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Pulmonary hyperpolarized 129 Xe morphometry for mapping xenon gas concentrations and alveolar oxygen partial pressure: Proof‐of‐concept demonstration in healthy and COPD subjects
Author(s) -
Ouriadov A.,
Farag A.,
Kirby M.,
McCormack D.G.,
Parraga G.,
Santyr G.E.
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25550
Subject(s) - xenon , imaging phantom , copd , nuclear magnetic resonance , magnetic resonance imaging , nuclear medicine , isotopes of xenon , chemistry , effective diffusion coefficient , diffusion , materials science , medicine , physics , radiology , organic chemistry , thermodynamics
Purpose Diffusion‐weighted (DW) hyperpolarized 129 Xe 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 (p A O 2 ) maps by extracting the unrestricted diffusion coefficient ( D 0 ) 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/cm 2 ) DW hyperpolarized 129 Xe images obtained in four never‐smokers and four COPD ex‐smokers. Morphometric parameters and D 0 maps were computed and the latter used to generate [Xe] and p A O 2 maps. Xenon concentration phantoms estimating a range of values mimicking those observed in vivo were also investigated. Results Xenon D 0 was significantly increased ( P = 0.035) in COPD (0.14 ± 0.03 cm 2 /s) compared with never‐smokers (0.12 ± 0.02 cm 2 /s). COPD ex‐smokers also had significantly decreased [Xe] (COPD = 8 ± 7% versus never‐smokers = 13 ± 8%, P = 0.012) and increased p A O 2 (COPD = 18 ± 3% versus never‐smokers = 15 ± 3%, P = 0.009) compared with never‐smokers. Phantom measurements showed the expected dependence of D 0 on [Xe] over the range of concentrations anticipated in vivo. Conclusion DW hyperpolarized 129 Xe MRI morphometry can be used to simultaneously map [Xe] and p A O 2 in addition to providing micro‐structural biomarkers of emphysematous destruction in COPD. Phantom measurements of D 0 ([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.