Magnetic resonance imaging of spin-polarization transfer of polarized Xe atoms dissolving into ethanol

Continuous flow production of concentrated hyperpolarized xenon gas from a dilute xenon gas mixture by buffer gas condensation

We present a new method for the continuous flow production of concentrated hyperpolarized xenon-129 (HP ¹²⁹Xe) gas from a dilute xenon (Xe) gas mixture with high nuclear spin polarization. A low vapor pressure (i.e., high boiling-point) gas was introduced as an alternative to molecular nitrogen (N₂), which is the conventional quenching gas for generating HP ¹²⁹Xe via Rb-Xe spin-exchange optical-pumping (SEOP). In contrast to the generally used method of extraction by freezing Xe after the SEOP process, the quenching gas separated as a liquid at moderately low temperature so that Xe was maintained in its gaseous state, allowing the continuous delivery of highly polarized concentrated Xe gas. We selected isobutene as the candidate quenching gas and our method was demonstrated experimentally while comparing its performance with N₂. Isobutene could be liquefied and removed from the Xe gas mixture using a cold trap, and the concentrated HP ¹²⁹Xe gas exhibited a significantly enhanced nuclear magnetic resonance (NMR) signal. Although the system requires further optimization depending on the intended purpose, our approach presented here could provide a simple means for performing NMR or magnetic resonance imaging (MRI) measurements continuously using HP ¹²⁹Xe with improved sensitivity.

Surface relaxation of polarized Xe atoms dissolved in deuterated ethanol

We measured the spin relaxation of polarized xenon atoms dissolved in deuterated ethanol. Surface relaxation was suppressed by coating the cell walls with deuterated eicosane. From the dependence of the decay rate on temperature and static magnetic field, we obtained the correlation time of random fluctuations of the local field at the liquid-solid interface. By varying the cell volume, the wall coating, and the surface area of the eicosane, we measured the contribution of the spin-rotation interaction to the relaxation. The use of both deuterated molecules enables us to distinguish surface relaxation from the magnetic dipole-dipole and spin-rotation interactions in solution.

Dissolution of laser-polarized xenon in benzene

The study of the dissolution of laser-polarized xenon in degassed deuterated benzene is reported. We show that the time evolution of the xenon signal implies that a transient convective process takes place. It is characterized by velocity-encoding magnetic resonance measurements and MRI experiments.