Xenon Surface Relaxivity: Potential Applications to Probing Lung Disease

Introduction Because hyperpolarized Xe gas NMR signals can result in four to five orders of magnitude polarization enhancement compared to thermal equilibrium signals even at high fields , hyperpolarized Xe gas MRI has shown great promise for lung imaging. Scientists have developed many techniques to assess lung properties, such as ADC (apparent diffusion coefficient) , XTC (Xenon polarization Transfer Contrast) , CSSR (chemical shift saturation recovery) , etc, in order to diagnose and evaluate the pulmonary function. Driehuys et al. has determined the thickness of the blood–gas barrier via imaging Xe alveolar-capillary gas transfer, and shown the utility of such method in a rat model of pulmonary fibrosis . The effective transverse relaxation (T2 ) in lung has been investigated by treating the lung as a porous medium . However, a drawback is that for any of these methods to be quantitative, a model of the lung is required. We believe that probing lung diseases by measuring xenon surface relaxivity in alveoli could offer unique advantages towards a model-free characterization. We demonstrated the probing of xenon surface relaxivity in phantoms and discuss potential application towards monitoring physiological changes in the alveoli surface properties.