Large dose hyperpolarized water with dissolution-DNP at high magnetic field

Hyperpolarized water is a valuable tool for magnetic resonance imaging and spectroscopy. Prior research has shown that it can enhance signal strength and improve the detection of physiological processes. However, the production of large volumes of hyperpolarized water remains a challenge. No prior work had resolved the scalability of dissolution dynamic nuclear polarization at high magnetic fields. This gap motivated the development of a new method to increase the volume and polarization efficiency. Existing methods often produce small volumes or lower polarization levels. The need for larger quantities is driven by applications in angiography and perfusion studies. This paper addresses the limitations of current techniques by exploring a high-field approach. The goal is to enable broader clinical and experimental use of hyperpolarized water.

The aim of this study is to develop and test a method for producing large volumes of hyperpolarized water using dissolution dynamic nuclear polarization at high magnetic fields. The specific problem is the limited scalability of existing methods. The motivation is to support advanced imaging techniques in large animals and clinical settings. The study focuses on optimizing polarization efficiency and volume yield. The researchers propose to use frequency-modulated microwave irradiation at 188GHz. This technique allows for higher polarization at lower temperatures. The study also examines the longitudinal relaxation time of the produced water. The ultimate goal is to enable practical applications in NMR and MRI.

The method involves dynamic nuclear polarization at 6.7T and 1.1K. Protons were polarized using frequency-modulated microwave irradiation at 188GHz. A two-phase system was used to extract the radical from the sample. The dissolution process was optimized to maximize polarization transfer. The polarization level was measured at 70% under these conditions. The sample was then dissolved in a fluid path suitable for clinical polarizers. The resulting hyperpolarized water was analyzed for polarization and volume. The longitudinal relaxation time was measured to assess stability.

The method achieved a polarization of 70% at 6.7T and 1.1K. Radical extraction reached 97.2±0.7% in the two-phase system. The final product was 16±1mL of 5.0M ¹H in D₂O. The polarization in the liquid state was 13.0±0.9%. This corresponds to a 4000±300 enhancement factor. The longitudinal relaxation time was 16±1 seconds. The volume produced is sufficient for angiography in large animals. The method is compatible with clinical polarizer systems.

The study demonstrates a scalable method for producing hyperpolarized water. The polarization efficiency and volume achieved are suitable for clinical applications. The method uses a two-phase system and high magnetic fields. The longitudinal relaxation time supports practical use in NMR and MRI. The researchers propose that this method can enable perfusion measurements. The results suggest potential for use in large animal studies. The fluid path is compatible with existing clinical equipment. The method provides a foundation for further development in hyperpolarized imaging.