Multibreath Alveolar Oxygen Tension Imaging

Purpose: This study tested the ability of a multibreath hyperpolarized HP He-3 MRI protocol to increase the accuracy of regional alveolar oxygen tension (PAO2) measurements by lessening the influence of gas-flow artifacts. Conventional single-breath PAO2 measurement has been susceptible to error induced by intervoxel gas flow, particularly when used to study subjects with moderate-to-severe chronic obstructive pulmonary disease (COPD). Methods: Both single-breath and multibreath PAO2 imaging schemes were implemented in seven human subjects (one healthy, three asymptomatic smokers, and three COPD). The number and location of voxels with nonphysiologic PAO2 values generated by intervoxel gas flow were compared between the two protocols. Results: The multibreath scheme resulted in a significantly lower total percentage of nonphysiologic PAO2 values (6.0%) than the single-breath scheme (13.7%) (P = 0.006). PAO2 maps showed several patterns of gas-flow artifacts that were present in the single-breath protocol but mitigated by the multibreath approach. Multibreath imaging also allowed for the analysis of slow-filling areas that presented no signal after a single breath. Conclusion: A multibreath approach enhances the accuracy and completeness of noninvasive PAO2 measurement by significantly lessening the proportion of nonphysiologic values generated by intervoxel gas flow. (C) 2015 Wiley Periodicals, Inc.