Pulmonary hyperpolarized 129Xe morphometry for mapping xenon gas concentrations and alveolar oxygen partial pressure: Proof-of-concept demonstration in healthy and COPD subjects

• Published in: Magnetic resonance in medicine Vol. 74; no. 6; pp. 1726 - 1732
• Main Authors: Ouriadov, A., Farag, A., Kirby, M., McCormack, D.G., Parraga, G., Santyr, G.E.
• Format: Journal Article
• Language: English
• Published: Hoboken Blackwell Publishing Ltd 01.12.2015; Wiley Subscription Services, Inc
• Subjects: diffusion; hyperpolarized; lung; lung, morphometry; morphometry; pAO2; xenon concentration
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.25550

Purpose Diffusion‐weighted (DW) hyperpolarized 129Xe morphometry magnetic resonance imaging (MRI) can be used to map regional differences in lung tissue micro‐structure. We aimed to generate absolute xenon concentration ([Xe]) and alveolar oxygen partial pressure (pAO2) maps by extracting the unrestricted diffusion coefficient (D0) of xenon as a morphometric parameter. Methods In this proof‐of‐concept demonstration, morphometry was performed using multi b‐value (0, 12, 20, 30 s/cm2) DW hyperpolarized 129Xe images obtained in four never‐smokers and four COPD ex‐smokers. Morphometric parameters and D0 maps were computed and the latter used to generate [Xe] and pAO2 maps. Xenon concentration phantoms estimating a range of values mimicking those observed in vivo were also investigated. Results Xenon D0 was significantly increased (P = 0.035) in COPD (0.14 ± 0.03 cm2/s) compared with never‐smokers (0.12 ± 0.02 cm2/s). COPD ex‐smokers also had significantly decreased [Xe] (COPD = 8 ± 7% versus never‐smokers = 13 ± 8%, P = 0.012) and increased pAO2 (COPD = 18 ± 3% versus never‐smokers = 15 ± 3%, P = 0.009) compared with never‐smokers. Phantom measurements showed the expected dependence of D0 on [Xe] over the range of concentrations anticipated in vivo. Conclusion DW hyperpolarized 129Xe MRI morphometry can be used to simultaneously map [Xe] and pAO2 in addition to providing micro‐structural biomarkers of emphysematous destruction in COPD. Phantom measurements of D0([Xe]) supported the hypotheses that differences in subjects may reflect differences in functional residual capacity. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc. Magn Reson Med 74:1726–1732, 2015. © 2014 Wiley Periodicals, Inc.