Spin-lattice relaxation of laser-polarized xenon in human blood

Abstract

The nuclear spin polarization of 129 Xe 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 (T 1 ) 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 129 Xe in blood, the latter interaction having greater effect. Consequently, relaxation times of 129 Xe in deoxygenated blood are shorter than in oxygenated blood. In samples with oxygenation equivalent to arterial and venous blood, the 129 Xe T 1 s at 37°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 129 Xe spin-lattice relaxation time in blood decreases at lower temperatures, but the ratio of T 1 in oxygenated blood to that in deoxygenated blood is the same at 37°C and 25°C. A competing ligand has been used to show that xenon binding to albumin contributes to the 129 Xe spin-lattice relaxation in blood plasma. This technique is promising for the study of xenon interactions with macromolecules.

High resolution spectroscopy and chemical shift imaging of hyperpolarized 129Xe dissolved in the human brain in vivo at 1.5 tesla

“…These earlier studies suggested the following peak assignments: 187.2 ppm, muscle 19, 20, 21; 192.7 ppm, white matter (and soft‐tissue in this study) 18, 19, 20, 21; 195.6 ppm, gray matter 18, 19, 20, 21; 199.6 ppm, aqueous solution (cerebrospinal fluid, plasma, and interstitial fluid in this study) 10, 11, 24, 25, 26 and fat/lipid tissue outside the brain 19, 20; and 217.2 ppm, red blood cells 4, 10, 24, 26.…”

“…In the bloodstream, dissolved HP 129 Xe is transported to distal organs by the systemic blood circulation. The longitudinal relaxation time $T_1$ of HP 129 Xe in the human blood is sufficiently long (6 s to 8 s for arterial‐oxygenated blood and 3 s to 4 s for venous‐deoxygenated blood) for it to be detected in the distal organs 10, 11, 12, 13.…”

Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials and organisms

“…This result suggests that under the conditions of their experiment (e.g., xenon dissolved in rat blood in vivo at 37 "C and 2 T) the xenon exchange between RBCS and plasma was contrast to the previous in vitro fast with respect to the the NMR time scale, in results involving xenon in human blood at higher fields and ambient conditions [224,225]. Indeed, this result is particularly surprising considering the new results of Bifone and co-workers [132], where the xenon exchange in human blood was still slow on the NMR time scale even though the experiments CSI experiments could become a powerful diagnostic tool, permitting lung ventilation and perfusion to be studied simultaneously.…”

“…Xenon has been shown to bind to various proteins in crystals and in solution [66,125,126,81,127,128,129,130,131,132]. The formation of xenon clathrates has also been investigated extensively with both thermally polarized and laser-polarized xenon (see for example, Refs.…”

Evidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution

“…Several studies have exploited sensitive xenon chemical shifts to characterize the interactions between xenon and organic compounds such as ␣-cyclodextrin (5) and cryptophane-A (6), the membrane protein channel gramicidin (7), and the globular proteins myoglobin and hemoglobin (8). In addition, it has been shown that the 129 Xe spin-lattice relaxation time (T 1 ) is reduced dramatically when xenon comes into contact with cyclodextrins (9), lipids (10), and proteins in blood (11)(12)(13)(14)(15). Recent advances in optical pumping technology (16) have further motivated such studies of xenon-molecule interactions by providing 129 Xe NMR signal enhancements of up to five orders of magnitude (17).…”