Structural and functional pulmonary imaging using hyperpolzarized xenon-129

• Main Author: Muradyan, Iga
• Format: Dissertation
• Language: English
• Subjects: biophysics, medical; health sciences, radiology; physics, nuclear

We describe applications of hyperpolarized 129 Xe to pulmonary imaging. Unique characteristics of this gas such as its polarizability and diffusibility in tissue allow probing important properties of the lungs. Three methods that study structure and function of the lungs, Chemical Shift Saturation Recovery (CSSR), Xenon polarization Transfer Contrast (XTC) and Dixon, and their application to human studies for the first time are the focus of this work.
CSSR measures the global fractional gas transport, F(t) in the lungs. Using this method the dynamics of gas exchange were studied. A model describing this process was derived and used to interpret data obtained with CSSR. Studies were conducted on a number of healthy subjects as well as patients with mild to moderate Interstitial Lung Disease. CSSR was able to distinguish the healthy group from the rest by the measured septal thickness.
XTC is an imaging technique, in which the gas-phase signal is attenuated by inverting the spins of 129 Xe particles dissolved into the parenchyma. Using this technique 2D maps of the fractional gas transport, F(t) occurring in the lungs were obtained. Studies were performed at two lung volumes, and showed the at lower volumes, fractional gas transport and therefore the alveolar surface per unit volume is higher for all subjects. Difference in the fractional gas transport from apex to base was detected in the supine position with greater values at the bases. Comparison between health non-smokers and asymptomatic smokers was made. We observed a higher mean value of F(t) and physiological heterogeneity in smokers compared to non-smokers. Preliminary results suggest that XTC is more sensitive to the early changes in the lungs compared to the gold standard tests, such as DLCO and FEV 1.
Dixon is another imaging modality, which can be used to measure local S/V. It provides a direct simultaneous measurement of the dissolved and gaseous phases of inspired Xe. It yields a 2D map of F(t). Higher values of F(t) accompanied by a larger spread was observed at lower lung volumes.