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Goodhart T, Seres P, Grenier J, Keen C, Stobbe R, Thompson RB. Dynamic changes in lung water density and volume following supine body positioning. Magn Reson Med 2024; 91:2612-2620. [PMID: 38247037 DOI: 10.1002/mrm.30017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 12/10/2023] [Accepted: 01/08/2024] [Indexed: 01/23/2024]
Abstract
PURPOSE Measure the changes in relative lung water density (rLWD), lung volume, and total lung water content as a function of time after supine body positioning. METHODS An efficient ultrashort-TE pulse sequence with a yarnball k-space trajectory was used to measure water density-weighted lung images for 25 min following supine body positioning (free breathing, 74-s acquisitions, 3D images at functional residual capacity, 18 time points) in 9 healthy volunteers. Global and regional (10 chest-to-back positions) rLWD, lung volume, and total lung water volume were measured in all subjects at all time points. Volume changes were validated with a nitrogen washout study in 3 participants. RESULTS Global rLWD increased significantly (p = 0.001) from 31.8 ± 5.5% to 34.8 ± 6.8%, while lung volumes decreased significantly (p < 0.001) from 2390 ± 620 mL to 2130 ± 630 mL over the same 25-min interval. Total lung water volume decreased slightly from 730 ± 125 mL to 706 ± 126 mL (p = 0.028). There was a significant chest-to-back gradient in rLWD (20.7 ± 4.6% to 39.9 ± 6.1%) at all time points with absolute increases of 1.8 ± 1.2% at the chest and 5.4 ± 1.9% at the back. Nitrogen washout studies yielded a similar reduction in lung volume (12.5 ± 0.9%) and time course following supine positioning. CONCLUSION Lung volumes during tidal breathing decrease significantly over tens of minutes following supine body positioning, with corresponding increases in lung water density (9.2 ± 4.4% relative increase). The total volume of lung water is slightly reduced over this interval (3.3 ± 4.0% relative change). Evaluation of rLWD should take time after supine positioning, and more generally, all sources of lung volume changes should be taken into consideration to avoid significant bias.
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Affiliation(s)
- Thomas Goodhart
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Peter Seres
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Justin Grenier
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Christopher Keen
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Rob Stobbe
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Richard B Thompson
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
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2
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Kizhakke Puliyakote AS, Tedjasaputra V, Petersen GM, Sá RC, Hopkins SR. Assessing the pulmonary vascular responsiveness to oxygen with proton MRI. J Appl Physiol (1985) 2024; 136:853-863. [PMID: 38385182 DOI: 10.1152/japplphysiol.00747.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 02/05/2024] [Accepted: 02/19/2024] [Indexed: 02/23/2024] Open
Abstract
Ventilation-perfusion matching occurs passively and is also actively regulated through hypoxic pulmonary vasoconstriction (HPV). The extent of HPV activity in humans, particularly normal subjects, is uncertain. Current evaluation of HPV assesses changes in ventilation-perfusion relationships/pulmonary vascular resistance with hypoxia and is invasive, or unsuitable for patients because of safety concerns. We used a noninvasive imaging-based approach to quantify the pulmonary vascular response to oxygen as a metric of HPV by measuring perfusion changes between breathing 21% and 30%O2 using arterial spin labeling (ASL) MRI. We hypothesized that the differences between 21% and 30%O2 images reflecting HPV release would be 1) significantly greater than the differences without [Formula: see text] changes (e.g., 21-21% and 30-30%O2) and 2) negatively associated with ventilation-perfusion mismatch. Perfusion was quantified in the right lung in normoxia (baseline), after 15 min of 30% O2 breathing (hyperoxia) and 15 min normoxic recovery (recovery) in healthy subjects (7 M, 7 F; age = 41.4 ± 19.6 yr). Normalized, smoothed, and registered pairs of perfusion images were subtracted and the mean square difference (MSD) was calculated. Separately, regional alveolar ventilation and perfusion were quantified from specific ventilation, proton density, and ASL imaging; the spatial variance of ventilation-perfusion (σ2V̇a/Q̇) distributions was calculated. The O2-responsive MSD was reproducible (R2 = 0.94, P < 0.0001) and greater (0.16 ± 0.06, P < 0.0001) than that from subtracted images collected under the same [Formula: see text] (baseline = 0.09 ± 0.04, hyperoxia = 0.08 ± 0.04, recovery = 0.08 ± 0.03), which were not different from one another (P = 0.2). The O2-responsive MSD was correlated with σ2V̇a/Q̇ (R2 = 0.47, P = 0.007). These data suggest that active HPV optimizes ventilation-perfusion matching in normal subjects. This noninvasive approach could be applied to patients with different disease phenotypes to assess HPV and ventilation-perfusion mismatch.NEW & NOTEWORTHY We developed a new proton MRI method to noninvasively quantify the pulmonary vascular response to oxygen. Using a hyperoxic stimulus to release HPV, we quantified the resulting redistribution of perfusion. The differences between normoxic and hyperoxic images were greater than those between images without [Formula: see text] changes and negatively correlated with ventilation-perfusion mismatch. This suggests that active HPV optimizes ventilation-perfusion matching in normal subjects. This approach is suitable for assessing patients with different disease phenotypes.
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Affiliation(s)
- Abhilash S Kizhakke Puliyakote
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States
- Department of Radiology, University of California, San Diego, La Jolla, California, United States
| | - Vincent Tedjasaputra
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States
- Department of Medicine, University of California, San Diego, La Jolla, California, United States
| | - Gregory M Petersen
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States
| | - Rui Carlos Sá
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States
- Department of Medicine, University of California, San Diego, La Jolla, California, United States
| | - Susan R Hopkins
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States
- Department of Radiology, University of California, San Diego, La Jolla, California, United States
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Cho Y, Fakhouri F, Ballinger MN, Englert JA, Hayes D, Kolipaka A, Ghadiali SN. Magnetic Resonance Elastography and Computational Modeling Identify Heterogeneous Lung Biomechanical Properties during Cystic Fibrosis. RESEARCH SQUARE 2024:rs.3.rs-4125891. [PMID: 38562870 PMCID: PMC10984019 DOI: 10.21203/rs.3.rs-4125891/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The lung is a dynamic mechanical organ and several pulmonary disorders are characterized by heterogeneous changes in the lung's local mechanical properties (i.e. stiffness). These alterations lead to abnormal lung tissue deformation (i.e. strain) which have been shown to promote disease progression. Although heterogenous mechanical properties may be important biomarkers of disease, there is currently no non-invasive way to measure these properties for clinical diagnostic purposes. In this study, we use a magnetic resonance elastography technique to measure heterogenous distributions of the lung's shear stiffness in healthy adults and in people with Cystic Fibrosis. Additionally, computational finite element models which directly incorporate the measured heterogenous mechanical properties were developed to assess the effects on lung tissue deformation. Results indicate that consolidated lung regions in people with Cystic Fibrosis exhibited increased shear stiffness and reduced spatial heterogeneity compared to surrounding non-consolidated regions. Accounting for heterogenous lung stiffness in healthy adults did not change the globally averaged strain magnitude obtained in computational models. However, computational models that used heterogenous stiffness measurements predicted significantly more variability in local strain and higher spatial strain gradients. Finally, computational models predicted lower strain variability and spatial strain gradients in consolidated lung regions compared to non-consolidated regions. These results indicate that spatial variability in shear stiffness alters local strain and strain gradient magnitudes in people with Cystic Fibrosis. This imaged-based modeling technique therefore represents a clinically viable way to non-invasively assess lung mechanics during both health and disease.
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Affiliation(s)
| | | | | | | | - Don Hayes
- Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine
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4
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Needleman SH, Kim M, McClelland JR, Naish JH, Tibiletti M, O'Connor JPB, Parker GJM. Independent component analysis (ICA) applied to dynamic oxygen-enhanced MRI (OE-MRI) for robust functional lung imaging at 3 T. Magn Reson Med 2024; 91:955-971. [PMID: 37984456 PMCID: PMC10952250 DOI: 10.1002/mrm.29912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 09/03/2023] [Accepted: 10/13/2023] [Indexed: 11/22/2023]
Abstract
PURPOSE Dynamic lung oxygen-enhanced MRI (OE-MRI) is challenging due to the presence of confounding signals and poor signal-to-noise ratio, particularly at 3 T. We have created a robust pipeline utilizing independent component analysis (ICA) to automatically extract the oxygen-induced signal change from confounding factors to improve the accuracy and sensitivity of lung OE-MRI. METHODS Dynamic OE-MRI was performed on healthy participants using a dual-echo multi-slice spoiled gradient echo sequence at 3 T and cyclical gas delivery. ICA was applied to each echo within a thoracic mask. The ICA component relating to the oxygen-enhancement signal was automatically identified using correlation analysis. The oxygen-enhancement component was reconstructed, and the percentage signal enhancement (PSE) was calculated. The lung PSE of current smokers was compared with nonsmokers; scan-rescan repeatability, ICA pipeline repeatability, and reproducibility between two vendors were assessed. RESULTS ICA successfully extracted a consistent oxygen-enhancement component for all participants. Lung tissue and oxygenated blood displayed the opposite oxygen-induced signal enhancements. A significant difference in PSE was observed between the lungs of current smokers and nonsmokers. The scan-rescan repeatability and the ICA pipeline repeatability were good. CONCLUSION The developed pipeline demonstrated sensitivity to the signal enhancements of the lung tissue and oxygenated blood at 3 T. The difference in lung PSE between current smokers and nonsmokers indicates a likely sensitivity to lung function alterations that may be seen in mild pathology, supporting future use of our methods in patient studies.
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Affiliation(s)
- Sarah H. Needleman
- Centre for Medical Image Computing (CMIC), Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | - Mina Kim
- Centre for Medical Image Computing (CMIC), Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | - Jamie R. McClelland
- Centre for Medical Image Computing (CMIC), Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
- Wellcome/EPSRC Centre for Interventional and Surgical Sciences (WEISS), Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | - Josephine H. Naish
- Bioxydyn LimitedManchesterUK
- BHF Manchester Centre for Heart and Lung Magnetic Resonance Research (MCMR), Manchester University NHS Foundation TrustManchesterUK
| | | | | | - Geoff J. M. Parker
- Centre for Medical Image Computing (CMIC), Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
- Bioxydyn LimitedManchesterUK
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Malis V, Kassai Y, Vucevic D, Bae WC, Ohno Y, Yen A, Miyazaki M. Lung T 2 * mapping using 3D ultrashort TE with tight intervals δTE. Magn Reson Med 2023; 90:2001-2010. [PMID: 37288577 PMCID: PMC10545378 DOI: 10.1002/mrm.29756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/05/2023] [Accepted: 05/23/2023] [Indexed: 06/09/2023]
Abstract
PURPOSE To develop 3D ultrashort-TE (UTE) sequences with tight TE intervals (δTE), allowing for accurateT 2 * $$ {\mathrm{T}}_2^{\ast } $$ mapping of lungs under free breathing. METHODS We have implemented a four-echo UTE sequence with δTE (< 0.5 ms). A Monte-Carlo simulation was performed to identify an optimal number of echoes that would result in a significant improvement in the accuracy of theT 2 * $$ {\mathrm{T}}_2^{\ast } $$ fit within an acceptable scan time. A validation study was conducted on a phantom with known shortT 2 * $$ {\mathrm{T}}_2^{\ast } $$ values (< 5 ms). The scanning protocol included a combination of a standard multi-echo UTE with six echoes (2.2-ms intervals) and a new four-echo UTE (TE < 2 ms) with tight TE intervals δTE. The human imaging was performed at 3 T on 6 adult volunteers.T 2 * $$ {\mathrm{T}}_2^{\ast } $$ mapping was performed with mono-exponential and bi-exponential models. RESULTS The simulation for the proposed 10-echo acquisition predicted over 2-fold improvement in the accuracy of estimating the shortT 2 * $$ {\mathrm{T}}_2^{\ast } $$ compared with the regular six-echo acquisition. In the phantom study, theT 2 * $$ {\mathrm{T}}_2^{\ast } $$ was measured up to three times more accurately compared with standard six-echo UTE. In human lungs,T 2 * $$ {\mathrm{T}}_2^{\ast } $$ maps were successfully obtained from 10 echoes, yielding average valuesT 2 * $$ {\mathrm{T}}_2^{\ast } $$ = 1.62 ± 0.48 ms for mono-exponential andT 2 s * $$ {\mathrm{T}}_{2s}^{\ast } $$ = 1.00 ± 0.53 ms for bi-exponential models. CONCLUSION A UTE sequence using δTE was implemented and validated on shortT 2 * $$ {\mathrm{T}}_2^{\ast } $$ phantoms. The sequence was successfully applied for lung imaging; the bi-exponential signal model fit for human lung imaging may provide valuable insights into the diseased human lungs.
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Affiliation(s)
- Vadim Malis
- Department of Radiology, University of California-San Diego, La Jolla, CA
| | | | - Diana Vucevic
- Department of Radiology, University of California-San Diego, La Jolla, CA
| | - Won C. Bae
- Department of Radiology, University of California-San Diego, La Jolla, CA
- Department of Radiology, VA San Diego Healthcare System, San Diego, CA
| | - Yoshiharu Ohno
- Department of Radiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
- Joint Research Laboratory of Advanced Medical Imaging, Fujita Health University, School of Medicine, Toyoake, Aichi, Japan
| | - Andrew Yen
- Department of Radiology, University of California-San Diego, La Jolla, CA
| | - Mitsue Miyazaki
- Department of Radiology, University of California-San Diego, La Jolla, CA
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Lindow T, Quadrelli S, Ugander M. Noninvasive Imaging Methods for Quantification of Pulmonary Edema and Congestion: A Systematic Review. JACC Cardiovasc Imaging 2023; 16:1469-1484. [PMID: 37632500 DOI: 10.1016/j.jcmg.2023.06.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 08/28/2023]
Abstract
Quantification of pulmonary edema and congestion is important to guide diagnosis and risk stratification, and to objectively evaluate new therapies in heart failure. Herein, we review the validation, diagnostic performance, and clinical utility of noninvasive imaging modalities in this setting, including chest x-ray, lung ultrasound (LUS), computed tomography (CT), nuclear medicine imaging methods (positron emission tomography [PET], single photon emission CT), and magnetic resonance imaging (MRI). LUS is a clinically useful bedside modality, and fully quantitative methods (CT, MRI, PET) are likely to be important contributors to a more accurate and precise evaluation of new heart failure therapies and for clinical use in conjunction with cardiac imaging. There are only a limited number of studies evaluating pulmonary congestion during stress. Taken together, noninvasive imaging of pulmonary congestion provides utility for both clinical and research assessment, and continued refinement of methodologic accuracy, validation, and workflow has the potential to increase broader clinical adoption.
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Affiliation(s)
- Thomas Lindow
- Kolling Institute, Royal North Shore Hospital and University of Sydney, Sydney, Australia; Department of Clinical Physiology, Research and Development, Växjö Central Hospital, Region Kronoberg, Sweden; Clinical Physiology, Clinical Sciences, Lund University, Sweden
| | - Scott Quadrelli
- Kolling Institute, Royal North Shore Hospital and University of Sydney, Sydney, Australia
| | - Martin Ugander
- Kolling Institute, Royal North Shore Hospital and University of Sydney, Sydney, Australia; Department of Clinical Physiology, Karolinska University Hospital, and Karolinska Institutet, Stockhom, Sweden.
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7
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Tan F, Zhu X, Chan M, Deveshwar N, Willmering MM, Lustig M, Larson PEZ. Pulmonary Ventilation Analysis Using 1H Ultra-Short Echo Time (UTE) Lung MRI: A Reproducibility Study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.22.563196. [PMID: 37961357 PMCID: PMC10634712 DOI: 10.1101/2023.10.22.563196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Purpose To evaluate methods for quantification of pulmonary ventilation with ultrashort echo time (UTE) MRI. Methods We performed a reproducibility study, acquiring two free-breathing 1H UTE lung MRIs on the same day for six healthy volunteers. The 1) 3D + t cyclic b-spline and 2) symmetric image normalization (SyN) methods for image registration were applied after respiratory phase-resolved image reconstruction. Ventilation maps were calculated using 1) Jacobian determinant of the deformation fields minus one, termed regional ventilation, and 2) intensity percentage difference between the registered and fixed image, termed specific ventilation. We compared the reproducibility of all four method combinations via statistical analysis. Results Split violin plots and Bland-Altman plots are shown for whole lungs and lung sections. The cyclic b-spline registration and Jacobian determinant regional ventilation quantification provide total ventilation volumes that match the segmentation tidal volume, smooth and uniform ventilation maps. The cyclic b-spline registration and specific ventilation combination yields the smallest standard deviation in the Bland-Altman plot. Conclusion Cyclic registration performs better than SyN for respiratory phase-resolved 1H UTE MRI ventilation quantification. Regional ventilation correlates better with segmentation lung volume, while specific ventilation is more reproducible.
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Affiliation(s)
- Fei Tan
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, CA
| | - Xucheng Zhu
- Work done at UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, CA, Currently at GE Healthcare, CA
| | - Marilynn Chan
- Pediatric Pulmonology, Department of Pediatrics, University of California, San Francisco, CA
| | - Nikhil Deveshwar
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, CA
| | - Matthew M Willmering
- Center for Pulmonary Imaging Research, Divisions of Pulmonary Medicine and Radiology, Cincinnati Children's Hospital Medical Center. Cincinnati, OH
| | - Michael Lustig
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA
| | - Peder E Z Larson
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, CA
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA
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8
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Thompson RB, Darquenne C. Magnetic Resonance Imaging of Aerosol Deposition. J Aerosol Med Pulm Drug Deliv 2023; 36:228-234. [PMID: 37523222 DOI: 10.1089/jamp.2023.29087.rbt] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023] Open
Abstract
Nuclear magnetic resonance imaging (MRI) uses non-ionizing radiation and offers a host of contrast mechanisms with the potential to quantify aerosol deposition. This chapter introduces the physics of MRI, its use in lung imaging, and more specifically, the methods that are used for the detection of regional distributions of inhaled particles. The most common implementation of MRI is based on imaging of hydrogen atoms (1H) in water. The regional deposition of aerosol particles can be measured by the perturbation of the acquired 1H signals via labeling of the aerosol with contrast agents. Existing in vitro human and in vivo animal model measurements of regional aerosol deposition in the respiratory tract are described, demonstrating the capability of MRI to assess aerosol deposition in the lung.
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Affiliation(s)
- Richard B Thompson
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Chantal Darquenne
- Department of Medicine, University of California San Diego, San Diego, California, USA
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Fakhouri FS, Joseph M, Ballinger M, Shukla V, Weimar D, Novak C, Ghadiali S, Kolipaka A. Magnetic Resonance Elastography (MRE) of Bleomycin-Induced Pulmonary Fibrosis in an Animal Model. Invest Radiol 2023; 58:299-306. [PMID: 36730906 PMCID: PMC10023269 DOI: 10.1097/rli.0000000000000935] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Idiopathic pulmonary fibrosis is responsible for 40,000 deaths annually in the United States. A hallmark of idiopathic pulmonary fibrosis is elevated collagen deposition, which alters lung stiffness. Clinically relevant ways to measure changes in lung stiffness during pulmonary fibrosis are not available, and new noninvasive imaging methods are needed to measure changes in lung mechanical properties. OBJECTIVES Magnetic resonance elastography (MRE) is an in vivo magnetic resonance imaging technique proven to detect changes in shear stiffness in different organs. This study used MRE, histology, and bronchoalveolar lavage (BAL) to study changes in the mechanical and structural properties of the lungs after bleomycin-induced pulmonary fibrosis in pigs. MATERIALS AND METHODS Pulmonary fibrosis was induced in 9 Yorkshire pigs by intratracheal instillation of 2 doses of bleomycin into the right lung only. Magnetic resonance elastography scans were performed at baseline and week 4 and week 8 postsurgery in a 1.5 T magnetic resonance imaging scanner using a spin-echo echo planar imaging sequence to measure changes in lung shear stiffness. At the time of each scan, a BAL was performed. After the final scan, whole lung tissue was removed and analyzed for histological changes. RESULTS Mean MRE-derived stiffness measurements at baseline, week 4, and week 8 for the control (left) lungs were 1.02 ± 0.27 kPa, 0.86 ± 0.29 kPa, and 0.68 ± 0.20 kPa, respectively. The ratio of the shear stiffness in the injured (right) lung to the uninjured control (left) lung at baseline, week 4, and week 8 was 0.98 ± 0.23, 1.52 ± 0.41, and 1.64 ± 0.40, respectively. High-dose animals showed increased protein in BAL fluid, elevated inflammation observed by the presence of patchy filtrates, and enhanced collagen and α-smooth muscle actin staining on histological sections. Low-dose animals and the control (left) lungs of high-dose animals did not show significant histopathological changes. CONCLUSION This study demonstrated that MRE can be used to detect changes in lung stiffness in pigs after bleomycin challenge.
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Affiliation(s)
- Faisal S. Fakhouri
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
- Department of Biomedical Technology, King Saud University, Riyadh, 12372, KSA
| | - Matthew Joseph
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210, USA
| | - Megan Ballinger
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210, USA
- Division of Pulmonary, Critical Care, and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Vasudha Shukla
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - David Weimar
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210, USA
- Division of Pulmonary, Critical Care, and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Caymen Novak
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210, USA
- Division of Pulmonary, Critical Care, and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Samir Ghadiali
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Division of Pulmonary, Critical Care, and Sleep Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Arunark Kolipaka
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
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Kizhakke Puliyakote AS, Prisk GK, Elliott AR, Kim NH, Pazar B, Sá RC, Asadi AK, Hopkins SR. The spatial-temporal dynamics of pulmonary blood flow are altered in pulmonary arterial hypertension. J Appl Physiol (1985) 2023; 134:969-979. [PMID: 36861672 PMCID: PMC10085549 DOI: 10.1152/japplphysiol.00463.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 02/16/2023] [Accepted: 02/27/2023] [Indexed: 03/03/2023] Open
Abstract
Global fluctuation dispersion (FDglobal), a spatial-temporal metric derived from serial images of the pulmonary perfusion obtained with MRI-arterial spin labeling, describes temporal fluctuations in the spatial distribution of perfusion. In healthy subjects, FDglobal is increased by hyperoxia, hypoxia, and inhaled nitric oxide. We evaluated patients with pulmonary arterial hypertension (PAH, 4F, aged 47 ± 15, mean pulmonary artery pressure 48 ± 7 mmHg) and healthy controls (CON, 7F, aged 47 ± 12) to test the hypothesis that FDglobal is increased in PAH. Images were acquired at ∼4-5 s intervals during voluntary respiratory gating, inspected for quality, registered using a deformable registration algorithm, and normalized. Spatial relative dispersion (RD = SD/mean) and the percent of the lung image with no measurable perfusion signal (%NMP) were also assessed. FDglobal was significantly increased in PAH (PAH = 0.40 ± 0.17, CON = 0.17 ± 0.02, P = 0.006, a 135% increase) with no overlap in values between the two groups, consistent with altered vascular regulation. Both spatial RD and %NMP were also markedly greater in PAH vs. CON (PAH RD = 1.46 ± 0.24, CON = 0.90 ± 0.10, P = 0.0004; PAH NMP = 13.4 ± 6.1%; CON = 2.3 ± 1.4%, P = 0.001 respectively) consistent with vascular remodeling resulting in poorly perfused regions of lung and increased spatial heterogeneity. The difference in FDglobal between normal subjects and patients with PAH in this small cohort suggests that spatial-temporal imaging of perfusion may be useful in the evaluation of patients with PAH. Since this MR imaging technique uses no injected contrast agents and has no ionizing radiation it may be suitable for use in diverse patient populations.NEW & NOTEWORTHY Using proton MRI-arterial spin labeling to obtain serial images of pulmonary perfusion, we show that global fluctuation dispersion (FDglobal), a metric of temporal fluctuations in the spatial distribution of perfusion, was significantly increased in female patients with pulmonary arterial hypertension (PAH) compared with healthy controls. This potentially indicates pulmonary vascular dysregulation. Dynamic measures using proton MRI may provide new tools for evaluating individuals at risk of PAH or for monitoring therapy in patients with PAH.
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Affiliation(s)
- Abhilash S Kizhakke Puliyakote
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - G Kim Prisk
- Department of Radiology, University of California, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Ann R Elliott
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Nick H Kim
- Department of Medicine, University of California, San Diego, California, United States
| | - Beni Pazar
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - Rui Carlos Sá
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Amran K Asadi
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - Susan R Hopkins
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
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Pavlova OS, Gulyaev MV, Gervits LL, Hurshkainen AA, Nikulin AV, Puchnin VM, Teploukhova ED, Kuropatkina TA, Anisimov NV, Medvedeva NA, Pirogov YA. Т 1 mapping of rat lungs in 19 F MRI using octafluorocyclobutane. Magn Reson Med 2023; 89:2318-2331. [PMID: 36744719 DOI: 10.1002/mrm.29606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 01/12/2023] [Accepted: 01/12/2023] [Indexed: 02/07/2023]
Abstract
PURPOSE To demonstrate the feasibility of using octafluorocyclobutane (OFCB, c-C4 F8 ) for T1 mapping of lungs in 19 F MRI. METHODS The study was performed at 7 T in three healthy rats and three rats with pulmonary hypertension. To increase the sensitivity of 19 F MRI, a bent-shaped RF coil with periodic metal strips structure was used. The double flip angle method was used to calculate normalized transmitting RF field (B1n + ) maps and for correcting T1 maps built with the variable flip angle (VFA) method. The ultrashort TE pulse sequence was applied for acquiring MR images throughout the study. RESULTS The dependencies of OFCB relaxation times on its partial pressure in mixtures with oxygen, air, helium, and argon were obtained. T1 of OFCB linearly depended on its partial pressure with the slope of about 0.35 ms/kPa in the case of free diffusion. RF field inhomogeneity leads to distortion of T1 maps built with the VFA method, and therefore to high standard deviation of T1 in these maps. To improve the accuracy of the T1 maps, the B1n + maps were applied for VFA correction. This contributed to a 2-3-fold decrease in the SD of T1 values in the corresponding maps compared with T1 maps calculated without the correction. Three-dimensional T1 maps were obtained, and the mean T1 in healthy rat lungs was 35 ± 10 ms, and in rat lungs with pulmonary hypertension - 41 ± 9 ms. CONCLUSION OFCB has a spin-rotational relaxation mechanism and can be used for 19 F T1 mapping of lungs. The calculated OFCB maps captured ventilation defects induced by edema.
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Affiliation(s)
- Olga S Pavlova
- Faculty of Medicine, Lomonosov Moscow State University, Moscow, Russia.,Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia
| | - Mikhail V Gulyaev
- Faculty of Medicine, Lomonosov Moscow State University, Moscow, Russia
| | - Lev L Gervits
- Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Moscow, Russia
| | - Anna A Hurshkainen
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | - Anton V Nikulin
- Center of Photonics and 2D Materials, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Viktor M Puchnin
- School of Physics and Engineering, ITMO University, St. Petersburg, Russia
| | | | | | | | | | - Yury A Pirogov
- Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia
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12
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Hsia CCW, Bates JHT, Driehuys B, Fain SB, Goldin JG, Hoffman EA, Hogg JC, Levin DL, Lynch DA, Ochs M, Parraga G, Prisk GK, Smith BM, Tawhai M, Vidal Melo MF, Woods JC, Hopkins SR. Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report. Ann Am Thorac Soc 2023; 20:161-195. [PMID: 36723475 PMCID: PMC9989862 DOI: 10.1513/annalsats.202211-915st] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MRI) using ultrashort-echo time (UTE) sequences has improved signal detection from lung parenchyma; contrast agents are used to deduce airway function, ventilation-perfusion-diffusion, and mechanics. Proton MRI can measure regional ventilation-perfusion ratio. Quantitative imaging (QI)-derived endpoints have been developed to identify structure-function phenotypes, including air-blood-tissue volume partition, bronchovascular remodeling, emphysema, fibrosis, and textural patterns indicating architectural alteration. Coregistered landmarks on paired images obtained at different lung volumes are used to infer airway caliber, air trapping, gas and blood transport, compliance, and deformation. This document summarizes fundamental "good practice" stereological principles in QI study design and analysis; evaluates technical capabilities and limitations of common imaging modalities; and assesses major QI endpoints regarding underlying assumptions and limitations, ability to detect and stratify heterogeneous, overlapping pathophysiology, and monitor disease progression and therapeutic response, correlated with and complementary to, functional indices. The goal is to promote unbiased quantification and interpretation of in vivo imaging data, compare metrics obtained using different QI modalities to ensure accurate and reproducible metric derivation, and avoid misrepresentation of inferred physiological processes. The role of imaging-based computational modeling in advancing these goals is emphasized. Fundamental principles outlined herein are critical for all forms of QI irrespective of acquisition modality or disease entity.
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13
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Koda R, Taniguchi H, Konno K, Yamakoshi Y. B-line Elastography Measurement of Lung Parenchymal Elasticity. ULTRASONIC IMAGING 2023; 45:30-41. [PMID: 36631936 DOI: 10.1177/01617346221149141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
This paper proposes a method to determine the elasticity of the lung parenchyma from the B-line Doppler signal observed using continuous shear wave elastography, which uses a small vibrator placed on the tissue surface to propagate continuous shear waves with a vibration frequency of approximately 100 Hz. Since the B-line is generated by multiple reflections in fluid-storing alveoli near the lung surface, the ultrasonic multiple-reflection signal from the B-line is affected by the Doppler shift due to shear waves propagating in the lung parenchyma. When multiple B-lines are observed, the propagation velocity can be estimated by measuring the difference in propagation time between the B-lines. Therefore, continuous shear wave elastography can be used to determine the elasticity of the lung parenchyma by measuring the phase difference of shear wave between the B-lines. In this study, three elastic sponges (soft, medium, and hard) with embedded glass beads were used to simulate fluid-storing alveoli. Shear wave velocity measured using the proposed method was compared with that calculated using Young's modulus obtained from compression measurement. Using the proposed method, the measured shear wave velocities (mean ± S.D.) were 3.78 ± 0.23, 4.24 ± 0.12, and 5.06 ± 0.05 m/s for soft, medium, and hard sponges, respectively, which deviated by a maximum of 5.37% from the values calculated using the measured Young's moduli. The shear wave velocities of the sponge phantom were in a velocity range similar to the mean shear wave velocities of healthy and diseased lungs reported by magnetic resonance elastography (3.25 and 4.54 m/s, respectively). B-line elastography may enable emergency diagnoses of acute lung disease using portable ultrasonic echo devices.
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Affiliation(s)
- Ren Koda
- Graduate School of Science and Technology, Gunma University, Kiryu, Gunma, Japan
| | - Hayato Taniguchi
- Department of Emergency Medicine, Graduate School of Medicine, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Kei Konno
- Clinical Laboratory Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Yoshiki Yamakoshi
- Graduate School of Science and Technology, Gunma University, Kiryu, Gunma, Japan
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14
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Fakhouri F, Kannengiesser S, Pfeuffer J, Gokun Y, Kolipaka A. Free-breathing MR elastography of the lungs: An in vivo study. Magn Reson Med 2022; 87:236-248. [PMID: 34463400 PMCID: PMC8616792 DOI: 10.1002/mrm.28986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 01/03/2023]
Abstract
PURPOSE Lung stiffness alters with many diseases; therefore, several MR elastography (MRE) studies were performed earlier to investigate the stiffness of the right lung during breathhold at residual volume and total lung capacity. The aims of this study were 1) to estimate shear stiffness of the lungs using MRE under free breathing and demonstrate the measurements' repeatability and reproducibility, and 2) to compare lung stiffness under free breathing to breathhold and as a function of age and gender. METHODS Twenty-five healthy volunteers were scanned on a 1.5 Tesla MRI scanner. Spin-echo dual-density spiral and a spin-echo EPI MRE sequences were used to measure shear stiffness of the lungs during free breathing and breathhold at midpoint of tidal volume, respectively. Concordance correlation coefficient and Bland-Altman analyses were performed to determine the repeatability and reproducibility of the spin-echo dual-density spiral-derived shear stiffness. Repeated measures analyses of variances were used to investigate differences in shear stiffness between spin-echo dual-density spiral and spin-echo EPI, right and left lungs, males and females, and different age groups. RESULTS Free-breathing MRE sequence was highly repeatable and reproducible (concordance correlation coefficient > 0.86 for both lungs). Lung stiffness was significantly lower in breathhold than in free breathing (P < .001), which can be attributed to potential stress relaxation of lung parenchyma or breathhold inconsistencies. However, there was no significant difference between different age groups (P = .08). The left lung showed slightly higher stiffness values than the right lung (P = .14). There is no significant difference in lung stiffness between genders. CONCLUSION This study demonstrated the feasibility of free-breathing lung MRE with excellent repeatability and reproducibility. Stiffness changes with age and during the respiratory cycle. However, gender does not influence lungs stiffness.
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Affiliation(s)
- Faisal Fakhouri
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA.,Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | | | - Josef Pfeuffer
- MR Application Development, Siemens Healthcare GmbH, Erlangen, Germany
| | - Yevgeniya Gokun
- Department of Biomedical Informatics, Center for Biostatistics, The Ohio State University, Columbus, OH 43210, USA
| | - Arunark Kolipaka
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA.,Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
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15
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Early Diagnosis and Real-Time Monitoring of Regional Lung Function Changes to Prevent Chronic Obstructive Pulmonary Disease Progression to Severe Emphysema. J Clin Med 2021; 10:jcm10245811. [PMID: 34945107 PMCID: PMC8708661 DOI: 10.3390/jcm10245811] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/07/2021] [Accepted: 12/09/2021] [Indexed: 02/04/2023] Open
Abstract
First- and second-hand exposure to smoke or air pollutants is the primary cause of chronic obstructive pulmonary disease (COPD) pathogenesis, where genetic and age-related factors predispose the subject to the initiation and progression of obstructive lung disease. Briefly, airway inflammation, specifically bronchitis, initiates the lung disease, leading to difficulty in breathing (dyspnea) and coughing as initial symptoms, followed by air trapping and inhibition of the flow of air into the lungs due to damage to the alveoli (emphysema). In addition, mucus obstruction and impaired lung clearance mechanisms lead to recurring acute exacerbations causing progressive decline in lung function, eventually requiring lung transplant and other lifesaving interventions to prevent mortality. It is noteworthy that COPD is much more common in the population than currently diagnosed, as only 16 million adult Americans were reported to be diagnosed with COPD as of 2018, although an additional 14 million American adults were estimated to be suffering from COPD but undiagnosed by the current standard of care (SOC) diagnostic, namely the spirometry-based pulmonary function test (PFT). Thus, the main issue driving the adverse disease outcome and significant mortality for COPD is lack of timely diagnosis in the early stages of the disease. The current treatment regime for COPD emphysema is most effective when implemented early, on COPD onset, where alleviating symptoms and exacerbations with timely intervention(s) can prevent steep lung function decline(s) and disease progression to severe emphysema. Therefore, the key to efficiently combatting COPD relies on early detection. Thus, it is important to detect early regional pulmonary function and structural changes to monitor modest disease progression for implementing timely interventions and effectively eliminating emphysema progression. Currently, COPD diagnosis involves using techniques such as COPD screening questionnaires, PFT, arterial blood gas analysis, and/or lung imaging, but these modalities are limited in their capability for early diagnosis and real-time disease monitoring of regional lung function changes. Hence, promising emerging techniques, such as X-ray phase contrast, photoacoustic tomography, ultrasound computed tomography, electrical impedance tomography, the forced oscillation technique, and the impulse oscillometry system powered by robust artificial intelligence and machine learning analysis capability are emerging as novel solutions for early detection and real time monitoring of COPD progression for timely intervention. We discuss here the scope, risks, and limitations of current SOC and emerging COPD diagnostics, with perspective on novel diagnostics providing real time regional lung function monitoring, and predicting exacerbation and/or disease onset for prognosis-based timely intervention(s) to limit COPD–emphysema progression.
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16
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Meadus WQ, Stobbe RW, Grenier JG, Beaulieu C, Thompson RB. Quantification of lung water density with UTE Yarnball MRI. Magn Reson Med 2021; 86:1330-1344. [PMID: 33811679 DOI: 10.1002/mrm.28800] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 02/17/2021] [Accepted: 03/19/2021] [Indexed: 12/26/2022]
Abstract
PURPOSE An efficient Yarnball ultrashort-TE k-space trajectory, in combination with an optimized pulse sequence design and automated image-processing approach, is proposed for fast and quantitative imaging of water density in the lung parenchyma. METHODS Three-dimensional Yarnball k-space trajectories (TE = 0.07 ms) were designed at 3 T for breath-hold and free-breathing navigator acquisitions targeting the lung parenchyma (full torso spatial coverage) with minimal T1 and T 2 ∗ weighting. A composite of all solid tissues surrounding the lungs (muscle, liver, heart, blood pool) was used for user-independent lung water density signal referencing and B1 -inhomogeneity correction needed for the calculation of relative lung water density images. Sponge phantom experiments were used to validate absolute water density quantification, and relative lung water density was evaluated in 10 healthy volunteers. RESULTS Phantom experiments showed excellent agreement between sponge wet weight and imaging-derived water density. Breath-hold (13 seconds) and free-breathing (~2 minutes) Yarnball acquisitions in volunteers (2.5-mm isotropic resolution) had negligible artifacts and good lung parenchyma SNR (>10). Whole-lung average relative lung water density values with fully automated analysis were 28.2 ± 1.9% and 28.6 ± 1.8% for breath-hold and free-breathing acquisitions, respectively, with good test-retest reproducibility (intraclass correlation coefficient = 0.86 and 0.95, respectively). CONCLUSIONS Quantitative lung water density imaging with an optimized Yarnball k-space acquisition approach is possible in a breath-hold or short free-breathing study with automated signal referencing and segmentation.
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Affiliation(s)
| | - Robert W Stobbe
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
| | - Justin G Grenier
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
| | - Christian Beaulieu
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
| | - Richard B Thompson
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
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17
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Hahn AD, Malkus A, Kammerman J, Higano N, Walkup LL, Woods J, Fain SB. Effects of neonatal lung abnormalities on parenchymal R 2 * estimates. J Magn Reson Imaging 2021; 53:1853-1861. [PMID: 33404085 DOI: 10.1002/jmri.27487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 12/08/2020] [Accepted: 12/10/2020] [Indexed: 11/09/2022] Open
Abstract
Infants admitted to the neonatal intensive care unit (NICU) often suffer from multifaceted pulmonary morbidities that are not well understood. Ultrashort echo time (UTE) magnetic resonance imaging (MRI) is a promising technique for pulmonary imaging in this population without requiring exposure to ionizing radiation. The aims of this study were to investigate the effect of neonatal pulmonary disease on R2 * and tissue density and to utilize numerical simulations to evaluate the effect of different alveolar structures on predicted R2 *.This was a prospective study, in which 17 neonatal human subjects (five control, seven with bronchopulmonary dysplasia [BPD], five with congenital diaphragmatic hernia [CDH]) were enrolled. Twelve subjects were male and five were female, with postmenstrual age (PMA) at MRI of 39.7 ± 4.7 weeks. A 1.5T/multiecho three-dimensional UTE MRI was used. Pulmonary R2 * and tissue density were compared across disease groups over the whole lung and regionally. A spherical shell alveolar model was used to predict the expected R2 * over a range of tissue densities and tissue susceptibilities. Tests for significantly different mean R2 * and tissue densities across disease groups were evaluated using analysis of variance, with subsequent pairwise group comparisons performed using t tests. Lung tissue density was lower in the ipsilateral lung in CDH compared to both controls and BPD patients (both p < 0.05), while only the contralateral lung in CDH (CDHc) had higher whole-lung R2 * than both controls and BPD (both p < 0.05). R2 * differences were significant between controls and CDHc within all tissue density ranges (all p < 0.05) with the exception of the 80%-90% range (p = 0.17). Simulations predicted an inverse relationship between alveolar tissue density and R2 * that matches empirical human data. Alveolar wall thickness had no effect on R2 * independent of density (p = 1). The inverse relationship between R2 * and tissue density is influenced by the presence of disease globally and regionally in neonates with BPD and CDH in the NICU. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.
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Affiliation(s)
- Andrew D Hahn
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
| | - Annelise Malkus
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
| | - Jeffery Kammerman
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
| | - Nara Higano
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Laura L Walkup
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Jason Woods
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Sean B Fain
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.,Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA
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18
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Comparison of phase-resolved functional lung (PREFUL) MRI derived perfusion and ventilation parameters at 1.5T and 3T in healthy volunteers. PLoS One 2020; 15:e0244638. [PMID: 33378373 PMCID: PMC7773267 DOI: 10.1371/journal.pone.0244638] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/15/2020] [Indexed: 11/20/2022] Open
Abstract
Purpose The purpose of this study is to evaluate the influence of different field strengths on perfusion and ventilation parameters, SNR and CNR derived by PREFUL MRI using predefined sequence parameters. Methods Data sets of free breathing 2d FLASH lung MRI were acquired from 15 healthy subjects at 1.5T and 3T (Magnetom Avanto and Skyra, Siemens Healthcare, Erlangen, Germany) with a maximum period of 3 days in between. The processed functional parameters regional ventilation (RVent), perfusion (Q), quantified perfusion (QQuant), perfusion defect percentage (QDP), ventilation defect percentage (VDP) and ventilation-perfusion match (VQM) were compared for systematic differences. Signal- and contrast-to-noise ratio (SNR and CNR) of both acquisitions were analyzed. Results RVent, Q, VDP, SNR and CNR presented no significant differences between 1.5T and 3T. QQuant (1.5T vs. 3T, P = 0.04), and QDP (1.5T vs. 3T, P≤0.01) decreased significantly at 3T. Consequently, VQM increased significantly (1.5T vs. 3T, P≤0.01). Skewness and kurtosis of the Q-values increased significantly at 3T (P≤0.01). The mean Sørensen-Dice coefficients between both series were 0.91 for QDP and 0.94 for VDP. The Bland-Altman analysis of both series showed mean differences of 4.29% for QDP, 1.23% for VDP and -5.15% for VQM. Using the above-mentioned parameters for three-day repeatability at two different scanners and field strengths, the retrospective power calculation showed, that a sample size of 15 can detect differences of 3.7% for QDP, of 2.9% for VDP and differences of 2.6% for VQM. Conclusion Significant differences in QDP may be related to field inhomogeneities, which is expressed by increasing skewness and kurtosis at 3T. QQuant reveals only poor reproducibility between 1.5T and 3T. RVent, Q, VDP, SNR and CNR were not altered significantly at the used sequence parameters. Healthy participants with minimal defects present high spatial agreement of QDP and VDP.
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19
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Kizhakke Puliyakote AS, Holverda S, Sá RC, Arai TJ, Theilmann RJ, Botros L, Bogaard HJ, Prisk GK, Hopkins SR. Prone positioning redistributes gravitational stress in the lung in normal conditions and in simulations of oedema. Exp Physiol 2020; 107:771-782. [PMID: 33347661 DOI: 10.1113/ep089037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/03/2020] [Indexed: 02/01/2023]
Abstract
NEW FINDINGS What is the central question of this study? How does the interaction between posture and gravity affect the stresses on the lung, particularly in highly inflated gravitationally non-dependent regions, which are potentially vulnerable to increased mechanical stress and injury? What is the main finding and its importance? Changes in stress attributable to gravity are not well characterized between postures. Using a new metric of gravitational stress, we show that regions of the lung near maximal inflation have the greatest gravitational stresses while supine, but not while prone. In simulations of increased lung weight consistent with severe pulmonary oedema, the prone lung has lower gravitational stress in vulnerable, non-dependent regions, potentially protecting them from overinflation and injury. ABSTRACT Prone posture changes the gravitational vector, and potentially the stress induced by tissue deformation, because a larger lung volume is gravitationally dependent when supine, but non-dependent when prone. To evaluate this, 10 normal subjects (six male and four female; age, means ± SD = 27 ± 6 years; height, 171 ± 9 cm; weight, 69 ± 13 kg; forced expiratory volume in the first second/forced expiratory volume as a percentage of predicted, 93 ± 6%) were imaged at functional residual capacity, supine and prone, using magnetic resonance imaging, to quantify regional lung density. We defined regional gravitational stress as the cumulative weight, per unit area, of the column of lung tissue below each point. Gravitational stress was compared between regions of differing inflation to evaluate differences between highly stretched, and thus potentially vulnerable, regions and less stretched lung. Using reference density values for normal lungs at total lung capacity (0.10 ± 0.03 g/ml), regions were classified as highly inflated (density < 0.13 g/ml, i.e., close to total lung capacity), intermediate (0.13 ≤ density < 0.16 g/ml) or normally inflated (density ≥ 0.16 g/ml). Gravitational stress differed between inflation categories while supine (-1.6 ± 0.3 cmH2 O highly inflated; -1.4 ± 0.3 cmH2 O intermediate; -1.1 ± 0.1 cmH2 O normally inflated; P = 0.05) but not while prone (-1.4 ± 0.2 cmH2 O highly inflated; -1.3 ± 0.2 cmH2 O intermediate; -1.3 ± 0.1 cmH2 O normally inflated; P = 0.39), and increased more with height from dependent lung while supine (-0.24 ± 0.02 cmH2 O/cm supine; -0.18 ± 0.04 cmH2 O/cm prone; P = 0.05). In simulated severe pulmonary oedema, the gradient in gravitational stress increased in both postures (all P < 0.0001), was greater in the supine posture than when prone (-0.57 ± 0.21 cmH2 O/cm supine; -0.34 ± 0.16 cmH2 O/cm prone; P = 0.0004) and was similar to the gradient calculated from supine computed tomography images in a patient with acute respiratory distress syndrome (-0.51 cmH2 O/cm). The non-dependent lung has greater gravitational stress while supine and might be protected while prone, particularly in the presence of oedema.
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Affiliation(s)
- Abhilash S Kizhakke Puliyakote
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Sebastiaan Holverda
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.,Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Rui C Sá
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.,Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Tatsuya J Arai
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Liza Botros
- Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Harm J Bogaard
- Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - G Kim Prisk
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.,Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Susan R Hopkins
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.,Department of Medicine, University of California, San Diego, La Jolla, CA, USA
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20
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Kizhakke Puliyakote AS, Elliott AR, Sá RC, Anderson KM, Crotty Alexander LE, Hopkins SR. Vaping disrupts ventilation-perfusion matching in asymptomatic users. J Appl Physiol (1985) 2020; 130:308-317. [PMID: 33180648 DOI: 10.1152/japplphysiol.00709.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Inhalation of e-cigarette's aerosols (vaping) has the potential to disrupt pulmonary gas exchange, but the effects in asymptomatic users are unknown. We assessed ventilation-perfusion (V̇A/Q̇) mismatch in asymptomatic e-cigarette users, using magnetic resonance imaging (MRI). We hypothesized that vaping induces V̇A/Q̇ mismatch through alterations in both ventilation and perfusion distributions. Nine young, asymptomatic "Vapers" with >1-yr vaping history, and no history of cardiopulmonary disease, were imaged supine using proton MRI, to assess the right lung at baseline and immediately after vaping. Seven young "Controls" were imaged at baseline only. Relative dispersion (SD/means) was used to quantify the heterogeneity of the individual ventilation and perfusion distributions. V̇A/Q̇ mismatch was quantified using the second moments of the ventilation and perfusion versus V̇A/Q̇ ratio distributions, log scale, LogSDV̇, and LogSDQ̇, respectively, analogous to the multiple inert gas elimination technique. Spirometry was normal in both groups. Ventilation heterogeneity was similar between groups at baseline (Vapers, 0.43 ± 0.13; Controls, 0.51 ± 0.11; P = 0.13) but increased after vaping (to 0.57 ± 0.17; P = 0.03). Perfusion heterogeneity was greater (P = 0.04) in Vapers at baseline (0.53 ± 0.06) compared with Controls (0.44 ± 0.10) but decreased after vaping (to 0.42 ± 0.07; P = 0.005). Vapers had greater (P = 0.01) V̇A/Q̇ mismatch at baseline compared with Controls (LogSDQ̇ = 0.61 ± 0.12 vs. 0.43 ± 0.12), which was increased after vaping (LogSDQ̇ = 0.73 ± 0.16; P = 0.03). V̇A/Q̇ mismatch is greater in Vapers and worsens after vaping. This suggests subclinical alterations in lung function not detected by spirometry.NEW & NOTEWORTHY This research provides evidence of vaping-induced disruptions in ventilation-perfusion matching in young, healthy, asymptomatic adults with normal spirometry who habitually vape. The changes in ventilation and perfusion distributions, both at baseline and acutely after vaping, and the potential implications on hypoxic vasoconstriction are particularly relevant in understanding the pathogenesis of vaping-induced dysfunction. Our imaging-based approach provides evidence of potential subclinical alterations in lung function below thresholds of detection using spirometry.
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Affiliation(s)
- Abhilash S Kizhakke Puliyakote
- Pulmonary Imaging Laboratory, Department of Radiology, UC San Diego Health Sciences, San Diego, California.,Department of Radiology, University of California, San Diego, California
| | - Ann R Elliott
- Pulmonary Imaging Laboratory, Department of Radiology, UC San Diego Health Sciences, San Diego, California.,Department of Medicine, University of California, San Diego, California
| | - Rui C Sá
- Pulmonary Imaging Laboratory, Department of Radiology, UC San Diego Health Sciences, San Diego, California.,Department of Medicine, University of California, San Diego, California
| | - Kevin M Anderson
- Pulmonary Imaging Laboratory, Department of Radiology, UC San Diego Health Sciences, San Diego, California.,Department of Radiology, University of California, San Diego, California
| | | | - Susan R Hopkins
- Pulmonary Imaging Laboratory, Department of Radiology, UC San Diego Health Sciences, San Diego, California.,Department of Radiology, University of California, San Diego, California.,Department of Medicine, University of California, San Diego, California
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21
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Hopkins SR, Sá RC, Prisk GK, Elliott AR, Kim NH, Pazar BJ, Printz BF, El-Said HG, Davis CK, Theilmann RJ. Abnormal pulmonary perfusion heterogeneity in patients with Fontan circulation and pulmonary arterial hypertension. J Physiol 2020; 599:343-356. [PMID: 33026102 DOI: 10.1113/jp280348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 10/06/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The distribution of pulmonary perfusion is affected by gravity, vascular branching structure and active regulatory mechanisms, which may be disrupted by cardiopulmonary disease, but this is not well studied, particularly in rare conditions. We evaluated pulmonary perfusion in patients who had undergone Fontan procedure, patients with pulmonary arterial hypertension (PAH) and two groups of controls using a proton magnetic resonance imaging technique, arterial spin labelling to measure perfusion. Heterogeneity was assessed by the relative dispersion (SD/mean) and gravitational gradients. Gravitational gradients were similar between all groups, but heterogeneity was significantly increased in both patient groups compared to controls and persisted after removing contributions from large blood vessels and gravitational gradients. Patients with Fontan physiology and patients with PAH have increased pulmonary perfusion heterogeneity that is not explainable by differences in mean perfusion, gravitational gradients, or large vessel anatomy. This probably reflects vascular remodelling in PAH and possibly in Fontan physiology. ABSTRACT Many factors affect the distribution of pulmonary perfusion, which may be disrupted by cardiopulmonary disease, but this is not well studied, particularly in rare conditions. An example is following the Fontan procedure, where pulmonary perfusion is passive, and heterogeneity may be increased because of the underlying pathophysiology leading to Fontan palliation, remodelling, or increased gravitational gradients from low flow. Another is pulmonary arterial hypertension (PAH), where gravitational gradients may be reduced secondary to high pressures, but remodelling may increase perfusion heterogeneity. We evaluated regional pulmonary perfusion in Fontan patients (n = 5), healthy young controls (Fontan control, n = 5), patients with PAH (n = 6) and healthy older controls (PAH control) using proton magnetic resonance imaging. Regional perfusion was measured using arterial spin labelling. Heterogeneity was assessed by the relative dispersion (SD/mean) and gravitational gradients. Mean perfusion was similar (Fontan = 2.50 ± 1.02 ml min-1 ml-1 ; Fontan control = 3.09 ± 0.58, PAH = 3.63 ± 1.95; PAH control = 3.98 ± 0.91, P = 0.26), and the slopes of gravitational gradients were not different (Fontan = -0.23 ± 0.09 ml min-1 ml-1 cm-1 ; Fontan control = -0.29 ± 0.23, PAH = -0.27 ± 0.09, PAH control = -0.25 ± 0.18, P = 0.91) between groups. Perfusion relative dispersion was greater in both Fontan and PAH than controls (Fontan = 1.46 ± 0.18; Fontan control = 0.99 ± 0.21, P = 0.005; PAH = 1.22 ± 0.27, PAH control = 0.91 ± 0.12, P = 0.02) but similar between patient groups (P = 0.13). These findings persisted after removing contributions from large blood vessels and gravitational gradients (all P < 0.05). We conclude that patients with Fontan physiology and PAH have increased pulmonary perfusion heterogeneity that is not explained by differences in mean perfusion, gravitational gradients, or large vessel anatomy. This probably reflects the effects of remodelling in PAH and possibly in Fontan physiology.
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Affiliation(s)
- Susan R Hopkins
- Department of Radiology, University of California, San Diego, CA, USA.,Department of Medicine, University of California, San Diego, CA, USA
| | - Rui C Sá
- Department of Medicine, University of California, San Diego, CA, USA
| | - G Kim Prisk
- Department of Radiology, University of California, San Diego, CA, USA.,Department of Medicine, University of California, San Diego, CA, USA
| | - Ann R Elliott
- Department of Medicine, University of California, San Diego, CA, USA
| | - Nick H Kim
- Department of Medicine, University of California, San Diego, CA, USA
| | - Beni J Pazar
- Department of Radiology, University of California, San Diego, CA, USA
| | - Beth F Printz
- Department of Radiology, University of California, San Diego, CA, USA.,Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
| | - Howaida G El-Said
- Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
| | - Christopher K Davis
- Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
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22
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Balasch A, Metze P, Stumpf K, Beer M, Büttner SM, Rottbauer W, Speidel T, Rasche V. 2D
Ultrashort Echo‐Time Functional Lung Imaging. J Magn Reson Imaging 2020; 52:1637-1644. [DOI: 10.1002/jmri.27269] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Anke Balasch
- Department of Internal Medicine II Ulm University Medical Centre Ulm Germany
| | - Patrick Metze
- Department of Internal Medicine II Ulm University Medical Centre Ulm Germany
| | - Kilian Stumpf
- Department of Internal Medicine II Ulm University Medical Centre Ulm Germany
| | - Meinrad Beer
- Department of Radiology Ulm University Medical Centre Ulm Germany
| | | | - Wolfgang Rottbauer
- Department of Internal Medicine II Ulm University Medical Centre Ulm Germany
| | - Tobias Speidel
- Core‐Facility Small Animal Imaging, Medical Faculty Ulm University Germany
| | - Volker Rasche
- Department of Internal Medicine II Ulm University Medical Centre Ulm Germany
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23
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Hopkins SR. Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches. Compr Physiol 2020; 10:1155-1205. [PMID: 32941684 DOI: 10.1002/cphy.c180042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ventilation-perfusion ( V ˙ A / Q ˙ ) matching, the regional matching of the flow of fresh gas to flow of deoxygenated capillary blood, is the most important mechanism affecting the efficiency of pulmonary gas exchange. This article discusses the measurement of V ˙ A / Q ˙ matching with three broad classes of techniques: (i) those based in gas exchange, such as the multiple inert gas elimination technique (MIGET); (ii) those derived from imaging techniques such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), computed tomography (CT), and electrical impedance tomography (EIT); and (iii) fluorescent and radiolabeled microspheres. The focus is on the physiological basis of these techniques that provide quantitative information for research purposes rather than qualitative measurements that are used clinically. The fundamental equations of pulmonary gas exchange are first reviewed to lay the foundation for the gas exchange techniques and some of the imaging applications. The physiological considerations for each of the techniques along with advantages and disadvantages are briefly discussed. © 2020 American Physiological Society. Compr Physiol 10:1155-1205, 2020.
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Affiliation(s)
- Susan R Hopkins
- Departments of Medicine and Radiology, University of California, San Diego, California, USA
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24
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Elliott AR, Kizhakke Puliyakote AS, Tedjasaputra V, Pazár B, Wagner H, Sá RC, Orr JE, Prisk GK, Wagner PD, Hopkins SR. Ventilation-perfusion heterogeneity measured by the multiple inert gas elimination technique is minimally affected by intermittent breathing of 100% O 2. Physiol Rep 2020; 8:e14488. [PMID: 32638530 PMCID: PMC7340847 DOI: 10.14814/phy2.14488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 05/04/2020] [Accepted: 05/07/2020] [Indexed: 11/24/2022] Open
Abstract
Proton magnetic resonance (MR) imaging to quantify regional ventilation-perfusion ( V ˙ A / Q ˙ ) ratios combines specific ventilation imaging (SVI) and separate proton density and perfusion measures into a composite map. Specific ventilation imaging exploits the paramagnetic properties of O2 , which alters the local MR signal intensity, in an FI O2 -dependent manner. Specific ventilation imaging data are acquired during five wash-in/wash-out cycles of breathing 21% O2 alternating with 100% O2 over ~20 min. This technique assumes that alternating FI O2 does not affect V ˙ A / Q ˙ heterogeneity, but this is unproven. We tested the hypothesis that alternating FI O2 exposure increases V ˙ A / Q ˙ mismatch in nine patients with abnormal pulmonary gas exchange and increased V ˙ A / Q ˙ mismatch using the multiple inert gas elimination technique (MIGET).The following data were acquired (a) breathing air (baseline), (b) breathing alternating air/100% O2 during an emulated-SVI protocol (eSVI), and (c) 20 min after ambient air breathing (recovery). MIGET heterogeneity indices of shunt, deadspace, ventilation versus V ˙ A / Q ˙ ratio, LogSD V ˙ , and perfusion versus V ˙ A / Q ˙ ratio, LogSD Q ˙ were calculated. LogSD V ˙ was not different between eSVI and baseline (1.04 ± 0.39 baseline, 1.05 ± 0.38 eSVI, p = .84); but was reduced compared to baseline during recovery (0.97 ± 0.39, p = .04). There was no significant difference in LogSD Q ˙ across conditions (0.81 ± 0.30 baseline, 0.79 ± 0.15 eSVI, 0.79 ± 0.20 recovery; p = .54); Deadspace was not significantly different (p = .54) but shunt showed a borderline increase during eSVI (1.0% ± 1.0 baseline, 2.6% ± 2.9 eSVI; p = .052) likely from altered hypoxic pulmonary vasoconstriction and/or absorption atelectasis. Intermittent breathing of 100% O2 does not substantially alter V ˙ A / Q ˙ matching and if SVI measurements are made after perfusion measurements, any potential effects will be minimized.
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Affiliation(s)
- Ann R. Elliott
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
| | - Abhilash S. Kizhakke Puliyakote
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
- Department of RadiologyUniversity of California San DiegoLa JollaCAUSA
| | - Vincent Tedjasaputra
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
| | - Beni Pazár
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
- Department of RadiologyUniversity of California San DiegoLa JollaCAUSA
| | - Harrieth Wagner
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
| | - Rui C. Sá
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
| | - Jeremy E. Orr
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
| | - G. Kim Prisk
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
- Department of RadiologyUniversity of California San DiegoLa JollaCAUSA
| | - Peter D. Wagner
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
| | - Susan R. Hopkins
- Department of MedicineUniversity of California San DiegoLa JollaCAUSA
- The Pulmonary Imaging LaboratoryUniversity of California San DiegoLa JollaCAUSA
- Department of RadiologyUniversity of California San DiegoLa JollaCAUSA
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25
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Hahn AD, Malkus A, Kammerman J, Higano N, Walkup L, Woods J, Fain SB. Characterization of R 2 ∗ and tissue density in the human lung: Application to neonatal imaging in the intensive care unit. Magn Reson Med 2019; 84:920-927. [PMID: 31855294 DOI: 10.1002/mrm.28137] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 11/26/2019] [Accepted: 11/26/2019] [Indexed: 02/06/2023]
Abstract
PURPOSE Novel demonstration of R 2 ∗ and tissue density estimation in infant lungs using 3D ultrashort echo time MRI. Differences between adult and neonates with no clinical indication of lung pathology is explored, as well as relationships between parameter estimates and gravitationally dependent position and lung inflation state. This provides a tool for probing physiologic processes that may be relevant to pulmonary disease and progression in newborns. METHODS R 2 ∗ and tissue density were estimated in a phantom consisting of standards allowing for ground truth comparisons and in human subjects (N = 5 infants, N = 4 adults, no clinical indication of lung dysfunction) using a 3D radial multiecho ultrashort echo time MRI sequence. Whole lung averages were compared between infants and adults. Dependence of the metrics on anterior-posterior position as well as between end-tidal inspiration and expiration were explored, in addition to the general relationship between R 2 ∗ and tissue density. RESULTS Estimates in the phantom did not differ significantly from ground truth. Neonates had significantly lower mean R 2 ∗ (P = .006) and higher mean tissue density (P = 1.5e-5) than adults. Tissue density and R 2 ∗ were both significantly dependent on anterior-posterior position and lung inflation state (P < .005). An overall inverse relationship was found between R 2 ∗ and tissue density, which was similar in both neonates and adults. CONCLUSION Estimation of tissue density and R 2 ∗ in free breathing, nonsedated, neonatal patients is feasible using multiecho ultrashort echo time MRI. R 2 ∗ was no different between infants and adults when matched for tissue density, although density of lung parenchyma was, on average, lower in adults than neonates.
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Affiliation(s)
- Andrew D Hahn
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - Annelise Malkus
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - Jeffery Kammerman
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin
| | - Nara Higano
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Laura Walkup
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Jason Woods
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati, College of Medicine, Cincinnati, Ohio
| | - Sean B Fain
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.,Department of Radiology, University of Wisconsin, Madison, Wisconsin.,Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin
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26
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Weiger M, Pruessmann KP. Short-T 2 MRI: Principles and recent advances. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:237-270. [PMID: 31779882 DOI: 10.1016/j.pnmrs.2019.07.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/14/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
Among current modalities of biomedical and diagnostic imaging, MRI stands out by virtue of its versatile contrast obtained without ionizing radiation. However, in various cases, e.g., water protons in tissues such as bone, tendon, and lung, MRI performance is limited by the rapid decay of resonance signals associated with short transverse relaxation times T2 or T2*. Efforts to address this shortcoming have led to a variety of specialized short-T2 techniques. Recent progress in this field expands the choice of methods and prompts fresh considerations with regard to instrumentation, data acquisition, and signal processing. In this review, the current status of short-T2 MRI is surveyed. In an attempt to structure the growing range of techniques, the presentation highlights overarching concepts and basic methodological options. The most frequently used approaches are described in detail, including acquisition strategies, image reconstruction, hardware requirements, means of introducing contrast, sources of artifacts, limitations, and applications.
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Affiliation(s)
- Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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27
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Tedjasaputra V, Sá RC, Anderson KM, Prisk GK, Hopkins SR. Heavy upright exercise increases ventilation-perfusion mismatch in the basal lung: indirect evidence for interstitial pulmonary edema. J Appl Physiol (1985) 2019; 127:473-481. [PMID: 31246558 DOI: 10.1152/japplphysiol.00056.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ventilation-perfusion (V̇a/Q̇) mismatch during exercise may result from interstitial pulmonary edema if increased pulmonary vascular pressure causes fluid efflux into the interstitium. If present, the increased fluid may compress small airways or blood vessels, disrupting V̇a/Q̇ matching, but this is unproven. We hypothesized that V̇a/Q̇ mismatch would be greatest in basal lung following heavy upright exercise, consistent with hydrostatic forces favoring edema accumulation in the gravitationally dependent lung. We applied new tools to reanalyze previously published magnetic resonance imaging data to determine regional V̇a/Q̇ mismatch following 45 min of heavy upright exercise in six athletes (V̇o2max = 61 ± 7 mL·kg-1·min-1). In the supine posture, regional alveolar ventilation and local perfusion were quantified from specific ventilation imaging, proton density, and arterial spin labeling data in a single sagittal slice of the right lung before exercise (PRE), 15 min after exercise (POST), and in recovery 60 min after exercise (REC). Indices of V̇a/Q̇ mismatch [second moments (log scale) of ventilation (LogSDV) and perfusion (LogSDQ) vs. V̇a/Q̇ distributions] were calculated for apical, middle, and basal lung thirds, which represent gravitationally nondependent, middle, and dependent regions, respectively, during upright exercise. LogSDV increased after exercise only in the basal lung (PRE 0.46 ± 0.06, POST 0.57 ± 0.14, REC 0.55 ±0.14, P = 0.01). Similarly, LogSDQ increased only in the basal lung (PRE 0.40 ± 0.06, POST 0.51 ± 0.10, REC 0.44 ± 0.09, P = 0.04). Increased V̇a/Q̇ mismatch in the basal lung after exercise is potentially consistent with interstitial pulmonary edema accumulating in gravitationally dependent lung during exercise.NEW & NOTEWORTHY We reanalyzed previously published MRI data with new tools and found increased ventilation-perfusion mismatch only in the basal lung of athletes following 45 min of cycling exercise. This is consistent with the development of interstitial edema in the gravitationally dependent lung during heavy exercise.
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Affiliation(s)
- Vincent Tedjasaputra
- Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California
| | - Rui C Sá
- Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California
| | - Kevin M Anderson
- Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California.,Pulmonary Imaging Laboratory, Department of Radiology, University of California, San Diego School of Medicine, La Jolla, California
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28
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Fakhouri F, Dong H, Kolipaka A. Magnetic resonance elastography of the lungs: A repeatability and reproducibility study. NMR IN BIOMEDICINE 2019; 32:e4102. [PMID: 31087728 DOI: 10.1002/nbm.4102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 02/25/2019] [Accepted: 03/07/2019] [Indexed: 05/17/2023]
Abstract
Lung diseases are one of the leading causes of death worldwide, from which four million people die annually. Lung diseases are associated with changes in the mechanical properties of the lungs. Several studies have shown the feasibility of using magnetic resonance elastography (MRE) to quantify the lungs' shear stiffness. The aim of this study is to investigate the reproducibility and repeatability of lung MRE, and its shear stiffness measurements, obtained using a modified spin echo-echo planar imaging (SE-EPI) MRE sequence. In this study, 21 healthy volunteers were scanned twice by repositioning the volunteers to image right lung both at residual volume (RV) and total lung capacity (TLC) to assess the reproducibility of lung shear stiffness measurements. Additionally, 19 out of the 21 volunteers were scanned immediately without moving the volunteers to test the repeatability of the modified SE-EPI MRE sequence. A paired t-test was performed to determine the significant difference between stiffness measurements obtained at RV and TLC. Concordance correlation and Bland-Altman's analysis were performed to determine the reproducibility and repeatability of the SE-EPI MRE-derived shear stiffness measurements. The SE-EPI MRE sequence is highly repeatable with a concordance correlation coefficient (CCC) of 0.95 at RV and 0.96 at TLC. Similarly, the stiffness measurements obtained across all volunteers were highly reproducible with a CCC of 0.95 at RV and 0.92 at TLC. The mean shear stiffness of the lung at RV was 0.93 ± 0.22 kPa and at TLC was 1.41 ± 0.41 kPa. TLC showed a significantly higher mean shear stiffness (P = 0.0004) compared with RV. Lung MRE stiffness measurements obtained using the SE-EPI sequence were reproducible and repeatable, both at RV and TLC. Lung shear stiffness changes across respiratory cycle with significantly higher stiffness at TLC than RV.
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Affiliation(s)
- Faisal Fakhouri
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Huiming Dong
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Arunark Kolipaka
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
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29
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Geier ET, Theilmann RJ, Darquenne C, Prisk GK, Sá RC. Quantitative Mapping of Specific Ventilation in the Human Lung using Proton Magnetic Resonance Imaging and Oxygen as a Contrast Agent. J Vis Exp 2019. [PMID: 31233033 DOI: 10.3791/59579] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Specific ventilation imaging (SVI) is a functional magnetic resonance imaging technique capable of quantifying specific ventilation - the ratio of the fresh gas entering a lung region divided by the region's end-expiratory volume - in the human lung, using only inhaled oxygen as a contrast agent. Regional quantification of specific ventilation has the potential to help identify areas of pathologic lung function. Oxygen in solution in tissue shortens the tissue's longitudinal relaxation time (T1), and thus a change in tissue oxygenation can be detected as a change in T1-weighted signal with an inversion recovery acquired image. Following an abrupt change between two concentrations of inspired oxygen, the rate at which lung tissue within a voxel equilibrates to a new steady-state reflects the rate at which resident gas is being replaced by inhaled gas. This rate is determined by specific ventilation. To elicit this sudden change in oxygenation, subjects alternately breathe 20-breath blocks of air (21% oxygen) and 100% oxygen while in the MRI scanner. A stepwise change in inspired oxygen fraction is achieved through use of a custom three-dimensional (3D)-printed flow bypass system with a manual switch during a short end-expiratory breath hold. To detect the corresponding change in T1, a global inversion pulse followed by a single shot fast spin echo sequence was used to acquire two-dimensional T1-weighted images in a 1.5 T MRI scanner, using an eight-element torso coil. Both single slice and multi-slice imaging are possible, with slightly different imaging parameters. Quantification of specific ventilation is achieved by correlating the time-course of signal intensity for each lung voxel with a library of simulated responses to the air/oxygen stimulus. SVI estimations of specific ventilation heterogeneity have been validated against multiple breath washout and proved to accurately determine the heterogeneity of the specific ventilation distribution.
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Affiliation(s)
- Eric T Geier
- Pulmonary Imaging Laboratory, Department of Medicine, University of California, San Diego
| | - Rebecca J Theilmann
- Pulmonary Imaging Laboratory, Department of Radiology, University of California, San Diego
| | - Chantal Darquenne
- Pulmonary Imaging Laboratory, Department of Medicine, University of California, San Diego
| | - G Kim Prisk
- Pulmonary Imaging Laboratory, Department of Medicine, University of California, San Diego
| | - Rui Carlos Sá
- Pulmonary Imaging Laboratory, Department of Medicine, University of California, San Diego;
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30
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Klimeš F, Voskrebenzev A, Gutberlet M, Kern A, Behrendt L, Kaireit TF, Czerner C, Renne J, Wacker F, Vogel-Claussen J. Free-breathing quantification of regional ventilation derived by phase-resolved functional lung (PREFUL) MRI. NMR IN BIOMEDICINE 2019; 32:e4088. [PMID: 30908743 DOI: 10.1002/nbm.4088] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 06/09/2023]
Abstract
PURPOSE To test the feasibility of regional fully quantitative ventilation measurement in free breathing derived by phase-resolved functional lung (PREFUL) MRI in the supine and prone positions. In addition, the influence of T2 * relaxation time on ventilation quantification is assessed. METHODS Twelve healthy volunteers underwent functional MRI at 1.5 T using a 2D triple-echo spoiled gradient echo sequence allowing for quantitative measurement of T2 * relaxation time. Minute ventilation (ΔV) was quantified by conventional fractional ventilation (FV) and the newly introduced regional ventilation (VR), which corrects volume errors due to image registration. ΔVFV versus ΔVVR and ΔVVR versus ΔVVR with T2 * correction were compared using Bland-Altman plots and correlation analysis. The repeatability and physiological plausibility of all measurements were tested in the supine and prone positions. RESULTS On global and regional scales a strong correlation was observed between ΔVFV versus ΔVVR and ΔVVR versus ΔVVRT2* (r > 0.93); however, regional Bland-Altman analysis showed systematic differences (p < 0.0001). Unlike ΔVVRT2* , ΔVVR and ΔVFV showed expected physiologic anterior-posterior gradients, which decreased in the supine but not in the prone position at second measurement during 3 min in the same position. For all quantification methods a moderate repeatability (coefficient of variation <20%) of ventilation was found. CONCLUSION A fully quantified regional ventilation measurement using ΔVVR in free breathing is feasible and shows physiologically plausible results. In contrast to conventional ΔVFV, volume errors due to image registration are eliminated with the ΔVVR approach. However, correction for the T2 * effect remains challenging.
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Affiliation(s)
- F Klimeš
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - A Voskrebenzev
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - M Gutberlet
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - A Kern
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - L Behrendt
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - T F Kaireit
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - C Czerner
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - J Renne
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - F Wacker
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
| | - J Vogel-Claussen
- Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hanover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research, Hanover, Germany
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Structural and Functional Pulmonary Magnetic Resonance Imaging in Pediatrics-From the Neonate to the Young Adult. Acad Radiol 2019; 26:424-430. [PMID: 30228041 DOI: 10.1016/j.acra.2018.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 06/11/2018] [Accepted: 08/21/2018] [Indexed: 12/25/2022]
Abstract
The clinical imaging modalities available to investigate pediatric pulmonary conditions such as bronchopulmonary dysplasia, cystic fibrosis, and asthma are limited primarily to chest x-ray radiograph and computed tomography. As the challenges that historically limited the application of magnetic resonance imaging (MRI) to the lung have been overcome, its clinical potential has greatly expanded. In this review article, recent advances in pulmonary MRI including ultrashort echo time and hyperpolarized-gas MRI techniques are discussed with an emphasis on pediatric research and translational applications.
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Wang Z, He M, Bier E, Rankine L, Schrank G, Rajagopal S, Huang YC, Kelsey C, Womack S, Mammarappallil J, Driehuys B. Hyperpolarized 129 Xe gas transfer MRI: the transition from 1.5T to 3T. Magn Reson Med 2018; 80:2374-2383. [PMID: 30024058 PMCID: PMC6318005 DOI: 10.1002/mrm.27377] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 03/29/2018] [Accepted: 05/03/2018] [Indexed: 11/09/2022]
Abstract
PURPOSE Hyperpolarized 129 Xe MRI depicting 3D ventilation, interstitial barrier uptake, and transfer to red blood cells (RBCs) has emerged as a powerful new means of detecting pulmonary disease. However, given the challenging susceptibility environment of the lung, such gas transfer imaging has, thus far, only been implemented at 1.5T. Here, we seek to demonstrate the feasibility of Dixon-based 129 Xe gas transfer MRI at 3T. METHODS Seven healthy subjects and six patients with pulmonary disorders were recruited to characterize 129 Xe spectral structure, optimize acquisition parameters, and acquire representative images. Imaging used randomized, gradient-spoiled 3D-radial encoding of 1000 gas (0.5° flip) and dissolved (20° flip) views, reconstructed into 3-mm isotropic voxels. The center of k-space was sampled when barrier and RBC compartments were 90° out of phase (TE90 ). A single dissolved phase spectrum was appended to the sequence to measure the global RBC-barrier ratio for Dixon-based decomposition. RESULTS A 0.69 ms sinc was found to generate minimal off-resonance gas-phase excitation (3.0 ± 0.3% of the dissolved-phase), yielding a TE90 = 0.47 ± 0.02 ms. The RBC and barrier resonance frequencies were shifted by 217.6 ± 0.6 ppm and 197.8 ± 0.2 ppm. The RBCT 2 * was estimated to be ∼1.1 ms, and therefore each read-out was limited to 1.3 ms. 129 Xe gas and dissolved-phase images have sufficient SNR to produce gas transfer maps of similar quality and sensitivity to pathology, as previously obtained at 1.5T. CONCLUSIONS Despite short dissolved-phaseT 2 * , 129 Xe gas transfer MRI is feasible at 3T.
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Affiliation(s)
- Ziyi Wang
- Biomedical Engineering, Duke University, Durham, North Carolina, United States
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
| | - Mu He
- Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
| | - Elianna Bier
- Medical Physics Graduate Program, Duke University, Durham, North Carolina, United States
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
| | - Leith Rankine
- Medical Physics Graduate Program, Duke University, Durham, North Carolina, United States
| | - Geoffry Schrank
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
| | - Sudarshan Rajagopal
- Division of Cardiology, Duke University Medical Center, Durham, North Carolina, United States
| | - Yuh-Chin Huang
- Division of Pulmonary, Allergy and Critical Care, Duke University Medical Center, Durham, North Carolina, United States
| | - Christopher Kelsey
- Radiation Oncology, Duke University School of Medicine, Durham, North Carolina, United States
| | - Samantha Womack
- Duke Image Analysis Laboratory, Duke University, Durham, North Carolina, United States
| | | | - Bastiaan Driehuys
- Biomedical Engineering, Duke University, Durham, North Carolina, United States
- Medical Physics Graduate Program, Duke University, Durham, North Carolina, United States
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
- Radiology, Duke University Medical Center, Durham, North Carolina, United States
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Burant A, Antonacci M, McCallister D, Zhang L, Branca RT. Effects of superparamagnetic iron oxide nanoparticles on the longitudinal and transverse relaxation of hyperpolarized xenon gas. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 291:53-62. [PMID: 29702362 PMCID: PMC5975651 DOI: 10.1016/j.jmr.2018.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/26/2018] [Accepted: 04/04/2018] [Indexed: 06/08/2023]
Abstract
SuperParamagnetic Iron Oxide Nanoparticles (SPIONs) are often used in magnetic resonance imaging experiments to enhance Magnetic Resonance (MR) sensitivity and specificity. While the effect of SPIONs on the longitudinal and transverse relaxation time of 1H spins has been well characterized, their effect on highly diffusive spins, like those of hyperpolarized gases, has not. For spins diffusing in linear magnetic field gradients, the behavior of the magnetization is characterized by the relative size of three length scales: the diffusion length, the structural length, and the dephasing length. However, for spins diffusing in non-linear gradients, such as those generated by iron oxide nanoparticles, that is no longer the case, particularly if the diffusing spins experience the non-linearity of the gradient. To this end, 3D Monte Carlo simulations are used to simulate the signal decay and the resulting image contrast of hyperpolarized xenon gas near SPIONs. These simulations reveal that signal loss near SPIONs is dominated by transverse relaxation, with little contribution from T1 relaxation, while simulated image contrast and experiments show that diffusion provides no appreciable sensitivity enhancement to SPIONs.
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Affiliation(s)
- Alex Burant
- Department of Physics and Astronomy, University of North Carolina at Chapel Hill, USA; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA
| | - Michael Antonacci
- Department of Physics and Astronomy, University of North Carolina at Chapel Hill, USA; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA
| | - Drew McCallister
- Department of Physics and Astronomy, University of North Carolina at Chapel Hill, USA; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA
| | - Le Zhang
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA; Department of Applied Physical Science, University of North Carolina at Chapel Hill, USA
| | - Rosa Tamara Branca
- Department of Physics and Astronomy, University of North Carolina at Chapel Hill, USA; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, USA.
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Non-contrast quantitative pulmonary perfusion using flow alternating inversion recovery at 3T: A preliminary study. Magn Reson Imaging 2017; 46:106-113. [PMID: 29154894 DOI: 10.1016/j.mri.2017.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 11/06/2017] [Accepted: 11/13/2017] [Indexed: 11/23/2022]
Abstract
PURPOSE To demonstrate the initial feasibility of non-contrast quantitative pulmonary perfusion imaging at 3T using flow alternating inversion recovery (FAIR), and to evaluate the intra-session and inter-session reliability of FAIR measurements at 3T. MATERIALS AND METHODS Nine healthy volunteers were imaged using our own implementation of FAIR pulse sequence at 3T. Quantitative FAIR perfusion, both with and without larger pulmonary vessels, was correlated with global phase contrast (PC) measured blood flow in the right pulmonary artery (RPA). The same volunteers were also imaged with SPECT perfusion using technetium-99m-macroaggregated albumin and relative dispersion (RD) was assessed between FAIR and SPECT perfusion. Four additional healthy volunteers were evaluated for FAIR repeatability, using intra-class correlation coefficient (ICC) and Bland-Altman analysis. p<0.05 was considered statistically significant. RESULTS FAIR perfusion across all subjects was 858±605mL/100g/min (with vessels) and 629±294mL/100g/min (without vessels) and correlated significantly with the PC measured blood flow in the RPA (r=0.62, p<0.01 with vessels; r=0.73, p<0.001 without vessels). The median RD of FAIR perfusion across all subjects was 0.73 (with vessels) and 0.49 (without vessels), compared against 0.23 with SPECT perfusion. The intra/inter-session ICC of FAIR perfusion with vessels was 0.95/0.59 and improved to 0.96/0.72, when vessels were removed. CONCLUSIONS Non-contrast quantitative pulmonary perfusion imaging using FAIR is feasible at 3T. This may serve as a reliable method to assess regional lung perfusion at 3T to characterize and monitor treatment response in chronic lung disease without the concerns of repeated exposure to ionizing radiation or the accumulation of exogenous contrast agent.
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Fibrosis imaging: Current concepts and future directions. Adv Drug Deliv Rev 2017; 121:9-26. [PMID: 29108860 DOI: 10.1016/j.addr.2017.10.013] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 10/26/2017] [Accepted: 10/30/2017] [Indexed: 02/08/2023]
Abstract
Fibrosis plays an important role in many different pathologies. It results from tissue injury, chronic inflammation, autoimmune reactions and genetic alterations, and it is characterized by the excessive deposition of extracellular matrix components. Biopsies are routinely employed for fibrosis diagnosis, but they suffer from several drawbacks, including their invasive nature, sampling variability and limited spatial information. To overcome these limitations, multiple different imaging tools and technologies have been evaluated over the years, including X-ray imaging, computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), positron emission tomography (PET) and single-photon emission computed tomography (SPECT). These modalities can provide anatomical, functional and molecular imaging information which is useful for fibrosis diagnosis and staging, and they may also hold potential for the longitudinal assessment of therapy responses. Here, we summarize the use of non-invasive imaging techniques for monitoring fibrosis in systemic autoimmune diseases, in parenchymal organs (such as liver, kidney, lung and heart), and in desmoplastic cancers. We also discuss how imaging biomarkers can be integrated in (pre-) clinical research to individualize and improve anti-fibrotic therapies.
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Wang Z, Robertson SH, Wang J, He M, Virgincar RS, Schrank GM, Bier EA, Rajagopal S, Huang YC, O'Riordan TG, Rackley CR, McAdams HP, Driehuys B. Quantitative analysis of hyperpolarized129Xe gas transfer MRI. Med Phys 2017; 44:2415-2428. [DOI: 10.1002/mp.12264] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 03/26/2017] [Accepted: 03/30/2017] [Indexed: 12/14/2022] Open
Affiliation(s)
- Ziyi Wang
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Department of Biomedical Engineering; Duke University; Durham NC 27708 USA
| | - Scott Haile Robertson
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Medical Physics Graduate Program; Duke University; Durham NC 27705 USA
| | - Jennifer Wang
- School of Medicine; Duke University; Durham NC 27710 USA
| | - Mu He
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Department of Electrical and Computer Engineering; Duke University; Durham NC 27708 USA
| | - Rohan S. Virgincar
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Department of Biomedical Engineering; Duke University; Durham NC 27708 USA
| | - Geoffry M. Schrank
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
| | - Elianna A. Bier
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Medical Physics Graduate Program; Duke University; Durham NC 27705 USA
| | | | - Yuh Chin Huang
- Department of Medicine; Division of Pulmonary, Allergy and Critical Care; Duke University Medical Center; Durham NC 27710 USA
| | | | - Craig R. Rackley
- Department of Medicine; Division of Pulmonary, Allergy and Critical Care; Duke University Medical Center; Durham NC 27710 USA
| | - H Page McAdams
- Department of Radiology; Duke University Medical Center; Durham NC 27710 USA
| | - Bastiaan Driehuys
- Center for In Vivo Microscopy; Duke University Medical Center; Durham NC 27710 USA
- Department of Biomedical Engineering; Duke University; Durham NC 27708 USA
- Medical Physics Graduate Program; Duke University; Durham NC 27705 USA
- Department of Radiology; Duke University Medical Center; Durham NC 27710 USA
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Sá RC, Henderson AC, Simonson T, Arai TJ, Wagner H, Theilmann RJ, Wagner PD, Prisk GK, Hopkins SR. Measurement of the distribution of ventilation-perfusion ratios in the human lung with proton MRI: comparison with the multiple inert-gas elimination technique. J Appl Physiol (1985) 2017; 123:136-146. [PMID: 28280105 DOI: 10.1152/japplphysiol.00804.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 02/23/2017] [Accepted: 03/07/2017] [Indexed: 11/22/2022] Open
Abstract
We have developed a novel functional proton magnetic resonance imaging (MRI) technique to measure regional ventilation-perfusion (V̇A/Q̇) ratio in the lung. We conducted a comparison study of this technique in healthy subjects (n = 7, age = 42 ± 16 yr, Forced expiratory volume in 1 s = 94% predicted), by comparing data measured using MRI to that obtained from the multiple inert gas elimination technique (MIGET). Regional ventilation measured in a sagittal lung slice using Specific Ventilation Imaging was combined with proton density measured using a fast gradient-echo sequence to calculate regional alveolar ventilation, registered with perfusion images acquired using arterial spin labeling, and divided on a voxel-by-voxel basis to obtain regional V̇A/Q̇ ratio. LogSDV̇ and LogSDQ̇, measures of heterogeneity derived from the standard deviation (log scale) of the ventilation and perfusion vs. V̇A/Q̇ ratio histograms respectively, were calculated. On a separate day, subjects underwent study with MIGET and LogSDV̇ and LogSDQ̇ were calculated from MIGET data using the 50-compartment model. MIGET LogSDV̇ and LogSDQ̇ were normal in all subjects. LogSDQ̇ was highly correlated between MRI and MIGET (R = 0.89, P = 0.007); the intercept was not significantly different from zero (-0.062, P = 0.65) and the slope did not significantly differ from identity (1.29, P = 0.34). MIGET and MRI measures of LogSDV̇ were well correlated (R = 0.83, P = 0.02); the intercept differed from zero (0.20, P = 0.04) and the slope deviated from the line of identity (0.52, P = 0.01). We conclude that in normal subjects, there is a reasonable agreement between MIGET measures of heterogeneity and those from proton MRI measured in a single slice of lung.NEW & NOTEWORTHY We report a comparison of a new proton MRI technique to measure regional V̇A/Q̇ ratio against the multiple inert gas elimination technique (MIGET). The study reports good relationships between measures of heterogeneity derived from MIGET and those derived from MRI. Although currently limited to a single slice acquisition, these data suggest that single sagittal slice measures of V̇A/Q̇ ratio provide an adequate means to assess heterogeneity in the normal lung.
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Affiliation(s)
- Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - A Cortney Henderson
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Tatum Simonson
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Harrieth Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Peter D Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California.,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; .,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
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38
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Sá RC, Zeman KL, Bennett WD, Prisk GK, Darquenne C. Regional Ventilation Is the Main Determinant of Alveolar Deposition of Coarse Particles in the Supine Healthy Human Lung During Tidal Breathing. J Aerosol Med Pulm Drug Deliv 2017; 30:322-331. [PMID: 28277885 DOI: 10.1089/jamp.2016.1336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND To quantify the relationship between regional lung ventilation and coarse aerosol deposition in the supine healthy human lung, we used oxygen-enhanced magnetic resonance imaging and planar gamma scintigraphy in seven subjects. METHODS Regional ventilation was measured in the supine posture in a 15 mm sagittal slice of the right lung. Deposition was measured by using planar gamma scintigraphy (coronal scans, 40 cm FOV) immediately postdeposition, 1 hour 30 minutes and 22 hours after deposition of 99mTc-labeled particles (4.9 μm MMAD, GSD 2.5), inhaled in the supine posture (flow 0.5 L/s, 15 breaths/min). The distribution of retained particles at different times was used to infer deposition in different airway regions, with 22 hours representing alveolar deposition. The fraction of total slice ventilation per quartile of lung height from the lung apex to the dome of the diaphragm at functional residual capacity was computed, and co-registered with deposition data-apices aligned-using a transmission scan as reference. The ratio of fractional alveolar deposition to fractional ventilation of each quartile (r) was used to evaluate ventilation and deposition matching (r > 1, regional aerosol deposition fraction larger than regional ventilation fraction). RESULTS r was not significantly different from 1 for all regions (1.04 ± 0.25, 1.08 ± 0.22, 1.03 ± 0.17, 0.92 ± 0.13, apex to diaphragm, p > 0.40) at the alveolar level (r22h). For retention times r0h and r1h30, only the diaphragmatic region at r1h30 differed significantly from 1. CONCLUSIONS These results support the hypothesis that alveolar deposition is directly proportional to ventilation for ∼5 μm particles that are inhaled in the supine posture and are consistent with previous simulation predictions that show that convective flow is the main determinant of aerosol transport to the lung periphery.
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Affiliation(s)
- Rui Carlos Sá
- 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California
| | - Kirby L Zeman
- 2 Department of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - William D Bennett
- 2 Department of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - G Kim Prisk
- 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California.,3 Pulmonary Imaging Laboratory, Department of Radiology, University of California , San Diego, La Jolla, California
| | - Chantal Darquenne
- 1 Pulmonary Imaging Laboratory, Department of Medicine, University of California , San Diego, La Jolla, California
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Marinelli JP, Levin DL, Vassallo R, Carter RE, Hubmayr RD, Ehman RL, McGee KP. Quantitative assessment of lung stiffness in patients with interstitial lung disease using MR elastography. J Magn Reson Imaging 2017; 46:365-374. [PMID: 28117930 DOI: 10.1002/jmri.25579] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 11/21/2016] [Indexed: 01/21/2023] Open
Abstract
PURPOSE To investigate the use of magnetic resonance elastography (MRE) in the quantitative assessment of pulmonary fibrosis by comparing quantitative shear stiffness measurements of lung parenchyma in patients diagnosed with fibrotic interstitial lung disease (ILD) and healthy controls. MATERIALS AND METHODS A 1.5T spin-echo, echo planar imaging MRE (SE-EPI MRE) pulse sequence was utilized to assess absolute lung shear stiffness in 15 patients with diagnosed ILD and in 11 healthy controls. Data were collected at residual volume (RV) and total lung capacity (TLC). Spirometry data were obtained immediately prior to scanning. To test for statistical significance between RV and TLC shear stiffness estimates a two-sample t-test was performed. To assess variability within individual subject shear stiffness estimates, the intraclass correlation coefficient (ICC) and Krippendorff's alpha were calculated. RESULTS Patients with ILD exhibited an average (±1 standard deviation) shear stiffness of 2.74 (±0.896) kPa at TLC and 1.32 (±0.300) kPa at RV. The corresponding values for healthy individuals were 1.33 (±0.195) kPa and 0.849 (±0.250) kPa, respectively. The difference in shear stiffness between RV and TLC was statistically significant (P < 0.001). At TLC, the ICC and alpha values were 0.909 and 0.887, respectively. At RV, the ICC and alpha values were 0.852 and 0.862, respectively. CONCLUSION In subjects with known fibrotic interstitial lung disease, parenchymal shear stiffness is increased when compared to normal controls at both RV and TLC, with TLC demonstrating the most significant difference. MRE-derived parenchymal shear stiffness is a promising new noninvasive imaging-based biomarker of interstitial lung disease. LEVEL OF EVIDENCE 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:365-374.
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Affiliation(s)
| | - David L Levin
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Robert Vassallo
- Department of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Rickey E Carter
- Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, USA
| | - Rolf D Hubmayr
- Department of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Richard L Ehman
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Kiaran P McGee
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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40
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Olsson LE, Hockings PD. In Vivo Measurements of T2 Relaxation Time of Mouse Lungs during Inspiration and Expiration. PLoS One 2016; 11:e0166879. [PMID: 27936061 PMCID: PMC5147840 DOI: 10.1371/journal.pone.0166879] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 11/04/2016] [Indexed: 11/19/2022] Open
Abstract
Purpose The interest in measurements of magnetic resonance imaging relaxation times, T1, T2, T2*, with intention to characterize healthy and diseased lungs has increased recently. Animal studies play an important role in this context providing models for understanding and linking the measured relaxation time changes to the underlying physiology or disease. The aim of this work was to study how the measured transversal relaxation time (T2) in healthy lungs is affected by normal respiration in mouse. Method T2 of lung was measured in anaesthetized freely breathing mice. Image acquisition was performed on a 4.7 T, Bruker BioSpec with a multi spin-echo sequence (Car-Purcell-Meiboom-Gill) in both end-expiration and end-inspiration. The echo trains consisted of ten echoes of inter echo time 3.5 ms or 4.0 ms. The proton density, T2 and noise floor were fitted to the measured signals of the lung parenchyma with a Levenberg-Marquardt least-squares three-parameter fit. Results T2 in the lungs was longer (p<0.01) at end-expiration (9.7±0.7 ms) than at end-inspiration (9.0±0.8 ms) measured with inter-echo time 3.5 ms. The corresponding relative proton density (lung/muscle tissue) was higher (p<0.001) during end-expiration, (0.61±0.06) than during end-inspiration (0.48±0.05). The ratio of relative proton density at end-inspiration to that at end-expiration was 0.78±0.09. Similar results were found for inter-echo time 4.0 ms and there was no significant difference between the T2 values or proton densities acquired with different interecho times. The T2 value increased linearly (p< 0.001) with proton density. Conclusion The measured T2 in-vivo is affected by diffusion across internal magnetic susceptibility gradients. In the lungs these gradients are modulated by respiration, as verified by calculations. In conclusion the measured T2 was found to be dependent on the size of the alveoli.
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Affiliation(s)
- Lars E. Olsson
- Department of Medical Radiation Physics, Translational Medicine, Lund University, Malmö, Sweden
- * E-mail:
| | - Paul D. Hockings
- Antaros Medical, BioVenture Hub, Mölndal, Sweden
- Medtech West, Chalmers University of Technology, Gothenburg, Sweden
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Arai TJ, Theilmann RJ, Sá RC, Villongco MT, Hopkins SR. The effect of lung deformation on the spatial distribution of pulmonary blood flow. J Physiol 2016; 594:6333-6347. [PMID: 27273807 PMCID: PMC5088230 DOI: 10.1113/jp272030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/31/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes. The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution. Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. ABSTRACT Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P = 0.10). The greatest expansion was seen in the dependent region (P < 0.0001: dependent vs non-dependent, P < 0.0001: dependent vs middle) and RLL (P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = -0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = -0.058(0.126), +1 litre = -0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500 ml = -0.075(0.152), +1 litre = -0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] (P = 0.01). However, there was no significant lobar redistribution (P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung.
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Affiliation(s)
- Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Michael T Villongco
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA.
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.
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Abstract
As pulmonary functional imaging moves beyond the realm of the radiologist and physicist, it is important that imagers have a common language and understanding of the relevant physiology of the lung. This review will focus on key physiological concepts and pitfalls relevant to functional lung imaging.
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Zapp J, Domsch S, Weingärtner S, Schad LR. Gaussian signal relaxation around spin echoes: Implications for precise reversible transverse relaxation quantification of pulmonary tissue at 1.5 and 3 Tesla. Magn Reson Med 2016; 77:1938-1945. [DOI: 10.1002/mrm.26280] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 04/22/2016] [Accepted: 04/29/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Jascha Zapp
- Computer Assisted Clinical MedicineHeidelberg UniversityMannheim Germany
| | - Sebastian Domsch
- Computer Assisted Clinical MedicineHeidelberg UniversityMannheim Germany
| | | | - Lothar R. Schad
- Computer Assisted Clinical MedicineHeidelberg UniversityMannheim Germany
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Theilmann RJ, Darquenne C, Elliott AR, Bailey BA, Conrad DJ. Characterizing Lung Disease in Cystic Fibrosis with Magnetic Resonance Imaging and Airway Physiology. PLoS One 2016; 11:e0157177. [PMID: 27337056 PMCID: PMC4919047 DOI: 10.1371/journal.pone.0157177] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 05/25/2016] [Indexed: 11/30/2022] Open
Abstract
Translational investigations in cystic fibrosis (CF) have a need for improved quantitative and longitudinal measures of disease status. To establish a non-invasive quantitative MRI technique to monitor lung health in patients with CF and correlate MR metrics with airway physiology as measured by multiple breath washout (MBW). Data were collected in 12 CF patients and 12 healthy controls. Regional (central and peripheral lung) measures of fractional lung water density (FLD: air to 100% fluid) were acquired both at FRC and TLC on a 1.5T MRI. The median FLD (mFLD) and the FRC-to-TLC mFLD ratio were calculated for each region at both lung volumes. Spirometry and MBW data were also acquired for each subject. Ventilation inhomogeneities were quantified by the lung clearance index (LCI) and by indices Scond* and Sacin* that assess inhomogeneities in the conducting (central) and acinar (peripheral) lung regions, respectively. MBW indices and mFLD at TLC (both regions) were significantly elevated in CF (p<0.01) compared to controls. The mFLD at TLC (central: R = 0.82) and the FRC-to-TLC mFLD ratio (peripheral: R = -0.77) were strongly correlated with Scond* and LCI. CF patients had high lung water content at TLC when compared to controls. This is likely due to the presence of retained airway secretions and airway wall edema (more water) and to limited expansions of air trapping areas (less air) in CF subjects. FRC-to-TLC ratios of mFLD strongly correlated with central ventilation inhomogeneities. These combined measures may provide a useful marker of both retained mucus and air trapping in CF lungs.
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Affiliation(s)
- Rebecca J. Theilmann
- Department of Radiology, University of California San Diego, San Diego, California, United States of America
- * E-mail:
| | - Chantal Darquenne
- Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Ann R. Elliott
- Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Barbara A. Bailey
- Department of Mathematics and Statistics, San Diego State University, San Diego, California, United States of America
| | - Douglas J. Conrad
- Department of Medicine, University of California San Diego, San Diego, California, United States of America
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45
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Higano NS, Hahn AD, Tkach JA, Cao X, Walkup LL, Thomen RP, Merhar SL, Kingma PS, Fain SB, Woods JC. Retrospective respiratory self-gating and removal of bulk motion in pulmonary UTE MRI of neonates and adults. Magn Reson Med 2016; 77:1284-1295. [PMID: 26972576 DOI: 10.1002/mrm.26212] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/09/2016] [Accepted: 02/20/2016] [Indexed: 12/30/2022]
Abstract
PURPOSE To implement pulmonary three-dimensional (3D) radial ultrashort echo-time (UTE) MRI in non-sedated, free-breathing neonates and adults with retrospective motion tracking of respiratory and intermittent bulk motion, to obtain diagnostic-quality, respiratory-gated images. METHODS Pulmonary 3D radial UTE MRI was performed at 1.5 tesla (T) during free breathing in neonates and adult volunteers for validation. Motion-tracking waveforms were obtained from the time course of each free induction decay's initial point (i.e., k-space center), allowing for respiratory-gated image reconstructions that excluded data acquired during bulk motion. Tidal volumes were calculated from end-expiration and end-inspiration images. Respiratory rates were calculated from the Fourier transform of the motion-tracking waveform during quiet breathing, with comparison to physiologic prediction in neonates and validation with spirometry in adults. RESULTS High-quality respiratory-gated anatomic images were obtained at inspiration and expiration, with less respiratory blurring at the expense of signal-to-noise for narrower gating windows. Inspiration-expiration volume differences agreed with physiologic predictions (neonates; Bland-Altman bias = 6.2 mL) and spirometric values (adults; bias = 0.11 L). MRI-measured respiratory rates compared well with the observed rates (biases = -0.5 and 0.2 breaths/min for neonates and adults, respectively). CONCLUSIONS Three-dimensional radial pulmonary UTE MRI allows for retrospective respiratory self-gating and removal of intermittent bulk motion in free-breathing, non-sedated neonates and adults. Magn Reson Med 77:1284-1295, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Nara S Higano
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Andrew D Hahn
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jean A Tkach
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Xuefeng Cao
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, University of Cincinnati, Cincinnati, Ohio, USA
| | - Laura L Walkup
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Robert P Thomen
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Stephanie L Merhar
- Division of Neonatology and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Paul S Kingma
- Division of Neonatology and Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Sean B Fain
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jason C Woods
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine and Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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46
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Carinci F, Meyer C, Breuer FA, Jakob PM. In vivo imaging of the spectral line broadening of the human lung in a single breathhold. J Magn Reson Imaging 2016; 44:745-57. [DOI: 10.1002/jmri.25192] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 01/25/2016] [Indexed: 11/09/2022] Open
Affiliation(s)
- Flavio Carinci
- Research Center Magnetic Resonance Bavaria (MRB); Würzburg Germany
- Department of Experimental Physics 5; University of Würzburg; Würzburg Germany
- Siemens Healthcare Gmbh; Erlangen Germany
| | - Cord Meyer
- Department of Experimental Physics 5; University of Würzburg; Würzburg Germany
| | - Felix A. Breuer
- Research Center Magnetic Resonance Bavaria (MRB); Würzburg Germany
| | - Peter M. Jakob
- Research Center Magnetic Resonance Bavaria (MRB); Würzburg Germany
- Department of Experimental Physics 5; University of Würzburg; Würzburg Germany
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47
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Comparison Between Magnetic Resonance Imaging and Computed Tomography of the Lung in Patients With Cystic Fibrosis With Regard to Clinical, Laboratory, and Pulmonary Functional Parameters. Invest Radiol 2015; 50:733-42. [DOI: 10.1097/rli.0000000000000178] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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48
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Zhang WJ, Hubbard Cristinacce PL, Bondesson E, Nordenmark LH, Young SS, Liu YZ, Singh D, Naish JH, Parker GJM. MR Quantitative Equilibrium Signal Mapping: A Reliable Alternative to CT in the Assessment of Emphysema in Patients with Chronic Obstructive Pulmonary Disease. Radiology 2015; 275:579-88. [DOI: 10.1148/radiol.14132953] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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49
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Molinari F, Madhuranthakam AJ, Lenkinski R, Bankier AA. Ultrashort echo time MRI of pulmonary water content: assessment in a sponge phantom at 1.5 and 3.0 Tesla. Diagn Interv Radiol 2015; 20:34-41. [PMID: 24317335 DOI: 10.5152/dir.2013.13232] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE We aimed to develop a predictive model for lung water content using ultrashort echo time (UTE) magnetic resonance imaging (MRI) and a sponge phantom. MATERIALS AND METHODS Image quality was preliminarily optimized, and the signal-to-noise ratio (SNR) of UTE was compared with that obtained from a three-dimensional fast gradient echo (FGRE) sequence. Four predetermined volumes of water (3.5, 3.0, 2.5, and 2.0 mL) were soaked in cellulose foam sponges 1.8 cm3 in size and were imaged with UTE-MRI at 1.5 and 3.0 Tesla (T). A multiple echo time experiment (range, 0.1-9.6 ms) was conducted, and the T2 signal decay curve was determined at each volume of water. A three-parameter equation was fitted to the measured signal, allowing for the calculation of proton density and T2*. The calculation error of proton density was determined as a function of echo time. The constants that allowed for the determination of unknown volumes of water from the measured proton density were calculated using linear regression. RESULTS UTE-MRI provided excellent image quality for the four phantoms and showed a higher SNR, compared to that of FGRE. Proton density decreased proportionally with the decreases in both lung water and field strength (from 3.5 to 2.0 mL; proton density range at 1.5 T, 30.5-17.3; at 3.0 T, 84.2-41.5). Minimum echo time less than 0.6 ms at 1.5 T and 1 ms at 3.0 T maintained calculation errors for proton density within the range of 0%-10%. The slopes of the lines for determining the unknown volumes of water with UTE-MRI were 0.12±0.003 at 1.5 T and 0.05±0.002 at 3.0 T (P < 0.0001). CONCLUSION In a sponge phantom imaged at 1.5 and 3.0 T, unknown volumes of water can be predicted with high accuracy using UTE-MRI.
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Affiliation(s)
- Francesco Molinari
- From the Department of Radiology (F.M. e-mail: , R.L., A.A.B.), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA; Global Applied Science Laboratory (A.J.M.), GE Healthcare, Boston, Massachusetts, USA
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50
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Miller GW, Mugler JP, Sá RC, Altes TA, Prisk GK, Hopkins SR. Advances in functional and structural imaging of the human lung using proton MRI. NMR IN BIOMEDICINE 2014; 27:1542-56. [PMID: 24990096 PMCID: PMC4515033 DOI: 10.1002/nbm.3156] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/30/2014] [Accepted: 06/01/2014] [Indexed: 05/05/2023]
Abstract
The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and oxygen-enhanced imaging techniques to quantify regional perfusion and ventilation, respectively, in standard units of measurement. By combining these techniques into a single scan, it is also possible to quantify the local ventilation-perfusion ratio, which is the most important determinant of gas-exchange efficiency in the lung. To demonstrate potential for accurate and meaningful measurements of lung function, this technique was used to study gravitational gradients of ventilation, perfusion, and ventilation-perfusion ratio in healthy subjects, yielding quantitative results consistent with expected regional variations. Such techniques can also be applied in the time domain, providing new tools for studying temporal dynamics of lung function. Temporal ASL measurements showed increased spatial-temporal heterogeneity of pulmonary blood flow in healthy subjects exposed to hypoxia, suggesting sensitivity to active control mechanisms such as hypoxic pulmonary vasoconstriction, and illustrating that to fully examine the factors that govern lung function it is necessary to consider temporal as well as spatial variability. Further development to increase spatial coverage and improve robustness would enhance the clinical applicability of these new functional imaging tools. In the realm of structural imaging, pulse sequence techniques such as ultrashort echo-time radial k-space acquisition, ultrafast steady-state free precession, and imaging-based diaphragm triggering can be combined to overcome the significant challenges associated with proton MRI in the lung, enabling high-quality three-dimensional imaging of the whole lung in a clinically reasonable scan time. Images of healthy and cystic fibrosis subjects using these techniques demonstrate substantial promise for non-contrast pulmonary angiography and detailed depiction of airway disease. Although there is opportunity for further optimization, such approaches to structural lung imaging are ready for clinical testing.
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Affiliation(s)
- G. Wilson Miller
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
- Address correspondence to: Wilson Miller, Radiology Research, 480 Ray C. Hunt Dr., Box 801339, Charlottesville, VA 22908, Phone: 434-243-9216, Fax: 434-924-9435,
| | - John P. Mugler
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
| | - Rui C. Sá
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
| | - Talissa A. Altes
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
| | - G. Kim Prisk
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
| | - Susan R. Hopkins
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
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