Simultaneous Imaging of Ventilation Distribution and Gas Exchange in the Human Lung using Hyperpolarized Xe129 MRI

Introduction: The high solubility of xenon in biological tissues, combined with an exquisite sensitivity to its environment that results in an enormous range of chemical shifts upon solution, make hyperpolarized Xe129 particularly attractive for exploring characteristics of lung function, such as gas exchange, that are not accessible by using hyperpolarized He3. With improvements in gas-polarization hardware [1], liter quantities of hyperpolarized Xe129 can be obtained with sufficient polarization to make direct dissolvedphase imaging in humans feasible during a single breath-hold period. Recently, Driehuys et al demonstrated breath-hold images of dissolved-phase Xe129 in humans following inhalation of 1 liter of Xe129 polarized to approximately 8% [2]. The large difference in chemical shift, and hence resonant frequency, between gas-phase and dissolved-phase Xe129 presents the opportunity to capture both components in the same image, thus potentially yielding, from a single breath-hold acquisition, simultaneous depiction of the regional distributions of the gas following inhalation and of the fraction of gas that exchanges into the lung parenchyma and blood. The purpose of this work was to demonstrate the feasibility of such a method in the healthy and diseased human lung.