xenon (129Xe), dissolution DNP, SEOP, Hyperpolarization, Hyperpolarized gas MRI, lung MRI","lastPublishedDoi":"10.21203/rs.3.rs-9236425/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9236425/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHyperpolarized \u0026sup1;\u0026sup2;⁹Xe gas is a powerful diagnostic tool in pulmonary MRI, uniquely enabling imaging of ventilation and gas exchange through its dissolved-phase signal. While xenon is conventionally hyperpolarized using spin-exchange optical pumping (SEOP), an alternative approach based on dynamic nuclear polarization (DNP) followed by sublimation has emerged. However, xenon DNP has so far been restricted to custom-built hardware and primarily explored for solid-state physics applications.\u003c/p\u003e \u003cp\u003eIn this work, we establish optimized conditions for solid-state polarization of xenon using a commercial DNP polarizer. The resulting robust and reproducible protocol enables in vivo imaging in porcine lungs, providing sufficient signal to extract biologically relevant information comparable to that obtained with SEOP. This work bridges a critical gap in xenon DNP, advancing it from proof-of-principle demonstrations on specialized systems to implementation on standardized instrumentation suitable for in vivo applications.\u003c/p\u003e","manuscriptTitle":"Hyperpolarized ¹²⁹Xe MRI Using Dissolution DNP on a Commercial Polarizer: From Solid-State Optimization to In Vivo Lung Imaging","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-29 10:15:02","doi":"10.21203/rs.3.rs-9236425/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"224067932760849344016036500641504864206","date":"2026-05-04T15:38:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"229091603122496212632868631173213090185","date":"2026-05-04T11:52:21+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-21T07:21:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-21T07:13:20+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-21T06:21:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-17T14:37:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-04-17T12:04:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a801c7ee-db56-4a94-80f8-19aa4da7c7c5","owner":[],"postedDate":"April 29th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"224067932760849344016036500641504864206","date":"2026-05-04T15:38:37+00:00","index":33,"fulltext":""},{"type":"reviewerAgreed","content":"229091603122496212632868631173213090185","date":"2026-05-04T11:52:21+00:00","index":32,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":66867749,"name":"Biological sciences/Biological techniques"},{"id":66867750,"name":"Physical sciences/Engineering"},{"id":66867751,"name":"Physical sciences/Optics and photonics"}],"tags":[],"updatedAt":"2026-04-29T10:15:03+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-29 10:15:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9236425","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9236425","identity":"rs-9236425","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}