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Álvarez MGM, Madhuranthakam AJ, Udayakumar D. Quantitative non-contrast perfusion MRI in the body using arterial spin labeling. MAGMA (NEW YORK, N.Y.) 2024:10.1007/s10334-024-01188-1. [PMID: 39105949 DOI: 10.1007/s10334-024-01188-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 05/10/2024] [Accepted: 07/02/2024] [Indexed: 08/07/2024]
Abstract
Arterial spin labeling (ASL) is a non-invasive magnetic resonance imaging (MRI) method that enables the assessment and the quantification of perfusion without the need for an exogenous contrast agent. ASL was originally developed in the early 1990s to measure cerebral blood flow. The utility of ASL has since then broadened to encompass various organ systems, offering insights into physiological and pathological states. In this review article, we present a synopsis of ASL for quantitative non-contrast perfusion MRI, as a contribution to the special issue titled "Quantitative MRI-how to make it work in the body?" The article begins with an introduction to ASL principles, followed by different labeling strategies, such as pulsed, continuous, pseudo-continuous, and velocity-selective approaches, and their role in perfusion quantification. We proceed to address the technical challenges associated with ASL in the body and outline some of the innovative approaches devised to surmount these issues. Subsequently, we summarize potential clinical applications, challenges, and state-of-the-art ASL methods to quantify perfusion in some of the highly perfused organs in the thorax (lungs), abdomen (kidneys, liver, pancreas), and pelvis (placenta) of the human body. The article concludes by discussing future directions for successful translation of quantitative ASL in body imaging.
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Affiliation(s)
| | - Ananth J Madhuranthakam
- Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Durga Udayakumar
- Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA.
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA.
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Triphan SMF, Bauman G, Konietzke P, Konietzke M, Wielpütz MO. Magnetic Resonance Imaging of Lung Perfusion. J Magn Reson Imaging 2024; 59:784-796. [PMID: 37466278 DOI: 10.1002/jmri.28912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 07/01/2023] [Accepted: 07/03/2023] [Indexed: 07/20/2023] Open
Abstract
"Lung perfusion" in the context of imaging conventionally refers to the delivery of blood to the pulmonary capillary bed through the pulmonary arteries originating from the right ventricle required for oxygenation. The most important physiological mechanism in the context of imaging is the so-called hypoxic pulmonary vasoconstriction (HPV, also known as "Euler-Liljestrand-Reflex"), which couples lung perfusion to lung ventilation. In obstructive airway diseases such as asthma, chronic-obstructive pulmonary disease (COPD), cystic fibrosis (CF), and asthma, HPV downregulates pulmonary perfusion in order to redistribute blood flow to functional lung areas in order to conserve optimal oxygenation. Imaging of lung perfusion can be seen as a reflection of lung ventilation in obstructive airway diseases. Other conditions that primarily affect lung perfusion are pulmonary vascular diseases, pulmonary hypertension, or (chronic) pulmonary embolism, which also lead to inhomogeneity in pulmonary capillary blood distribution. Several magnetic resonance imaging (MRI) techniques either dependent on exogenous contrast materials, exploiting periodical lung signal variations with cardiac action, or relying on intrinsic lung voxel attributes have been demonstrated to visualize lung perfusion. Additional post-processing may add temporal information and provide quantitative information related to blood flow. The most widely used and robust technique, dynamic-contrast enhanced MRI, is available in clinical routine assessment of COPD, CF, and pulmonary vascular disease. Non-contrast techniques are important research tools currently requiring clinical validation and cross-correlation in the absence of a viable standard of reference. First data on many of these techniques in the context of observational studies assessing therapy effects have just become available. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 5.
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Affiliation(s)
- Simon M F Triphan
- Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany
- Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany
- Department of Diagnostic and Interventional Radiology with Nuclear Medicine, Thoraxklinik at University Hospital Heidelberg, Heidelberg, Germany
| | - Grzegorz Bauman
- Division of Radiological Physics, Department of Radiology, University Hospital of Basel, Basel, Switzerland
- Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland
| | - Philip Konietzke
- Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany
- Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany
- Department of Diagnostic and Interventional Radiology with Nuclear Medicine, Thoraxklinik at University Hospital Heidelberg, Heidelberg, Germany
| | - Marilisa Konietzke
- Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany
- Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany
- Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riß, Germany
| | - Mark O Wielpütz
- Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany
- Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany
- Department of Diagnostic and Interventional Radiology with Nuclear Medicine, Thoraxklinik at University Hospital Heidelberg, Heidelberg, Germany
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O’Regan PW, Stevens NE, Logan N, Ryan DJ, Maher MM. Paediatric Thoracic Imaging in Cystic Fibrosis in the Era of Cystic Fibrosis Transmembrane Conductance Regulator Modulation. CHILDREN (BASEL, SWITZERLAND) 2024; 11:256. [PMID: 38397368 PMCID: PMC10888261 DOI: 10.3390/children11020256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/07/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024]
Abstract
Cystic fibrosis (CF) is one of the most common progressive life-shortening genetic conditions worldwide. Ground-breaking translational research has generated therapies that target the primary cystic fibrosis transmembrane conductance regulator (CFTR) defect, known as CFTR modulators. A crucial aspect of paediatric CF disease is the development and progression of irreversible respiratory disease in the absence of clinical symptoms. Accurate thoracic diagnostics have an important role to play in this regard. Chest radiographs are non-specific and insensitive in the context of subtle changes in early CF disease, with computed tomography (CT) providing increased sensitivity. Recent advancements in imaging hardware and software have allowed thoracic CTs to be acquired in paediatric patients at radiation doses approaching that of a chest radiograph. CFTR modulators slow the progression of CF, reduce the frequency of exacerbations and extend life expectancy. In conjunction with advances in CT imaging techniques, low-dose thorax CT will establish a central position in the routine care of children with CF. International guidelines regarding the choice of modality and timing of thoracic imaging in children with CF are lagging behind these rapid technological advances. The continued progress of personalised medicine in the form of CFTR modulators will promote the emergence of personalised radiological diagnostics.
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Affiliation(s)
- Patrick W. O’Regan
- Department of Radiology, Cork University Hospital, T12 DC4A Cork, Ireland
- Department of Radiology, School of Medicine, University College Cork, T12 AK54 Cork, Ireland
| | - Niamh E. Stevens
- Department of Surgery, Mercy University Hospital, T12 WE28 Cork, Ireland
| | - Niamh Logan
- Department of Medicine, Mercy University Hospital, T12 WE28 Cork, Ireland
| | - David J. Ryan
- Department of Radiology, Cork University Hospital, T12 DC4A Cork, Ireland
- Department of Radiology, School of Medicine, University College Cork, T12 AK54 Cork, Ireland
| | - Michael M. Maher
- Department of Radiology, Cork University Hospital, T12 DC4A Cork, Ireland
- Department of Radiology, School of Medicine, University College Cork, T12 AK54 Cork, Ireland
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Kay FU, Madhuranthakam AJ. MR Perfusion Imaging of the Lung. Magn Reson Imaging Clin N Am 2024; 32:111-123. [PMID: 38007274 DOI: 10.1016/j.mric.2023.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2023]
Abstract
Lung perfusion assessment is critical for diagnosing and monitoring a variety of respiratory conditions. MRI perfusion provides a radiation-free technique, making it an ideal choice for longitudinal imaging in younger populations. This review focuses on the techniques and applications of MRI perfusion, including contrast-enhanced (CE) MRI and non-CE methods such as arterial spin labeling (ASL), fourier decomposition (FD), and hyperpolarized 129-Xenon (129-Xe) MRI. ASL leverages endogenous water protons as tracers for a non-invasive measure of lung perfusion, while FD offers simultaneous measurements of lung perfusion and ventilation, enabling the generation of ventilation/perfusion mapsHyperpolarized 129-Xe MRI emerges as a novel tool for assessing regional gas exchange in the lungs. Despite the promise of MRI perfusion techniques, challenges persist, including competition with other imaging techniques and the need for additional validation and standardization. In conditions such as cystic fibrosis and lung cancer, MRI has displayed encouraging results, whereas in diseases like chronic obstructive pulmonary disease, further validation remains necessary. In conclusion, while MRI perfusion techniques hold immense potential for a comprehensive, non-invasive assessment of lung function and perfusion, their broader clinical adoption hinges on technological advancements, collaborative research, and rigorous validation.
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Affiliation(s)
- Fernando U Kay
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
| | - Ananth J Madhuranthakam
- Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA; Advanced Imaging Research Center, University of Texas Southwestern Medical Center, North Campus 2201 Inwood Road, Dallas, TX 75390-8568, USA
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Ohno Y, Ozawa Y, Nagata H, Ueda T, Yoshikawa T, Takenaka D, Koyama H. Lung Magnetic Resonance Imaging: Technical Advancements and Clinical Applications. Invest Radiol 2024; 59:38-52. [PMID: 37707840 DOI: 10.1097/rli.0000000000001017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
ABSTRACT Since lung magnetic resonance imaging (MRI) became clinically available, limited clinical utility has been suggested for applying MRI to lung diseases. Moreover, clinical applications of MRI for patients with lung diseases or thoracic oncology may vary from country to country due to clinical indications, type of health insurance, or number of MR units available. Because of this situation, members of the Fleischner Society and of the Japanese Society for Magnetic Resonance in Medicine have published new reports to provide appropriate clinical indications for lung MRI. This review article presents a brief history of lung MRI in terms of its technical aspects and major clinical indications, such as (1) what is currently available, (2) what is promising but requires further validation or evaluation, and (3) which developments warrant research-based evaluations in preclinical or patient studies. We hope this article will provide Investigative Radiology readers with further knowledge of the current status of lung MRI and will assist them with the application of appropriate protocols in routine clinical practice.
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Affiliation(s)
- Yoshiharu Ohno
- From the Department of Diagnostic Radiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan (Y. Ohno); Joint Research Laboratory of Advanced Medical Imaging, Fujita Health University School of Medicine, Toyoake, Aichi, Japan (Y. Ohno and H.N.); Department of Radiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan (Y. Ozawa and T.U.); Department of Diagnostic Radiology, Hyogo Cancer Center, Akashi, Hyogo, Japan (T.Y., D.T.); and Department of Radiology, Advanced Diagnostic Medical Imaging, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan (H.K.)
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Greer JS, Wang Y, Udayakumar D, Hussain T, Madhuranthakam AJ. On the application of pseudo-continuous arterial spin labeled MRI for pulmonary perfusion imaging. Magn Reson Imaging 2023; 104:80-87. [PMID: 37769882 DOI: 10.1016/j.mri.2023.09.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/21/2023] [Accepted: 09/25/2023] [Indexed: 10/03/2023]
Abstract
PURPOSE To evaluate different approaches for the effective assessment of pulmonary perfusion with a pseudo-continuous arterial spin labeled (pCASL) MRI. MATERIALS AND METHODS Four different approaches were evaluated: 1) Cardiac-triggered inferior vena cava (IVC) labeling; 2) IVC labeling with cardiac-triggered acquisition; 3) Right pulmonary artery (RPA) labeling with cardiac-triggered acquisition; and 4) Cardiac-triggered RPA labeling with background suppression (BGS). Each approach was evaluated in 5 healthy volunteers (n = 20) using coefficient of variation (COV) across averages. Approach 4 was also compared against a flow alternating inversion recovery (FAIR). RESULTS The IVC labeling (Approach 1) achieved perfusion-weighted images of both lungs, although this approach was more sensitive to variations in heart rate. Cardiac-triggered acquisitions using IVC (Approach 2) and RPA (Approach 3) labeling improved signal consistencies, but were incompatible with BGS. The cardiac-triggered RPA labeling with BGS (Approach 4) achieved a COV of 0.34 ± 0.03 (p < 0.05 compared to IVC labeling approaches) and resulted in perfusion value of 434 ± 64 mL/100 g/min, which was comparable to 451 ± 181 mL/100 g/min measured by FAIR (p = 0.82). DISCUSSION Pulmonary perfusion imaging using pCASL-MRI is highly sensitive to cardiac phase, and requires approaches to minimize flow-induced signal variations. Cardiac-triggered RPA labeling with BGS achieves reduced COV and enables robust pulmonary perfusion imaging.
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Affiliation(s)
- Joshua S Greer
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA; Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yiming Wang
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Durga Udayakumar
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA; Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Tarique Hussain
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA; Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Ananth J Madhuranthakam
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA; Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA.
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Kizhakke Puliyakote AS, Prisk GK, Elliott AR, Kim NH, Pazar B, Sá RC, Asadi AK, Hopkins SR. The spatial-temporal dynamics of pulmonary blood flow are altered in pulmonary arterial hypertension. J Appl Physiol (1985) 2023; 134:969-979. [PMID: 36861672 PMCID: PMC10085549 DOI: 10.1152/japplphysiol.00463.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 02/16/2023] [Accepted: 02/27/2023] [Indexed: 03/03/2023] Open
Abstract
Global fluctuation dispersion (FDglobal), a spatial-temporal metric derived from serial images of the pulmonary perfusion obtained with MRI-arterial spin labeling, describes temporal fluctuations in the spatial distribution of perfusion. In healthy subjects, FDglobal is increased by hyperoxia, hypoxia, and inhaled nitric oxide. We evaluated patients with pulmonary arterial hypertension (PAH, 4F, aged 47 ± 15, mean pulmonary artery pressure 48 ± 7 mmHg) and healthy controls (CON, 7F, aged 47 ± 12) to test the hypothesis that FDglobal is increased in PAH. Images were acquired at ∼4-5 s intervals during voluntary respiratory gating, inspected for quality, registered using a deformable registration algorithm, and normalized. Spatial relative dispersion (RD = SD/mean) and the percent of the lung image with no measurable perfusion signal (%NMP) were also assessed. FDglobal was significantly increased in PAH (PAH = 0.40 ± 0.17, CON = 0.17 ± 0.02, P = 0.006, a 135% increase) with no overlap in values between the two groups, consistent with altered vascular regulation. Both spatial RD and %NMP were also markedly greater in PAH vs. CON (PAH RD = 1.46 ± 0.24, CON = 0.90 ± 0.10, P = 0.0004; PAH NMP = 13.4 ± 6.1%; CON = 2.3 ± 1.4%, P = 0.001 respectively) consistent with vascular remodeling resulting in poorly perfused regions of lung and increased spatial heterogeneity. The difference in FDglobal between normal subjects and patients with PAH in this small cohort suggests that spatial-temporal imaging of perfusion may be useful in the evaluation of patients with PAH. Since this MR imaging technique uses no injected contrast agents and has no ionizing radiation it may be suitable for use in diverse patient populations.NEW & NOTEWORTHY Using proton MRI-arterial spin labeling to obtain serial images of pulmonary perfusion, we show that global fluctuation dispersion (FDglobal), a metric of temporal fluctuations in the spatial distribution of perfusion, was significantly increased in female patients with pulmonary arterial hypertension (PAH) compared with healthy controls. This potentially indicates pulmonary vascular dysregulation. Dynamic measures using proton MRI may provide new tools for evaluating individuals at risk of PAH or for monitoring therapy in patients with PAH.
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Affiliation(s)
- Abhilash S Kizhakke Puliyakote
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - G Kim Prisk
- Department of Radiology, University of California, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Ann R Elliott
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Nick H Kim
- Department of Medicine, University of California, San Diego, California, United States
| | - Beni Pazar
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - Rui Carlos Sá
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Medicine, University of California, San Diego, California, United States
| | - Amran K Asadi
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
| | - Susan R Hopkins
- Pulmonary Imaging Laboratory, UC San Diego Health Sciences, San Diego, California, United States
- Department of Radiology, University of California, San Diego, California, United States
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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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Qin Q, Alsop DC, Bolar DS, Hernandez‐Garcia L, Meakin J, Liu D, Nayak KS, Schmid S, van Osch MJP, Wong EC, Woods JG, Zaharchuk G, Zhao MY, Zun Z, Guo J. Velocity-selective arterial spin labeling perfusion MRI: A review of the state of the art and recommendations for clinical implementation. Magn Reson Med 2022; 88:1528-1547. [PMID: 35819184 PMCID: PMC9543181 DOI: 10.1002/mrm.29371] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 05/16/2022] [Accepted: 06/08/2022] [Indexed: 12/11/2022]
Abstract
This review article provides an overview of the current status of velocity-selective arterial spin labeling (VSASL) perfusion MRI and is part of a wider effort arising from the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group. Since publication of the 2015 consensus paper on arterial spin labeling (ASL) for cerebral perfusion imaging, important advancements have been made in the field. The ASL community has, therefore, decided to provide an extended perspective on various aspects of technical development and application. Because VSASL has the potential to become a principal ASL method because of its unique advantages over traditional approaches, an in-depth discussion was warranted. VSASL labels blood based on its velocity and creates a magnetic bolus immediately proximal to the microvasculature within the imaging volume. VSASL is, therefore, insensitive to transit delay effects, in contrast to spatially selective pulsed and (pseudo-) continuous ASL approaches. Recent technical developments have improved the robustness and the labeling efficiency of VSASL, making it a potentially more favorable ASL approach in a wide range of applications where transit delay effects are of concern. In this review article, we (1) describe the concepts and theoretical basis of VSASL; (2) describe different variants of VSASL and their implementation; (3) provide recommended parameters and practices for clinical adoption; (4) describe challenges in developing and implementing VSASL; and (5) describe its current applications. As VSASL continues to undergo rapid development, the focus of this review is to summarize the fundamental concepts of VSASL, describe existing VSASL techniques and applications, and provide recommendations to help the clinical community adopt VSASL.
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Affiliation(s)
- Qin Qin
- The Russell H. Morgan Department of Radiology and Radiological ScienceJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - David C. Alsop
- Department of RadiologyBeth Israel Deaconess Medical Center and Harvard Medical SchoolBostonMassachusettsUSA
| | - Divya S. Bolar
- Center for Functional Magnetic Resonance Imaging, Department of RadiologyUniversity of CaliforniaSan Diego La JollaCaliforniaUSA
| | | | - James Meakin
- Department of Radiology, Nuclear Medicine and AnatomyRadboud University Medical CenterNijmegenThe Netherlands
| | - Dapeng Liu
- The Russell H. Morgan Department of Radiology and Radiological ScienceJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Krishna S. Nayak
- Magnetic Resonance Engineering Laboratory, Ming Hsieh Department of Electrical EngineeringUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | - Sophie Schmid
- C.J. Gorter Center for high field MRI, Department of RadiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Matthias J. P. van Osch
- C.J. Gorter Center for high field MRI, Department of RadiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Eric C. Wong
- Center for Functional Magnetic Resonance Imaging, Department of RadiologyUniversity of CaliforniaSan Diego La JollaCaliforniaUSA
| | - Joseph G. Woods
- Center for Functional Magnetic Resonance Imaging, Department of RadiologyUniversity of CaliforniaSan Diego La JollaCaliforniaUSA
| | - Greg Zaharchuk
- Department of RadiologyStanford UniversityStanfordCaliforniaUSA
| | - Moss Y. Zhao
- Department of RadiologyStanford UniversityStanfordCaliforniaUSA
| | - Zungho Zun
- Department of RadiologyWeill Cornell MedicineNew YorkNew YorkUSA
| | - Jia Guo
- Department of BioengineeringUniversity of California RiversideRiversideCaliforniaUSA
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Buxton RB, Prisk GK, Hopkins SR. A novel nonlinear analysis of blood flow dynamics applied to the human lung. J Appl Physiol (1985) 2022; 132:1546-1559. [PMID: 35421317 DOI: 10.1152/japplphysiol.00715.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The spatial/temporal dynamics of blood flow in the human lung can be measured noninvasively with magnetic resonance imaging (MRI) using arterial spin labeling (ASL). We report a novel data analysis method using nonlinear prediction to identify dynamic interactions between blood flow units (image voxels), potentially providing a probe of underlying vascular control mechanisms. The approach first estimates the linear relationship (predictability) of one voxel time series with another using correlation analysis, and after removing the linear component estimates the nonlinear relationship with a numerical mutual information approach. Dimensionless global metrics for linear prediction (FL) and nonlinear prediction (FNL) represent the average amplitude of fluctuations in one voxel estimated by another voxel, as a percentage of the global average voxel flow. A proof-of-principle test of this approach analyzed experimental data from a study of high-altitude pulmonary edema (HAPE), providing two groups exhibiting known differences in vascular reactivity. Subjects were mountaineers divided into HAPE-susceptible (S, n=4) and HAPE-resistant (R, n=5) groups based on prior history at high altitude. Dynamic ASL measurements in the lung in normoxia (N, FIO2=0.21) and hypoxia (H, FIO2=0.13±0.01) were compared. The nonlinear prediction metric FNL decreased with hypoxia (7.4±1.3(N) vs. 6.3±0.7(H), P=0.03) and was significantly different between groups (7.4±1.2 (R) vs. 6.2±14.1 (S), P=0.03). This proof-of-principle test demonstrates that this nonlinear analysis approach applied to ASL data is sensitive to physiological effects even in small subject cohorts, and potentially can be used in a wide range of studies in health and disease in the lung and other organs.
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Affiliation(s)
| | | | - Susan Roberta Hopkins
- Department of Radiology, University of California San Diego.,Department of Medicine, University of California San Diego
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Magnetic resonance imaging of cystic fibrosis: Multi-organ imaging in the age of CFTR modulator therapies. J Cyst Fibros 2021; 21:e148-e157. [PMID: 34879996 DOI: 10.1016/j.jcf.2021.11.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 11/15/2021] [Accepted: 11/15/2021] [Indexed: 12/18/2022]
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Gabrielyan M, Tisdall MD, Kammer C, Higgins C, Arratia PE, Detre JA. A perfusion phantom for ASL MRI based on impinging jets. Magn Reson Med 2021; 86:1145-1158. [PMID: 33772869 DOI: 10.1002/mrm.28697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/21/2020] [Accepted: 01/05/2021] [Indexed: 11/07/2022]
Abstract
PURPOSE We present a novel perfusion phantom for validation of arterial spin labeled (ASL) perfusion MRI methods and protocols. METHODS Impinging jets, driven by a peristaltic pump, were used to achieve perfusion-like mixing of magnetically labeled inflowing fluid within a perfusion compartment. The phantom was validated by varying pump rates and obtaining ASL-MRI data at multiple postlabeling delays using a pseudo-continuous ASL sequence with a 3D stack-of-spirals readout. An additional data set was acquired using a pseudo-continuous ASL sequence with a 2D EPI readout. Phantom sensitivity to pseudo-continuous ASL labeling efficiency was also tested. RESULTS Fluid dynamics simulations predicted that maximum mixing would occur near the central axis of the perfusion compartment. Experimentally observed signal changes within this region were reproducible and well fit by the standard Buxton general kinetic model. Simulations and experimental data showed no label outflow from the perfusion chamber and calculated perfusion rates, averaged over the entire phantom volume, agreed with the expected volumetric flow rates provided by the flow pump. Phantom sensitivity to pseudo-continuous ASL labeling parameters was also demonstrated. CONCLUSION Perfusion-like signal can be simulated using impinging jets to create a well-mixed compartment. Observed perfusion and transit time values were reproducible and within the physiological range for brain perfusion. This phantom design has a broad range of potential applications in both basic and clinical research involving ASL MRI.
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Affiliation(s)
- Marianna Gabrielyan
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - M Dylan Tisdall
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Christoph Kammer
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Christopher Higgins
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Paulo E Arratia
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John A Detre
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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13
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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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14
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Hopkins SR, Sá RC, Prisk GK, Elliott AR, Kim NH, Pazar BJ, Printz BF, El-Said HG, Davis CK, Theilmann RJ. Abnormal pulmonary perfusion heterogeneity in patients with Fontan circulation and pulmonary arterial hypertension. J Physiol 2020; 599:343-356. [PMID: 33026102 DOI: 10.1113/jp280348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 10/06/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The distribution of pulmonary perfusion is affected by gravity, vascular branching structure and active regulatory mechanisms, which may be disrupted by cardiopulmonary disease, but this is not well studied, particularly in rare conditions. We evaluated pulmonary perfusion in patients who had undergone Fontan procedure, patients with pulmonary arterial hypertension (PAH) and two groups of controls using a proton magnetic resonance imaging technique, arterial spin labelling to measure perfusion. Heterogeneity was assessed by the relative dispersion (SD/mean) and gravitational gradients. Gravitational gradients were similar between all groups, but heterogeneity was significantly increased in both patient groups compared to controls and persisted after removing contributions from large blood vessels and gravitational gradients. Patients with Fontan physiology and patients with PAH have increased pulmonary perfusion heterogeneity that is not explainable by differences in mean perfusion, gravitational gradients, or large vessel anatomy. This probably reflects vascular remodelling in PAH and possibly in Fontan physiology. ABSTRACT Many factors affect the distribution of pulmonary perfusion, which may be disrupted by cardiopulmonary disease, but this is not well studied, particularly in rare conditions. An example is following the Fontan procedure, where pulmonary perfusion is passive, and heterogeneity may be increased because of the underlying pathophysiology leading to Fontan palliation, remodelling, or increased gravitational gradients from low flow. Another is pulmonary arterial hypertension (PAH), where gravitational gradients may be reduced secondary to high pressures, but remodelling may increase perfusion heterogeneity. We evaluated regional pulmonary perfusion in Fontan patients (n = 5), healthy young controls (Fontan control, n = 5), patients with PAH (n = 6) and healthy older controls (PAH control) using proton magnetic resonance imaging. Regional perfusion was measured using arterial spin labelling. Heterogeneity was assessed by the relative dispersion (SD/mean) and gravitational gradients. Mean perfusion was similar (Fontan = 2.50 ± 1.02 ml min-1 ml-1 ; Fontan control = 3.09 ± 0.58, PAH = 3.63 ± 1.95; PAH control = 3.98 ± 0.91, P = 0.26), and the slopes of gravitational gradients were not different (Fontan = -0.23 ± 0.09 ml min-1 ml-1 cm-1 ; Fontan control = -0.29 ± 0.23, PAH = -0.27 ± 0.09, PAH control = -0.25 ± 0.18, P = 0.91) between groups. Perfusion relative dispersion was greater in both Fontan and PAH than controls (Fontan = 1.46 ± 0.18; Fontan control = 0.99 ± 0.21, P = 0.005; PAH = 1.22 ± 0.27, PAH control = 0.91 ± 0.12, P = 0.02) but similar between patient groups (P = 0.13). These findings persisted after removing contributions from large blood vessels and gravitational gradients (all P < 0.05). We conclude that patients with Fontan physiology and PAH have increased pulmonary perfusion heterogeneity that is not explained by differences in mean perfusion, gravitational gradients, or large vessel anatomy. This probably reflects the effects of remodelling in PAH and possibly in Fontan physiology.
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Affiliation(s)
- Susan R Hopkins
- Department of Radiology, University of California, San Diego, CA, USA.,Department of Medicine, University of California, San Diego, CA, USA
| | - Rui C Sá
- Department of Medicine, University of California, San Diego, CA, USA
| | - G Kim Prisk
- Department of Radiology, University of California, San Diego, CA, USA.,Department of Medicine, University of California, San Diego, CA, USA
| | - Ann R Elliott
- Department of Medicine, University of California, San Diego, CA, USA
| | - Nick H Kim
- Department of Medicine, University of California, San Diego, CA, USA
| | - Beni J Pazar
- Department of Radiology, University of California, San Diego, CA, USA
| | - Beth F Printz
- Department of Radiology, University of California, San Diego, CA, USA.,Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
| | - Howaida G El-Said
- Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
| | - Christopher K Davis
- Rady Children's Hospital-San Diego, San Diego, CA, USA.,Department of Pediatrics, University of California, San Diego, CA, USA
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15
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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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16
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Seith F, Pohmann R, Schwartz M, Küstner T, Othman AE, Kolb M, Scheffler K, Nikolaou K, Schick F, Martirosian P. Imaging Pulmonary Blood Flow Using Pseudocontinuous Arterial Spin Labeling (PCASL) With Balanced Steady-State Free-Precession (bSSFP) Readout at 1.5T. J Magn Reson Imaging 2020; 52:1767-1782. [PMID: 32627293 DOI: 10.1002/jmri.27276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 06/13/2020] [Accepted: 06/15/2020] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Quantitative assessment of pulmonary blood flow and visualization of its temporal and spatial distribution without contrast media is of clinical significance. PURPOSE To assess the potential of electrocardiogram (ECG)-triggered pseudocontinuous arterial spin labeling (PCASL) imaging with balanced steady-state free-precession (bSSFP) readout to measure lung perfusion under free-breathing (FB) conditions and to study temporal and spatial characteristics of pulmonary blood flow. STUDY TYPE Prospective, observational. SUBJECTS Fourteen volunteers; three patients with pulmonary embolism. FIELD STRENGTH/SEQUENCES 1.5T, PCASL-bSSFP. ASSESSMENT The pulmonary trunk was labeled during systole. The following examinations were performed: 1) FB and timed breath-hold (TBH) examinations with a postlabeling delay (PLD) of 1000 msec, and 2) TBH examinations with multiple PLDs (100-1500 msec). Scan-rescan measurements were performed in four volunteers and one patient. Images were registered and the perfusion was evaluated in large vessels, small vessels, and parenchyma. Mean structural similarity indices (MSSIM) was computed and time-to-peak (TTP) of parenchymal perfusion in multiple PLDs was evaluated. Image quality reading was performed with three independent blinded readers. STATISTICAL TESTS Wilcoxon test to compare MSSIM, perfusion, and Likert scores. Spearman's correlation to correlate TTP and cardiac cycle duration. The repeatability coefficient (RC) and within-subject coefficient of variation (wCV) for scan-rescan measurements. Intraclass correlation coefficient (ICC) for interreader agreement. RESULTS Image registration resulted in a significant (P < 0.05) increase of MSSIM. FB perfusion values were 6% higher than TBH (3.28 ± 1.09 vs. 3.10 ± 0.99 mL/min/mL). TTP was highly correlated with individuals' cardiac cycle duration (Spearman = 0.89, P < 0.001). RC and wCV were better for TBH than FB (0.13-0.19 vs. 0.47-1.54 mL/min/mL; 6-7 vs. 19-60%). Image quality was rated very good, with ICCs 0.71-0.89. DATA CONCLUSION ECG-triggered PCASL-bSSFP imaging of the lung at 1.5T can provide very good image quality and quantitative perfusion maps even under FB. The course of labeled blood through the lung shows a strong dependence on the individuals' cardiac cycle duration. LEVEL OF EVIDENCE 2 TECHNICAL EFFICACY STAGE: 2 J. MAGN. RESON. IMAGING 2020;52:1767-1782.
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Affiliation(s)
- Ferdinand Seith
- Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
| | - Rolf Pohmann
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
| | - Martin Schwartz
- Section on Experimental Radiology, Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany.,Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany
| | - Thomas Küstner
- Section on Experimental Radiology, Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany.,Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany
| | - Ahmed E Othman
- Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
| | - Manuel Kolb
- Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
| | - Klaus Scheffler
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany.,Department for Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany
| | - Konstantin Nikolaou
- Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
| | - Fritz Schick
- Section on Experimental Radiology, Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
| | - Petros Martirosian
- Section on Experimental Radiology, Diagnostic and Interventional Radiology, University Department of Radiology, University Hospital of Tuebingen, Tuebingen, Germany
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Voskrebenzev A, Vogel-Claussen J. Proton MRI of the Lung: How to Tame Scarce Protons and Fast Signal Decay. J Magn Reson Imaging 2020; 53:1344-1357. [PMID: 32166832 DOI: 10.1002/jmri.27122] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/20/2020] [Accepted: 02/20/2020] [Indexed: 12/19/2022] Open
Abstract
Pulmonary proton MRI techniques offer the unique possibility of assessing lung function and structure without the requirement for hyperpolarization or dedicated hardware, which is mandatory for multinuclear acquisition. Five popular approaches are presented and discussed in this review: 1) oxygen enhanced (OE)-MRI; 2) arterial spin labeling (ASL); 3) Fourier decomposition (FD) MRI and other related methods including self-gated noncontrast-enhanced functional lung (SENCEFUL) MR and phase-resolved functional lung (PREFUL) imaging; 4) dynamic contrast-enhanced (DCE) MRI; and 5) ultrashort TE (UTE) MRI. While DCE MRI is the most established and well-studied perfusion measurement, FD MRI offers a free-breathing test without any contrast agent and is predestined for application in patients with renal failure or with low compliance. Additionally, FD MRI and related methods like PREFUL and SENCEFUL can act as an ionizing radiation-free V/Q scan, since ventilation and perfusion information is acquired simultaneously during one scan. For OE-MRI, different concentrations of oxygen are applied via a facemask to assess the regional change in T1 , which is caused by the paramagnetic property of oxygen. Since this change is governed by a combination of ventilation, diffusion, and perfusion, a compound functional measurement can be achieved with OE-MRI. The known problem of fast T2 * decay of the lung parenchyma leading to a low signal-to-noise ratio is bypassed by the UTE acquisition strategy. Computed tomography (CT)-like images allow the assessment of lung structure with high spatial resolution without ionizing radiation. Despite these different branches of proton MRI, common trends are evident among pulmonary proton MRI: 1) free-breathing acquisition with self-gating; 2) application of UTE to preserve a stronger parenchymal signal; and 3) transition from 2D to 3D acquisition. On that note, there is a visible convergence of the different methods and it is not difficult to imagine that future methods will combine different aspects of the presented methods.
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Affiliation(s)
- Andreas Voskrebenzev
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), Member of the German Lung Research Center (DZL), Hannover, Germany
| | - Jens Vogel-Claussen
- Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), Member of the German Lung Research Center (DZL), Hannover, Germany
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18
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Update on MR imaging of the pulmonary vasculature. Int J Cardiovasc Imaging 2019; 35:1483-1497. [PMID: 31030315 DOI: 10.1007/s10554-019-01603-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 04/11/2019] [Indexed: 01/01/2023]
Abstract
Magnetic resonance imaging (MRI) plays an increasingly important role in the non-invasive evaluation of the pulmonary vasculature. MR angiographic (MRA) techniques provide morphological information, while MR perfusion techniques provide functional information of the pulmonary vasculature. Contrast-enhanced MRA can be performed at high spatial resolution using 3D T1-weighted spoiled gradient echo sequence or at high temporal resolution using time-resolved techniques. Non-contrast MRA can be performed using 3D steady state free precession, double inversion fast spin echo, time of flight or phase contrast sequences. MR perfusion can be done using dynamic contrast-enhanced technique or using non-contrast techniques such as arterial spin labelling and time-resolved imaging of lungs during free breathing with Fourier decomposition analysis. MRI is used in the evaluation of acute and chronic pulmonary embolism, pulmonary hypertension and other vascular abnormalities, congenital anomalies and neoplasms. In this article, we review the different MR techniques used in the evaluation of pulmonary vasculature and its clinical applications.
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Non-contrast quantitative pulmonary perfusion using flow alternating inversion recovery at 3T: A preliminary study. Magn Reson Imaging 2017; 46:106-113. [PMID: 29154894 DOI: 10.1016/j.mri.2017.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 11/06/2017] [Accepted: 11/13/2017] [Indexed: 11/23/2022]
Abstract
PURPOSE To demonstrate the initial feasibility of non-contrast quantitative pulmonary perfusion imaging at 3T using flow alternating inversion recovery (FAIR), and to evaluate the intra-session and inter-session reliability of FAIR measurements at 3T. MATERIALS AND METHODS Nine healthy volunteers were imaged using our own implementation of FAIR pulse sequence at 3T. Quantitative FAIR perfusion, both with and without larger pulmonary vessels, was correlated with global phase contrast (PC) measured blood flow in the right pulmonary artery (RPA). The same volunteers were also imaged with SPECT perfusion using technetium-99m-macroaggregated albumin and relative dispersion (RD) was assessed between FAIR and SPECT perfusion. Four additional healthy volunteers were evaluated for FAIR repeatability, using intra-class correlation coefficient (ICC) and Bland-Altman analysis. p<0.05 was considered statistically significant. RESULTS FAIR perfusion across all subjects was 858±605mL/100g/min (with vessels) and 629±294mL/100g/min (without vessels) and correlated significantly with the PC measured blood flow in the RPA (r=0.62, p<0.01 with vessels; r=0.73, p<0.001 without vessels). The median RD of FAIR perfusion across all subjects was 0.73 (with vessels) and 0.49 (without vessels), compared against 0.23 with SPECT perfusion. The intra/inter-session ICC of FAIR perfusion with vessels was 0.95/0.59 and improved to 0.96/0.72, when vessels were removed. CONCLUSIONS Non-contrast quantitative pulmonary perfusion imaging using FAIR is feasible at 3T. This may serve as a reliable method to assess regional lung perfusion at 3T to characterize and monitor treatment response in chronic lung disease without the concerns of repeated exposure to ionizing radiation or the accumulation of exogenous contrast agent.
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20
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Sá RC, Henderson AC, Simonson T, Arai TJ, Wagner H, Theilmann RJ, Wagner PD, Prisk GK, Hopkins SR. Measurement of the distribution of ventilation-perfusion ratios in the human lung with proton MRI: comparison with the multiple inert-gas elimination technique. J Appl Physiol (1985) 2017; 123:136-146. [PMID: 28280105 DOI: 10.1152/japplphysiol.00804.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 02/23/2017] [Accepted: 03/07/2017] [Indexed: 11/22/2022] Open
Abstract
We have developed a novel functional proton magnetic resonance imaging (MRI) technique to measure regional ventilation-perfusion (V̇A/Q̇) ratio in the lung. We conducted a comparison study of this technique in healthy subjects (n = 7, age = 42 ± 16 yr, Forced expiratory volume in 1 s = 94% predicted), by comparing data measured using MRI to that obtained from the multiple inert gas elimination technique (MIGET). Regional ventilation measured in a sagittal lung slice using Specific Ventilation Imaging was combined with proton density measured using a fast gradient-echo sequence to calculate regional alveolar ventilation, registered with perfusion images acquired using arterial spin labeling, and divided on a voxel-by-voxel basis to obtain regional V̇A/Q̇ ratio. LogSDV̇ and LogSDQ̇, measures of heterogeneity derived from the standard deviation (log scale) of the ventilation and perfusion vs. V̇A/Q̇ ratio histograms respectively, were calculated. On a separate day, subjects underwent study with MIGET and LogSDV̇ and LogSDQ̇ were calculated from MIGET data using the 50-compartment model. MIGET LogSDV̇ and LogSDQ̇ were normal in all subjects. LogSDQ̇ was highly correlated between MRI and MIGET (R = 0.89, P = 0.007); the intercept was not significantly different from zero (-0.062, P = 0.65) and the slope did not significantly differ from identity (1.29, P = 0.34). MIGET and MRI measures of LogSDV̇ were well correlated (R = 0.83, P = 0.02); the intercept differed from zero (0.20, P = 0.04) and the slope deviated from the line of identity (0.52, P = 0.01). We conclude that in normal subjects, there is a reasonable agreement between MIGET measures of heterogeneity and those from proton MRI measured in a single slice of lung.NEW & NOTEWORTHY We report a comparison of a new proton MRI technique to measure regional V̇A/Q̇ ratio against the multiple inert gas elimination technique (MIGET). The study reports good relationships between measures of heterogeneity derived from MIGET and those derived from MRI. Although currently limited to a single slice acquisition, these data suggest that single sagittal slice measures of V̇A/Q̇ ratio provide an adequate means to assess heterogeneity in the normal lung.
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Affiliation(s)
- Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - A Cortney Henderson
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Tatum Simonson
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, California.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Harrieth Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Peter D Wagner
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - G Kim Prisk
- Department of Medicine, University of California, San Diego, La Jolla, California.,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, California; .,Department of Radiology, University of California, San Diego, La Jolla, California; and.,The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California
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Abstract
CLINICAL/METHODICAL ISSUE Separate assessment of respiratory mechanics, gas exchange and pulmonary circulation is essential for the diagnosis and therapy of pulmonary diseases. Due to the global character of the information obtained clinical lung function tests are often not sufficiently specific in the differential diagnosis or have a limited sensitivity in the detection of early pathological changes. STANDARD RADIOLOGICAL METHODS The standard procedures of pulmonary imaging are computed tomography (CT) for depiction of the morphology as well as perfusion/ventilation scintigraphy and single photon emission computed tomography (SPECT) for functional assessment. METHODICAL INNOVATIONS Magnetic resonance imaging (MRI) with hyperpolarized gases, O2-enhanced MRI, MRI with fluorinated gases and Fourier decomposition MRI (FD-MRI) are available for assessment of pulmonary ventilation. For assessment of pulmonary perfusion dynamic contrast-enhanced MRI (DCE-MRI), arterial spin labeling (ASL) and FD-MRI can be used. PERFORMANCE Imaging provides a more precise insight into the pathophysiology of pulmonary function on a regional level. The advantages of MRI are a lack of ionizing radiation, which allows a protective acquisition of dynamic data as well as the high number of available contrasts and therefore accessible lung function parameters. ACHIEVEMENTS Sufficient clinical data exist only for certain applications of DCE-MRI. For the other techniques, only feasibility studies and case series of different sizes are available. The clinical applicability of hyperpolarized gases is limited for technical reasons. PRACTICAL RECOMMENDATIONS The clinical application of the techniques described, except for DCE-MRI, should be restricted to scientific studies.
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Affiliation(s)
- G Sommer
- Klinik für Radiologie und Nuklearmedizin, Universitätsspital Basel, Petersgraben 4, 4031, Basel, Schweiz.
| | - G Bauman
- Klinik für Radiologie und Nuklearmedizin - Radiologische Physik, Universitätsspital Basel, Petersgraben 4, 4031, Basel, Schweiz
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22
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Arai TJ, Theilmann RJ, Sá RC, Villongco MT, Hopkins SR. The effect of lung deformation on the spatial distribution of pulmonary blood flow. J Physiol 2016; 594:6333-6347. [PMID: 27273807 PMCID: PMC5088230 DOI: 10.1113/jp272030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/31/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes. The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution. Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. ABSTRACT Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P = 0.10). The greatest expansion was seen in the dependent region (P < 0.0001: dependent vs non-dependent, P < 0.0001: dependent vs middle) and RLL (P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = -0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = -0.058(0.126), +1 litre = -0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500 ml = -0.075(0.152), +1 litre = -0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] (P = 0.01). However, there was no significant lobar redistribution (P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung.
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Affiliation(s)
- Tatsuya J Arai
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
- Department of Radiology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Rebecca J Theilmann
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Rui Carlos Sá
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Michael T Villongco
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA
| | - Susan R Hopkins
- Department of Medicine, University of California, San Diego, La Jolla, CA, USA.
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA.
- The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, CA, USA.
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Yazdani M, Lau CT, Lempel JK, Yadav R, El-Sherief AH, Azok JT, Renapurkar RD. Historical Evolution of Imaging Techniques for the Evaluation of Pulmonary Embolism. Radiographics 2016; 35:1245-62. [PMID: 26172362 DOI: 10.1148/rg.2015140280] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
As we celebrate the 100th anniversary of the founding of the Radiological Society of North America (RSNA), it seems fitting to look back at the major accomplishments of the radiology community in the diagnosis of pulmonary embolism. Few diseases have so consistently captured the attention of the medical community. Since the first description of pulmonary embolism by Virchow in the 1850s, clinicians have struggled to reach a timely diagnosis of this common condition because of its nonspecific and often confusing clinical picture. As imaging tests started to gain importance in the 1900s, the approach to diagnosing pulmonary embolism also began to change. Rapid improvements in angiography, ventilation-perfusion imaging, and cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging have constantly forced health care professionals to rethink how they diagnose pulmonary embolism. Needless to say, the way pulmonary embolism is diagnosed today is distinctly different from how it was diagnosed in Virchow's era; and imaging, particularly CT, now forms the cornerstone of diagnostic evaluation. Currently, radiology offers a variety of tests that are fast and accurate and can provide anatomic and functional information, thus allowing early diagnosis and triage of cases. This review provides a historical journey into the evolution of these imaging tests and highlights some of the major breakthroughs achieved by the radiology community and RSNA in this process. Also highlighted are areas of ongoing research and development in this field of imaging as radiologists seek to combat some of the newer challenges faced by modern medicine, such as rising health care costs and radiation dose hazards.
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Affiliation(s)
- Milad Yazdani
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Charles T Lau
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Jason K Lempel
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Ruchi Yadav
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Ahmed H El-Sherief
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Joseph T Azok
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
| | - Rahul D Renapurkar
- From the Sections of Thoracic Imaging (M.Y., C.T.L., J.K.L., R.Y., A.H.E., J.T.Z., R.D.R.) and Nuclear Medicine (R.Y., R.D.R.), Imaging Institute, Thoracic Imaging L10, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195
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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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25
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Donnola SB, Dasenbrook EC, Weaver D, Lu L, Gupta K, Prabhakaran A, Yu X, Chmiel JF, McBennett K, Konstan MW, Drumm ML, Flask CA. Preliminary comparison of normalized T1 and non-contrast perfusion MRI assessments of regional lung disease in cystic fibrosis patients. J Cyst Fibros 2015; 16:283-290. [PMID: 26719281 DOI: 10.1016/j.jcf.2015.11.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/19/2015] [Accepted: 11/23/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Previous studies have shown that Magnetic Resonance Imaging (MRI) techniques can be used to non-invasively assess lung disease in CF patients. In this study, we compare the sensitivity of normalized T1 (nT1) and non-contrast perfusion MRI techniques to detect regional lung disease in CF patients. MATERIALS AND METHODS MRI data were obtained for eight adult CF patients without overt pulmonary exacerbation (FEV1=45-127%) and six healthy volunteers on a Siemens Espree 1.5T MRI scanner. Sagittal nT1 and perfusion data were acquired for each subject's left and right lungs. A region-of-interest analysis was used to calculate mean nT1 and perfusion values in the individual lobes of the left and right lungs for each subject. RESULTS In comparison to healthy controls, CF subjects showed a significant decrease in nT1 values in the upper lobe of the left lung as well as in the upper and anterior lobes of the right lung (p<0.001). Similar nT1 differences were observed with in the CF cohort in comparison to their respective posterior lobes (p<0.001). Pulmonary perfusion for the CF subjects was also significantly reduced in the upper lobe of the right lung (p<0.05). Significant correlations with spirometry were also observed for both nT1 (left upper lobe: p<0.01) and perfusion (left and right upper lobes (p≤0.05)). Additionally, significant correlations were observed between nT1 and perfusion in the upper lobes of the left (p=0.05) and right lungs (p=0.005). CONCLUSIONS This pilot study confirms that both the nT1 and non-contrast perfusion MRI techniques can sensitively detect regional lung changes in patients with CF. While both imaging methods were able to detect regional lung disease, the additional nT1 reductions in the CF patients suggests that nT1 may be more sensitive to regional CF lung disease.
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Affiliation(s)
- Shannon B Donnola
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA
| | - Elliott C Dasenbrook
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Department of Medicine, Case Western Reserve University, Cleveland, OH, USA; Rainbow Babies and Children's Hospital, Cleveland, OH, USA
| | - David Weaver
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Rainbow Babies and Children's Hospital, Cleveland, OH, USA
| | - Lan Lu
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA; Department of Urology, Case Western Reserve University, Cleveland, OH, USA
| | - Karishma Gupta
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA
| | | | - Xin Yu
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA; Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | - James F Chmiel
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Rainbow Babies and Children's Hospital, Cleveland, OH, USA
| | - Kimberly McBennett
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Department of Medicine, Case Western Reserve University, Cleveland, OH, USA; Rainbow Babies and Children's Hospital, Cleveland, OH, USA
| | - Michael W Konstan
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Rainbow Babies and Children's Hospital, Cleveland, OH, USA
| | - Mitchell L Drumm
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Department of Genetics, Case Western Reserve University, Cleveland, OH, USA
| | - Chris A Flask
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA; Department of Pediatrics, Case Western Reserve University, Cleveland, OH, USA; Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
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26
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Walker SC, Asadi AK, Hopkins SR, Buxton RB, Prisk GK. A statistical clustering approach to discriminating perfusion from conduit vessel signal contributions in a pulmonary ASL MR image. NMR IN BIOMEDICINE 2015; 28:1117-1124. [PMID: 26182890 PMCID: PMC4537803 DOI: 10.1002/nbm.3358] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 05/17/2015] [Accepted: 06/14/2015] [Indexed: 06/04/2023]
Abstract
The measurement of pulmonary perfusion (blood delivered to the capillary bed within a voxel) using arterial spin labeling (ASL) magnetic resonance imaging is often complicated by signal artifacts from conduit vessels that carry blood destined for voxels at a distant location in the lung. One approach to dealing with conduit vessel contributions involves the application of an absolute threshold on the ASL signal. While useful for identifying a subset of the most dominant high signal conduit image features, signal thresholding cannot discriminate between perfusion and conduit vessel contributions at intermediate and low signal. As an alternative, this article discusses a data-driven statistical approach based on statistical clustering for characterizing and discriminating between capillary perfusion and conduit vessel contributions over the full signal spectrum. An ASL flow image is constructed from the difference between a pair of tagged magnetic resonance images. However, when viewed as a bivariate projection that treats the image pair as independent measures (rather than the univariate quantity that results from the subtraction of the two images), the signal associated with capillary perfusion contributions is observed to cluster independently of the signal associated with conduit vessel contributions. Analyzing the observed clusters using a Gaussian mixture model makes it possible to discriminate between conduit vessel and capillary-perfusion-dominated signal contributions over the full signal spectrum of the ASL image. As a demonstration of feasibility, this study compares the proposed clustering approach with the standard absolute signal threshold strategy in a small number of test images.
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Affiliation(s)
| | - Amran K. Asadi
- Department of Medicine, University of California, San Diego
| | - Susan R. Hopkins
- Department of Medicine, University of California, San Diego
- Department of Radiology, University of California, San Diego
| | | | - G. Kim Prisk
- Department of Medicine, University of California, San Diego
- Department of Radiology, University of California, San Diego
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27
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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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28
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Miller GW, Mugler JP, Sá RC, Altes TA, Prisk GK, Hopkins SR. Advances in functional and structural imaging of the human lung using proton MRI. NMR IN BIOMEDICINE 2014; 27:1542-56. [PMID: 24990096 PMCID: PMC4515033 DOI: 10.1002/nbm.3156] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/30/2014] [Accepted: 06/01/2014] [Indexed: 05/05/2023]
Abstract
The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and oxygen-enhanced imaging techniques to quantify regional perfusion and ventilation, respectively, in standard units of measurement. By combining these techniques into a single scan, it is also possible to quantify the local ventilation-perfusion ratio, which is the most important determinant of gas-exchange efficiency in the lung. To demonstrate potential for accurate and meaningful measurements of lung function, this technique was used to study gravitational gradients of ventilation, perfusion, and ventilation-perfusion ratio in healthy subjects, yielding quantitative results consistent with expected regional variations. Such techniques can also be applied in the time domain, providing new tools for studying temporal dynamics of lung function. Temporal ASL measurements showed increased spatial-temporal heterogeneity of pulmonary blood flow in healthy subjects exposed to hypoxia, suggesting sensitivity to active control mechanisms such as hypoxic pulmonary vasoconstriction, and illustrating that to fully examine the factors that govern lung function it is necessary to consider temporal as well as spatial variability. Further development to increase spatial coverage and improve robustness would enhance the clinical applicability of these new functional imaging tools. In the realm of structural imaging, pulse sequence techniques such as ultrashort echo-time radial k-space acquisition, ultrafast steady-state free precession, and imaging-based diaphragm triggering can be combined to overcome the significant challenges associated with proton MRI in the lung, enabling high-quality three-dimensional imaging of the whole lung in a clinically reasonable scan time. Images of healthy and cystic fibrosis subjects using these techniques demonstrate substantial promise for non-contrast pulmonary angiography and detailed depiction of airway disease. Although there is opportunity for further optimization, such approaches to structural lung imaging are ready for clinical testing.
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Affiliation(s)
- G. Wilson Miller
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
- Address correspondence to: Wilson Miller, Radiology Research, 480 Ray C. Hunt Dr., Box 801339, Charlottesville, VA 22908, Phone: 434-243-9216, Fax: 434-924-9435,
| | - John P. Mugler
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
- Department of Biomedical Engineering University of Virginia Charlottesville, VA
| | - Rui C. Sá
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
| | - Talissa A. Altes
- Center for In-Vivo Hyperpolarized Gas MRI, Department of Radiology & Medical Imaging
| | - G. Kim Prisk
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
| | - Susan R. Hopkins
- Department of Medicine, Pulmonary Imaging Laboratory, University of California, San Diego La Jolla, CA
- Department of Radiology, University of California, San Diego La Jolla, CA
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29
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Gao Y, Goodnough CL, Erokwu BO, Farr GW, Darrah R, Lu L, Dell KM, Yu X, Flask CA. Arterial spin labeling-fast imaging with steady-state free precession (ASL-FISP): a rapid and quantitative perfusion technique for high-field MRI. NMR IN BIOMEDICINE 2014; 27:996-1004. [PMID: 24891124 PMCID: PMC4110188 DOI: 10.1002/nbm.3143] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/28/2014] [Accepted: 04/30/2014] [Indexed: 05/03/2023]
Abstract
Arterial spin labeling (ASL) is a valuable non-contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either echo-planar imaging (EPI) or true fast imaging with steady-state free precession (true FISP) readouts, which are prone to off-resonance artifacts on high-field MRI scanners. We have developed a rapid ASL-FISP MRI acquisition for high-field preclinical MRI scanners providing perfusion-weighted images with little or no artifacts in less than 2 s. In this initial implementation, a flow-sensitive alternating inversion recovery (FAIR) ASL preparation was combined with a rapid, centrically encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 and 9.4 T (249 ± 38 and 241 ± 17 mL/min/100 g, respectively). The utility of this method was further demonstrated in the detection of significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL-FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high-field MRI scanners with minimal image artifacts.
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Affiliation(s)
- Ying Gao
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Candida L. Goodnough
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | | | - George W. Farr
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
- Aeromics, LLC, Cleveland, OH 44106
| | - Rebecca Darrah
- Frances Payne Bolton School of Nursing, Case Western Reserve University, Cleveland, OH 44106
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH 44106
| | - Lan Lu
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Urology, Case Western Reserve University, Cleveland, OH 44106
| | - Katherine M. Dell
- CWRU Center for the Study of Kidney Disease and Biology, MetroHealth Campus, Case Western Reserve University, Cleveland, OH 44109
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
| | - Xin Yu
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | - Chris A. Flask
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
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30
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Hall ET, Sá RC, Holverda S, Arai TJ, Dubowitz DJ, Theilmann RJ, Prisk GK, Hopkins SR. The effect of supine exercise on the distribution of regional pulmonary blood flow measured using proton MRI. J Appl Physiol (1985) 2013; 116:451-61. [PMID: 24356515 DOI: 10.1152/japplphysiol.00659.2013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Zone model of pulmonary perfusion predicts that exercise reduces perfusion heterogeneity because increased vascular pressure redistributes flow to gravitationally nondependent lung, and causes dilation and recruitment of blood vessels. However, during exercise in animals, perfusion heterogeneity as measured by the relative dispersion (RD, SD/mean) is not significantly decreased. We evaluated the effect of exercise on pulmonary perfusion in six healthy supine humans using magnetic resonance imaging (MRI). Data were acquired at rest, while exercising (∼27% of maximal oxygen consumption) using a MRI-compatible ergometer, and in recovery. Images were acquired in most of the right lung in the sagittal plane at functional residual capacity, using a 1.5-T MR scanner equipped with a torso coil. Perfusion was measured using arterial spin labeling (ASL-FAIRER) and regional proton density using a fast multiecho gradient-echo sequence. Perfusion images were corrected for coil-based signal heterogeneity, large conduit vessels removed and quantified (in ml·min(-1)·ml(-1)) (perfusion), and also normalized for density and quantified (in ml·min(-1)·g(-1)) (density-normalized perfusion, DNP) accounting for tissue redistribution. DNP increased during exercise (11.1 ± 3.5 rest, 18.8 ± 2.3 exercise, 13.2 ± 2.2 recovery, ml·min(-1)·g(-1), P < 0.0001), and the increase was largest in nondependent lung (110 ± 61% increase in nondependent, 63 ± 35% in mid, 70 ± 33% in dependent, P < 0.005). The RD of perfusion decreased with exercise (0.93 ± 0.21 rest, 0.73 ± 0.13 exercise, 0.94 ± 0.18 recovery, P < 0.005). The RD of DNP showed a similar trend (0.82 ± 0.14 rest, 0.75 ± 0.09 exercise, 0.81 ± 0.10 recovery, P = 0.13). In conclusion, in contrast to animal studies, in supine humans, mild exercise decreased perfusion heterogeneity, consistent with Zone model predictions.
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Affiliation(s)
- E T Hall
- Department of Medicine, University of California, San Diego, La Jolla, California
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31
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Liszewski MC, Hersman FW, Altes TA, Ohno Y, Ciet P, Warfield SK, Lee EY. Magnetic resonance imaging of pediatric lung parenchyma, airways, vasculature, ventilation, and perfusion: state of the art. Radiol Clin North Am 2013; 51:555-82. [PMID: 23830786 DOI: 10.1016/j.rcl.2013.04.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Magnetic resonance (MR) imaging is a noninvasive imaging modality, particularly attractive for pediatric patients given its lack of ionizing radiation. Despite many advantages, the physical properties of the lung (inherent low signal-to-noise ratio, magnetic susceptibility differences at lung-air interfaces, and respiratory and cardiac motion) have posed technical challenges that have limited the use of MR imaging in the evaluation of thoracic disease in the past. However, recent advances in MR imaging techniques have overcome many of these challenges. This article discusses these advances in MR imaging techniques and their potential role in the evaluation of thoracic disorders in pediatric patients.
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Affiliation(s)
- Mark C Liszewski
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, 330 Longwood Avenue, Boston, MA 02115, USA
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32
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Sommer G, Bauman G, Koenigkam-Santos M, Draenkow C, Heussel CP, Kauczor HU, Schlemmer HP, Puderbach M. Non-contrast-enhanced preoperative assessment of lung perfusion in patients with non-small-cell lung cancer using Fourier decomposition magnetic resonance imaging. Eur J Radiol 2013; 82:e879-87. [PMID: 24041434 DOI: 10.1016/j.ejrad.2013.06.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 06/12/2013] [Accepted: 06/17/2013] [Indexed: 12/23/2022]
Abstract
OBJECTIVE To investigate non-contrast-enhanced Fourier decomposition MRI (FD MRI) for assessment of regional lung perfusion in patients with Non-Small-Cell Lung Cancer (NSCLC) in comparison to dynamic contrast-enhanced MRI (DCE MRI). METHODS Time-resolved non-contrast-enhanced images of the lungs were acquired prospectively in 15 patients using a 2D balanced steady-state free precession (b-SSFP) sequence. After non-rigid registration of the native image data, perfusion-weighted images were calculated by separating periodic changes of lung proton density at the cardiac frequency using FD. DCE MRI subtraction datasets were acquired as standard of reference. Both datasets were analyzed visually for perfusion defects. Then segmentation analyses were performed to describe perfusion of pulmonary lobes semi-quantitatively as percentages of total lung perfusion. Overall FD MRI perfusion signal was compared to velocity-encoded flow measurements in the pulmonary trunk as an additional fully quantitative reference. RESULTS Image quality ratings of FD MRI were significantly inferior to those of DCE MRI (P<0.0001). Sensitivity, specificity, and accuracy of FD MRI for visual detection of perfusion defects were 84%, 92%, and 91%. Semi-quantitative evaluation of lobar perfusion provided high agreement between FD MRI and DCE MRI for both entire lungs and upper lobes, but less agreement in the lower parts of both lungs. FD perfusion signal showed high linear correlation with pulmonary arterial blood flow. CONCLUSION FD MRI is a promising technique that allows for assessing regional lung perfusion in NSCLC patients without contrast media or ionizing radiation. However, for being applied in clinical routine, image quality and robustness of the technique need to be further improved.
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Affiliation(s)
- Gregor Sommer
- Department of Radiology (E010), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Translational Lung Research Center Heidelberg (TLRC-H), Member of the German Center for Lung Research, Heidelberg, Germany; Clinic of Radiology and Nuclear Medicine, University of Basel Hospital, Petersgraben 4, 4031 Basel, Switzerland.
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33
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Henderson AC, Sá RC, Theilmann RJ, Buxton RB, Prisk GK, Hopkins SR. The gravitational distribution of ventilation-perfusion ratio is more uniform in prone than supine posture in the normal human lung. J Appl Physiol (1985) 2013; 115:313-24. [PMID: 23620488 DOI: 10.1152/japplphysiol.01531.2012] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The gravitational gradient of intrapleural pressure is suggested to be less in prone posture than supine. Thus the gravitational distribution of ventilation is expected to be more uniform prone, potentially affecting regional ventilation-perfusion (Va/Q) ratio. Using a novel functional lung magnetic resonance imaging technique to measure regional Va/Q ratio, the gravitational gradients in proton density, ventilation, perfusion, and Va/Q ratio were measured in prone and supine posture. Data were acquired in seven healthy subjects in a single sagittal slice of the right lung at functional residual capacity. Regional specific ventilation images quantified using specific ventilation imaging and proton density images obtained using a fast gradient-echo sequence were registered and smoothed to calculate regional alveolar ventilation. Perfusion was measured using arterial spin labeling. Ventilation (ml·min(-1)·ml(-1)) images were combined on a voxel-by-voxel basis with smoothed perfusion (ml·min(-1)·ml(-1)) images to obtain regional Va/Q ratio. Data were averaged for voxels within 1-cm gravitational planes, starting from the most gravitationally dependent lung. The slope of the relationship between alveolar ventilation and vertical height was less prone than supine (-0.17 ± 0.10 ml·min(-1)·ml(-1)·cm(-1) supine, -0.040 ± 0.03 prone ml·min(-1)·ml(-1)·cm(-1), P = 0.02) as was the slope of the perfusion-height relationship (-0.14 ± 0.05 ml·min(-1)·ml(-1)·cm(-1) supine, -0.08 ± 0.09 prone ml·min(-1)·ml(-1)·cm(-1), P = 0.02). There was a significant gravitational gradient in Va/Q ratio in both postures (P < 0.05) that was less in prone (0.09 ± 0.08 cm(-1) supine, 0.04 ± 0.03 cm(-1) prone, P = 0.04). The gravitational gradients in ventilation, perfusion, and regional Va/Q ratio were greater supine than prone, suggesting an interplay between thoracic cavity configuration, airway and vascular tree anatomy, and the effects of gravity on Va/Q matching.
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Affiliation(s)
- A Cortney Henderson
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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Johnson KM, Fain SB, Schiebler ML, Nagle S. Optimized 3D ultrashort echo time pulmonary MRI. Magn Reson Med 2012; 70:1241-50. [PMID: 23213020 DOI: 10.1002/mrm.24570] [Citation(s) in RCA: 234] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 10/09/2012] [Accepted: 10/27/2012] [Indexed: 12/17/2022]
Abstract
PURPOSE To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging. METHODS 3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phantom studies. Their effects on lung and airway visualization in five healthy male human subjects (mean age 32 years) were compared qualitatively through blinded ordinal scoring by two cardiothoracic radiologists using a nonparametric Friedman test (P < 0.05). Relative signal difference between endobronchial air and adjacent lung tissue, normalized to nearby vessel, was used as a surrogate for lung tissue signal. Quantitative measures were compared using the paired Student's t-test (P < 0.05). Finally, clinical feasibility was investigated in a patient with interstitial fibrosis. RESULTS Simulation and phantom studies showed up to 67% improvement in SNR and reduced blurring for short T2* species using all three optimizations. In vivo images showed decreased artifacts and improved lung tissue and airway visualization both qualitatively and quantitatively. CONCLUSION The use of limited field-of-view excitation, variable readout gradients, and radial oversampling significantly improve the technical quality of 3D radial ultrashort echo time lung images.
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Affiliation(s)
- Kevin M Johnson
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
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Bauman G, Eichinger M. Ventilation and perfusion magnetic resonance imaging of the lung. Pol J Radiol 2012; 77:37-46. [PMID: 22802864 PMCID: PMC3389953 DOI: 10.12659/pjr.882579] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 01/19/2012] [Indexed: 02/02/2023] Open
Abstract
A close interaction between the respiratory pump, pulmonary parenchyma and blood circulation is essential for a normal lung function. Many pulmonary diseases present, especially in their initial phase, a variable regional impairment of ventilation and perfusion. In the last decades various techniques have been established to measure the lung function. Besides the global pulmonary function tests (PFTs) imaging techniques gained increasing importance to detect local variations in lung function, especially for ventilation and perfusion assessment. Imaging modalities allow for a deeper regional insight into pathophysiological processes and enable improved planning of invasive procedures. In contrast to computed tomography (CT) and the nuclear medicine techniques, magnetic resonance imaging (MRI), as a radiation free imaging modality gained increasing importance since the early 1990 for the assessment of pulmonary function. The major inherent problems of lung tissue, namely the low proton density and the pulmonary and cardiac motion, were overcome in the last years by a constant progress in MR technology. Some MR techniques are still under development, a process which is driven by scientific questions regarding the physiology and pathophysiology of pulmonary diseases, as well as by the need for fast and robust clinically applicable imaging techniques as safe therapy monitoring tools. MRI can be considered a promising ionizing-free alternative to techniques like CT or nuclear medicine techniques for the evaluation of lung function. The goal of this article is to provide an overview on selected MRI techniques for the assessment of pulmonary ventilation and perfusion.
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Affiliation(s)
- Grzegorz Bauman
- German Cancer Research Center, Department of Medical Physics in Radiology, Heidelberg, Germany
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Wheaton AJ, Miyazaki M. Non-contrast enhanced MR angiography: Physical principles. J Magn Reson Imaging 2012; 36:286-304. [DOI: 10.1002/jmri.23641] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Gaass T, Dinkel J, Bauman G, Zaiss M, Hintze C, Haase A, Laun F. Non-contrast-enhanced MRI of the pulmonary blood volume using two-compartment-modeled T1-relaxation. J Magn Reson Imaging 2012; 36:397-404. [DOI: 10.1002/jmri.23674] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 03/09/2012] [Indexed: 11/10/2022] Open
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Abstract
Pulmonary magnetic resonance (MR) imaging has been put forward as a new research and diagnostic tool mainly to overcome the limitations of computed tomography and nuclear medicine studies. However, pulmonary MR imaging has been difficult to use because of inherently low proton density, a multitude of air-tissue interfaces, which create significant magnetic field distortions and are commonly referred to as susceptibility artifacts; diminishing signal in the lung; and respiratory and/or cardiac motion artifacts. To overcome these drawbacks of pulmonary MR imaging, technical advances made during the last decade in sequencing, scanner and coil, adaptation of parallel imaging techniques, and utilization of contrast media have been reported as being useful for functional and morphologic assessment of various pulmonary diseases including airway diseases. This review article covers (1) pulmonary MR techniques for morphologic and functional assessment of airway diseases, and (2) pulmonary MR imaging for cystic fibrosis, asthma, and chronic obstructive pulmonary disease. Pulmonary MR imaging provides not only morphology-related but also pulmonary function-related information. It has the potential to replace nuclear medicine studies for the identification of regional pulmonary function and may perform a complementary role in airway disease assessment instead of nuclear medicine study. We believe that the findings of further basic studies as well as clinical applications of this new technique will validate the real significance of pulmonary MR imaging for the future of airway disease assessment and its usefulness for diagnostic radiology and pulmonary medicine.
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Henderson AC, Sá RC, Barash IA, Holverda S, Buxton RB, Hopkins SR, Prisk GK. Rapid intravenous infusion of 20 mL/kg saline alters the distribution of perfusion in healthy supine humans. Respir Physiol Neurobiol 2011; 180:331-41. [PMID: 22227320 DOI: 10.1016/j.resp.2011.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 12/09/2011] [Accepted: 12/22/2011] [Indexed: 11/29/2022]
Abstract
Rapid intravenous saline infusion, a model meant to replicate the initial changes leading to pulmonary interstitial edema, increases pulmonary arterial pressure in humans. We hypothesized that this would alter lung perfusion distribution. Six healthy subjects (29 ± 6 years) underwent magnetic resonance imaging to quantify perfusion using arterial spin labeling. Regional proton density was measured using a fast-gradient echo sequence, allowing blood delivered to the slice to be normalized for density and quantified in mL/min/g. Contributions from flow in large conduit vessels were minimized using a flow cutoff value (blood delivered > 35% maximum in mL/min/cm(3)) in order to obtain an estimate of blood delivered to the capillary bed (perfusion). Images were acquired supine at baseline, after infusion of 20 mL/kg saline, and after a short upright recovery period for a single sagittal slice in the right lung during breath-holds at functional residual capacity. Thoracic fluid content measured by impedance cardiography was elevated post-infusion by up to 13% (p<0.0001). Forced expiratory volume in 1s was reduced by 5.1% post-20 mL/kg (p=0.007). Infusion increased perfusion in nondependent lung by up to 16% (6.4 ± 1.6 mL/min/g baseline, 7.3 ± 1.8 post, 7.4 ± 1.7 recovery, p=0.03). Including conduit vessels, blood delivered in dependent lung was unchanged post-infusion; however, was increased at recovery (9.4 ± 2.7 mL/min/g baseline, 9.7 ± 2.0 post, 11.3 ± 2.2 recovery, p=0.01). After accounting for changes in conduit vessels, there were no significant changes in perfusion in dependent lung following infusion (7.8 ± 1.9 mL/min/g baseline, 7.9 ± 2.0 post, 8.5 ± 2.1 recovery, p=0.36). There were no significant changes in lung density. These data suggest that saline infusion increased perfusion to nondependent lung, consistent with an increase in intravascular pressures. Dependent lung may have been "protected" from increases in perfusion following infusion due to gravitational compression of the pulmonary vasculature.
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Affiliation(s)
- A C Henderson
- Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0623, United States.
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Ley S, Ley-Zaporozhan J. Pulmonary perfusion imaging using MRI: clinical application. Insights Imaging 2011; 3:61-71. [PMID: 22695999 PMCID: PMC3292645 DOI: 10.1007/s13244-011-0140-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 11/16/2011] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Lung perfusion is one of the key components of oxygenation. It is hampered in pulmonary arterial diseases and secondary due to parenchymal diseases. METHODS Assessment is frequently required during the workup of a patient for either of these disease categories. RESULTS This review provides insight into imaging techniques, qualitative and quantitative evaluation, and focuses on clinical application of MR perfusion. CONCLUSION The two major techniques, non-contrast-enhanced (arterial spin labeling) and contrast-enhanced perfusion techniques, are discussed.
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Affiliation(s)
- Sebastian Ley
- Division of Cardiothoracic Imaging, Department of Medical Imaging, Toronto General Hospital, University of Toronto and University Health Network, Toronto General Hospital, 585 University Avenue, Toronto, Ontario, M5G 2N2, Canada,
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Non-invasive pulmonary perfusion assessment in young patients with cystic fibrosis using an arterial spin labeling MR technique at 1.5 T. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2011; 25:155-62. [DOI: 10.1007/s10334-011-0271-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 05/09/2011] [Accepted: 06/21/2011] [Indexed: 10/18/2022]
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Eichinger M, Heussel CP, Kauczor HU, Tiddens H, Puderbach M. Computed tomography and magnetic resonance imaging in cystic fibrosis lung disease. J Magn Reson Imaging 2011; 32:1370-8. [PMID: 21105141 DOI: 10.1002/jmri.22374] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Computed tomography (CT) is the current "gold standard" for assessment of lung morphology and is so far the most reliable imaging modality for monitoring cystic fibrosis (CF) lung disease. CT has a much higher radiation exposure than chest x-ray. The cumulative radiation dose for life-long repeated CT scans has limited its use for CF patients as their life expectancy increases. Clearly, no dose would be preferable over low dose when the same or more relevant information can be obtained. Magnetic resonance imaging (MRI) is comparable to CT with regard to the detection of most morphological changes in the CF lung. It is thought to be less sensitive to detect small airway disease. At the same time, MRI is superior to CT when it comes to the assessment of functional changes such as altered pulmonary perfusion. The recommendation is to further reduce radiation dose related to the use of CT and to use MRI in the follow-up of morphological changes where possible.
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Affiliation(s)
- Monika Eichinger
- German Cancer Research Center (DKFZ) Heidelberg, Radiology (E010), Heidelberg, Germany
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Henzler T, Schmid-Bindert G, Schoenberg SO, Fink C. Diffusion and perfusion MRI of the lung and mediastinum. Eur J Radiol 2011; 76:329-36. [PMID: 20627435 DOI: 10.1016/j.ejrad.2010.05.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 05/05/2010] [Indexed: 11/29/2022]
Abstract
With ongoing technical improvements such as multichannel MRI, systems with powerful gradients as well as the development of innovative pulse sequence techniques implementing parallel imaging, MRI has now entered the stage of a radiation-free alternative to computed tomography (CT) for chest imaging in clinical practice. Whereas in the past MRI of the lung was focused on morphological aspects, current MRI techniques also enable functional imaging of the lung allowing for a comprehensive assessment of lung disease in a single MRI exam. Perfusion imaging can be used for the visualization of regional pulmonary perfusion in patients with different lung diseases such as lung cancer, chronic obstructive lung disease, pulmonary embolism or for the prediction of postoperative lung function in lung cancer patients. Over the past years diffusion-weighted MR imaging (DW-MRI) of the thorax has become feasible with a significant reduction of the acquisition time, thus minimizing artifacts from respiratory and cardiac motion. In chest imaging, DW-MRI has been mainly suggested for the characterization of lung cancer, lymph nodes and pulmonary metastases. In this review article recent MR perfusion and diffusion techniques of the lung and mediastinum as well as their clinical applications are reviewed.
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Affiliation(s)
- Thomas Henzler
- Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim - Heidelberg University, Germany.
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Martirosian P, Boss A, Schraml C, Schwenzer NF, Graf H, Claussen CD, Schick F. Magnetic resonance perfusion imaging without contrast media. Eur J Nucl Med Mol Imaging 2010; 37 Suppl 1:S52-64. [PMID: 20461372 DOI: 10.1007/s00259-010-1456-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Principles of magnetic resonance imaging techniques providing perfusion-related contrast weighting without administration of contrast media are reported and analysed systematically. Especially common approaches to arterial spin labelling (ASL) perfusion imaging allowing quantitative assessment of specific perfusion rates are described in detail. The potential of ASL for perfusion imaging was tested in several types of tissue. METHODS After a systematic comparison of technical aspects of continuous and pulsed ASL techniques the standard kinetic model and tissue properties of influence to quantitative measurements of perfusion are reported. For the applications demonstrated in this paper a flow-sensitive alternating inversion recovery (FAIR) ASL perfusion preparation approach followed by true fast imaging with steady precession (true FISP) data recording was developed and implemented on whole-body scanners operating at 0.2, 1.5 and 3 T for quantitative perfusion measurement in various types of tissue. RESULTS ASL imaging provides a non-invasive tool for assessment of tissue perfusion rates in vivo. Images recorded from kidney, lung, brain, salivary gland and thyroid gland provide a spatial resolution of a few millimetres and sufficient signal to noise ratio in perfusion maps after 2-5 min of examination time. CONCLUSIONS Newly developed ASL techniques provide especially high image quality and quantitative perfusion maps in tissues with relatively high perfusion rates (as also present in many tumours). Averaging of acquisitions and image subtraction procedures are mandatory, leading to the necessity of synchronization of data recording to breathing in abdominal and thoracic organs.
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Hopkins SR, Arai TJ, Henderson AC, Levin DL, Buxton RB, Kim Prisk G. Lung volume does not alter the distribution of pulmonary perfusion in dependent lung in supine humans. J Physiol 2010; 588:4759-68. [PMID: 20921195 DOI: 10.1113/jphysiol.2010.196063] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
There is a gravitational influence on pulmonary perfusion, including in the most dependent lung, where perfusion is reduced, termed Zone 4. Studies using xenon-133 show Zone 4 behaviour, present in the dependent 4 cm at total lung capacity (TLC), affects the dependent 11 cm at functional residual capacity (FRC) and almost all the lung at residual volume (RV). These differences were ascribed to increased resistance in extra-alveolar vessels at low lung volumes although other mechanisms have been proposed. To further evaluate the behaviour of perfusion in dependent lung using a technique that directly measures pulmonary perfusion and corrects for tissue distribution by measuring regional proton density, seven healthy subjects (age = 38 ± 6 years, FEV₁ = 104 ± 7% predicted) underwent magnetic resonance imaging in supine posture. Data were acquired in the right lung during breath-holds at RV, FRC and TLC. Arterial spin labelling quantified regional pulmonary perfusion, which was normalized for regional proton density measured using a fast low-angle shot technique. The height of the onset of Zone 4 behaviour was not different between lung volumes (P = 0.23). There were no significant differences in perfusion (expressed as ml min⁻¹ g⁻¹) between lung volumes in the gravitationally intermediate (RV = 8.9 ± 3.1, FRC = 8.1 ± 2.9, TLC = 7.4 ± 3.6; P = 0.26) and dependent lung (RV = 6.6 ± 2.4, FRC = 6.1 ± 2.1, TLC = 6.4 ± 2.6; P = 0.51). However, at TLC perfusion was significantly lower in non-dependent lung than at FRC or RV (3.6 ± 3.3, 7.7 ± 1.5, 7.9 ± 2.0, respectively; P < 0.001). These data suggest that the mechanism of the reduction in perfusion in dependent lung is unlikely to be a result of lung volume related increases in resistance in extra-alveolar vessels. In supine posture, the gravitational influence on perfusion is remarkably similar over most of the lung, irrespective of lung volume.
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Affiliation(s)
- Susan R Hopkins
- Department of Medicine, Division of Physiology, University of California, San Diego, La Jolla, CA 92093-0623, USA.
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Initial experience of dual-energy lung perfusion CT using a dual-source CT system in children. Pediatr Radiol 2010; 40:1536-44. [PMID: 20596701 DOI: 10.1007/s00247-010-1759-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 05/10/2010] [Accepted: 05/14/2010] [Indexed: 12/13/2022]
Abstract
Initial experience of dual-source dual-energy (DE) lung perfusion CT in children is described. In addition to traditional identification of pulmonary emboli, the assessment of lung perfusion is technically feasible with dual-source DE CT in children with acceptable radiation dose. This article describes how to perform dual-source DE lung perfusion CT in children, including the optimization of intravenous injection method and CT dose parameters. How to produce weighted-average CT images for the assessment of pulmonary emboli and colour-coded perfusion maps for the assessment of regional lung perfusion is also detailed. Lung perfusion status can then be evaluated on perfusion maps by means of either qualitative or quantitative analysis. Potential advantages and disadvantages of this emerging CT technique compared to lung perfusion scintigraphy and cardiac MRI are discussed.
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The role of advanced imaging techniques in cystic fibrosis follow-up: is there a place for MRI? Pediatr Radiol 2010; 40:844-9. [PMID: 20432002 DOI: 10.1007/s00247-010-1589-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Accepted: 01/24/2010] [Indexed: 12/24/2022]
Abstract
Cystic fibrosis (CF) lung disease is caused by mutations in the CFTR-gene and remains one of the most frequent lethal inherited diseases in the Caucasian population. Given the progress in CF therapy and the consecutive improvement in prognosis, monitoring of disease progression and effectiveness of therapeutic interventions with repeated imaging of the CF lung plays an increasingly important role. So far, the chest radiograph has been the most widely used imaging modality to monitor morphological changes in the CF lung. CT is the gold standard for assessment of morphological changes of airways and lung parenchyma. Considering the necessity of life-long repeated imaging studies, the cumulative radiation doses reached with CT is problematic for CF patients. A sensitive, non-invasive and quantitative technique without radiation exposure is warranted for monitoring of disease activity. In previous studies, MRI proved to be comparable to CT regarding the detection of morphological changes in the CF lung without using ionising radiation. Furthermore, MRI was shown to be superior to CT regarding assessment of functional changes of the lung. This review presents the typical morphological and functional MR imaging findings with respect to MR-based follow-up of CF lung disease. MRI offers a variety of techniques for morphological and functional imaging of the CF lung. Using this radiation free technique short- and long-term follow-up studies are possible enabling an individualised guidance of the therapy.
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Wu WC, St Lawrence KS, Licht DJ, Wang DJJ. Quantification issues in arterial spin labeling perfusion magnetic resonance imaging. Top Magn Reson Imaging 2010; 21:65-73. [PMID: 21613872 DOI: 10.1097/rmr.0b013e31821e570a] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Arterial spin labeling (ASL) perfusion magnetic resonance imaging has gained wide acceptance for its value in clinical and neuroscience applications during recent years. Its capability for noninvasive and absolute perfusion quantification is a key characteristic that makes ASL attractive for many clinical applications. In the present review, we discuss the main parameters or factors that affect the reliability and accuracy of ASL perfusion measurements. Our secondary goal was to outline potential solutions that may improve the reliability and accuracy of ASL in clinical settings. It was found that, through theoretical analyses, flow quantification is most sensitive to tagging efficiency and estimation of the equilibrium magnetization of blood signal (M(0b)). Variations of blood T1 have a greater effect on perfusion quantification than variations of tissue T1. Arterial transit time becomes an influential factor when it is longer than the postlabeling delay time. The T2's of blood and tissue impose minimal effects on perfusion calculation at field strengths equal to or lower than 3.0 T. Subsequently, we proposed various approaches for in vivo estimation or calibration of the above parameters, such as the use of phase-contrast magnetic resonance imaging for calibration of the labeling efficiency as well as the use of inversion recovery TrueFISP (true fast imaging with steady-state precession) sequence for blood T1 mapping. We also list representative clinical cases in which implicit assumptions for ASL perfusion quantification may be violated, such as the venous outflow effect in children with sickle cell disease. Finally, an optimal imaging protocol including in vivo measurements of several critical parameters was recommended for clinical ASL studies.
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Affiliation(s)
- Wen-Chau Wu
- Graduate Institute of Oncology and Graduate Institute of Clinical Medicine, National Taiwan University, Taipei, Taiwan
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Demonstration of pulmonary perfusion heterogeneity induced by gravity and lung inflation using arterial spin labeling. Eur J Radiol 2010; 73:249-54. [DOI: 10.1016/j.ejrad.2008.11.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2008] [Accepted: 11/20/2008] [Indexed: 11/22/2022]
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