Relaxation and exchange dynamics of hyperpolarized super(129)Xe in human blood

• Published in: Magnetic resonance in medicine 2015-08, Vol.74 (2), p.303-311
• Main Authors: Norquay, Graham, Leung, General, Stewart, Neil J, Tozer, Gillian M, Wolber, Jan, Wild, Jim M
• Format: Article
• Language: English
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.25417

Purpose super(129)Xe-blood NMR was performed over the full blood oxygenation range to evaluate super(129)Xe relaxation and exchange dynamics in human blood. Methods Hyperpolarized super(129)Xe was equilibrated with blood and isolated plasma, and NMR was performed at 1.5 T. Results The super(129)Xe relaxation rate was found to increase nonlinearly with decreasing blood oxygenation. Three constants were extrapolated: [Formulaomitted]=11.1, a "relaxivity index" characterizing the rate of change of super(129)Xe relaxation as a function of blood oxygenation, and [Formulaomitted]=0.13 s super(-1) and [Formulaomitted]= 0.42 s super(-1), the super(129)Xe relaxation rates in oxygenated blood and deoxygenated blood, respectively. In addition, rate constants, [Formulaomitted] 0.022 ms super(-1) and [Formulaomitted]=0.062 ms super(-1), were determined for xenon diffusing between red blood cells (RBCs) and plasma (hematocrit=48%). The super(129)Xe-O sub(2) relaxivity in plasma, [Formulaomitted]= 0.075 s super(-1) mM super(-1), and the super(129)Xe relaxation rate in isolated plasma (without dissolved O sub(2)), [Formulaomitted]= 0.046 s super(-1), were also calculated. Finally, intrinsic super(129)Xe-RBC relaxation rates, [Formulaomitted]= 0.19 s super(-1) and [Formulaomitted]= 0.84 s super(-1), in oxygenated blood and deoxygenated blood, respectively, were calculated. Conclusion The relaxation and exchange analysis performed in this study should provide a sound experimental basis upon which to design future MR experiments for dissolved xenon transport from the lungs to distal tissues. Magn Reson Med 74:303-311, 2015.