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Spin-Lattice Relaxation of Laser-Polarized Xenon in Human Blood
Jan Wolber, Andrea Cherubini, Andrzej S. K. Dzik-Jurasz, Martin O. Leach and Angelo Bifone
Proceedings of the National Academy of Sciences of the United States of America
Vol. 96, No. 7 (Mar. 30, 1999), pp. 3664-3669
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/47695
Page Count: 6
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The nuclear spin polarization of 129Xe can be enhanced by several orders of magnitude by using optical pumping techniques. The increased sensitivity of xenon NMR has allowed imaging of lungs as well as other in vivo applications. The most critical parameter for efficient delivery of laser-polarized xenon to blood and tissues is the spin-lattice relaxation time (T1) of xenon in blood. In this work, the relaxation of laser-polarized xenon in human blood is measured in vitro as a function of blood oxygenation. Interactions with dissolved oxygen and with deoxyhemoglobin are found to contribute to the spin-lattice relaxation time of 129Xe in blood, the latter interaction having greater effect. Consequently, relaxation times of 129Xe in deoxygenated blood are shorter than in oxygenated blood. In samples with oxygenation equivalent to arterial and venous blood, the 129Xe T1s at 37 degrees C and a magnetic field of 1.5 T were 6.4 s × 0.5 s and 4.0 s × 0.4 s, respectively. The 129Xe spin-lattice relaxation time in blood decreases at lower temperatures, but the ratio of T1 in oxygenated blood to that in deoxygenated blood is the same at 37 degrees C and 25 degrees C. A competing ligand has been used to show that xenon binding to albumin contributes to the 129Xe spin-lattice relaxation in blood plasma. This technique is promising for the study of xenon interactions with macromolecules.
Proceedings of the National Academy of Sciences of the United States of America © 1999 National Academy of Sciences