Imaging Dynamic Expiration: Feasibility of MRI Spirometry Using Hyperpolarized Xenon Gas

To examine the feasibility of imaging-based spirometry using high-temporal-resolution projection MRI and hyperpolarized xenon 129 (¹²⁹Xe) gas.

In this prospective exploratory study, five healthy participants (age range, 25-45 years; three men) underwent an MRI spirometry technique using inhaled hyperpolarized ¹²⁹Xe and rapid two-dimensional projection MRI. Participants inhaled ¹²⁹Xe, then performed a forced expiratory maneuver while in an MR imager. Images of the lungs during expiration were captured in time intervals as short as 250 msec. Volume-corrected images of the lungs at expiration commencement (0 second), 1 second after expiration, and 6 seconds after expiration were extracted to generate forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC ratio pulmonary maps. For comparison, participants performed conventional spirometry in the sitting position using room air, in the supine position using room air, and in the supine position using a room air and ¹²⁹Xe mixture. Paired t tests with Bonferroni corrections for multiple comparisons were used for statistical analyses.

The mean MRI-derived FEV₁/FVC value was lower in comparison with conventional spirometry (0.52 ± 0.03 vs 0.70 ± 0.05, P < .01), which may reflect selective ¹²⁹Xe retention. A secondary finding of this study was that 1 L of inhaled ¹²⁹Xe negatively impacted pulmonary function as measured by conventional spirometry (in supine position), which reduced measured FEV₁ (2.70 ± 0.90 vs 3.04 ± 0.85, P < .01) and FEV₁/FVC (0.70 ± 0.05 vs 0.79 ± 0.04, P < .01).

A forced expiratory maneuver was successfully imaged with hyperpolarized ¹²⁹Xe and high-temporal-resolution MRI. Derivation of regional lung spirometric maps was feasible.Keywords: MR-Imaging, MR-Dynamic Contrast Enhanced, MR-Functional Imaging, Pulmonary, Thorax, Diaphragm, Lung, Pleura, Physics Supplemental material is available for this article. © RSNA, 2021.