On the oxygenation-dependent 129Xe T1 in blood

Abstract

The spin-lattice relaxation time, T1, of hyperpolarized 129Xe in blood is sensitive to blood oxygenation. In particular, it has been shown that 129Xe T1 is shorter in venous blood than in arterial blood. We have studied the T1 of hyperpolarized 129Xe dissolved in human blood as a function of blood oxygenation level, sO2, in the physiological oxygenation range. We show that the 129Xe relaxation rate, T1-1, varies in a nonlinear fashion as a function of sO2. This finding suggests that direct interaction of xenon with the paramagnetic heme group of deoxyhemoglobin is not the dominant oxygenation-dependent relaxation mechanism for 129Xe in blood. These results corroborate the idea that the oxygenation-dependence of 129Xe T1 is determined by conformational changes of hemoglobin induced by oxygen binding. Copyright (C) 2000 John Wiley and Sons, Ltd.