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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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Taskiran NP, Hiura GT, Zhang X, Barr RG, Dashnaw SM, Hoffman EA, Malinsky D, Oelsner EC, Prince MR, Smith BM, Sun Y, Sun Y, Wild JM, Shen W, Hughes EW. Mapping Alveolar Oxygen Partial Pressure in COPD Using Hyperpolarized Helium-3: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study. Tomography 2022; 8:2268-2284. [PMID: 36136886 PMCID: PMC9498778 DOI: 10.3390/tomography8050190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/05/2022] [Accepted: 09/05/2022] [Indexed: 11/24/2022] Open
Abstract
Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) 3He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP 3He MRI measuring pAO2, apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm2/s) correlated with emphysema and heterogeneity in pAO2 measurements. Strong correlations were found between the heterogeneity of global pAO2 as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic pAO2 values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between pAO2 SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas pAO2 heterogeneity and the fraction of non-physiological pAO2 results increase in mild to moderate COPD. Measurements of pAO2 are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation.
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Affiliation(s)
- Naz P. Taskiran
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
- Correspondence: (N.P.T.); (E.W.H.); Tel.: +1-347-3693052 (N.P.T.); +1-626-4838731 (E.W.H.)
| | - Grant T. Hiura
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
| | - Xuzhe Zhang
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - R. Graham Barr
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
| | - Stephen M. Dashnaw
- Neurological Institute, Radiology, Columbia University, New York, NY 10032, USA
| | - Eric A. Hoffman
- Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Daniel Malinsky
- Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Elizabeth C. Oelsner
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
| | - Martin R. Prince
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
- Department of Radiology, Weill Cornell Medicine, New York, NY 10065, USA
| | - Benjamin M. Smith
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
- Department of Medicine, McGill University, Montreal, QC H3G 2M1, Canada
| | - Yanping Sun
- Division of General Medicine, Columbia University Irving Medial Center, New York, NY 10032, USA
| | - Yifei Sun
- Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Jim M. Wild
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield S10 2TN, UK
| | - Wei Shen
- Division of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Columbia University Irving Medical Center, New York, NY 10032, USA
- Institute of Human Nutrition, College of Physicians & Surgeons, Columbia University Irving Medical Center, New York, NY 10032, USA
- Columbia Magnetic Resonance Research Center (CMRRC), Columbia University, New York, NY 10027, USA
| | - Emlyn W. Hughes
- Department of Physics, Columbia University, New York, NY 10027, USA
- Correspondence: (N.P.T.); (E.W.H.); Tel.: +1-347-3693052 (N.P.T.); +1-626-4838731 (E.W.H.)
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Ohno Y, Hanamatsu S, Obama Y, Ueda T, Ikeda H, Hattori H, Murayama K, Toyama H. Overview of MRI for pulmonary functional imaging. Br J Radiol 2021; 95:20201053. [PMID: 33529053 DOI: 10.1259/bjr.20201053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Morphological evaluation of the lung is important in the clinical evaluation of pulmonary diseases. However, the disease process, especially in its early phases, may primarily result in changes in pulmonary function without changing the pulmonary structure. In such cases, the traditional imaging approaches to pulmonary morphology may not provide sufficient insight into the underlying pathophysiology. Pulmonary imaging community has therefore tried to assess pulmonary diseases and functions utilizing not only nuclear medicine, but also CT and MR imaging with various technical approaches. In this review, we overview state-of-the art MR methods and the future direction of: (1) ventilation imaging, (2) perfusion imaging and (3) biomechanical evaluation for pulmonary functional imaging.
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Affiliation(s)
- Yoshiharu Ohno
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan.,Joint Research Laboratory of Advanced Medical Imaging, Fujita Health University School of Medicine, Toyoake, Japan
| | - Satomu Hanamatsu
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
| | - Yuki Obama
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
| | - Takahiro Ueda
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
| | - Hirotaka Ikeda
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
| | - Hidekazu Hattori
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
| | - Kazuhiro Murayama
- Joint Research Laboratory of Advanced Medical Imaging, Fujita Health University School of Medicine, Toyoake, Japan
| | - Hiroshi Toyama
- Department of Radiology, Fujita Health University, School of Medicine, Toyoake, Japan
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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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5
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Woods JC, Conradi MS. 3He diffusion MRI in human lungs. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 292:90-98. [PMID: 29705031 PMCID: PMC6386180 DOI: 10.1016/j.jmr.2018.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 03/05/2018] [Accepted: 04/11/2018] [Indexed: 06/08/2023]
Abstract
Hyperpolarized 3He gas allows the air spaces of the lungs to be imaged via MRI. Imaging of restricted diffusion is addressed here, which allows the microstructure of the lung to be characterized through the physical restrictions to gas diffusion presented by airway and alveolar walls in the lung. Measurements of the apparent diffusion coefficient (ADC) of 3He at time scales of milliseconds and seconds are compared; measurement of acinar airway sizes by determination of the microscopic anisotropy of diffusion is discussed. This is where Dr. JJH Ackerman's influence was greatest in aiding the formation of the Washington University 3He group, involving early a combination of physicists, radiologists, and surgeons, as the first applications of 3He ADC were to COPD and its destruction/modification of lung microstructure via emphysema. The sensitivity of the method to early COPD is demonstrated, as is its validation by direct comparison to histology. More recently the method has been used broadly in adult and pediatric obstructive lung diseases, from severe asthma to cystic fibrosis to bronchopulmonary dysplasia, a result of premature birth. These applications of the technique are discussed briefly.
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Affiliation(s)
- Jason C Woods
- Center for Pulmonary Imaging Research, Departments of Radiology and Pediatrics (Pulmonary Medicine), Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, ML 5033, Cincinnati, OH 45229, USA; Department of Physics, Washington University, One Brookings Drive, CB 1105, St Louis, MO 63130, USA.
| | - Mark S Conradi
- ABQMR, Inc., 2301 Yale Blvd. SE, Suite C2, Albuquerque, NM 87106, USA; Department of Physics, Washington University, One Brookings Drive, CB 1105, St Louis, MO 63130, USA.
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Kern AL, Vogel-Claussen J. Hyperpolarized gas MRI in pulmonology. Br J Radiol 2018; 91:20170647. [PMID: 29271239 PMCID: PMC5965996 DOI: 10.1259/bjr.20170647] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 12/12/2017] [Accepted: 12/08/2017] [Indexed: 01/20/2023] Open
Abstract
Lung diseases have a high prevalence amongst the world population and their early diagnosis has been pointed out to be key for successful treatment. However, there is still a lack of non-invasive examination methods with sensitivity to early, local deterioration of lung function. Proton-based lung MRI is particularly challenging due to short T2* times and low proton density within the lung tissue. Hyperpolarized gas MRI is aan emerging technology providing a richness of methodologies which overcome the aforementioned problems. Unlike proton-based MRI, lung MRI of hyperpolarized gases may rely on imaging of spins in the lung's gas spaces or inside the lung tissue and thereby add substantial value and diagnostic potential to lung MRI. This review article gives an introduction to the MR physics of hyperpolarized media and presents the current state of hyperpolarized gas MRI of 3Headvasd and 129Xe in pulmonology. Key applications, ranging from static and dynamic ventilation imaging as well as oxygen-pressure mapping to 129Xe dissolved-phase imaging and spectroscopy are presented. Hyperpolarized gas MRI is compared to alternative examination methods based on MRI and future directions of hyperpolarized gas MRI are discussed.
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Adamson EB, Ludwig KD, Mummy DG, Fain SB. Magnetic resonance imaging with hyperpolarized agents: methods and applications. Phys Med Biol 2017; 62:R81-R123. [PMID: 28384123 DOI: 10.1088/1361-6560/aa6be8] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the past decade, hyperpolarized (HP) contrast agents have been under active development for MRI applications to address the twin challenges of functional and quantitative imaging. Both HP helium (3He) and xenon (129Xe) gases have reached the stage where they are under study in clinical research. HP 129Xe, in particular, is poised for larger scale clinical research to investigate asthma, chronic obstructive pulmonary disease, and fibrotic lung diseases. With advances in polarizer technology and unique capabilities for imaging of 129Xe gas exchange into lung tissue and blood, HP 129Xe MRI is attracting new attention. In parallel, HP 13C and 15N MRI methods have steadily advanced in a wide range of pre-clinical research applications for imaging metabolism in various cancers and cardiac disease. The HP [1-13C] pyruvate MRI technique, in particular, has undergone phase I trials in prostate cancer and is poised for investigational new drug trials at multiple institutions in cancer and cardiac applications. This review treats the methodology behind both HP gases and HP 13C and 15N liquid state agents. Gas and liquid phase HP agents share similar technologies for achieving non-equilibrium polarization outside the field of the MRI scanner, strategies for image data acquisition, and translational challenges in moving from pre-clinical to clinical research. To cover the wide array of methods and applications, this review is organized by numerical section into (1) a brief introduction, (2) the physical and biological properties of the most common polarized agents with a brief summary of applications and methods of polarization, (3) methods for image acquisition and reconstruction specific to improving data acquisition efficiency for HP MRI, (4) the main physical properties that enable unique measures of physiology or metabolic pathways, followed by a more detailed review of the literature describing the use of HP agents to study: (5) metabolic pathways in cancer and cardiac disease and (6) lung function in both pre-clinical and clinical research studies, concluding with (7) some future directions and challenges, and (8) an overall summary.
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Affiliation(s)
- Erin B Adamson
- Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States of America
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Yablonskiy DA, Sukstanskii AL, Quirk JD. Diffusion lung imaging with hyperpolarized gas MRI. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3448. [PMID: 26676342 PMCID: PMC4911335 DOI: 10.1002/nbm.3448] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 10/20/2015] [Accepted: 10/22/2015] [Indexed: 05/28/2023]
Abstract
Lung imaging using conventional 1 H MRI presents great challenges because of the low density of lung tissue, lung motion and very fast lung tissue transverse relaxation (typical T2 * is about 1-2 ms). MRI with hyperpolarized gases (3 He and 129 Xe) provides a valuable alternative because of the very strong signal originating from inhaled gas residing in the lung airspaces and relatively slow gas T2 * relaxation (typical T2 * is about 20-30 ms). However, in vivo human experiments should be performed very rapidly - usually during a single breath-hold. In this review, we describe the recent developments in diffusion lung MRI with hyperpolarized gases. We show that a combination of the results of modeling of gas diffusion in lung airspaces and diffusion measurements with variable diffusion-sensitizing gradients allows the extraction of quantitative information on the lung microstructure at the alveolar level. From an MRI scan of less than 15 s, this approach, called in vivo lung morphometry, allows the provision of quantitative values and spatial distributions of the same physiological parameters as measured by means of 'standard' invasive stereology (mean linear intercept, surface-to-volume ratio, density of alveoli, etc.). In addition, the approach makes it possible to evaluate some advanced Weibel parameters characterizing lung microstructure: average radii of alveolar sacs and ducts, as well as the depth of their alveolar sleeves. Such measurements, providing in vivo information on the integrity of pulmonary acinar airways and their changes in different diseases, are of great importance and interest to a broad range of physiologists and clinicians. We also discuss a new type of experiment based on the in vivo lung morphometry technique combined with quantitative computed tomography measurements, as well as with gradient echo MRI measurements of hyperpolarized gas transverse relaxation in the lung airspaces. Such experiments provide additional information on the blood vessel volume fraction, specific gas volume and length of the acinar airways, and allow the evaluation of lung parenchymal and non-parenchymal tissue. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
| | | | - James D Quirk
- Department of Radiology, Washington University, St. Louis, MO, USA
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9
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Zhong J, Ruan W, Han Y, Sun X, Ye C, Zhou X. Fast Determination of Flip Angle and T1 in Hyperpolarized Gas MRI During a Single Breath-Hold. Sci Rep 2016; 6:25854. [PMID: 27169670 PMCID: PMC4864326 DOI: 10.1038/srep25854] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 04/25/2016] [Indexed: 01/06/2023] Open
Abstract
MRI of hyperpolarized media, such as (129)Xe and (3)He, shows great potential for clinical applications. The optimal use of the available spin polarization requires accurate flip angle calibrations and T1 measurements. Traditional flip angle calibration methods are time-consuming and suffer from polarization losses during T1 relaxation. In this paper, we propose a method to simultaneously calibrate flip angles and measure T1 in vivo during a breath-hold time of less than 4 seconds. We demonstrate the accuracy, robustness and repeatability of this method and contrast it with traditional methods. By measuring the T1 of hyperpolarized gas, the oxygen pressure in vivo can be calibrated during the same breath hold. The results of the calibration have been applied in variable flip angle (VFA) scheme to obtain a stable steady-state transverse magnetization. Coupled with this method, the ultra-short TE (UTE) and constant VFA (CVFA) schemes are expected to give rise to new applications of hyperpolarized media.
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Affiliation(s)
- Jianping Zhong
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Weiwei Ruan
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - Yeqing Han
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - Xianping Sun
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - Chaohui Ye
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xin Zhou
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
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Baldi S, Hartley R, Brightling C, Gupta S. Asthma. IMAGING 2016. [DOI: 10.1183/2312508x.10002815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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11
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Kruger SJ, Nagle SK, Couch MJ, Ohno Y, Albert M, Fain SB. Functional imaging of the lungs with gas agents. J Magn Reson Imaging 2016; 43:295-315. [PMID: 26218920 PMCID: PMC4733870 DOI: 10.1002/jmri.25002] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 06/26/2015] [Indexed: 12/22/2022] Open
Abstract
This review focuses on the state-of-the-art of the three major classes of gas contrast agents used in magnetic resonance imaging (MRI)-hyperpolarized (HP) gas, molecular oxygen, and fluorinated gas--and their application to clinical pulmonary research. During the past several years there has been accelerated development of pulmonary MRI. This has been driven in part by concerns regarding ionizing radiation using multidetector computed tomography (CT). However, MRI also offers capabilities for fast multispectral and functional imaging using gas agents that are not technically feasible with CT. Recent improvements in gradient performance and radial acquisition methods using ultrashort echo time (UTE) have contributed to advances in these functional pulmonary MRI techniques. The relative strengths and weaknesses of the main functional imaging methods and gas agents are compared and applications to measures of ventilation, diffusion, and gas exchange are presented. Functional lung MRI methods using these gas agents are improving our understanding of a wide range of chronic lung diseases, including chronic obstructive pulmonary disease, asthma, and cystic fibrosis in both adults and children.
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Affiliation(s)
- Stanley J. Kruger
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
| | - Scott K. Nagle
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
- Department of Radiology, University of Wisconsin – Madison, WI, U.S.A
- Department of Pediatrics, University of Wisconsin – Madison, WI, U.S.A
| | - Marcus J. Couch
- Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada
- Biotechnology Program, Lakehead University, Thunder Bay, ON, Canada
| | - Yoshiharu Ohno
- Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Mitchell Albert
- Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada
- Department of Chemistry, Lakehead University, Thunder Bay, ON, Canada
| | - Sean B. Fain
- Department of Medical Physics, University of Wisconsin – Madison, WI, U.S.A
- Department of Radiology, University of Wisconsin – Madison, WI, U.S.A
- Department of Biomedical Engineering, University of Wisconsin – Madison, WI, U.S.A
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13
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Yablonskiy DA, Sukstanskii AL, Quirk JD, Woods JC, Conradi MS. Probing lung microstructure with hyperpolarized noble gas diffusion MRI: theoretical models and experimental results. Magn Reson Med 2016; 71:486-505. [PMID: 23554008 DOI: 10.1002/mrm.24729] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The introduction of hyperpolarized gases ((3)He and (129)Xe) has opened the door to applications for which gaseous agents are uniquely suited-lung MRI. One of the pulmonary applications, diffusion MRI, relies on measuring Brownian motion of inhaled hyperpolarized gas atoms diffusing in lung airspaces. In this article we provide an overview of the theoretical ideas behind hyperpolarized gas diffusion MRI and the results obtained over the decade-long research. We describe a simple technique based on measuring gas apparent diffusion coefficient (ADC) and an advanced technique, in vivo lung morphometry, that quantifies lung microstructure both in terms of Weibel parameters (acinar airways radii and alveolar depth) and standard metrics (mean linear intercept, surface-to-volume ratio, and alveolar density) that are widely used by lung researchers but were previously available only from invasive lung biopsy. This technique has the ability to provide unique three-dimensional tomographic information on lung microstructure from a less than 15 s MRI scan with results that are in good agreement with direct histological measurements. These safe and sensitive diffusion measurements improve our understanding of lung structure and functioning in health and disease, providing a platform for monitoring the efficacy of therapeutic interventions in clinical trials.
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A method for mapping regional oxygen and CO2 transfer in the lung. Respir Physiol Neurobiol 2015; 222:29-47. [PMID: 26563454 DOI: 10.1016/j.resp.2015.10.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 10/02/2015] [Accepted: 10/25/2015] [Indexed: 11/22/2022]
Abstract
This paper presents a novel approach to visualizing regional lung function, through quantitative three-dimensional maps of O2 and CO2 transfer rates. These maps describe the contribution of anatomical regions to overall gas exchange and demonstrate how transfer rates of the two gas species' differ regionally. An algorithm for generating such maps is presented, and for illustration, regional gas transfer maps were generated using values of ventilation and perfusion imaged by PET/CT for a healthy subject and an asthmatic patient after bronchoprovocation. In a sensitivity analysis, compartment values of gas transfer showed minor sensitivity to imaging noise in the ventilation and perfusion data, and moderate sensitivity to estimation errors in global lung input values, chiefly global alveolar ventilation, followed by cardiac output and arterial-venous O2 content difference. Gas transfer maps offer an intuitive display of physiologically relevant lung function at a regional level, the potential for an improved understanding of pulmonary gas exchange in health and disease, and potentially a presurgical evaluation tool.
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Hartley R, Baldi S, Brightling C, Gupta S. Novel imaging approaches in adult asthma and their clinical potential. Expert Rev Clin Immunol 2015; 11:1147-62. [PMID: 26289375 DOI: 10.1586/1744666x.2015.1072049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Currently, imaging in asthma is confined to chest radiography and CT. The emergence of new imaging techniques and tremendous improvement of existing imaging methods, primarily due to technological advancement, has completely changed its research and clinical prospects. In research, imaging in asthma is now being employed to provide quantitative assessment of morphology, function and pathogenic processes at the molecular level. The unique ability of imaging for non-invasive, repeated, quantitative, and in vivo assessment of structure and function in asthma could lead to identification of 'imaging biomarkers' with potential as outcome measures in future clinical trials. Emerging imaging techniques and their utility in the research and clinical setting is discussed in this review.
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Affiliation(s)
- Ruth Hartley
- a 1 Department of Infection, Inflammation and Immunity, Institute for Lung Health, University of Leicester, Leicester, LE3 9QP, UK
| | - Simonetta Baldi
- a 1 Department of Infection, Inflammation and Immunity, Institute for Lung Health, University of Leicester, Leicester, LE3 9QP, UK
| | - Chris Brightling
- a 1 Department of Infection, Inflammation and Immunity, Institute for Lung Health, University of Leicester, Leicester, LE3 9QP, UK
| | - Sumit Gupta
- a 1 Department of Infection, Inflammation and Immunity, Institute for Lung Health, University of Leicester, Leicester, LE3 9QP, UK.,b 2 Radiology Department, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, LE3 9QP, UK
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Walkup LL, Woods JC. Translational applications of hyperpolarized 3He and 129Xe. NMR IN BIOMEDICINE 2014; 27:1429-1438. [PMID: 24953709 DOI: 10.1002/nbm.3151] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/07/2014] [Accepted: 05/19/2014] [Indexed: 06/03/2023]
Abstract
Clinical magnetic resonance imaging of the lung is technologically challenging, yet over the past two decades hyperpolarized noble gas ((3)He and (129)Xe) imaging has demonstrated the ability to measure multiple pulmonary functional biomarkers. There is a growing need for non-ionizing, non-invasive imaging techniques due to increased concern about cancer risk from ionizing radiation, but the translation of hyperpolarized gas imaging to the pulmonary clinic has been stunted by limited access to the technology. New developments may open doors to greater access and more translation to clinical studies. Here we briefly review a few translational applications of hyperpolarized gas MRI in the contexts of ventilation, diffusion, and dissolved-phase imaging, as well as comparing and contrasting (3)He and (129)Xe gases for these applications. Simple static ventilation MRI reveals regions of the lung not participating in normal ventilation, and these defects have been observed in many pulmonary diseases. Biomarkers related to airspace size and connectivity can be quantified by apparent diffusion coefficient measurements of hyperpolarized gas, and have been shown to be more sensitive to small changes in lung morphology than standard clinical pulmonary functional tests and have been validated by quantitative histology. Parameters related to gas uptake and exchange and lung tissue density can be determined using (129)Xe dissolved-phase MRI. In most cases functional biomarkers can be determined via MRI of either gas, but for some applications one gas may be preferred, such as (3)He for long-range diffusion measurements and (129)Xe for dissolved-phase imaging. Greater access to hyperpolarized gas imaging coupled with newly developing therapeutics makes pulmonary medicine poised for a potential revolution, further adding to the prospects of personalized medicine already evidenced by advancements in molecular biology. Hyperpolarized gas researchers have the opportunity to contribute to this revolution, particularly if greater clinical application of hyperpolarized gas imaging is realized.
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Affiliation(s)
- Laura L Walkup
- Center for Pulmonary Imaging Research, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
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Hamedani H, Shaghaghi H, Kadlecek SJ, Xin Y, Han B, Siddiqui S, Rajaei J, Ishii M, Rossman M, Rizi RR. Vertical gradients in regional alveolar oxygen tension in supine human lung imaged by hyperpolarized 3He MRI. NMR IN BIOMEDICINE 2014; 27:1439-50. [PMID: 25395184 PMCID: PMC5033039 DOI: 10.1002/nbm.3227] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 09/22/2014] [Accepted: 09/22/2014] [Indexed: 06/04/2023]
Abstract
The purpose of this study was to evaluate whether regional alveolar oxygen tension (P(A)O2) vertical gradients imaged with hyperpolarized (3)He can identify smoking-induced pulmonary alterations. These gradients are compared with common clinical measurements including pulmonary function tests (PFTs), the six minute walk test, and the St. George's Respiratory Questionnaire. 8 healthy non-smokers, 12 asymptomatic smokers, and 7 symptomatic subjects with chronic obstructive pulmonary disease (COPD) underwent two sets of back-to-back P(A)O2 imaging acquisitions in the supine position in two opposite directions (top to bottom and bottom to top), followed by clinically standard pulmonary tests. The whole-lung mean, standard deviation (DP(A)O2) and vertical gradients of P(A)O2 along the slices were extracted, and the results were compared with clinically derived metrics. Statistical tests were performed to analyze the differences between cohorts. The anterior-posterior vertical gradients and DP(A)O2 effectively differentiated all three cohorts (p < 0.05). The average vertical gradient P(A)O2 in healthy subjects was -1.03 ± 0.51 Torr/cm toward lower values in the posterior/dependent regions. The directional gradient was absent in smokers (0.36 ± 1.22 Torr/cm) and was in the opposite direction in COPD subjects (2.18 ± 1.54 Torr/cm). The vertical gradients correlated with smoking history (p = 0.004); body mass index (p = 0.037), PFT metrics (forced expiratory volume in 1 s, p = 0.025; residual volume/total lung capacity percent predicted, p = 0.033) and with distance walked in 6 min (p = 0.009). Regional P(A)O2 data indicate that cigarette smoke induces physiological alterations that are not being detected by the most widely used physiological tests.
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Affiliation(s)
- Hooman Hamedani
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Hoora Shaghaghi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Stephen J. Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Biao Han
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Sarmad Siddiqui
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Jennia Rajaei
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
| | - Masaru Ishii
- Departments of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, MD, United States
| | - Milton Rossman
- Department of Pulmonary and Critical Care, Johns Hopkins University of Pennsylvania, Philadelphia, PA, Baltimore, MD, United States
| | - Rahim R. Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States
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Couch MJ, Ball IK, Li T, Fox MS, Ouriadov AV, Biman B, Albert MS. Inert fluorinated gas MRI: a new pulmonary imaging modality. NMR IN BIOMEDICINE 2014; 27:1525-1534. [PMID: 25066661 DOI: 10.1002/nbm.3165] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 06/06/2014] [Accepted: 06/12/2014] [Indexed: 06/03/2023]
Abstract
Fluorine-19 ((19)F) MRI of the lungs using inhaled inert fluorinated gases can potentially provide high quality images of the lungs that are similar in quality to those from hyperpolarized (HP) noble gas MRI. Inert fluorinated gases have the advantages of being nontoxic, abundant, and inexpensive compared with HP gases. Due to the high gyromagnetic ratio of (19)F, there is sufficient thermally polarized signal for imaging, and averaging within a single breath-hold is possible due to short longitudinal relaxation times. Therefore, the gases do not need to be hyperpolarized prior to their use in MRI. This eliminates the need for an expensive polarizer and expensive isotopes. Inert fluorinated gas MRI of the lungs has been previously demonstrated in animals, and more recently in healthy volunteers and patients with lung diseases. The ongoing improvements in image quality demonstrate the potential of (19)F MRI for visualizing the distribution of ventilation in human lungs and detecting functional biomarkers. In this brief review, the development of inert fluorinated gas MRI, current progress, and future prospects are discussed. The current state of HP noble gas MRI is also briefly discussed in order to provide context to the development of this new imaging modality. Overall, this may be a viable clinical imaging modality that can provide useful information for the diagnosis and management of chronic respiratory diseases.
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Affiliation(s)
- Marcus J Couch
- Lakehead University, Thunder Bay, Ontario, Canada; Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada
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Ruppert K. Biomedical imaging with hyperpolarized noble gases. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2014; 77:116701. [PMID: 25360484 DOI: 10.1088/0034-4885/77/11/116701] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hyperpolarized noble gases (HNGs), polarized to approximately 50% or higher, have led to major advances in magnetic resonance (MR) imaging of porous structures and air-filled cavities in human subjects, particularly the lung. By boosting the available signal to a level about 100 000 times higher than that at thermal equilibrium, air spaces that would otherwise appear as signal voids in an MR image can be revealed for structural and functional assessments. This review discusses how HNG MR imaging differs from conventional proton MR imaging, how MR pulse sequence design is affected and how the properties of gas imaging can be exploited to obtain hitherto inaccessible information in humans and animals. Current and possible future imaging techniques, and their application in the assessment of normal lung function as well as certain lung diseases, are described.
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Siddiqui S, Xin Y, Emami K, D'Armiento J, Shiomi T, Profka H, Mongkolwisetwara P, Rizi R. Hyperpolarized (3)He diffusion MRI and histology of secreted frizzled related protein-1 (SFRP1) deficient lungs in a Murine model. Magn Reson Imaging 2014; 32:535-40. [PMID: 24629512 DOI: 10.1016/j.mri.2014.01.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 12/04/2013] [Accepted: 01/27/2014] [Indexed: 12/25/2022]
Abstract
Secreted frizzled related protein-1 (SFRP1) plays a key role in many diverse processes, including embryogenesis, tissue repair, bone formation, and tumor genesis. Previous studies have shown the effects of the SFRP1 gene on lung development using the SFRP1 knockout mouse model via histological and physiological studies. In this study, the feasibility of ADC (acquired via HP (3)He) to detect altered lung structure in the SFRP1 knockout (SFRP1(-/-)) mice was investigated, and compared to analysis by histology. This study consisted of two groups, the wild-type (WT) mice and the knockout (KO) mice with n=6 mice for each group. (3)He ADC MRI and histology were performed on all of the animals. The global Lm values of WT and KO mice were 35.0±0.8μm and 38.4±3.8μm, respectively, which translated to an increase of 9.58% in the Lm of KO mice. The mean global ADCs for the WT and KO mice were 0.12±0.01cm(2)/s and 0.13±0.01cm(2)/s, respectively, which equated to a relative increase of 8.0% in the KO mice compared to the WT mice. In the sub-analysis of the anterior, medial and posterior lung regions, Lm increased by 10.50%, 6.66% and 11.84% in the KO mice, respectively, whereas the differences in ADC between the two groups in the anterior, medial, and posterior regions were 7.3%, 8.3%, and 4.6%, respectively. These results suggest that HP MRI measurements can be used as a suitable substitute for histology to obtain valuable information about lung geometry non-invasively. This technique is also advantageous as regional measurements can be performed, which can identify lung destruction more precisely. Most importantly, this approach extends far beyond the specific pathology analyzed in this study, as it can be applied to many other pathological conditions in the lung tissue, as well to many other embryonic studies.
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Affiliation(s)
- Sarmad Siddiqui
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.
| | - Yi Xin
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Kiarash Emami
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Takayuki Shiomi
- Department of Medicine, Columbia University, New York, NY, USA
| | - Harrilla Profka
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Rahim Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
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22
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Kadlecek S, Hamedani H, Xu Y, Emami K, Xin Y, Ishii M, Rizi R. Regional alveolar partial pressure of oxygen measurement with parallel accelerated hyperpolarized gas MRI. Acad Radiol 2013; 20:1224-33. [PMID: 24029054 DOI: 10.1016/j.acra.2013.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/19/2013] [Accepted: 07/03/2013] [Indexed: 11/16/2022]
Abstract
RATIONALE AND OBJECTIVES Alveolar oxygen tension (Pao2) is sensitive to the interplay between local ventilation, perfusion, and alveolar-capillary membrane permeability, and thus reflects physiologic heterogeneity of healthy and diseased lung function. Several hyperpolarized helium ((3)He) magnetic resonance imaging (MRI)-based Pao2 mapping techniques have been reported, and considerable effort has gone toward reducing Pao2 measurement error. We present a new Pao2 imaging scheme, using parallel accelerated MRI, which significantly reduces measurement error. MATERIALS AND METHODS The proposed Pao2 mapping scheme was computer-simulated and was tested on both phantoms and five human subjects. Where possible, correspondence between actual local oxygen concentration and derived values was assessed for both bias (deviation from the true mean) and imaging artifact (deviation from the true spatial distribution). RESULTS Phantom experiments demonstrated a significantly reduced coefficient of variation using the accelerated scheme. Simulation results support this observation and predict that correspondence between the true spatial distribution and the derived map is always superior using the accelerated scheme, although the improvement becomes less significant as the signal-to-noise ratio increases. Paired measurements in the human subjects, comparing accelerated and fully sampled schemes, show a reduced Pao2 distribution width for 41 of 46 slices. CONCLUSION In contrast to proton MRI, acceleration of hyperpolarized imaging has no signal-to-noise penalty; its use in Pao2 measurement is therefore always beneficial. Comparison of multiple schemes shows that the benefit arises from a longer time-base during which oxygen-induced depolarization modifies the signal strength. Demonstration of the accelerated technique in human studies shows the feasibility of the method and suggests that measurement error is reduced here as well, particularly at low signal-to-noise levels.
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Affiliation(s)
- Stephen Kadlecek
- Department of Radiology, University of Pennsylvania, 308C Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
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23
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Mugler JP, Altes TA. Hyperpolarized 129Xe MRI of the human lung. J Magn Reson Imaging 2013; 37:313-31. [PMID: 23355432 DOI: 10.1002/jmri.23844] [Citation(s) in RCA: 240] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Accepted: 08/29/2012] [Indexed: 11/07/2022] Open
Abstract
By permitting direct visualization of the airspaces of the lung, magnetic resonance imaging (MRI) using hyperpolarized gases provides unique strategies for evaluating pulmonary structure and function. Although the vast majority of research in humans has been performed using hyperpolarized (3)He, recent contraction in the supply of (3)He and consequent increases in price have turned attention to the alternative agent, hyperpolarized (129) Xe. Compared to (3)He, (129)Xe yields reduced signal due to its smaller magnetic moment. Nonetheless, taking advantage of advances in gas-polarization technology, recent studies in humans using techniques for measuring ventilation, diffusion, and partial pressure of oxygen have demonstrated results for hyperpolarized (129)Xe comparable to those previously demonstrated using hyperpolarized (3)He. In addition, xenon has the advantage of readily dissolving in lung tissue and blood following inhalation, which makes hyperpolarized (129)Xe particularly attractive for exploring certain characteristics of lung function, such as gas exchange and uptake, which cannot be accessed using (3)He. Preliminary results from methods for imaging (129) Xe dissolved in the human lung suggest that these approaches will provide new opportunities for quantifying relationships among gas delivery, exchange, and transport, and thus show substantial potential to broaden our understanding of lung disease. Finally, recent changes in the commercial landscape of the hyperpolarized-gas field now make it possible for this innovative technology to move beyond the research laboratory.
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Affiliation(s)
- John P Mugler
- Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology and Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
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24
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Kutscher HL, Gao D, Li S, Massa CB, Cervelli J, Deshmukh M, Joseph LB, Laskin DL, Sinko PJ. Toxicodynamics of rigid polystyrene microparticles on pulmonary gas exchange in mice: implications for microemboli-based drug delivery systems. Toxicol Appl Pharmacol 2012; 266:214-23. [PMID: 23142466 DOI: 10.1016/j.taap.2012.10.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/13/2012] [Accepted: 10/17/2012] [Indexed: 10/27/2022]
Abstract
The toxicodynamic relationship between the number and size of pulmonary microemboli resulting from uniformly sized, rigid polystyrene microparticles (MPs) administered intravenously and their potential effects on pulmonary gas exchange were investigated. CD-1 male mice (6-8 weeks) were intravenously administered 10, 25 and 45 μm diameter MPs. Oxygen hemoglobin saturation in the blood (SpO(2)) was measured non-invasively using a pulse oximeter while varying inhaled oxygen concentration (F(I)O(2)). The resulting data were fit to a physiologically based non-linear mathematical model that estimates 2 parameters: ventilation-perfusion ratio (V(A)/Q) and shunt (percentage of deoxygenated blood returning to systemic circulation). The number of MPs administered prior to a statistically significant reduction in normalized V(A)/Q was dependent on particle size. MP doses that resulted in a significant reduction in normalized V(A)/Q one day post-treatment were 4000, 40,000 and 550,000 MPs/g for 45, 25 and 10 μm MPs, respectively. The model estimated V(A)/Q and shunt returned to baseline levels 7 days post-treatment. Measuring SpO(2) alone was not sufficient to observe changes in gas exchange; however, when combined with model-derived V(A)/Q and shunt early reversible toxicity from pulmonary microemboli was detected suggesting that the model and physical measurements are both required for assessing toxicity. Moreover, it appears that the MP load required to alter gas exchange in a mouse prior to lethality is significantly higher than the anticipated required MP dose for effective drug delivery. Overall, the current results indicate that the microemboli-based approach for targeted pulmonary drug delivery is potentially safe and should be further explored.
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Affiliation(s)
- H L Kutscher
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
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25
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Fain S, Schiebler ML, McCormack DG, Parraga G. Imaging of lung function using hyperpolarized helium-3 magnetic resonance imaging: Review of current and emerging translational methods and applications. J Magn Reson Imaging 2011; 32:1398-408. [PMID: 21105144 DOI: 10.1002/jmri.22375] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
During the past several years there has been extensive development and application of hyperpolarized helium-3 (HP (3)He) magnetic resonance imaging (MRI) in clinical respiratory indications such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, radiation-induced lung injury, and transplantation. This review focuses on the state-of-the-art of HP (3)He MRI and its application to clinical pulmonary research. This is not an overview of the physics of the method, as this topic has been covered previously. We focus here on the potential of this imaging method and its challenges in demonstrating new types of information that has the potential to influence clinical research and decision making in pulmonary medicine. Particular attention is given to functional imaging approaches related to ventilation and diffusion-weighted imaging with applications in chronic obstructive pulmonary disease, cystic fibrosis, asthma, and radiation-induced lung injury. The strengths and challenges of the application of (3)He MRI in these indications are discussed along with a comparison to established and emerging imaging techniques.
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Affiliation(s)
- Sean Fain
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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26
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Ley S, Grünig E, Kiely DG, van Beek E, Wild J. Computed tomography and magnetic resonance imaging of pulmonary hypertension: Pulmonary vessels and right ventricle. J Magn Reson Imaging 2011; 32:1313-24. [PMID: 21105137 DOI: 10.1002/jmri.22373] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Pulmonary hypertension (PH) is very heterogeneous and the classification identifies five major groups including many associated disease processes. The treatment of PH depends on the underlying cause and accurate classification is paramount. A comprehensive assessment to identify the cause and severity of PH is therefore needed. Furthermore, follow-up assessments are required to monitor changes in disease status and response to therapy. Traditionally, the diagnostic imaging work-up of PH comprised mainly echocardiography, invasive right heart catheterization, and ventilation/perfusion scintigraphy. Due to technical advances, multidetector row computed tomography (CT) and magnetic resonance imaging (MRI) have become important and complementary investigations in the evaluation of patients with suspected PH. Both modalities are reviewed and recommendations for clinical use are given.
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Affiliation(s)
- Sebastian Ley
- Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany.
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27
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Kraayvanger RJ, Bidinosti CP, Dominguez-Viqueira W, Parra-Robles J, Fox M, Lam WW, Santyr GE. Measurement of alveolar oxygen partial pressure in the rat lung using Carr-Purcell-Meiboom-Gill spin-spin relaxation times of hyperpolarized 3He and 129Xe at 74 mT. Magn Reson Med 2011; 64:1484-90. [PMID: 20593371 DOI: 10.1002/mrm.22520] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, (3) He and (129) Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R(2) ) of (3) He at low magnetic field strengths (<0.1 T) in vivo. R(2) measurements can be achieved efficiently using the Carr-Purcell-Meiboom-Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R(2) values of hyperpolarized (3) He and (129) Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for (3) He and (129) Xe were determined to be (5.2 ± 0.6) × 10(-6) Pa(-1) sec(-1) and (7.3 ± 0.4) × 10(-6) Pa(-1) s(-1) compared with spin-lattice relaxivity constants of (4.0 ± 0.4) × 10(-6) Pa(-1) s(-1) and (4.3 ± 1.3) × 10(-6) Pa(-1) s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using (3) He in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For (129) Xe, multicomponent relaxation was observed with one component exhibiting an increase in R(2) with decreasing alveolar oxygen partial pressure.
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Affiliation(s)
- Ryan J Kraayvanger
- Imaging Research Laboratories, Robarts Research Institute, London, Canada
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28
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Stephen MJ, Emami K, Woodburn JM, Chia E, Kadlecek S, Zhu J, Pickup S, Ishii M, Rizi RR, Rossman M. Quantitative assessment of lung ventilation and microstructure in an animal model of idiopathic pulmonary fibrosis using hyperpolarized gas MRI. Acad Radiol 2010; 17:1433-43. [PMID: 20934126 DOI: 10.1016/j.acra.2010.06.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 06/24/2010] [Accepted: 06/24/2010] [Indexed: 11/16/2022]
Abstract
RATIONALE AND OBJECTIVES The use of hyperpolarized (3)He magnetic resonance imaging as a quantitative lung imaging tool has progressed rapidly in the past decade, mostly in the assessment of the airway diseases chronic obstructive pulmonary disease and asthma. This technique has shown potential to assess both structural and functional information in healthy and diseased lungs. In this study, the regional measurements of structure and function were applied to a bleomycin rat model of interstitial lung disease. MATERIALS AND METHODS Male Sprague-Dawley rats (weight, 300-350 g) were administered intratracheal bleomycin. After 3 weeks, apparent diffusion coefficient and fractional ventilation were measured by (3)He magnetic resonance imaging and pulmonary function testing using a rodent-specific plethysmography chamber. Sensitized and healthy animals were then compared using threshold analysis to assess the potential sensitivity of these techniques to pulmonary abnormalities. RESULTS No significant changes were observed in total lung volume and compliance between the two groups. Airway resistance elevated and forced expiratory volume significantly declined in the 3-week bleomycin rats, and fractional ventilation was significantly decreased compared to control animals (P < .0004). The apparent diffusion coefficient of (3)He showed a smaller change but still a significant decrease in 3-week bleomycin animals (P < .05). CONCLUSIONS Preliminary results suggest that quantitative (3)He magnetic resonance imaging can be a sensitive and noninvasive tool to assess changes in an animal interstitial lung disease model. This technique may be useful for longitudinal animal studies and also in the investigation of human interstitial lung diseases.
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Affiliation(s)
- Michael J Stephen
- Department of Pulmonary and Critical Care, 834 W Gates Building, University of Pennsylvania, Philadelphia, PA 19104, USA
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29
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Scholz AWK, Eberle B, Heussel CP, David M, Schmittner MD, Quintel M, Schreiber LM, Weiler N. Ventilation-Perfusion Ratio in Perflubron During Partial Liquid Ventilation. Anesth Analg 2010; 110:1661-8. [DOI: 10.1213/ane.0b013e3181d3e1d5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
Hyperpolarized gas magnetic resonance imaging has been explored extensively as a promising tool for the quantitative evaluation of regional pulmonary pathophysiology. This noninvasive technique is capable of providing both structural information down to the level of the alveolar microstructure and functional information, such as dynamic ventilation, intrapulmonary partial pressure of oxygen, and alveolar surface area. This study reviews the role of hyperpolarized 3-helium and 129-xenon magnetic resonance imaging in this research.
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31
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Miller GW, Mugler JP, Altes TA, Cai J, Mata JF, de Lange EE, Tobias WA, Cates GD, Brookeman JR. A short-breath-hold technique for lung pO2 mapping with 3He MRI. Magn Reson Med 2010; 63:127-36. [PMID: 19918891 PMCID: PMC3320736 DOI: 10.1002/mrm.22181] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Accepted: 07/29/2009] [Indexed: 11/06/2022]
Abstract
A pulse-sequence strategy was developed for generating regional maps of alveolar oxygen partial pressure (pO2) in a single 6-sec breath hold, for use in human subjects with impaired lung function. Like previously described methods, pO2 values are obtained by measuring the oxygen-induced T1 relaxation of inhaled hyperpolarized 3He. Unlike other methods, only two 3He images are acquired: one with reverse-centric and the other with centric phase-encoding order. This phase-encoding arrangement minimizes the effects of regional flip-angle variations, so that an accurate map of instantaneous pO2 can be calculated from two images acquired a few seconds apart. By combining this phase-encoding strategy with variable flip angles, the vast majority of the hyperpolarized magnetization goes directly into the T1 measurement, minimizing noise in the resulting pO2 map. The short-breath-hold pulse sequence was tested in phantoms containing known O2 concentrations. The mean difference between measured and prepared pO2 values was 1 mm Hg. The method was also tested in four healthy volunteers and three lung-transplant patients. Maps of healthy subjects were largely uniform, whereas focal regions of abnormal pO2 were observed in diseased subjects. Mean pO2 values varied with inhaled O2 concentration. Mean pO2 was consistent with normal steady-state values in subjects who inhaled 3He diluted only with room air.
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Affiliation(s)
- G Wilson Miller
- Center for In-Vivo Hyperpolarized Gas MR Imaging, Department of Radiology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
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32
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Quantitative assessment of lung using hyperpolarized magnetic resonance imaging. Ann Am Thorac Soc 2009; 6:431-8. [PMID: 19687215 DOI: 10.1513/pats.200902-008aw] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Improvements in the quantitative assessment of structure, function, and metabolic activity in the lung, combined with improvements in the spatial resolution of those assessments, enhance the diagnosis and evaluation of pulmonary disorders. Radiologic methods are among the most attractive techniques for the comprehensive assessment of the lung, as they allow quantitative assessment of this organ through measurements of a number of structural, functional, and metabolic parameters. Hyperpolarized nuclei magnetic resonance imaging (MRI) has opened up new territories for the quantitative assessment of lung function and structure with an unprecedented spatial resolution and sensitivity. This review article presents a survey of recent developments in the field of pulmonary imaging using hyperpolarized nuclei MRI for quantitative imaging of different aspects of the lung, as well as preclinical applications of these techniques to diagnose and evaluate specific pulmonary diseases. After presenting a brief overview of various hyperpolarization techniques, this survey divides the research activities of the field into four broad areas: lung microstructure, ventilation, oxygenation, and perfusion. Finally, it discusses the challenges currently faced by researchers in this field to translate this rich body of methodology into wider-scale clinical applications.
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Matsuoka S, Hunsaker AR, Gill RR, Jacobson FL, Ohno Y, Patz S, Hatabu H. Functional MR imaging of the lung. Magn Reson Imaging Clin N Am 2008; 16:275-89, ix. [PMID: 18474332 DOI: 10.1016/j.mric.2008.03.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Recent development of MR techniques has overcome many problems, such as susceptibility artifacts or motion artifact, allowing both static and dynamic MR lung imaging and providing quantitative information of pulmonary function, including perfusion, ventilation, and respiratory motion. Dynamic contrast-enhanced MR perfusion imaging is suitable for the evaluation of angiogenesis of pulmonary solitary nodules. (129)Xe MR imaging is potentially a robust technique for the evaluation of various pulmonary function and may replace (3)He. The information provided by these new MR imaging methods is proving useful in research and in clinical applications in various lung diseases.
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Affiliation(s)
- Shin Matsuoka
- Department of Radiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA
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Tsai LL, Mair RW, Rosen MS, Patz S, Walsworth RL. An open-access, very-low-field MRI system for posture-dependent 3He human lung imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 193:274-85. [PMID: 18550402 PMCID: PMC2572034 DOI: 10.1016/j.jmr.2008.05.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 05/14/2008] [Accepted: 05/14/2008] [Indexed: 05/20/2023]
Abstract
We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in vivo hyperpolarized 3He imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, including asthma and obesity. The imager uses a bi-planar B(0) coil design that produces an optimized 65 G (6.5 mT) magnetic field for 3He MRI at 210 kHz. Three sets of bi-planar coils produce the x, y, and z magnetic field gradients while providing a 79-cm inter-coil gap for the imaging subject. We use solenoidal Q-spoiled RF coils for operation at low frequencies, and are able to exploit insignificant sample loading to allow for pre-tuning/matching schemes and for accurate pre-calibration of flip angles. We obtain sufficient SNR to acquire 2D 3He images with up to 2.8mm resolution, and present initial 2D and 3D 3He images of human lungs in both supine and upright orientations. 1H MRI can also be performed for diagnostic and calibration reasons.
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Affiliation(s)
- L. L. Tsai
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139
- Harvard Medical School, Boston, MA 02115
| | - R. W. Mair
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138
| | - M. S. Rosen
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
| | - S. Patz
- Harvard Medical School, Boston, MA 02115
- Department of Radiology, Brigham and Women’s Hospital, Boston, MA 02115
| | - R. L. Walsworth
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138
- Department of Physics, Harvard University, Cambridge, MA 02138
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Tsai LL, Mair RW, Li CH, Rosen MS, Patz S, Walsworth RL. Posture-dependent human 3He lung imaging in an open-access MRI system: initial results. Acad Radiol 2008; 15:728-39. [PMID: 18486009 PMCID: PMC2474800 DOI: 10.1016/j.acra.2007.10.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 09/24/2007] [Accepted: 10/17/2007] [Indexed: 11/28/2022]
Abstract
RATIONALE AND OBJECTIVES The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized (3)He magnetic resonance imaging (MRI) of the human lung, and most other common radiologic imaging modalities including positron emission tomography and computed tomography, restrict subjects to lying horizontally, minimizing most gravitational effects. MATERIALS AND METHODS In this article, we review the motivation for posture-dependent studies of human lung function and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized (3)He gas and an open-access MRI instrument. The open geometry of this MRI system features a "walk-in" capability that permits subjects to be imaged in vertical and horizontal positions and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane. RESULTS Initial results include two-dimensional lung images acquired with approximately 4 x 8 mm in-plane resolution and three-dimensional images with approximately 2-cm slice thickness. CONCLUSIONS Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical.
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Affiliation(s)
- Leo L Tsai
- Harvard-Smithsonian Center for Astrophysics, 60 Garden St, MS 59, Cambridge, MA 02138, USA
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Conradi MS, Yablonskiy DA, Woods JC, Gierada DS, Bartel SET, Haywood SE, Menard C. The role of collateral paths in long-range diffusion of 3He in lungs. Acad Radiol 2008; 15:675-82. [PMID: 18486004 DOI: 10.1016/j.acra.2007.09.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 08/28/2007] [Accepted: 09/07/2007] [Indexed: 10/22/2022]
Abstract
RATIONALE AND OBJECTIVES The hyperpolarized (3)He long-range diffusion coefficient (LRDC) in lungs is sensitive to changes in lung structure due to emphysema, reflecting the increase in collateral paths resulting from tissue destruction. However, no clear understanding of LRDC in healthy lungs has emerged. Here we compare LRDC measured in healthy lungs with computer simulations of diffusion along the airway tree with no collateral connections. MATERIALS AND METHODS Computer simulations of diffusion of spatially modulated spin magnetization were performed in computer-generated, symmetric-branching models of lungs and compared with existing LRDC measurements in canine and human lungs. RESULTS The simulations predict LRDC values of order 0.001 cm(2)/sec, approximately 20 times smaller than the measured LRDC. We consider and rule out possible mechanisms for LRDC not included in the simulations: incomplete breath hold, cardiac motion, and passage of dissolved (3)He through airway walls. However, a very low density of small (micron) holes in the airways is shown to account for the observed LRDC. CONCLUSION It is proposed that LRDC in healthy lungs is determined by small collateral pathways.
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Holmes JH, O'Halloran RL, Brodsky EK, Jung Y, Block WF, Fain SB. 3D hyperpolarized He-3 MRI of ventilation using a multi-echo projection acquisition. Magn Reson Med 2008; 59:1062-71. [PMID: 18429034 PMCID: PMC3001140 DOI: 10.1002/mrm.21437] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Accepted: 09/12/2007] [Indexed: 11/07/2022]
Abstract
A method is presented for high-resolution 3D imaging of the whole lung using inhaled hyperpolarized (HP) He-3 MR with multiple half-echo radial trajectories that can accelerate imaging through undersampling. A multiple half-echo radial trajectory can be used to reduce the level of artifact for undersampled 3D projection reconstruction (PR) imaging by increasing the amount of data acquired per unit time for HP He-3 lung imaging. The point spread functions (PSFs) for breath-held He-3 MRI using multiple half-echo trajectories were evaluated using simulations to predict the effects of T(2)* and gas diffusion on image quality. Results from PSF simulations were consistent with imaging results in volunteer studies showing improved image quality with increasing number of echoes using up to 8 half-echoes. The 8-half-echo acquisition is shown to accommodate lost breath-holds as short as 6 sec using a retrospective reconstruction at reduced resolution and also to allow reduced breath-hold time compared with an equivalent Cartesian trajectory. Furthermore, preliminary results from a 3D dynamic inhalation-exhalation maneuver are demonstrated using the 8-half-echo trajectory. Results demonstrate the first high-resolution 3D PR imaging of ventilation and respiratory dynamics in humans using HP He-3 MR.
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Affiliation(s)
- James H Holmes
- Department of Medical Physics, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI 53792, USA
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38
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Adolphi NL, Kuethe DO. Quantitative mapping of ventilation-perfusion ratios in lungs by19F MR imaging ofT1 of inert fluorinated gases. Magn Reson Med 2008; 59:739-46. [DOI: 10.1002/mrm.21579] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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39
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Emami K, Cadman RV, Woodburn JM, Fischer MC, Kadlecek SJ, Zhu J, Pickup S, Guyer RA, Law M, Vahdat V, Friscia ME, Ishii M, Yu J, Gefter WB, Shrager JB, Rizi RR. Early changes of lung function and structure in an elastase model of emphysema--a hyperpolarized 3He MRI study. J Appl Physiol (1985) 2007; 104:773-86. [PMID: 18063806 DOI: 10.1152/japplphysiol.00482.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Early changes of lung function and structure were studied in the presence of an elastase-induced model of emphysema in 35 Sprague-Dawley rats at mild (5 U/100 g) and moderate (10 U/100 g) severities. Lung ventilation was measured on a regional basis (at a planar resolution of 3.2 mm) by hyperpolarized 3He MRI at 5 and 10 wk after model induction. Subsequent to imaging, average alveolar diameter was measured from histological slices taken from the centers of each lobe. Changes of mean fractional ventilation, mean linear intercept, and intrasubject heterogeneity of ventilation were studied during disease progression. Mean fractional ventilation was significantly different between healthy controls (0.23 +/- 0.04) and emphysematous animals at both time points in the 10-unit group (0.06 +/- 0.02 and 0.12 +/- 0.05, respectively). Changes in average alveolar diameter were not statistically observable until the 10th wk between healthy (37 +/- 10 microm) and emphysematous rats (73 +/- 25 and 95 +/- 31 microm, for 5 and 10 units, respectively). Assessment of function-structure correlation suggested that the majority of the decline in fractional ventilation occurred in the first 5 wk, while enlargement of alveolar diameters appeared primarily between the 5th and 10th wk. A thresholding metric, based on the 20th percentile of fractional ventilation over the entire lung, was utilized to detect the onset of the disease with confidence, independent of whether the regional ventilation measurements were normalized with respect to the delivered tidal volume and estimated functional residual capacity of each individual rat.
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Affiliation(s)
- Kiarash Emami
- Dept. of Radiology, University of Pennsylvania, B1 Stellar-Chance Laboratories, 422 Curie Blvd., Philadelphia, PA 19104-6100, USA.
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40
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Brook BS, Murphy CM, Breen D, Miles AW, Tilley DG, Wilson AJ. Quantification of lung injury using ventilation and perfusion distributions obtained from gamma scintigraphy. Physiol Meas 2007; 28:1451-64. [PMID: 18057511 DOI: 10.1088/0967-3334/28/12/001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper explores the potential of isotope V/Q lung scans to quantify lung disease. Areas of restricted perfusion in subjects with a pulmonary embolus (PE) were identified in 3D reconstructions of V/Q images achieved using anatomical data from the Visible Human Project. From these, the extent of lung damage was quantified. Significant differences in the values of both LogSD V and LogSD Q (p > 0.05) obtained from plots of V and Q against Log(V/Q) were found between normal subjects and subjects with a PE, but no correlation was found between either of these parameters and the degree of lung damage in subjects with a PE (p > 0.05). Whilst V/Q values were log normally distributed, the V/Q distributions from the subjects with a PE failed to show the bimodal distribution predicted from theoretical considerations and MIGET measurements previously reported. There was a statistically significant difference in the mean and standard deviation values of the V/Q distributions between normal subject and subjects with a PE (p < 0.05) but not in the median values (p > 0.05). There was no correlation between the mean, median and standard deviation of the distributions from the subjects with a PE and the percentage of damage present (p > 0.05).
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Affiliation(s)
- B S Brook
- School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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41
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Holmes JH, Korosec FR, Du J, O'Halloran RL, Sorkness RL, Grist TM, Kuhlman JE, Fain SB. Imaging of lung ventilation and respiratory dynamics in a single ventilation cycle using hyperpolarized He-3 MRI. J Magn Reson Imaging 2007; 26:630-6. [PMID: 17685417 DOI: 10.1002/jmri.20965] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To image respiratory dynamics and three-dimensional (3D) ventilation during inhalation, breath-hold, and exhalation for evaluation of obstructive lung disease using a single dose of hyperpolarized (HP) He-3 during MRI. MATERIALS AND METHODS A single 2D-3D projections inside Z encoding (PRIZE)-2D acquisition was performed that consisted of a rapid 2D radial acquisition phase during inhalation of the HP He-3, a 3D acquisition phase during a breath-hold interval, and finally the same 2D radial acquisition during a forced exhalation maneuver followed by tidal breathing. The 3D PRIZE acquisition was comprised of radial sampling in the coronal plane and Fourier encoding in the patient's anterior-posterior direction. Nine patients with mild/moderate to severe asthma were studied (two individuals were studied twice) using this technique. RESULTS Breath-hold and dynamic imaging results showed physiological abnormalities and were compared with results from standard spirometry, body plethysmography, and computed tomography (CT). Dynamic images depicted regions of differential gas clearance and trapping observed during and after forced exhalation that were corroborated as regions of air trapping on CT imaging. CONCLUSION The 2D-3D PRIZE-2D acquisition allowed for 3D depiction of ventilation during a breath-hold, as well as detection of gas trapping. Imaging results were confirmed with spirometry, body plethysmography, and CT.
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Affiliation(s)
- James H Holmes
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA
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42
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Oxygen-sensitive 3He-MRI in bronchiolitis obliterans after lung transplantation. Eur Radiol 2007; 18:530-7. [PMID: 17926041 PMCID: PMC2755794 DOI: 10.1007/s00330-007-0778-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 07/31/2007] [Accepted: 08/27/2007] [Indexed: 10/27/2022]
Abstract
Oxygen-sensitive 3He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO2) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive 3He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, 3He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO2 in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (-1.75 mbar/s versus -0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive 3He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive 3He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients.
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43
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Fain SB, Korosec FR, Holmes JH, O'Halloran R, Sorkness RL, Grist TM. Functional lung imaging using hyperpolarized gas MRI. J Magn Reson Imaging 2007; 25:910-23. [PMID: 17410561 DOI: 10.1002/jmri.20876] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The noninvasive assessment of lung function using imaging is increasingly of interest for the study of lung diseases, including chronic obstructive pulmonary disease (COPD) and asthma. Hyperpolarized gas MRI (HP MRI) has demonstrated the ability to detect changes in ventilation, perfusion, and lung microstructure that appear to be associated with both normal lung development and disease progression. The physical characteristics of HP gases and their application to MRI are presented with an emphasis on current applications. Clinical investigations using HP MRI to study asthma, COPD, cystic fibrosis, pediatric chronic lung disease, and lung transplant are reviewed. Recent advances in polarization, pulse sequence development for imaging with Xe-129, and prototype low magnetic field systems dedicated to lung imaging are highlighted as areas of future development for this rapidly evolving technology.
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Affiliation(s)
- Sean B Fain
- Department of Medical Physics, University of Wisconsin, Madison, WI 53792, USA.
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44
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Cieślar K, Alsaid H, Stupar V, Gaillard S, Canet-Soulas E, Fissoune R, Crémillieux Y. Measurement of nonlinear pO2 decay in mouse lungs using 3He-MRI. NMR IN BIOMEDICINE 2007; 20:383-91. [PMID: 17451167 DOI: 10.1002/nbm.1124] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Spatial and temporal variations in oxygen partial pressure (pO(2)) during breath-hold can be exploited to obtain important regional parameters of lung function. In the course of apnea, the oxygen concentration is known to decay exponentially. Therefore, the initial pO(2) (p(0)) can be used to represent local ventilation, and the oxygen depletion time constant can characterize perfusion. The protocol, based on a nonlinear model of pO(2) decay, was validated in six healthy mice. Parametric maps of p(0) and oxygen depletion time constant were obtained for pure (3)He and (3)He/air mixture. The mean measured values of p(0) were 77 +/- 9 mbar for the pure (3)He insufflation and 107 +/- 5 mbar for (3)He/air mixture, in agreement with the predefined p(0) values: 75 +/- 15 mbar and 123 +/- 15 mbar, respectively. The mean measured oxygen depletion time constants were 6.5 +/- 0.2 s for pure (3)He and 7.1 +/- 0.8 s for the (3)He/air mixture, in agreement with physiology.
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45
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Cieślar K, Stupar V, Canet-Soulas E, Gaillard S, Crémillieux Y. Alveolar oxygen partial pressure and oxygen depletion rate mapping in rats using 3He ventilation imaging. Magn Reson Med 2007; 57:423-30. [PMID: 17152086 DOI: 10.1002/mrm.21110] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A hyperpolarized 3He ventilation imaging protocol was implemented to assess alveolar pO2 values and the oxygen depletion rate in rats. The imaging protocol, which is based on spiral k-space sampling, was designed to acquire a high signal-to-noise ratio (SNR) T1-weighted ventilation series of images in a single breath-hold. Simulations were performed to estimate the accuracy and dependence of the pO2 imaging protocol on the image SNR and the RF flip-angle determination. The imaging protocol was validated in vitro in phantoms and in vivo in rats. Imaging sessions were carried out for different inhaled O2 concentrations ranging from 20% to 40%. Parametric maps of alveolar pO2 and oxygen depletion rate were generated from the series of images. For each investigated animal, the differences in measured alveolar pO2 values are in agreement with the changes in inhaled O2 concentration. The oxygen depletion rates, ranging between 0.7 and 8.0 mbar s-1, are in close agreement with the published values for healthy rats.
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46
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Abdeen N, Cross A, Cron G, White S, Rand T, Miller D, Santyr G. Measurement of xenon diffusing capacity in the rat lung by hyperpolarized 129Xe MRI and dynamic spectroscopy in a single breath-hold. Magn Reson Med 2006; 56:255-64. [PMID: 16767751 DOI: 10.1002/mrm.20943] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We used the dual capability of hyperpolarized 129Xe for spectroscopy and imaging to develop new measures of xenon diffusing capacity in the rat lung that (analogously to the diffusing capacity of carbon monoxide or DLCO) are calculated as a product of total lung volume and gas transfer rate constants divided by the pressure gradient. Under conditions of known constant pressure breath-hold, the volume is measured by hyperpolarized 129Xe MRI, and the transfer rate is measured by dynamic spectroscopy. The new quantities (xenon diffusing capacity in lung parenchyma (DLXeLP)), xenon diffusing capacity in RBCs (DLXeRBC), and total lung xenon diffusing capacity (DLXe)) were measured in six normal rats and six rats with lung inflammation induced by instillation of fungal spores of Stachybotrys chartarum. DLXeLP, DLXeRBC, and DLXe were 56 +/- 10 ml/min/mmHg, 64 +/- 35 ml/min/mmHg, and 29 +/- 9 ml/min/mmHg, respectively, for normal rats, and 27 +/- 9 ml/min/mmHg, 42 +/- 27 ml/min/mmHg, and 16 +/- 7 ml/min/mmHg, respectively, for diseased rats. Lung volumes and gas transfer times for LP (TtrLP) were 16 +/- 2 ml and 22 +/- 3 ms, respectively, for normal rats and 12 +/- 2 ml and 35 +/- 8 ms, respectively, for diseased rats. Xenon diffusing capacities may be useful for measuring changes in gas exchange associated with inflammation and other lung diseases.
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Affiliation(s)
- Nishard Abdeen
- Department of Physics, Carleton University, Ottawa, Ontario, Canada.
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47
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Hopkins SR, Levin DL, Emami K, Kadlecek S, Yu J, Ishii M, Rizi RR. Advances in magnetic resonance imaging of lung physiology. J Appl Physiol (1985) 2006; 102:1244-54. [PMID: 17158249 DOI: 10.1152/japplphysiol.00738.2006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This review presents an overview of some recent magnetic resonance imaging (MRI) techniques for measuring aspects of local physiology in the lung. MRI is noninvasive, relatively high resolution, and does not expose subjects to ionizing radiation. Conventional MRI of the lung suffers from low signal intensity caused by the low proton density and the large degree of microscopic field inhomogeneity that degrades the magnetic resonance signal and interferes with image acquisition. However, in recent years, there have been rapid advances in both hardware and software design, allowing these difficulties to be minimized. This review focuses on some newer techniques that measure regional perfusion, ventilation, gas diffusion, ventilation-to-perfusion ratio, partial pressure of oxygen, and lung water. These techniques include contrast-enhanced and arterial spin-labeling techniques for measuring perfusion, hyperpolarized gas techniques for measuring regional ventilation, and apparent diffusion coefficient and multiecho and gradient echo techniques for measuring proton density and lung water. Some of the major advantages and disadvantages of each technique are discussed. In addition, some of the physiological issues associated with making measurements are discussed, along with strategies for understanding large and complex data sets.
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Affiliation(s)
- Susan R Hopkins
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA.
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48
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Chang YV, Conradi MS. Relaxation and diffusion of perfluorocarbon gas mixtures with oxygen for lung MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 181:191-8. [PMID: 16707266 DOI: 10.1016/j.jmr.2006.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/29/2006] [Accepted: 04/04/2006] [Indexed: 05/09/2023]
Abstract
We report measurements of free diffusivity D(0) and relaxation times T(1) and T(2) for pure C(2)F(6) and C(3)F(8) and their mixtures with oxygen. A simplified relaxation theory is presented and used to fit the data. The results enable spatially localized relaxation time measurements to determine the local gas concentration in lung MR images, so the free diffusivity D(0) is then known. Comparison of the measured diffusion to D(0) will express the extent of diffusion restriction and allow the local surface-to-volume ratio to be found.
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Affiliation(s)
- Yulin V Chang
- Department of Physics, Washington University, St. Louis, MO 63130, USA.
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49
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Hoffman EA, Simon BA, McLennan G. State of the Art. A structural and functional assessment of the lung via multidetector-row computed tomography: phenotyping chronic obstructive pulmonary disease. PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY 2006; 3:519-32. [PMID: 16921136 PMCID: PMC2647643 DOI: 10.1513/pats.200603-086ms] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 05/30/2006] [Indexed: 11/20/2022]
Abstract
With advances in multidetector-row computed tomography (MDCT), it is now possible to image the lung in 10 s or less and accurately extract the lungs, lobes, and airway tree to the fifth- through seventh-generation bronchi and to regionally characterize lung density, texture, ventilation, and perfusion. These methods are now being used to phenotype the lung in health and disease and to gain insights into the etiology of pathologic processes. This article outlines the application of these methodologies with specific emphasis on chronic obstructive pulmonary disease. We demonstrate the use of our methods for assessing regional ventilation and perfusion and demonstrate early data that show, in a sheep model, a regionally intact hypoxic pulmonary vasoconstrictor (HPV) response with an apparent inhibition of HPV regionally in the presence of inflammation. We present the hypothesis that, in subjects with pulmonary emphysema, one major contributing factor leading to parenchymal destruction is the lack of a regional blunting of HPV when the regional hypoxia is related to regional inflammatory events (bronchiolitis or alveolar flooding). If maintaining adequate blood flow to inflamed lung regions is critical to the nondestructive resolution of inflammatory events, the pathologic condition whereby HPV is sustained in regions of inflammation would likely have its greatest effect in the lung apices where blood flow is already reduced in the upright body posture.
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Affiliation(s)
- Eric A Hoffman
- Department of Radiology, University of Iowa, 200 Hawkins Drive, CC701 GH, Iowa City, 52242, USA.
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50
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Musch G, Venegas JG. Positron emission tomography imaging of regional pulmonary perfusion and ventilation. Ann Am Thorac Soc 2006; 2:522-7, 508-9. [PMID: 16352758 PMCID: PMC2713340 DOI: 10.1513/pats.200508-088ds] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Positron emission tomography (PET) imaging is a noninvasive, quantitative method to assess pulmonary perfusion and ventilation in vivo. The core of this article focuses on the use of [13N]nitrogen (13N2) and PET to assess regional gas exchange. Regional perfusion and shunt can be measured with the 13N2-saline bolus infusion technique. A bolus of 13N2, dissolved in saline solution, is injected intravenously at the start of a brief apnea, while the tracer kinetics in the lung is measured by a sequence of PET frames. Because of its low solubility in blood, virtually all 13N2 delivered to aerated lung regions diffuses into the alveolar airspace, where it accumulates in proportion to regional perfusion during the apnea. In contrast, lung regions that are perfused but are not aerated and do not exchange gas (i.e., "shunting" units) do not retain 13N2 during apnea and the tracer concentration drops after the initial peak. Accurate estimates of regional perfusion and regional shunt can be derived by applying a mathematical model to the pulmonary kinetics of a 13N2-saline bolus. When breathing is resumed, specific alveolar ventilation can be calculated from the tracer washout rate, because 13N2 is eliminated almost exclusively by ventilation. Because of the rapid elimination of the tracer, 13N2 infusion scans can be followed by 13N2 inhalation scans that allow determination of regional gas fraction. This article describes insights into the pathophysiology of acute lung injury, pulmonary embolism, and asthma that have been gained by PET imaging of regional gas exchange.
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Affiliation(s)
- Guido Musch
- Department of Anesthesia and Critical Care, CLN 309, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
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