Pulmonary Hyperpolarized 129Xe Morphometry for Mapping Xenon Gas Concentrations and Alveolar Oxygen Partial Pressure: Proof-Of-Concept Demonstration in Healthy and COPD Subjects

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Abstract

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.

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