IMAGES IN PULMONARY, CRITICAL CARE, SLEEP MEDICINE AND THE SCIENCES Magnetic Resonance Imaging of Ventilation and Perfusion Changes in Response to Pulmonary Endarterectomy in Chronic Thromboembolic Pulmonary Hypertension Helen Marshall1, David G. Kiely2, Juan Parra-Robles1, David Capener1, Martin H. Deppe1, Edwin J. R. van Beek3, Andrew J. Swift1, Smitha Rajaram1, Judith Hurdman2, Robin Condliffe2, Charles A. Elliot2, and Jim M. Wild1 1 Academic Radiology, University of Sheffield, Sheffield, United Kingdom; 2Pulmonary Vascular Disease Unit, Royal Hallamshire Hospital, Sheffield, United Kingdom; and 3CRIC Edinburgh, University of Edinburgh, Edinburgh, United Kingdom
Figure 1. Coronal magnetic resonance images before (top) and after (bottom) pulmonary endarterectomy. (A, E ) Ventilation, (B, F ) blood perfusion, (C, G) pulmonary tissue that is both ventilated and perfused, and (D, H) histograms of ventilation (blue) and perfusion (red ).
A 41-year-old woman with chronic thromboembolic pulmonary hypertension (CTEPH) underwent pulmonary endarterectomy. Mean pulmonary artery pressure fell from 53 to 28 mm Hg, and World Health Organization class from III to II. Hyperpolarized 3He magnetic resonance imaging (MRI) and dynamic contrast enhanced perfusion MRI were used to assess regional lung ventilation (Figures 1A and 1E) and perfusion (Figures 1B and 1F) before and after endarterectomy. Ventilation and perfusion images were quantified in two ways. In the first, images were segmented by setting signal thresholds that defined voxels as either ventilated or not ventilated (1) and either perfused or not perfused. After exclusion of the dead space (large airways and blood vessels), the ventilated lung volume, perfused lung volume, and the volume of the lungs both ventilated and perfused (Figures 1C and 1G) were calculated. In the second approach, histograms were generated for each image slice to quantitatively represent the distributions of ventilation and perfusion (Figures 1D and 1H). The level of ventilation in a given voxel was expressed on a scale normalized to the maximum ventilation within the lung parenchyma for that image slice. The same This work was supported by Bayer research grant R/134012 (J.M.W. and D.G.K.). Am J Respir Crit Care Med Vol 190, Iss 5, pp e18–e19, Sep 1, 2014 Copyright © 2014 by the American Thoracic Society DOI: 10.1164/rccm.201310-1842IM Internet address: www.atsjournals.org
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IMAGES IN PULMONARY, CRITICAL CARE, SLEEP MEDICINE AND THE SCIENCES procedure was followed to generate perfusion histograms. Histogram frequency was normalized to the number of voxels within the lung for that image slice. At baseline (Figures 1A–1D), large regions of the lung were ventilated but not perfused. After endarterectomy (Figures 1E–1H) lung ventilated volume increased by 0.2 L, perfused lung volume by 0.8 L, and the volume of the lungs both ventilated and perfused by 0.8 L. Histogram analysis (Figures 1D and 1H) showed better ventilation–perfusion matching after endarterectomy. The method provides a safe and sensitive means of assessment of regional ventilation and perfusion distributions in CTEPH, and is suitable for monitoring response to intervention. This multinuclear MRI technique (1, 2) provides much higher spatial resolution images (3 3 3 3 10 mm) than traditional ventilation–perfusion scintigraphy (3) with no ionizing radiation dose. In a clinical context, hyperpolarized gas MRI and perfusion MRI are not yet as readily available as scintigraphy, but are attainable on clinical MRI scanners : : and together offer an attractive nonionizing alternative for the study of regional V/Q in a range of pulmonary diseases. The Institutional Review Board for Human Studies approved the protocols and written consent was obtained from the patient. n Author disclosures are available with the text of this article at www.atsjournals.org.
References 1. Woodhouse N, Wild JM, Paley MNJ, Fichele S, Said Z, Swift AJ, van Beek EJR. Combined helium-3/proton magnetic resonance imaging measurement of ventilated lung volumes in smokers compared to never-smokers. J Magn Reson Imaging 2005;21:365–369. 2. Rajaram S, Swift AJ, Telfer A, Hurdman J, Marshall H, Lorenz E, Capener D, Davies C, Hill C, Elliot C, et al. 3D contrast-enhanced lung
perfusion MRI is an effective screening tool for chronic thromboembolic pulmonary hypertension: results from the ASPIRE Registry. Thorax 2013;68:677–678. 3. Tunariu N, Gibbs SJR, Win Z, Gin-Sing W, Graham A, Gishen P, Al-Nahhas A. Ventilation-perfusion scintigraphy is more sensitive than multidetector CTPA in detecting chronic thromboembolic pulmonary disease as a treatable cause of pulmonary hypertension. J Nucl Med 2007;48:680–684.
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Figure 1. Coronal magnetic resonance images before (top) and after (bottom) pulmonary endarterectomy. (A, E ) Ventilation, (B, F ) blood perfusion, (C, G) pulmonary tissue that is both ventilated and perfused, and (D, H) histograms of ventilation (blue) and perfusion (red ).
A 41-year-old woman with chronic thromboembolic pulmonary hypertension (CTEPH) underwent pulmonary endarterectomy. Mean pulmonary artery pressure fell from 53 to 28 mm Hg, and World Health Organization class from III to II. Hyperpolarized 3He magnetic resonance imaging (MRI) and dynamic contrast enhanced perfusion MRI were used to assess regional lung ventilation (Figures 1A and 1E) and perfusion (Figures 1B and 1F) before and after endarterectomy. Ventilation and perfusion images were quantified in two ways. In the first, images were segmented by setting signal thresholds that defined voxels as either ventilated or not ventilated (1) and either perfused or not perfused. After exclusion of the dead space (large airways and blood vessels), the ventilated lung volume, perfused lung volume, and the volume of the lungs both ventilated and perfused (Figures 1C and 1G) were calculated. In the second approach, histograms were generated for each image slice to quantitatively represent the distributions of ventilation and perfusion (Figures 1D and 1H). The level of ventilation in a given voxel was expressed on a scale normalized to the maximum ventilation within the lung parenchyma for that image slice. The same This work was supported by Bayer research grant R/134012 (J.M.W. and D.G.K.). Am J Respir Crit Care Med Vol 190, Iss 5, pp e18–e19, Sep 1, 2014 Copyright © 2014 by the American Thoracic Society DOI: 10.1164/rccm.201310-1842IM Internet address: www.atsjournals.org
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American Journal of Respiratory and Critical Care Medicine Volume 190 Number 5 | September 1 2014
IMAGES IN PULMONARY, CRITICAL CARE, SLEEP MEDICINE AND THE SCIENCES procedure was followed to generate perfusion histograms. Histogram frequency was normalized to the number of voxels within the lung for that image slice. At baseline (Figures 1A–1D), large regions of the lung were ventilated but not perfused. After endarterectomy (Figures 1E–1H) lung ventilated volume increased by 0.2 L, perfused lung volume by 0.8 L, and the volume of the lungs both ventilated and perfused by 0.8 L. Histogram analysis (Figures 1D and 1H) showed better ventilation–perfusion matching after endarterectomy. The method provides a safe and sensitive means of assessment of regional ventilation and perfusion distributions in CTEPH, and is suitable for monitoring response to intervention. This multinuclear MRI technique (1, 2) provides much higher spatial resolution images (3 3 3 3 10 mm) than traditional ventilation–perfusion scintigraphy (3) with no ionizing radiation dose. In a clinical context, hyperpolarized gas MRI and perfusion MRI are not yet as readily available as scintigraphy, but are attainable on clinical MRI scanners : : and together offer an attractive nonionizing alternative for the study of regional V/Q in a range of pulmonary diseases. The Institutional Review Board for Human Studies approved the protocols and written consent was obtained from the patient. n Author disclosures are available with the text of this article at www.atsjournals.org.
References 1. Woodhouse N, Wild JM, Paley MNJ, Fichele S, Said Z, Swift AJ, van Beek EJR. Combined helium-3/proton magnetic resonance imaging measurement of ventilated lung volumes in smokers compared to never-smokers. J Magn Reson Imaging 2005;21:365–369. 2. Rajaram S, Swift AJ, Telfer A, Hurdman J, Marshall H, Lorenz E, Capener D, Davies C, Hill C, Elliot C, et al. 3D contrast-enhanced lung
perfusion MRI is an effective screening tool for chronic thromboembolic pulmonary hypertension: results from the ASPIRE Registry. Thorax 2013;68:677–678. 3. Tunariu N, Gibbs SJR, Win Z, Gin-Sing W, Graham A, Gishen P, Al-Nahhas A. Ventilation-perfusion scintigraphy is more sensitive than multidetector CTPA in detecting chronic thromboembolic pulmonary disease as a treatable cause of pulmonary hypertension. J Nucl Med 2007;48:680–684.
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