Hyperpolarized 3He and 129Xe magnetic resonance imaging apparent diffusion coefficients: physiological relevance in older never- and ex-smokers

Authors

  • Miranda Kirby,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    2. Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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  • Alexei Ouriadov,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
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  • Sarah Svenningsen,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    2. Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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  • Amir Owrangi,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    2. Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario, Canada
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  • Andrew Wheatley,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
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  • Roya Etemad-Rezai,

    1. Department of Medical Imaging, The University of Western Ontario, London, Ontario, Canada
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  • Giles E. Santyr,

    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    2. Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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  • David G. McCormack,

    1. Division of Respirology, Department of Medicine, The University of Western Ontario, London, Ontario, Canada
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  • Grace Parraga

    Corresponding author
    1. Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    2. Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
    3. Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario, Canada
    4. Department of Medical Imaging, The University of Western Ontario, London, Ontario, Canada
    • Correspondence

      Grace Parraga, Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, Ontario, Canada N6A 5B7.

      Tel: 519-931-5265

      Fax: 519-931-5260

      E-mail: gparraga@robarts.ca

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  • Funding Information

    This study was funded by the Canadian Institutes of Health Research. M. Kirby gratefully acknowledges Ph.D. scholarship support from the Natural Sciences and Engineering Research Council (NSERC, Canada) and G. Parraga gratefully acknowledges support from a Canadian Institutes of Health Research (CIHR) New Investigator Award. Ongoing research funding from CIHR Team Grant CIF# 97687 (Thoracic Imaging Network of Canada, TinCAN) is also gratefully acknowledged.

Abstract

Noble gas pulmonary magnetic resonance imaging (MRI) is transitioning away from 3He to 129Xe gas, but the physiological/clinical relevance of 129Xe apparent diffusion coefficient (ADC) parenchyma measurements is not well understood. Therefore, our objective was to generate 129Xe MRI ADC for comparison with 3He ADC and with well-established measurements of alveolar structure and function in older never-smokers and ex-smokers with chronic obstructive pulmonary disease (COPD). In four never-smokers and 10 COPD ex-smokers, 3He (b = 1.6 sec/cm2) and 129Xe (b = 12, 20, and 30 sec/cm2) ADC, computed tomography (CT) density-threshold measurements, and the diffusing capacity for carbon monoxide (DLCO) were measured. To understand regional differences, the anterior–posterior (APG) and superior–inferior (∆SI) ADC differences were evaluated. Compared to never-smokers, COPD ex-smokers showed greater 3He ADC (P = 0.006), 129Xe ADCb12 (P = 0.006), and ADCb20 (P = 0.006), but not for ADCb30 (P > 0.05). Never-smokers and COPD ex-smokers had significantly different APG for 3He ADC (P = 0.02), 129Xe ADCb12 (P = 0.006), and ADCb20 (P = 0.01), but not for ADCb30 (P > 0.05). ∆SI for never- and ex-smokers was significantly different for 3He ADC (P = 0.046), but not for 129Xe ADC (P > 0.05). There were strong correlations for DLCO with 3He ADC and 129Xe ADCb12 (both r = −0.95, P < 0.05); in a multivariate model 129Xe ADCb12 was the only significant predictor of DLCO (P = 0.049). For COPD ex-smokers, CT relative area <−950 HU (RA950) correlated with 3He ADC (r = 0.90, P = 0.008) and 129Xe ADCb12 (r = 0.85, P = 0.03). In conclusion, while 129Xe ADCb30 may be appropriate for evaluating subclinical or mild emphysema, in this small group of never-smokers and ex-smokers with moderate-to-severe emphysema, 129Xe ADCb12 provided a physiologically appropriate estimate of gas exchange abnormalities and alveolar microstructure.

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