Purpose: To demonstrate the feasibility of a multi-breath xenon-polarization transfer contrast (XTC) MR imaging approach for simultaneously evaluating regional ventilation and gas exchange parameters.

Methods: Imaging was performed in five healthy volunteers and six chronic obstructive pulmonary disease (COPD) patients. The multi-breath XTC protocol consisted of three repeated schemes of six wash-in breaths of a xenon mixture and four normoxic wash-out breaths, with and without selective saturation of either the tissue membrane or red blood cell (RBC) resonances. Acquisitions were performed at end-exhalation while subjects maintained tidal breathing throughout the session. The no-saturation, membrane-saturation, and RBC-saturation images were fit to a per-breath gas replacement model for extracting voxelwise tidal volume (TV), functional residual capacity (FRC), and fractional ventilation (FV), as well as tissue- and RBC-gas exchange (f_Mem and f_RBC , respectively). The sensitivity of the derived model was also evaluated via simulations.

Results: With the exception of FRC, whole-lung averages for all metrics were decreased in the COPD subjects compared to the healthy cohort, significantly so for FV, f_RBC , and f_Mem . Heterogeneity was higher overall in the COPD subjects, particularly for f_RBC , f_Mem , and f_RBC:Mem . The anterior-to-posterior gradient associated with the gravity-dependence of lung function in supine imaging was also evident for FV, f_RBC , and f_Mem values in the healthy subjects, but noticeably absent in the COPD cohort.

Conclusion: Multi-breath XTC imaging generated high-resolution, co-registered maps of ventilation and gas exchange parameters acquired during tidal breathing and with low per-breath xenon doses. Clear differences between healthy and COPD subjects were apparent and consistent with spirometry.