%0 Journal Article %J Journal of Physical Chemistry B %D 1999 %T NMR with a continuously circulating flow of laser-polarized Xe-129 %A Seydoux, R. %A Pines, A. %A Haake, M. %A Reimer, J. A. %K zeolites %X

In this paper we describe the construction of an apparatus for optical pumping of Xe-129 in a circulating gas system connected to a probe for static high-field NMR. The optimal working conditions for the optical pumping under flow are explored, yielding a continuous gas now with a steady-state spin-polarization of about 2%. It is shown that on various types of high surface area materials a steady-state of adsorbed laser-polarized xenon can be;reached with polarizations of about 0.3%. NMR spectroscopy of this layer is greatly facilitated due to the renewable magnetization under the continuous-flow conditions allowing unprecedented fast detection of two-dimensional NMR experiments with laser-polarized Xe. The steady-state spin-polarization of adsorbed Xe-129 gives rise to cross-relaxation to surface nuclei such as H-1 and Si-29. A direct spin-polarization-induced nuclear Overhauser effect (SPINOE) to heteronuclei is observed with an enhancement factor of about 20-30. A method is presented for simple modulation of the spin-polarization direction in the fringe field of the high-field magnet; this is exploited to obtain difference SPINOE spectra to highlight only the surface nuclei. Furthermore, a transfer via cross-polarization (CP) from adsorbed Xe to surface protons is demonstrated to select surface groups with reduced mobility compared to SPINOE detection.

%B Journal of Physical Chemistry B %V 103 %P 4629-4637 %8 Jun 3 %@ 1089-5647 %G English %U ://WOS:000080702600011 %N 22 %M WOS:000080702600011 %! NMR with a continuously circulating flow of laser-polarized Xe-129 %R Doi 10.1021/Jp9821984 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 1996 %T NMR of laser-polarized xenon in human blood %A Bifone, A. %A Song, Y. Q. %A Seydoux, R. %A Taylor, R. E. %A Goodson, B. M. %A Pietrass, T. %A Budinger, T. F. %A Navon, G. %A Pines, A. %K gas %X

By means of optical pumping with laser light it is possible to enhance the nuclear spin polarization of gaseous xenon by four to five orders of magnitude, The enhanced polarization has allowed advances in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI), including polarization transfer to molecules and imaging of lungs and other void spaces, A critical issue for such applications is the delivery of xenon to the sample while maintaining the polarization, Described herein is an efficient method for the introduction of laser-polarized xenon into systems of biological and medical interest for the purpose of obtaining highly enhanced NMR/MRI signals. Using this method, we have made the first observation of the time-resolved process of xenon penetrating the red blood cells in fresh human blood-the xenon residence time constant in the red blood cells was measured to be 20.4+/-2 ms. The potential of certain biologically compatible solvents for delivery of laser-polarized xenon to tissues for NMR/MRI is discussed in light of their respective relaxation and partitioning properties.

%B Proceedings of the National Academy of Sciences of the United States of America %V 93 %P 12932-12936 %8 Nov 12 %@ 0027-8424 %G English %U ://WOS:A1996VT05400048 %N 23 %M WOS:A1996VT05400048 %! NMR of laser-polarized xenon in human blood %R Doi 10.1073/Pnas.93.23.12932