101
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Duyn JH, Schenck J. Contributions to magnetic susceptibility of brain tissue. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3546. [PMID: 27240118 PMCID: PMC5131875 DOI: 10.1002/nbm.3546] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 02/19/2016] [Accepted: 03/31/2016] [Indexed: 05/08/2023]
Abstract
This review discusses the major contributors to the subtle magnetic properties of brain tissue and how they affect MRI contrast. With the increased availability of high-field scanners, the use of magnetic susceptibility contrast for the study of human brain anatomy and function has increased dramatically. This has not only led to novel applications, but has also improved our understanding of the complex relationship between MRI contrast and magnetic susceptibility. Chief contributors to the magnetic susceptibility of brain tissue have been found to include myelin as well as iron. In the brain, iron exists in various forms with diverse biological roles, many of which are now only starting to be uncovered. An interesting aspect of magnetic susceptibility contrast is its sensitivity to the microscopic distribution of iron and myelin, which provides opportunities to extract information at spatial scales well below MRI resolution. For example, in white matter, the myelin sheath that surrounds the axons can provide tissue contrast that is dependent on the axonal orientation and reflects the relative size of intra- and extra-axonal water compartments. The extraction of such ultrastructural information, together with quantitative information about iron and myelin concentrations, is an active area of research geared towards the characterization of brain structure and function, and their alteration in disease. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Jeff H. Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular
Imaging, National Institutes of Neurological Disorders and Stroke, National
Institutes of Health, Bethesda, Maryland 20892, USA
| | - John Schenck
- MRI Technologies and Systems, General Electric
Global Research Center, 1 Research Circle, Schenectady, New York 12309, USA
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102
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Yablonskiy DA, Sukstanskii AL. Effects of biological tissue structural anisotropy and anisotropy of magnetic susceptibility on the gradient echo MRI signal phase: theoretical background. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3655. [PMID: 27862452 PMCID: PMC6375105 DOI: 10.1002/nbm.3655] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 07/18/2016] [Accepted: 09/09/2016] [Indexed: 05/11/2023]
Abstract
Quantitative susceptibility mapping is a potentially powerful technique for mapping tissue magnetic susceptibility from gradient recalled echo (GRE) MRI signal phase. In this review, we present up-to-date theoretical developments in analyzing the relationships between GRE signal phase and the underlying tissue microstructure and magnetic susceptibility at the cellular level. Two important phenomena contributing to the GRE signal phase are at the focus of this review - tissue structural anisotropy (e.g. cylindrical axonal bundles in white matter) and magnetic susceptibility anisotropy. One of the most intriguing and challenging problems in this field is calculating the so-called Lorentzian contribution to the phase shift induced by the local environment - magnetized tissue structures that have dimensions smaller than the imaging voxel (e.g. cells, cellular components, blood capillaries). In this review, we briefly discuss a "standard" approach to this problem, based on introduction of an imaginary Lorentzian cavity, as well as a more recent method - the generalized Lorentzian tensor approach (GLTA) - that is based on a statistical approach and a direct solution of the magnetostatic Maxwell equations. The latter adequately accounts for both types of anisotropy: the anisotropy of magnetic susceptibility and the structural tissue anisotropy. In the GLTA the frequency shift due to the local environment is characterized by the Lorentzian tensor L^, which has a substantially different structure than the susceptibility tensor χ^. While the components of χ^ are compartmental susceptibilities "weighted" by their volume fractions, the components of L^ are weighted by specific numerical factors depending on tissue geometrical microsymmetry. In multi-compartment structures, the components of the Lorentzian tensor also depend on the compartmental relaxation properties, hence the MR pulse sequence settings. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Dmitriy A. Yablonskiy
- Correspondence to: D.A. Yablonskiy, Mallinckrodt Institute of Radiology, St Louis, MO, USA.
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103
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Puwal S, Roth BJ, Basser PJ. Heterogeneous anisotropic magnetic susceptibility of the myelin-water layers causes local magnetic field perturbations in axons. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3628. [PMID: 27731911 PMCID: PMC6130896 DOI: 10.1002/nbm.3628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 06/23/2016] [Accepted: 08/17/2016] [Indexed: 05/23/2023]
Abstract
One goal of MRI is to determine the myelin water fraction in neural tissue. One approach is to measure the reduction in T2 * arising from microscopic perturbations in the magnetic field caused by heterogeneities in the magnetic susceptibility of myelin. In this paper, analytic expressions for the induced magnetic field distribution are derived within and around an axon, assuming that the myelin susceptibility is anisotropic. Previous models considered the susceptibility to be piecewise continuous, whereas this model considers a sinusoidally varying susceptibility. Many conclusions are common in both models. When the magnetic field is applied perpendicular to the axon, the magnetic field in the intraaxonal space is uniformly perturbed, the magnetic field in the myelin sheath oscillates between the lipid and water layers, and the magnetic field in the extracellular space just outside the myelin sheath is heterogeneous. These field heterogeneities cause the spins to dephase, shortening T2 *. When the magnetic field is applied along the axon, the field is homogeneous within water-filled regions, including between lipid layers. Therefore the spins do not dephase and the magnetic susceptibility has no effect on T2 *. Generally, the response of an axon is given as the superposition of these two contributions. The sinusoidal model uses a different set of approximations compared with the piecewise model, so their common predictions indicate that the models are not too sensitive to the details of the myelin-water distribution. Other predictions, such as the sensitivity to water diffusion between myelin and water layers, may highlight differences between the two approaches. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Steffan Puwal
- Department of Physics, Oakland University, Rochester, MI, USA
| | - Bradley J Roth
- Department of Physics, Oakland University, Rochester, MI, USA
| | - Peter J Basser
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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104
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Li W, Liu C, Duong TQ, van Zijl PC, Li X. Susceptibility tensor imaging (STI) of the brain. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3540. [PMID: 27120169 PMCID: PMC5083244 DOI: 10.1002/nbm.3540] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 05/23/2023]
Abstract
Susceptibility tensor imaging (STI) is a recently developed MRI technique that allows quantitative determination of orientation-independent magnetic susceptibility parameters from the dependence of gradient echo signal phase on the orientation of biological tissues with respect to the main magnetic field. By modeling the magnetic susceptibility of each voxel as a symmetric rank-2 tensor, individual magnetic susceptibility tensor elements as well as the mean magnetic susceptibility and magnetic susceptibility anisotropy can be determined for brain tissues that would still show orientation dependence after conventional scalar-based quantitative susceptibility mapping to remove such dependence. Similar to diffusion tensor imaging, STI allows mapping of brain white matter fiber orientations and reconstruction of 3D white matter pathways using the principal eigenvectors of the susceptibility tensor. In contrast to diffusion anisotropy, the main determinant factor of the susceptibility anisotropy in brain white matter is myelin. Another unique feature of the susceptibility anisotropy of white matter is its sensitivity to gadolinium-based contrast agents. Mechanistically, MRI-observed susceptibility anisotropy is mainly attributed to the highly ordered lipid molecules in the myelin sheath. STI provides a consistent interpretation of the dependence of phase and susceptibility on orientation at multiple scales. This article reviews the key experimental findings and physical theories that led to the development of STI, its practical implementations, and its applications for brain research. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Wei Li
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Chunlei Liu
- Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, NC 27710
- Department of Radiology, School of Medicine, Duke University, Durham, NC 27710
| | - Timothy Q. Duong
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
- Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
| | - Peter C.M. van Zijl
- F.M. Kirby Research Center for functional brain imaging, Kennedy Krieger Institute, Baltimore, MD, 21205
- Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205
| | - Xu Li
- F.M. Kirby Research Center for functional brain imaging, Kennedy Krieger Institute, Baltimore, MD, 21205
- Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205
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105
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Lee J, Nam Y, Choi JY, Kim EY, Oh SH, Kim DH. Mechanisms of T 2 * anisotropy and gradient echo myelin water imaging. NMR IN BIOMEDICINE 2017; 30:e3513. [PMID: 27060968 DOI: 10.1002/nbm.3513] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/26/2016] [Accepted: 02/17/2016] [Indexed: 06/05/2023]
Abstract
In MRI, structurally aligned molecular or micro-organization (e.g. axonal fibers) can be a source of substantial signal variations that depend on the structural orientation and the applied magnetic field. This signal anisotropy gives us a unique opportunity to explore information that exists at a resolution several orders of magnitude smaller than that of typical MRI. In this review, one of the signal anisotropies, T2 * anisotropy in white matter, and a related imaging method, gradient echo myelin water imaging (GRE-MWI), are explored. The T2 * anisotropy has been attributed to isotropic and anisotropic magnetic susceptibility of myelin and compartmentalized microstructure of white matter fibers (i.e. axonal, myelin, and extracellular space). The susceptibility and microstructure create magnetic frequency shifts that change with the relative orientation of the fiber and the main magnetic field, generating the T2 * anisotropy. The resulting multi-component magnitude decay and nonlinear phase evolution have been utilized for GRE-MWI, assisting in resolving the signal fraction of the multiple compartments in white matter. The GRE-MWI method has been further improved by signal compensation techniques including physiological noise compensation schemes. The T2 * anisotropy and GRE-MWI provide microstructural information on a voxel (e.g. fiber orientation and tissue composition), and may serve as sensitive biomarkers for microstructural changes in the brain. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea
| | - Yoonho Nam
- Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Joon Yul Choi
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea
| | - Eung Yeop Kim
- Department of Radiology, Gachon University Gil Medical Center, Incheon, Korea
| | - Se-Hong Oh
- Imaging Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Dong-Hyun Kim
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea
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106
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Nunes D, Cruz TL, Jespersen SN, Shemesh N. Mapping axonal density and average diameter using non-monotonic time-dependent gradient-echo MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 277:117-130. [PMID: 28282586 DOI: 10.1016/j.jmr.2017.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/23/2017] [Accepted: 02/25/2017] [Indexed: 06/06/2023]
Abstract
White Matter (WM) microstructures, such as axonal density and average diameter, are crucial to the normal function of the Central Nervous System (CNS) as they are closely related with axonal conduction velocities. Conversely, disruptions of these microstructural features may result in severe neurological deficits, suggesting that their noninvasive mapping could be an important step towards diagnosing and following pathophysiology. Whereas diffusion based MRI methods have been proposed to map these features, they typically entail the application of powerful gradients, which are rarely available in the clinic, or extremely long acquisition schemes to extract information from parameter-intensive models. In this study, we suggest that simple and time-efficient multi-gradient-echo (MGE) MRI can be used to extract the axon density from susceptibility-driven non-monotonic decay in the time-dependent signal. We show, both theoretically and with simulations, that a non-monotonic signal decay will occur for multi-compartmental microstructures - such as axons and extra-axonal spaces, which were here used as a simple model for the microstructure - and that, for axons parallel to the main magnetic field, the axonal density can be extracted. We then experimentally demonstrate in ex-vivo rat spinal cords that its different tracts - characterized by different microstructures - can be clearly contrasted using the MGE-derived maps. When the quantitative results are compared against ground-truth histology, they reflect the axonal fraction (though with a bias, as evident from Bland-Altman analysis). As well, the extra-axonal fraction can be estimated. The results suggest that our model is oversimplified, yet at the same time evidencing a potential and usefulness of the approach to map underlying microstructures using a simple and time-efficient MRI sequence. We further show that a simple general-linear-model can predict the average axonal diameters from the four model parameters, and map these average axonal diameters in the spinal cords. While clearly further modelling and theoretical developments are necessary, we conclude that salient WM microstructural features can be extracted from simple, SNR-efficient multi-gradient echo MRI, and that this paves the way towards easier estimation of WM microstructure in vivo.
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Affiliation(s)
- Daniel Nunes
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Av. Brasilia 1400-038, Lisbon, Portugal
| | - Tomás L Cruz
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Av. Brasilia 1400-038, Lisbon, Portugal
| | - Sune N Jespersen
- Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Clinical Institute, Aarhus University, Aarhus, Denmark; Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | - Noam Shemesh
- Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Av. Brasilia 1400-038, Lisbon, Portugal.
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107
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Ropele S, Langkammer C. Iron quantification with susceptibility. NMR IN BIOMEDICINE 2017; 30:e3534. [PMID: 27119601 DOI: 10.1002/nbm.3534] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/19/2016] [Accepted: 03/11/2016] [Indexed: 05/26/2023]
Abstract
Iron is an essential trace element involved in a variety of biological mechanisms in the human body. Disturbances of iron homeostasis have been observed in several inflammatory and degenerative diseases, which have raised strong interest in non-invasive iron mapping techniques. Numerous MRI techniques have been proposed so far, mostly based on the field changes induced by the magnetic properties of iron. Each of these approaches has a specific sensitivity for iron and its microstructural environment. Quantitative susceptibility mapping is the latest development and provides a direct measure of bulk susceptibility. However, field changes induced by iron are not always directly related to the concentration of iron, but rather reflect the structure of iron compounds and its cellular distribution. This review provides an overview of the most relevant iron compounds in the human body, their magnetic properties and their cellular distribution. In addition, MRI methods based on direct or indirect susceptibility changes are presented and discussed with respect to technical aspects and clinical applicability. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Stefan Ropele
- Department of Neurology, Medical University of Graz, Graz, Austria
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108
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He Q, Ma Y, Fan S, Shao H, Sheth V, Bydder GM, Du J. Direct magnitude and phase imaging of myelin using ultrashort echo time (UTE) pulse sequences: A feasibility study. Magn Reson Imaging 2017; 39:194-199. [PMID: 28219648 DOI: 10.1016/j.mri.2017.02.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 02/01/2017] [Accepted: 02/16/2017] [Indexed: 12/19/2022]
Abstract
In this paper, we aimed to investigate the feasibility of direct visualization of myelin, including myelin lipid and myelin basic protein (MBP), using two-dimensional ultrashort echo time (2D UTE) sequences and utilize phase information as a contrast mechanism in phantoms and in volunteers. The standard UTE sequence was used to detect both myelin and long T2 signal. An adiabatic inversion recovery UTE (IR-UTE) sequence was used to selectively detect myelin by suppressing signal from long T2 water protons. Magnitude and phase imaging and T2* were investigated on myelin lipid and MBP in the forms of lyophilized powders as well as paste-like phantoms with the powder mixed with D2O, and rubber phantoms as well as healthy volunteers. Contrast to noise ratio (CNR) between white and gray matter was measured. Both magnitude and phase images were generated for myelin and rubber phantoms as well white matter in vivo using the IR-UTE sequence. T2* values of ~300μs were comparable for myelin paste phantoms and the short T2* component in white matter of the brain in vivo. Mean CNR between white and gray matter in IR-UTE imaging was increased from -7.3 for the magnitude images to 57.4 for the phase images. The preliminary results suggest that the IR-UTE sequence allows simultaneous magnitude and phase imaging of myelin in vitro and in vivo.
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Affiliation(s)
- Qun He
- Department of Radiology, University of California, San Diego, United States; Ningbo Jansen NMR Technology Co., Ltd., Cixi, Zhejiang Province, China
| | - Yajun Ma
- Department of Radiology, University of California, San Diego, United States
| | - Shujuan Fan
- Department of Radiology, University of California, San Diego, United States
| | - Hongda Shao
- Department of Radiology, University of California, San Diego, United States
| | - Vipul Sheth
- Department of Radiology, University of California, San Diego, United States
| | - Graeme M Bydder
- Department of Radiology, University of California, San Diego, United States
| | - Jiang Du
- Department of Radiology, University of California, San Diego, United States.
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109
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Schindler MK, Sati P, Reich DS. Insights from Ultrahigh Field Imaging in Multiple Sclerosis. Neuroimaging Clin N Am 2017; 27:357-366. [PMID: 28391792 DOI: 10.1016/j.nic.2016.12.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ultrahigh-field (≥7 T) magnetic resonance (MR) imaging is being used at many leading academic medical centers to study neurologic disorders. The improved spatial resolution and anatomic detail are due to the increase in signal-to-noise and contrast-to-noise ratio at higher magnetic field strengths. Ultrahigh-field MR imaging improves multiple sclerosis (MS) lesion detection, with particular sensitivity to detect cortical lesions. The increase in magnetic susceptibility effects inherent to ultrahigh field can be used to detect pathologic features of MS lesions, including a central vein, potentially useful for diagnostic considerations, and heterogeneity among MS lesions, potentially useful in determining lesion outcomes.
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Affiliation(s)
- Matthew K Schindler
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Medical Center Boulevard, 10 Center Drive, MSC 1400, Bethesda, MD 20892, USA
| | - Pascal Sati
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Medical Center Boulevard, 10 Center Drive, MSC 1400, Bethesda, MD 20892, USA
| | - Daniel S Reich
- Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Medical Center Boulevard, 10 Center Drive, MSC 1400, Bethesda, MD 20892, USA.
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110
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Cronin MJ, Wang N, Decker KS, Wei H, Zhu WZ, Liu C. Exploring the origins of echo-time-dependent quantitative susceptibility mapping (QSM) measurements in healthy tissue and cerebral microbleeds. Neuroimage 2017; 149:98-113. [PMID: 28126551 DOI: 10.1016/j.neuroimage.2017.01.053] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 01/19/2017] [Accepted: 01/22/2017] [Indexed: 12/20/2022] Open
Abstract
Quantitative susceptibility mapping (QSM) is increasingly used to measure variation in tissue composition both in the brain and in other areas of the body in a range of disease pathologies. Although QSM measurements were originally believed to be independent of the echo time (TE) used in the gradient-recalled echo (GRE) acquisition from which they are derived; recent literature (Sood et al., 2016) has shown that these measurements can be highly TE-dependent in a number of brain regions. In this work we systematically investigate possible causes of this effect through analysis of apparent frequency and QSM measurements derived from data acquired at multiple TEs in vivo in healthy brain regions and in cerebral microbleeds (CMBs); QSM data acquired in a gadolinium-doped phantom; and in QSM data derived from idealized simulated phase data. Apparent frequency measurements in the optic radiations (OR) and central corpus callosum (CC) were compared to those predicted by a 3-pool white matter model, however the model failed to fully explain contrasting frequency profiles measured in the OR and CC. Our results show that TE-dependent QSM measurements can be caused by a failure of phase unwrapping algorithms in and around strong susceptibility sources such as CMBs; however, in healthy brain regions this behavior appears to result from intrinsic non-linear phase evolution in the MR signal. From these results we conclude that care must be taken when deriving frequency and QSM measurements in strong susceptibility sources due to the inherent limitations in phase unwrapping; and that while signal compartmentalization due to tissue microstructure and content is a plausible cause of TE-dependent frequency and QSM measurements in healthy brain regions, better sampling of the MR signal and more complex models of tissue are needed to fully exploit this relationship.
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Affiliation(s)
- Matthew J Cronin
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA; Brain Imaging and Analysis Center, Duke University, Durham, NC 27710, USA
| | - Nian Wang
- Brain Imaging and Analysis Center, Duke University, Durham, NC 27710, USA
| | - Kyle S Decker
- Brain Imaging and Analysis Center, Duke University, Durham, NC 27710, USA
| | - Hongjiang Wei
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA; Brain Imaging and Analysis Center, Duke University, Durham, NC 27710, USA
| | - Wen-Zhen Zhu
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Chunlei Liu
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA; Brain Imaging and Analysis Center, Duke University, Durham, NC 27710, USA.
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111
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Abstract
Myelin is critical for healthy brain function. An accurate in vivo measure of myelin content has important implications for understanding brain plasticity and neurodegenerative diseases. Myelin water imaging is a magnetic resonance imaging method which can be used to visualize myelination in the brain and spinal cord in vivo. This review presents an overview of myelin water imaging data acquisition and analysis, post-mortem validation work, findings in both animal and human studies and a brief discussion about other MR techniques purported to provide in vivo myelin content. Multi-echo T2 relaxation approaches continue to undergo development and whole-brain imaging time now takes less than 10 minutes; the standard analysis method for this type of data acquisition is a non-negative least squares approach. Alternate methods including the multi-flip angle gradient echo mcDESPOT are also being used for myelin water imaging. Histological validation studies in animal and human brain and spinal cord tissue demonstrate high specificity of myelin water imaging for myelin. Potential confounding factors for in vivo myelin water fraction measurement include the presence of myelin debris and magnetization exchange processes. Myelin water imaging has successfully been used to study animal models of injury, applied in healthy human controls and can be used to assess damage and injury in conditions such as multiple sclerosis, neuromyelitis optica, schizophrenia, phenylketonuria, neurofibromatosis, niemann pick’s disease, stroke and concussion. Other quantitative magnetic resonance approaches that are sensitive to, but not specific for, myelin exist including magnetization transfer, diffusion tensor imaging and T1 weighted imaging.
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Affiliation(s)
- Alex L MacKay
- Department of Radiology, University of British Columbia, Vancouver, Canada.,Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
| | - Cornelia Laule
- Department of Radiology, University of British Columbia, Vancouver, Canada.,Department of Pathology & Laboratory Medicine, University of British Columbia, Vancouver, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, Canada
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112
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Massire A, Taso M, Besson P, Guye M, Ranjeva JP, Callot V. High-resolution multi-parametric quantitative magnetic resonance imaging of the human cervical spinal cord at 7T. Neuroimage 2016; 143:58-69. [DOI: 10.1016/j.neuroimage.2016.08.055] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 08/24/2016] [Accepted: 08/25/2016] [Indexed: 11/17/2022] Open
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113
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Gil R, Khabipova D, Zwiers M, Hilbert T, Kober T, Marques JP. An in vivo study of the orientation-dependent and independent components of transverse relaxation rates in white matter. NMR IN BIOMEDICINE 2016; 29:1780-1790. [PMID: 27809376 DOI: 10.1002/nbm.3616] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 08/06/2016] [Accepted: 08/08/2016] [Indexed: 06/06/2023]
Abstract
Diffusion-weighted imaging (DWI) provides information that allows the estimation of white-matter (WM) fibre orientation and distribution, but it does not provide information about myelin density, fibre concentration or fibre size within each voxel. On the other hand, quantitative relaxation contrasts (like the apparent transverse relaxation, R2∗) offer iron and myelin-related contrast, but their dependence on the orientation of microstructure with respect to the applied magnetic field, B0 , is often neglected. The aim of this work was to combine the fibre orientation information retrieved from the DWI acquisition and the sensitivity to microstructural information from quantitative relaxation parameters. The in vivo measured quantitative transverse relaxation maps (R2 and R2∗) were decomposed into their orientation-dependent and independent components, using the DWI fibre orientation information as prior knowledge. The analysis focused on major WM fibre bundles such as the forceps major (FMj), forceps minor (FMn), cingulum (CG) and corticospinal tracts (CST). The orientation-dependent R2 parameters, despite their small size (0-1.5 Hz), showed higher variability across different fibre populations, while those derived from R2∗, although larger (3.1-4.5 Hz), were mostly bundle-independent. With this article, we have, for the first time, attempted the in vivo characterization of the orientation-(in)dependent components of the transverse relaxation rates and demonstrated that the orientation of WM fibres influences both R2 and R2∗ contrasts.
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Affiliation(s)
- Rita Gil
- Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands
- Champalimaud Center for the Unknown, Lisbon, Portugal
| | - Diana Khabipova
- Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Marcel Zwiers
- Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands
| | - Tom Hilbert
- Advanced Clinical Imaging Technology (HC CEMEA SUI DI BM PI), Siemens Healthcare AG, Lausanne, Switzerland
- Department of Radiology, University Hospital (CHUV), Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Tobias Kober
- Advanced Clinical Imaging Technology (HC CEMEA SUI DI BM PI), Siemens Healthcare AG, Lausanne, Switzerland
- Department of Radiology, University Hospital (CHUV), Lausanne, Switzerland
- LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - José P Marques
- Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, The Netherlands
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114
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Groeschel S, Hagberg GE, Schultz T, Balla DZ, Klose U, Hauser TK, Nägele T, Bieri O, Prasloski T, MacKay AL, Krägeloh-Mann I, Scheffler K. Assessing White Matter Microstructure in Brain Regions with Different Myelin Architecture Using MRI. PLoS One 2016; 11:e0167274. [PMID: 27898701 PMCID: PMC5127571 DOI: 10.1371/journal.pone.0167274] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 11/13/2016] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVE We investigate how known differences in myelin architecture between regions along the cortico-spinal tract and frontal white matter (WM) in 19 healthy adolescents are reflected in several quantitative MRI parameters that have been proposed to non-invasively probe WM microstructure. In a clinically feasible scan time, both conventional imaging sequences as well as microstructural MRI parameters were assessed in order to quantitatively characterise WM regions that are known to differ in the thickness of their myelin sheaths, and in the presence of crossing or parallel fibre organisation. RESULTS We found that diffusion imaging, MR spectroscopy (MRS), myelin water fraction (MWF), Magnetization Transfer Imaging, and Quantitative Susceptibility Mapping were myelin-sensitive in different ways, giving complementary information for characterising WM microstructure with different underlying fibre architecture. From the diffusion parameters, neurite density (NODDI) was found to be more sensitive than fractional anisotropy (FA), underlining the limitation of FA in WM crossing fibre regions. In terms of sensitivity to different myelin content, we found that MWF, the mean diffusivity and chemical-shift imaging based MRS yielded the best discrimination between areas. CONCLUSION Multimodal assessment of WM microstructure was possible within clinically feasible scan times using a broad combination of quantitative microstructural MRI sequences. By assessing new microstructural WM parameters we were able to provide normative data and discuss their interpretation in regions with different myelin architecture, as well as their possible application as biomarker for WM disorders.
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Affiliation(s)
| | - Gisela E. Hagberg
- High Field Magnetic Resonance, Max-Planck Institute for Biological Cybernetics, Tübingen, Germany
- Biomedical Magnetic Resonance, University Hospital Tübingen, Germany
| | - Thomas Schultz
- Institute of Computer Science, University of Bonn, Germany
| | - Dávid Z. Balla
- Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Uwe Klose
- Department of Diagnostic and Interventional Neuroradiology, University Hospital, Tübingen, Germany
| | - Till-Karsten Hauser
- Department of Diagnostic and Interventional Neuroradiology, University Hospital, Tübingen, Germany
| | - Thomas Nägele
- Department of Diagnostic and Interventional Neuroradiology, University Hospital, Tübingen, Germany
| | - Oliver Bieri
- Radiological Physics, University of Basel, Basel, Switzerland
| | | | | | | | - Klaus Scheffler
- High Field Magnetic Resonance, Max-Planck Institute for Biological Cybernetics, Tübingen, Germany
- Biomedical Magnetic Resonance, University Hospital Tübingen, Germany
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115
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Wallace MN, Cronin MJ, Bowtell RW, Scott IS, Palmer AR, Gowland PA. Histological Basis of Laminar MRI Patterns in High Resolution Images of Fixed Human Auditory Cortex. Front Neurosci 2016; 10:455. [PMID: 27774049 PMCID: PMC5054214 DOI: 10.3389/fnins.2016.00455] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 09/21/2016] [Indexed: 12/26/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) studies of the auditory region of the temporal lobe would benefit from the availability of image contrast that allowed direct identification of the primary auditory cortex, as this region cannot be accurately located using gyral landmarks alone. Previous work has suggested that the primary area can be identified in magnetic resonance (MR) images because of its relatively high myelin content. However, MR images are also affected by the iron content of the tissue and in this study we sought to confirm that different MR image contrasts did correlate with the myelin content in the gray matter and were not primarily affected by iron content as is the case in the primary visual and somatosensory areas. By imaging blocks of fixed post-mortem cortex in a 7 T scanner and then sectioning them for histological staining we sought to assess the relative contribution of myelin and iron to the gray matter contrast in the auditory region. Evaluating the image contrast in T2*-weighted images and quantitative R2* maps showed a reasonably high correlation between the myelin density of the gray matter and the intensity of the MR images. The correlation with T1-weighted phase sensitive inversion recovery (PSIR) images was better than with the previous two image types, and there were clearly differentiated borders between adjacent cortical areas in these images. A significant amount of iron was present in the auditory region, but did not seem to contribute to the laminar pattern of the cortical gray matter in MR images. Similar levels of iron were present in the gray and white matter and although iron was present in fibers within the gray matter, these fibers were fairly uniformly distributed across the cortex. Thus, we conclude that T1- and T2*-weighted imaging sequences do demonstrate the relatively high myelin levels that are characteristic of the deep layers in primary auditory cortex and allow it and some of the surrounding areas to be reliably distinguished.
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Affiliation(s)
- Mark N Wallace
- Medical Research Council Institute of Hearing Research, University of Nottingham Nottingham, UK
| | - Matthew J Cronin
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham Nottingham, UK
| | - Richard W Bowtell
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham Nottingham, UK
| | - Ian S Scott
- Neuropathology Laboratory, Nottingham University Hospitals NHS Trust, Queen's Medical Centre Nottingham, UK
| | - Alan R Palmer
- Medical Research Council Institute of Hearing Research, University of Nottingham Nottingham, UK
| | - Penny A Gowland
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham Nottingham, UK
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116
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Barbara TM. White matter shifts in MRI: Rehabilitating the Lorentz sphere in magnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 270:40-46. [PMID: 27393892 DOI: 10.1016/j.jmr.2016.06.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 06/22/2016] [Accepted: 06/25/2016] [Indexed: 06/06/2023]
Abstract
A thorough exposition and analysis of the role of the Lorentz sphere in magnetic resonance is presented from the fundamental standpoint of macroscopic magnetostatics. The analysis will be useful to those interested in understanding susceptibility and chemical shift contributions to frequency shifts in magnetic resonance. Though the topic is mature, recent research on white matter shifts in the brain promotes the notion of replacing the Lorentz sphere with a generalized Lorentzian cylinder, and has put into question the long standing spherical approach when elongated structures are present. The cavity shape issue can be resolved by applying Helmholtz's theorem, which can be expressed in a differential and an integral formulation. The general validity of the Lorentz sphere for any situation is confirmed. Furthermore, a clear exposition of the "generalized approach" is offered, using the language of Lorentz's theory. With the rehabilitation of the Lorentz sphere settled, one must consider alternative contributions to white matter shifts and a likely candidate is the effect of molecular environment on chemical shifts.
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Affiliation(s)
- Thomas M Barbara
- Advanced Imaging Research Center, Oregon Health and Sciences University, Portland, OR 97239, United States.
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117
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De Santis S, Assaf Y, Jeurissen B, Jones DK, Roebroeck A. T1 relaxometry of crossing fibres in the human brain. Neuroimage 2016; 141:133-142. [PMID: 27444568 PMCID: PMC5035137 DOI: 10.1016/j.neuroimage.2016.07.037] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/13/2016] [Accepted: 07/15/2016] [Indexed: 12/13/2022] Open
Abstract
A comprehensive tract-based characterisation of white matter should include the ability to quantify myelin and axonal attributes irrespective of the complexity of fibre organisation within the voxel. Recently, a new experimental framework that combines inversion recovery and diffusion MRI, called inversion recovery diffusion tensor imaging (IR-DTI), was introduced and applied in an animal study. IR-DTI provides the ability to assign to each unique fibre population within a voxel a specific value of the longitudinal relaxation time, T1, which is a proxy for myelin content. Here, we apply the IR-DTI approach to the human brain in vivo on 7 healthy subjects for the first time. We demonstrate that the approach is able to measure differential tract properties in crossing fibre areas, reflecting the different myelination of tracts. We also show that tract-specific T1 has less inter-subject variability compared to conventional T1 in areas of crossing fibres, suggesting increased specificity to distinct fibre populations. Finally we show in simulations that changes in myelination selectively affecting one fibre bundle in crossing fibre areas can potentially be detected earlier using IR-DTI. We apply the inversion recovery DTI approach to the human brain in vivo for the first time. We demonstrate that IR-DTI can measure tract-specific T1 in crossing fibres. IR-DTI T1 has less inter-subject variability compared to conventional T1 in crossing fibres. Changes in myelination affecting one fibre in crossing fibres can be detected earlier using IR-DTI.
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Affiliation(s)
- Silvia De Santis
- CUBRIC, School of Psychology, Cardiff University, Cardiff CF24 4HQ,UK; Maastricht University, Maastricht, The Netherlands.
| | - Yaniv Assaf
- Department of Neurobiology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ben Jeurissen
- iMinds-Vision Lab, Dept. of Physics, University of Antwerp, Antwerp, Belgium
| | - Derek K Jones
- CUBRIC, School of Psychology, Cardiff University, Cardiff CF24 4HQ,UK; Neuroscience & Mental Health Research Institute, Cardiff University, CF10 3AT,UK
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118
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Alonso-Ortiz E, Levesque IR, Paquin R, Pike GB. Field inhomogeneity correction for gradient echo myelin water fraction imaging. Magn Reson Med 2016; 78:49-57. [DOI: 10.1002/mrm.26334] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/06/2016] [Accepted: 06/16/2016] [Indexed: 12/20/2022]
Affiliation(s)
- Eva Alonso-Ortiz
- Medical Physics Unit, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,McConnell Brain Imaging Centre, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada
| | - Ives R Levesque
- Medical Physics Unit, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,Department of Oncology, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,Research Institute of the McGill University Health Centre, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada
| | | | - G Bruce Pike
- Medical Physics Unit, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,McConnell Brain Imaging Centre, McGill University, 3801 University Street, Montreal, QC, H3A 2B4, Canada.,Department of Radiology and Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
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119
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Desmond KL, Al-Ebraheem A, Janik R, Oakden W, Kwiecien JM, Dabrowski W, Rola R, Geraki K, Farquharson MJ, Stanisz GJ, Bock NA. Differences in iron and manganese concentration may confound the measurement of myelin from R1 and R2 relaxation rates in studies of dysmyelination. NMR IN BIOMEDICINE 2016; 29:985-998. [PMID: 27226282 DOI: 10.1002/nbm.3549] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/20/2016] [Accepted: 04/10/2016] [Indexed: 06/05/2023]
Abstract
A model of dysmyelination, the Long Evans Shaker (les) rat, was used to study the contribution of myelin to MR tissue properties in white matter. A large region of white matter was identified in the deep cerebellum and was used for measurements of the MR relaxation rate constants, R1 = 1/T1 and R2 = 1/T2 , at 7 T. In this study, R1 of the les deep cerebellar white matter was found to be 0.55 ± 0.08 s (-1) and R2 was found to be 15 ± 1 s(-1) , revealing significantly lower R1 and R2 in les white matter relative to wild-type (wt: R1 = 0.69 ± 0.05 s(-1) and R2 = 18 ± 1 s(-1) ). These deviated from the expected ΔR1 and ΔR2 values, given a complete lack of myelin in the les white matter, derived from the literature using values of myelin relaxivity, and we suspect that metals could play a significant role. The absolute concentrations of the paramagnetic transition metals iron (Fe) and manganese (Mn) were measured by a micro-synchrotron radiation X-ray fluorescence (μSRXRF) technique, with significantly greater Fe and Mn in les white matter than in wt (in units of μg [metal]/g [wet weight tissue]: les: Fe concentration,19 ± 1; Mn concentration, 0.71 ± 0.04; wt: Fe concentration,10 ± 1; Mn concentration, 0.47 ± 0.04). These changes in Fe and Mn could explain the deviations in R1 and R2 from the expected values in white matter. Although it was found that the influence of myelin still dominates R1 and R2 in wt rats, there were non-negligible changes in the contribution of the metals to relaxation. Although there are already problems with the estimation of myelin from R1 and R2 changes in disease models with pathology that also affects the relaxation rate constants, this study points to a specific pitfall in the estimation of changes in myelin in diseases or models with disrupted concentrations of paramagnetic transition metals. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Kimberly L Desmond
- Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
- Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Alia Al-Ebraheem
- School of Interdisciplinary Science, Medical Radiation Sciences program, McMaster University, Hamilton, ON, Canada
| | - Rafal Janik
- Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada
- Medical Biophysics, University of Toronto, ON, Canada
| | - Wendy Oakden
- Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada
- Medical Biophysics, University of Toronto, ON, Canada
| | - Jacek M Kwiecien
- Pathology & Molecular Medicine, McMaster University, Hamilton, ON, Canada
- Department of Clinical Pathomorphology, Lublin Medical University, Lublin, Poland
| | - Wojciech Dabrowski
- Anaesthesiology and Intensive Therapy, Lublin Medical University, Lublin, Poland
| | - Radoslaw Rola
- Neurosurgery & Pediatric Neurosurgery, Lublin Medical University, Lublin, Poland
| | - Kalotina Geraki
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, UK
| | - Michael J Farquharson
- School of Interdisciplinary Science, Medical Radiation Sciences program, McMaster University, Hamilton, ON, Canada
| | - Greg J Stanisz
- Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada
- Medical Biophysics, University of Toronto, ON, Canada
- Neurosurgery & Pediatric Neurosurgery, Lublin Medical University, Lublin, Poland
| | - Nicholas A Bock
- Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
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120
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Li W, Long JA, Watts L, Shen Q, Liu Y, Jiang Z, Duong TQ. Spatiotemporal changes in diffusion, T2 and susceptibility of white matter following mild traumatic brain injury. NMR IN BIOMEDICINE 2016; 29:896-903. [PMID: 27149577 PMCID: PMC4909565 DOI: 10.1002/nbm.3536] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 03/09/2016] [Accepted: 03/16/2016] [Indexed: 06/05/2023]
Abstract
Impaired white matter integrity in traumatic brain injury (TBI) can lead to deficits in various neurological functions. The differentiation of the underlying pathological processes, e.g. edema, demyelination, axonal damage, to name a few, is of key clinical interest for the assessment of white matter injury. In this study, a combination of T2 , diffusion and susceptibility MRI was used to study the spatiotemporal changes in white matter at 1 h, 3 h, and 1, 2, 7 and 14 days following TBI, using a rat controlled cortical impact (CCI) model. Based on radial diffusivity (RD), the rats were divided into two groups: group 1 showed widespread increases in RD along the corpus callosum of the ipsilesional hemisphere at day 2, and group 2 showed normal RD. Based on this group separation, group 1 also showed similar widespread changes in fractional anisotropy (FA) and T2 at day 2, and group 2 showed normal FA and T2 . The widespread changes in RD and T2 in group 1 on day 2 were apparently dominated by edema, which obscured possible myelin and axonal damage. In contrast, the susceptibility of group 1 showed more localized increases near the impact site on day 2, and otherwise similar contrast to the contralesional hemisphere. The localized susceptibility increase is probably a result of demyelination and axonal injury. The extent of brain damage between the two groups revealed by MRI was consistent with behavioral results, with the first group showing significantly increased forelimb asymmetry and increased forelimb foot fault deficits. Our results suggest that the combination of T2 , diffusion and susceptibility MRI may provide an opportunity for the differential assessment of edema and axonal damage in TBI. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Wei Li
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA
- Department of Ophthalmology, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Justin Alexander Long
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | | | | | | | - Zhao Jiang
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Timothy Q. Duong
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA
- Department of Ophthalmology, University of Texas Health Science Center at San Antonio, TX 78229, USA
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121
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van Gelderen P, Jiang X, Duyn JH. Rapid measurement of brain macromolecular proton fraction with transient saturation transfer MRI. Magn Reson Med 2016; 77:2174-2185. [PMID: 27342121 DOI: 10.1002/mrm.26304] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/18/2016] [Accepted: 05/19/2016] [Indexed: 01/08/2023]
Abstract
PURPOSE To develop an efficient MRI approach to estimate the nonwater proton fraction (f) in human brain. METHODS We implement a brief, efficient magnetization transfer (MT) pulse that selectively saturates the magnetization of the (semi-) solid protons, and monitor the transfer of this saturation to the water protons as a function of delay after saturation. RESULTS Analysis of the transient MT effect with two-pool model allowed robust extraction of f at both 3 and 7 T. This required estimating the longitudinal relaxation rate constant (R1,MP and R1,WP ) for both proton pools, which was achieved with the assumption of uniform R1,MP and R1,WP across brain tissues. Resulting values of f were approximately 50% higher than reported previously, which is partly attributed to MT-pulse efficiency and R1,MP being higher than assumed previously. CONCLUSION Experiments performed on human brain in vivo at 3 and 7 T demonstrate the ability of the method to robustly determine f in a scan time of approximately 5 min. Magn Reson Med 77:2174-2185, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Xu Jiang
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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122
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Sood S, Urriola J, Reutens D, O'Brien K, Bollmann S, Barth M, Vegh V. Echo time-dependent quantitative susceptibility mapping contains information on tissue properties. Magn Reson Med 2016; 77:1946-1958. [PMID: 27221590 DOI: 10.1002/mrm.26281] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/29/2016] [Accepted: 04/29/2016] [Indexed: 12/12/2022]
Abstract
PURPOSE Magnetic susceptibility is a physical property of matter that varies depending on chemical composition and abundance of different molecular species. Interest is growing in mapping of magnetic susceptibility in the human brain using magnetic resonance imaging techniques, but the influences affecting the mapped values are not fully understood. METHODS We performed quantitative susceptibility mapping on 7 Tesla (T) multiple echo time gradient recalled echo data and evaluated the trend in 10 regions of the human brain. Temporal plots of susceptibility were performed in the caudate, pallidum, putamen, thalamus, insula, red nucleus, substantia nigra, internal capsule, corpus callosum, and fornix. We implemented an existing three compartment signal model and used optimization to fit the experimental result to assess the influences that could be responsible for our findings. RESULTS The temporal trend in susceptibility is different for different brain regions, and subsegmentation of specific regions suggests that differences are likely to be attributable to variations in tissue structure and composition. Using a signal model, we verified that a nonlinear temporal behavior in experimentally computed susceptibility within imaging voxels may be the result of the heterogeneous composition of tissue properties. CONCLUSIONS Decomposition of voxel constituents into meaningful parameters may lead to informative measures that reflect changes in tissue microstructure. Magn Reson Med 77:1946-1958, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Surabhi Sood
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
| | - Javier Urriola
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
| | - David Reutens
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
| | | | - Steffen Bollmann
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
| | - Markus Barth
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
| | - Viktor Vegh
- Centre for Advanced Imaging, the University of Queensland, Brisbane, Australia
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123
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Abstract
Over the past few decades, MRI-based visualization of demyelinated CNS lesions has become pivotal to the diagnosis and monitoring of multiple sclerosis (MS). In this Review, we outline current efforts to correlate imaging findings with the pathology of lesion development in MS, and the pitfalls that are being encountered in this research. Multimodal imaging at high and ultra-high magnetic field strengths is yielding biologically relevant insights into the pathophysiology of blood-brain barrier dynamics and both active and chronic inflammation, as well as mechanisms of lesion healing and remyelination. Here, we parallel the results in humans with advances in imaging of a primate model of MS - experimental autoimmune encephalomyelitis (EAE) in the common marmoset - in which demyelinated lesions resemble their human counterparts far more closely than do EAE lesions in the rodent. This approach holds promise for the identification of innovative biological markers, and for next-generation clinical trials that will focus more on tissue protection and repair.
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124
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Abstract
PURPOSE OF REVIEW Current computational neuroanatomy based on MRI focuses on morphological measures of the brain. We present recent methodological developments in quantitative MRI (qMRI) that provide standardized measures of the brain, which go beyond morphology. We show how biophysical modelling of qMRI data can provide quantitative histological measures of brain tissue, leading to the emerging field of in-vivo histology using MRI (hMRI). RECENT FINDINGS qMRI has greatly improved the sensitivity and specificity of computational neuroanatomy studies. qMRI metrics can also be used as direct indicators of the mechanisms driving observed morphological findings. For hMRI, biophysical models of the MRI signal are being developed to directly access histological information such as cortical myelination, axonal diameters or axonal g-ratio in white matter. Emerging results indicate promising prospects for the combined study of brain microstructure and function. SUMMARY Non-invasive brain tissue characterization using qMRI or hMRI has significant implications for both research and clinics. Both approaches improve comparability across sites and time points, facilitating multicentre/longitudinal studies and standardized diagnostics. hMRI is expected to shed new light on the relationship between brain microstructure, function and behaviour, both in health and disease, and become an indispensable addition to computational neuroanatomy.
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125
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Aggarwal M, Kageyama Y, Li X, van Zijl PC. B0 -orientation dependent magnetic susceptibility-induced white matter contrast in the human brainstem at 11.7T. Magn Reson Med 2016; 75:2455-63. [PMID: 27018784 DOI: 10.1002/mrm.26208] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 02/12/2016] [Accepted: 02/18/2016] [Indexed: 01/17/2023]
Abstract
PURPOSE To investigate B0 -field-orientation dependent white matter contrast in the human brainstem based on R2 * and frequency difference (Δf) mapping from gradient echo (GRE) imaging at 11.7T. METHODS Multi-echo GRE data were acquired from two fixed human brainstem specimens at multiple orientations with respect to the static B0 field. The B0 -orientation dependent modulation curves of R2 * and Δf measurements between short and long echo time regimes were used to reconstruct maps of three-dimensional (3D) white matter orientation vectors. The results were compared with maps from diffusion MRI, susceptibility tensor imaging, and histological staining of the same specimens. RESULTS R2 * and Δf maps demonstrated distinct and significant contrast modulation between the corticospinal tract (CST) and transverse pontine fibers (TPF) dependent on B0 orientation. Interleaved fiber orientations of the CST and TPF could be sensitively resolved based on field-orientation-dependent fitting of the R2 * and Δf measurements. The fitted 3D orientation vector maps and peak-to-peak amplitude of R2 * and Δf modulation exhibited close correspondence to primary eigenvector and anisotropy maps derived from diffusion MRI. The amplitude of B0 -orientation dependent R2 * modulation was significantly (P < 0.005) higher in the CST compared with TPF, while fractional anisotropies were comparable. CONCLUSION The findings of this study demonstrate the potential of B0 -orientation dependent susceptibility-induced R2 * and Δf contrasts to probe tract-specific orientation and microstructure in white matter. Magn Reson Med 75:2455-2463, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Manisha Aggarwal
- Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Yusuke Kageyama
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Xu Li
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Peter C van Zijl
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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Qin S, Liu F, Turner IW, Yu Q, Yang Q, Vegh V. Characterization of anomalous relaxation using the time-fractional Bloch equation and multiple echo T2*-weighted magnetic resonance imaging at 7 T. Magn Reson Med 2016; 77:1485-1494. [DOI: 10.1002/mrm.26222] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/25/2016] [Accepted: 02/28/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Shanlin Qin
- School of Mathematical Sciences; Queensland University of Technology; GPO Box 2434 Brisbane Qld 4001 Australia
| | - Fawang Liu
- School of Mathematical Sciences; Queensland University of Technology; GPO Box 2434 Brisbane Qld 4001 Australia
| | - Ian W. Turner
- School of Mathematical Sciences; Queensland University of Technology; GPO Box 2434 Brisbane Qld 4001 Australia
- ARC Centre of Excellence for Mathematical and Statistical Frontiers; Melbourne Victoria Australia
| | - Qiang Yu
- Centre for Advanced Imaging, the University of Queensland; Brisbane Queensland Australia
| | - Qianqian Yang
- School of Mathematical Sciences; Queensland University of Technology; GPO Box 2434 Brisbane Qld 4001 Australia
| | - Viktor Vegh
- Centre for Advanced Imaging, the University of Queensland; Brisbane Queensland Australia
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127
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Sukstanskii AL, Wen J, Cross AH, Yablonskiy DA. Simultaneous multi-angular relaxometry of tissue with MRI (SMART MRI): Theoretical background and proof of concept. Magn Reson Med 2016; 77:1296-1306. [PMID: 26991525 DOI: 10.1002/mrm.26176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 01/29/2016] [Accepted: 01/31/2016] [Indexed: 01/09/2023]
Abstract
PURPOSE Accurate measurement of tissue-specific relaxation parameters is an ultimate goal of quantitative MRI. The objective of this study is to introduce a new technique, simultaneous multiangular relaxometry of tissue with MRI (SMART MRI), which provides naturally coregistered quantitative spin density, longitudinal and transverse relaxation rate constant maps along with parameters characterizing magnetization transfer (MT) effects. THEORY AND METHODS SMART MRI is based on a gradient-recalled echo MRI sequence with multiple flip angles and multiple gradient echoes and a derived theoretical expression for the MR signal generated in this experimental conditions. The theory, based on Bloch-McConnell equations, takes into consideration cross-relaxation between two water pools: "free" and "bound" to macromolecules. It describes the role of cross-relaxation effects in formation of longitudinal and transverse relaxation of "free" water signal, thus providing background for measurements of these effects without using MT pulses. Bayesian analysis is used to optimize SMART MRI sequence parameters. RESULTS Data obtained on three participants demonstrate feasibility of the proposed approach. CONCLUSION SMART MRI provides quantitative measurements of longitudinal and transverse relaxation rate constants of "free" water signal affected by cross-relaxation effects. It also provides information on some essential MT parameters without requiring off-resonance MT pulses. Magn Reson Med 77:1296-1306, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
| | - Jie Wen
- Department of Radiology, Washington University, St. Louis, Missouri, USA
| | - Anne H Cross
- Department of Radiology, Washington University, St. Louis, Missouri, USA
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128
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Spring cleaning: time to rethink imaging research lines in MS? J Neurol 2016; 263:1893-902. [PMID: 26886204 DOI: 10.1007/s00415-016-8060-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 02/03/2016] [Accepted: 02/03/2016] [Indexed: 12/15/2022]
Abstract
Together with recently advanced MRI technological capability, new needs and updated questions are emerging in imaging research in multiple sclerosis (MS), especially with respect to the identification of novel in vivo biomarkers of MS-relevant pathological processes. Expected benefits will involve approaches to diagnosis and clinical classification. In detail, three main points of discussion are addressed in this review: (1) new imaging biomarkers (centrifugal/centripetal lesion enhancement, central vein, paramagnetic rims at the lesion edge, subpial cortical demyelination); (2) thinking about high-resolution MR from a pathological perspective (from postmortem to in vivo staging); and (3) the clinical utility of quantitative MRI. In this context, research efforts should increasingly be focused on the direct in vivo visualization of "hidden" inflammation, beyond what can be detected with conventional gadolinium-based methods, as well as remyelination and repair, since these are likely to represent critical pathological processes and potential therapeutic targets. Concluding remarks concern the limitations, challenges, and ultimately clinical role of non-conventional MRI techniques.
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129
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Ulrich X, Yablonskiy DA. Separation of cellular and BOLD contributions to T2* signal relaxation. Magn Reson Med 2016; 75:606-15. [PMID: 25754288 PMCID: PMC4565789 DOI: 10.1002/mrm.25610] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 12/12/2014] [Accepted: 12/17/2014] [Indexed: 01/05/2023]
Abstract
PURPOSE The development of a reliable clinical technique for quantitative measurements of the parameters defining the BOLD effect, i.e., oxygen extraction fraction (OEF), and deoxygenated cerebral blood volume, dCBV, is needed to study brain function in health and disease. Herein we propose such a technique that is based on a widely available gradient recalled echo (GRE) MRI. THEORY AND METHODS Our method is based on GRE with multiple echoes and a model of signal decay (Yablonskiy, MRM 1998) that takes into account microscopic cellular (R2), mesoscopic (BOLD), and macroscopic (background field gradients) contributions to the GRE signal decay with additional accounting for physiologic fluctuations. RESULTS Using 3 Tesla MRI, we generate high resolution quantitative maps of R2*, R2, R2', and tissue concentration of deoxyhemoglobin, the latter providing a quantitative version of SWI. Our results for OEF and dCBV in gray matter are in a reasonable agreement with the literature data. CONCLUSION The proposed approach allows generating high resolution maps of hemodynamic parameters using clinical MRI. The technique can be applied to study such tissues as gray matter, tumors, etc.; however, it requires further development for use in tissues where extra- and intracellular compartments possess substantially different frequencies and relaxation properties (e.g., white matter).
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Affiliation(s)
- Xialing Ulrich
- Department of Radiology, Washington University, St. Louis MO, 63130, USA
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130
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Uddin MN, Lebel RM, Wilman AH. Value of transverse relaxometry difference methods for iron in human brain. Magn Reson Imaging 2016; 34:51-9. [DOI: 10.1016/j.mri.2015.09.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 05/06/2015] [Accepted: 09/11/2015] [Indexed: 01/14/2023]
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131
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van Gelderen P, Jiang X, Duyn JH. Effects of magnetization transfer on T1 contrast in human brain white matter. Neuroimage 2015; 128:85-95. [PMID: 26724780 DOI: 10.1016/j.neuroimage.2015.12.032] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 12/17/2015] [Accepted: 12/20/2015] [Indexed: 11/17/2022] Open
Abstract
MRI based on T1 relaxation contrast is increasingly being used to study brain morphology and myelination. Although it provides for excellent distinction between the major tissue types of gray matter, white matter, and CSF, reproducible quantification of T1 relaxation rates is difficult due to the complexity of the contrast mechanism and dependence on experimental details. In this work, we perform simulations and inversion-recovery MRI measurements at 3T and 7T to show that substantial measurement variability results from unintended and uncontrolled perturbation of the magnetization of MRI-invisible (1)H protons of lipids and macromolecules. This results in bi-exponential relaxation, with a fast component whose relative contribution under practical conditions can reach 20%. This phenomenon can strongly affect apparent relaxation rates, affect contrast between tissue types, and result in contrast variations over the brain. Based on this novel understanding, ways are proposed to minimize this experimental variability and its effect on T1 contrast, quantification accuracy and reproducibility.
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Affiliation(s)
- Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Xu Jiang
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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132
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Foundations of MRI phase imaging and processing for Quantitative Susceptibility Mapping (QSM). Z Med Phys 2015; 26:6-34. [PMID: 26702760 DOI: 10.1016/j.zemedi.2015.10.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 09/18/2015] [Accepted: 10/27/2015] [Indexed: 01/27/2023]
Abstract
Quantitative Susceptibility Mapping (QSM) is a novel MRI based technique that relies on estimates of the magnetic field distribution in the tissue under examination. Several sophisticated data processing steps are required to extract the magnetic field distribution from raw MRI phase measurements. The objective of this review article is to provide a general overview and to discuss several underlying assumptions and limitations of the pre-processing steps that need to be applied to MRI phase data before the final field-to-source inversion can be performed. Beginning with the fundamental relation between MRI signal and tissue magnetic susceptibility this review covers the reconstruction of magnetic field maps from multi-channel phase images, background field correction, and provides an overview of state of the art QSM solution strategies.
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133
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Wisnieff C, Liu T, Wang Y, Spincemaille P. The influence of molecular order and microstructure on the R2* and the magnetic susceptibility tensor. Magn Reson Imaging 2015; 34:682-9. [PMID: 26692502 DOI: 10.1016/j.mri.2015.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 12/03/2015] [Accepted: 12/07/2015] [Indexed: 01/07/2023]
Abstract
In this work, we demonstrate that in the presence of ordered sub-voxel structure such as tubular organization, biomaterials with molecular isotropy exhibits only apparent R2* anisotropy, while biomaterials with molecular anisotropy exhibit both apparent R2* and susceptibility anisotropy by means of susceptibility tensor imaging (STI). To this end, R2* and STI from gradient echo magnitude and phase data were examined in phantoms made from carbon fiber and Gadolinium (Gd) solutions with and without intrinsic molecular order and sub-voxel structure as well as in the in vivo brain. Confidence in the tensor reconstructions was evaluated with a wild bootstrap analysis. Carbon fiber showed both apparent anisotropy in R2* and anisotropy in STI, while the Gd filled capillary tubes only showed apparent anisotropy on R2*. Similarly, white matter showed anisotropic R2* and magnetic susceptibility with higher confidence, while the cerebral veins displayed only strong apparent R2* tensor anisotropy. Ordered sub-voxel tissue microstructure leads to apparent R2* anisotropy, which can be found in both white matter tracts and cerebral veins. However, additional molecular anisotropy is required for magnetic susceptibility anisotropy, which can be found in white matter tracts but not in cerebral veins.
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Affiliation(s)
- Cynthia Wisnieff
- Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Tian Liu
- Department of Radiology, Weill Cornell Medical College, New York, NY, USA; Medimagemetric, LLC, New York, NY, USA
| | - Yi Wang
- Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA; Department of Radiology, Weill Cornell Medical College, New York, NY, USA
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134
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Nam Y, Kim DH, Lee J. Physiological noise compensation in gradient-echo myelin water imaging. Neuroimage 2015; 120:345-9. [PMID: 26172308 DOI: 10.1016/j.neuroimage.2015.07.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/02/2015] [Accepted: 07/05/2015] [Indexed: 11/30/2022] Open
Abstract
In MRI, physiological noise which originates from cardiac and respiratory functions can induce substantial errors in detecting small signals in the brain. In this work, we explored the effects of the physiological noise and their compensation methods in gradient-echo myelin water imaging (GRE-MWI). To reduce the cardiac function induced inflow noise, flow saturation RF pulses were applied to the inferior portion of the head, saturating inflow blood signals. For the respiratory function induced B0 fluctuation compensation, a navigator echo was acquired, and respiration induced phase errors were corrected during reconstruction. After the compensations, the resulting myelin water images show substantially improved image quality and reproducibility. These improvements confirm the importance and usefulness of the physiological noise compensations in GRE-MWI.
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Affiliation(s)
- Yoonho Nam
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea.
| | - Dong-Hyun Kim
- Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
| | - Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea.
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135
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Özcan A, Türkbey B, Choyke PL, Akin O, Aras Ö, Mun SK. Interactive Feature Space Explorer© for multi-modal magnetic resonance imaging. Magn Reson Imaging 2015; 33:804-15. [PMID: 25868623 PMCID: PMC4458231 DOI: 10.1016/j.mri.2015.03.007] [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: 12/16/2014] [Revised: 03/14/2015] [Accepted: 03/30/2015] [Indexed: 10/23/2022]
Abstract
Wider information content of multi-modal biomedical imaging is advantageous for detection, diagnosis and prognosis of various pathologies. However, the necessity to evaluate a large number images might hinder these advantages and reduce the efficiency. Herein, a new computer aided approach based on the utilization of feature space (FS) with reduced reliance on multiple image evaluations is proposed for research and routine clinical use. The method introduces the physician experience into the discovery process of FS biomarkers for addressing biological complexity, e.g., disease heterogeneity. This, in turn, elucidates relevant biophysical information which would not be available when automated algorithms are utilized. Accordingly, the prototype platform was designed and built for interactively investigating the features and their corresponding anatomic loci in order to identify pathologic FS regions. While the platform might be potentially beneficial in decision support generally and specifically for evaluating outlier cases, it is also potentially suitable for accurate ground truth determination in FS for algorithm development. Initial assessments conducted on two different pathologies from two different institutions provided valuable biophysical perspective. Investigations of the prostate magnetic resonance imaging data resulted in locating a potential aggressiveness biomarker in prostate cancer. Preliminary findings on renal cell carcinoma imaging data demonstrated potential for characterization of disease subtypes in the FS.
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Affiliation(s)
- Alpay Özcan
- Arlington Innovation Center: Health Research, Virginia Polytechnic Institute and State University, 900 N. Glebe Road, Arlington VA 22203, USA.
| | - Barış Türkbey
- Molecular Imaging Program, National Cancer Institute, National Institutes of Health, 10 Center Dr., MSC 1182, Bldg. 10, Rm. 1B40, Bethesda, MD 20892-1088, USA.
| | - Peter L Choyke
- Molecular Imaging Program, National Cancer Institute, National Institutes of Health, 10 Center Dr., MSC 1182, Bldg. 10, Rm. 1B40, Bethesda, MD 20892-1088, USA.
| | - Oguz Akin
- Memorial Sloan Kettering Cancer Center, 1275 York Ave C276, New York, NY 10065, USA.
| | - Ömer Aras
- Memorial Sloan Kettering Cancer Center, 1275 York Ave C276, New York, NY 10065, USA.
| | - Seong K Mun
- Arlington Innovation Center: Health Research, Virginia Polytechnic Institute and State University, 900 N. Glebe Road, Arlington VA 22203, USA.
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136
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Li X, Harrison DM, Liu H, Jones CK, Oh J, Calabresi PA, van Zijl PCM. Magnetic susceptibility contrast variations in multiple sclerosis lesions. J Magn Reson Imaging 2015; 43:463-73. [PMID: 26073973 DOI: 10.1002/jmri.24976] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 05/29/2015] [Accepted: 06/01/2015] [Indexed: 11/05/2022] Open
Abstract
PURPOSE Recent magnetic resonance imaging (MRI) studies have revealed heterogeneous magnetic susceptibility contrasts in multiple sclerosis (MS) lesions. Due to its sensitivity to disease-related iron and myelin changes, magnetic susceptibility-based measures may better reflect some pathological features of MS lesions. Hence, we sought to characterize MS lesions using combined R2* mapping and quantitative susceptibility mapping (QSM). MATERIALS AND METHODS In all, 306 MS lesions were selected from 24 MS patients who underwent 7T MRI. Maps of R2*, frequency, and quantitative susceptibility were calculated using acquired multiecho gradient echo (GRE) phase data. Lesions were categorized based on their image intensity or their anatomical locations. R2* and susceptibility values were quantified in each lesion based on manually drawn lesion masks and compared between lesion groups showing different contrast patterns. Correlations between R2* and susceptibility were also tested in these lesion groups. RESULTS In 38% of selected lesions the frequency map did not show the same contrast pattern as the susceptibility map. While most lesions (93%) showed hypointensity on R2*, the susceptibility contrast in lesions varied, with 40% being isointense and 58% being hyperintense in the lesion core. Significant correlations (r = 0.31, P < 0.001) between R2* and susceptibility were found in susceptibility hyperintense lesions, but not in susceptibility isointense lesions. In addition, a higher proportion (74%) of periventricular lesions was found to be susceptibility hyperintense as compared to subcortical (53%) or juxtacortical (38%) lesions. CONCLUSION Combining R2* and QSM is useful to characterize heterogeneity in MS lesions.
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Affiliation(s)
- Xu Li
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.,Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Daniel M Harrison
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Hongjun Liu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.,Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Department of Radiology, Guangdong Academy of Medical Sciences, Guangdong General Hospital, Guangzhou, China
| | - Craig K Jones
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.,Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jiwon Oh
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Peter A Calabresi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Peter C M van Zijl
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.,Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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137
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Nam Y, Lee J, Hwang D, Kim DH. Improved estimation of myelin water fraction using complex model fitting. Neuroimage 2015; 116:214-21. [PMID: 25858448 DOI: 10.1016/j.neuroimage.2015.03.081] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 02/28/2015] [Accepted: 03/17/2015] [Indexed: 01/20/2023] Open
Abstract
In gradient echo (GRE) imaging, three compartment water modeling (myelin water, axonal water and extracellular water) in white matter has been demonstrated to show different frequency shifts that depend on the relative orientation of fibers and the B0 field. This finding suggests that in GRE-based myelin water imaging, a signal model may need to incorporate frequency offset terms and become a complex-valued model. In the current study, three different signal models and fitting approaches (a magnitude model fitted to magnitude data, a complex model fitted to magnitude data, and a complex model fitted to complex data) were investigated to address the reliability of each model in the estimation of the myelin water signal. For the complex model fitted to complex data, a new fitting approach that does not require background phase removal was proposed. When the three models were compared, the results from the new complex model fitting showed the most stable parameter estimation.
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Affiliation(s)
- Yoonho Nam
- Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea; Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea
| | - Jongho Lee
- Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea.
| | - Dosik Hwang
- Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Dong-Hyun Kim
- Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
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138
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Li X, van Gelderen P, Sati P, de Zwart JA, Reich DS, Duyn JH. Detection of demyelination in multiple sclerosis by analysis of [Formula: see text] relaxation at 7 T. Neuroimage Clin 2015; 7:709-714. [PMID: 26594617 PMCID: PMC4593862 DOI: 10.1016/j.nicl.2015.02.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/25/2015] [Accepted: 02/27/2015] [Indexed: 10/27/2022]
Abstract
Multiple sclerosis (MS) is a relatively common cause of inflammatory demyelinating lesions of the central nervous system. In an attempt to detect and characterize ongoing demyelination in MS patient brains, we used a novel magnetic resonance imaging (MRI) technique, involving the fitting of a three-component model to the [Formula: see text] relaxation behavior at high-field (7 T). This model allowed estimation of the amount of myelin water (and thus indirectly myelin content), axonal water, and interstitial water. In this study, 25 relapsing-remitting MS patients underwent a 7 T MRI from which 12 gadolinium-enhancing lesions, 61 non-enhancing lesions, and their corresponding contralateral normal appearing white matter (NAWM) regions were analyzed. In both enhancing and non-enhancing lesions, the amplitude of myelin water was significantly decreased, and interstitial and axonal water were increased relative to the contralateral NAWM. Longer relaxation time [Formula: see text] of interstitial and axonal water, and lower frequency shift of axonal water, were also observed in both enhancing and non-enhancing lesions when compared to the contralateral NAWM. No significant difference was found between enhancing lesions and non-enhancing lesions. These findings suggest that the fitting of a three-component model to the [Formula: see text] decay curve in MS lesions may help to quantify myelin loss.
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Affiliation(s)
- Xiaozhen Li
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
- Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Center for Alzheimer Disease Research, Karolinska Institutet, Stockholm SE-141 57, Sweden
| | - Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Pascal Sati
- Translational Neuroradiology Unit, Division of Neuroimmunology and Neurovirology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jacco A. de Zwart
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Daniel S. Reich
- Translational Neuroradiology Unit, Division of Neuroimmunology and Neurovirology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeff H. Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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139
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Foxley S, Domowicz M, Karczmar GS, Schwartz N. 3D high spectral and spatial resolution imaging of ex vivo mouse brain. Med Phys 2015; 42:1463-72. [PMID: 25735299 PMCID: PMC5148176 DOI: 10.1118/1.4908203] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Widely used MRI methods show brain morphology both in vivo and ex vivo at very high resolution. Many of these methods (e.g., T2*-weighted imaging, phase-sensitive imaging, or susceptibility-weighted imaging) are sensitive to local magnetic susceptibility gradients produced by subtle variations in tissue composition. However, the spectral resolution of commonly used methods is limited to maintain reasonable run-time combined with very high spatial resolution. Here, the authors report on data acquisition at increased spectral resolution, with 3-dimensional high spectral and spatial resolution MRI, in order to analyze subtle variations in water proton resonance frequency and lineshape that reflect local anatomy. The resulting information compliments previous studies based on T2* and resonance frequency. METHODS The proton free induction decay was sampled at high resolution and Fourier transformed to produce a high-resolution water spectrum for each image voxel in a 3D volume. Data were acquired using a multigradient echo pulse sequence (i.e., echo-planar spectroscopic imaging) with a spatial resolution of 50 × 50 × 70 μm(3) and spectral resolution of 3.5 Hz. Data were analyzed in the spectral domain, and images were produced from the various Fourier components of the water resonance. This allowed precise measurement of local variations in water resonance frequency and lineshape, at the expense of significantly increased run time (16-24 h). RESULTS High contrast T2*-weighted images were produced from the peak of the water resonance (peak height image), revealing a high degree of anatomical detail, specifically in the hippocampus and cerebellum. In images produced from Fourier components of the water resonance at -7.0 Hz from the peak, the contrast between deep white matter tracts and the surrounding tissue is the reverse of the contrast in water peak height images. This indicates the presence of a shoulder in the water resonance that is not present at +7.0 Hz and may be specific to white matter anatomy. Moreover, a frequency shift of 6.76 ± 0.55 Hz was measured between the molecular and granular layers of the cerebellum. This shift is demonstrated in corresponding spectra; water peaks from voxels in the molecular and granular layers are consistently 2 bins apart (7.0 Hz, as dictated by the spectral resolution) from one another. CONCLUSIONS High spectral and spatial resolution MR imaging has the potential to accurately measure the changes in the water resonance in small voxels. This information can guide optimization and interpretation of more commonly used, more rapid imaging methods that depend on image contrast produced by local susceptibility gradients. In addition, with improved sampling methods, high spectral and spatial resolution data could be acquired in reasonable run times, and used for in vivo scans to increase sensitivity to variations in local susceptibility.
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Affiliation(s)
| | - Miriam Domowicz
- Department of Pediatrics, University of Chicago, Chicago, Illinois 60637
| | | | - Nancy Schwartz
- Department of Pediatrics, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
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Lehto LJ, Garwood M, Gröhn O, Corum CA. Phase imaging in brain using SWIFT. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 252:20-28. [PMID: 25625826 PMCID: PMC4404316 DOI: 10.1016/j.jmr.2014.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 12/12/2014] [Accepted: 12/15/2014] [Indexed: 06/04/2023]
Abstract
The majority of MRI phase imaging is based on gradient recalled echo (GRE) sequences. This work studies phase contrast behavior due to small off-resonance frequency offsets in brain using SWIFT, a FID-based sequence with nearly zero acquisition delay. 1D simulations and a phantom study were conducted to describe the behavior of phase accumulation in SWIFT. Imaging experiments of known brain phase contrast properties were conducted in a perfused rat brain comparing GRE and SWIFT. Additionally, a human brain sample was imaged. It is demonstrated how SWIFT phase is orientation dependent and correlates well with GRE, linking SWIFT phase to similar off-resonance sources as GRE. The acquisition time is shown to be analogous to TE for phase accumulation time. Using experiments with and without a magnetization transfer preparation, the likely effect of myelin water pool contribution is seen as a phase increase for all acquisition times. Due to the phase accumulation during acquisition, SWIFT phase contrast can be sensitized to small frequency differences between white and gray matter using low acquisition bandwidths.
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Affiliation(s)
- Lauri Juhani Lehto
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; Center for Magnetic Resonance Research, University of Minnesota, 2021 6th Street SE, Minneapolis, MN 55455, USA.
| | - Michael Garwood
- Center for Magnetic Resonance Research, University of Minnesota, 2021 6th Street SE, Minneapolis, MN 55455, USA.
| | - Olli Gröhn
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.
| | - Curtis Andrew Corum
- Center for Magnetic Resonance Research, University of Minnesota, 2021 6th Street SE, Minneapolis, MN 55455, USA.
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141
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Wang Y, Liu T. Quantitative susceptibility mapping (QSM): Decoding MRI data for a tissue magnetic biomarker. Magn Reson Med 2015; 73:82-101. [PMID: 25044035 PMCID: PMC4297605 DOI: 10.1002/mrm.25358] [Citation(s) in RCA: 570] [Impact Index Per Article: 63.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/13/2014] [Accepted: 06/18/2014] [Indexed: 01/03/2023]
Abstract
In MRI, the main magnetic field polarizes the electron cloud of a molecule, generating a chemical shift for observer protons within the molecule and a magnetic susceptibility inhomogeneity field for observer protons outside the molecule. The number of water protons surrounding a molecule for detecting its magnetic susceptibility is vastly greater than the number of protons within the molecule for detecting its chemical shift. However, the study of tissue magnetic susceptibility has been hindered by poor molecular specificities of hitherto used methods based on MRI signal phase and T2* contrast, which depend convolutedly on surrounding susceptibility sources. Deconvolution of the MRI signal phase can determine tissue susceptibility but is challenged by the lack of MRI signal in the background and by the zeroes in the dipole kernel. Recently, physically meaningful regularizations, including the Bayesian approach, have been developed to enable accurate quantitative susceptibility mapping (QSM) for studying iron distribution, metabolic oxygen consumption, blood degradation, calcification, demyelination, and other pathophysiological susceptibility changes, as well as contrast agent biodistribution in MRI. This paper attempts to summarize the basic physical concepts and essential algorithmic steps in QSM, to describe clinical and technical issues under active development, and to provide references, codes, and testing data for readers interested in QSM.
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Affiliation(s)
- Yi Wang
- Radiology, Weill Medical College of Cornell UniversityNew York, New York, USA
- Biomedical Engineering, Cornell UniversityIthaca, New York, USA
- Biomedical Engineering, Kyung Hee UniversitySeoul, South Korea
| | - Tian Liu
- MedImageMetric, LLCNew York, New York, USA
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142
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Li W, Wang N, Yu F, Han H, Cao W, Romero R, Tantiwongkosi B, Duong TQ, Liu C. A method for estimating and removing streaking artifacts in quantitative susceptibility mapping. Neuroimage 2014; 108:111-22. [PMID: 25536496 DOI: 10.1016/j.neuroimage.2014.12.043] [Citation(s) in RCA: 233] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Revised: 12/13/2014] [Accepted: 12/16/2014] [Indexed: 12/17/2022] Open
Abstract
Quantitative susceptibility mapping (QSM) is a novel MRI method for quantifying tissue magnetic property. In the brain, it reflects the molecular composition and microstructure of the local tissue. However, susceptibility maps reconstructed from single-orientation data still suffer from streaking artifacts which obscure structural details and small lesions. We propose and have developed a general method for estimating streaking artifacts and subtracting them from susceptibility maps. Specifically, this method uses a sparse linear equation and least-squares (LSQR)-algorithm-based method to derive an initial estimation of magnetic susceptibility, a fast quantitative susceptibility mapping method to estimate the susceptibility boundaries, and an iterative approach to estimate the susceptibility artifact from ill-conditioned k-space regions only. With a fixed set of parameters for the initial susceptibility estimation and subsequent streaking artifact estimation and removal, the method provides an unbiased estimate of tissue susceptibility with negligible streaking artifacts, as compared to multi-orientation QSM reconstruction. This method allows for improved delineation of white matter lesions in patients with multiple sclerosis and small structures of the human brain with excellent anatomical details. The proposed methodology can be extended to other existing QSM algorithms.
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Affiliation(s)
- Wei Li
- Brain Imaging and Analysis Center, Duke University, Durham NC 27705, USA; Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA; Department of Ophthalmology, University of Texas Health Science Center at San Antonio, TX 78229, USA.
| | - Nian Wang
- Brain Imaging and Analysis Center, Duke University, Durham NC 27705, USA
| | - Fang Yu
- Department of Radiology, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Hui Han
- Brain Imaging and Analysis Center, Duke University, Durham NC 27705, USA
| | - Wei Cao
- Brain Imaging and Analysis Center, Duke University, Durham NC 27705, USA; Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Rebecca Romero
- Department of Neurology, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Bundhit Tantiwongkosi
- Department of Radiology, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Timothy Q Duong
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, TX 78229, USA
| | - Chunlei Liu
- Brain Imaging and Analysis Center, Duke University, Durham NC 27705, USA; Department of Radiology, School of Medicine, Duke University, Durham NC 27705, USA.
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143
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Yablonskiy DA, Sukstanskii AL. Generalized Lorentzian Tensor Approach (GLTA) as a biophysical background for quantitative susceptibility mapping. Magn Reson Med 2014; 73:757-64. [PMID: 25426775 DOI: 10.1002/mrm.25538] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 10/20/2014] [Accepted: 10/30/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE Quantitative susceptibility mapping (QSM) is a potentially powerful technique for mapping tissue magnetic susceptibility from gradient recalled echo (GRE) MRI. Herein we aim to derive the relationships between GRE signal phase and the underlying tissue microstructure and magnetic susceptibility at the cellular level. METHODS We use Maxwell's equations and a statistical approach to derive the expression for the magnetic-susceptibility-induced MR signal frequency shift of the GRE signal in single- and multicompartment systems, in which inhomogeneous magnetic field is induced by the cellular constituents (proteins, lipids, iron, etc.) distributed in intra- and extracellular spaces. RESULTS We introduce the Generalized Lorentzian Tensor Approach (GLTA) that accounts for both types of anisotropy: the anisotropy of magnetic susceptibility and the structural tissue anisotropy. In the GLTA the frequency shift due to the local environment is characterized by the Lorentzian tensor L⁁ which has a substantially different structure than the susceptibility tensor χ⁁. While components of χ⁁ are simply compartmental susceptibilities "weighted" by their relative volumes, the components of L⁁ are weighted by specific numerical factors depending on tissue micro-symmetry and parameters related to the MR pulse sequence. We also provide equations bridging phenomenological and microscopic considerations. CONCLUSION The GLTA provides a consistent background for deciphering phase data.
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144
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Ward RJ, Zucca FA, Duyn JH, Crichton RR, Zecca L. The role of iron in brain ageing and neurodegenerative disorders. Lancet Neurol 2014; 13:1045-60. [PMID: 25231526 DOI: 10.1016/s1474-4422(14)70117-6] [Citation(s) in RCA: 1113] [Impact Index Per Article: 111.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SUMMARY In the CNS, iron in several proteins is involved in many important processes such as oxygen transportation, oxidative phosphorylation, myelin production, and the synthesis and metabolism of neurotransmitters. Abnormal iron homoeostasis can induce cellular damage through hydroxyl radical production, which can cause the oxidation and modification of lipids, proteins, carbohydrates, and DNA. During ageing, different iron complexes accumulate in brain regions associated with motor and cognitive impairment. In various neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, changes in iron homoeostasis result in altered cellular iron distribution and accumulation. MRI can often identify these changes, thus providing a potential diagnostic biomarker of neurodegenerative diseases. An important avenue to reduce iron accumulation is the use of iron chelators that are able to cross the blood-brain barrier, penetrate cells, and reduce excessive iron accumulation, thereby affording neuroprotection.
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Affiliation(s)
- Roberta J Ward
- Centre for Neuroinflammation and Neurodegeneration, Department of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK; Faculte de Science, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Fabio A Zucca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Robert R Crichton
- Faculte de Science, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Luigi Zecca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy.
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145
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Govindarajan ST, Cohen-Adad J, Sormani MP, Fan AP, Louapre C, Mainero C. Reproducibility of T2 * mapping in the human cerebral cortex in vivo at 7 tesla MRI. J Magn Reson Imaging 2014; 42:290-6. [PMID: 25407671 DOI: 10.1002/jmri.24789] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 10/16/2014] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND To assess the test-retest reproducibility of cortical mapping of T2 * relaxation rates at 7 Tesla (T) MRI. T2 * maps have been used for studying cortical myelo-architecture patterns in vivo and for characterizing conditions associated with changes in iron and/or myelin concentration. METHODS T2 * maps were calculated from 7T multi-echo T2 *-weighted images acquired during separate scanning sessions on 8 healthy subjects. The reproducibility of surface-based cortical T2 * mapping was assessed at different depths of the cortex; from pial surface (0% depth) towards gray/white matter boundary (100% depth), across cortical regions and hemispheres, using coefficients of variation (COVs = SD/mean) between each couple (scan-rescan) of average T2 * measurements. RESULTS Average cortical T2 * was significantly different among 25%, 50%, and 75% depths (analysis of variance, P < 0.001). Coefficient of variations were very low within cortical regions, and whole cortex (average COV = 0.83-1.79%), indicating a high degree of reproducibility in T2 * measures. CONCLUSION Surface-based mapping of T2 * relaxation rates as a function of cortical depth is reproducible and could prove useful for studying the laminar architecture of the cerebral cortex in vivo, and for investigating physiological and pathological states associated with changes in iron and/or myelin concentration.
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Affiliation(s)
| | - Julien Cohen-Adad
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.,Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
| | | | - Audrey P Fan
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.,Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Céline Louapre
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Caterina Mainero
- Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA.,Harvard Medical School, Boston, Massachusetts, USA
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146
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van Gelderen P, Mandelkow H, de Zwart JA, Duyn JH. A torque balance measurement of anisotropy of the magnetic susceptibility in white matter. Magn Reson Med 2014; 74:1388-96. [PMID: 25399830 DOI: 10.1002/mrm.25524] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/07/2014] [Accepted: 10/16/2014] [Indexed: 12/11/2022]
Abstract
PURPOSE Recent MRI studies have suggested that the magnetic susceptibility of white matter (WM) in the human brain is anisotropic, providing a new contrast mechanism for the visualization of fiber bundles and allowing the extraction of cellular compartment-specific information. This study provides an independent confirmation and quantification of this anisotropy. METHODS Anisotropic magnetic susceptibility results in a torque exerted on WM when placed in a uniform magnetic field, tending to align the WM fibers with the field. To quantify the effect, excised spinal cord samples were placed in a torque balance inside the magnet of a 7 T MRI system and the magnetic torque was measured as function of orientation. RESULTS All tissue samples (n = 5) showed orienting effects, confirming the presence of anisotropic susceptibility. Analysis of the magnetic torque resulted in reproducible values for the WM volume anisotropy that ranged from 13.6 to 19.2 ppb. CONCLUSION The independently determined anisotropy values confirm estimates inferred from MRI experiments and validate the use of anisotropy to extract novel information about brain fiber structure and myelination.
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Affiliation(s)
- Peter van Gelderen
- Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Hendrik Mandelkow
- Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Jacco A de Zwart
- Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Jeff H Duyn
- Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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147
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Haacke EM, Liu S, Buch S, Zheng W, Wu D, Ye Y. Quantitative susceptibility mapping: current status and future directions. Magn Reson Imaging 2014; 33:1-25. [PMID: 25267705 DOI: 10.1016/j.mri.2014.09.004] [Citation(s) in RCA: 353] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/14/2014] [Accepted: 09/22/2014] [Indexed: 01/13/2023]
Abstract
Quantitative susceptibility mapping (QSM) is a new technique for quantifying magnetic susceptibility. It has already found various applications in quantifying in vivo iron content, calcifications and changes in venous oxygen saturation. The accuracy of susceptibility mapping is dependent on several factors. In this review, we evaluate the entire process of QSM from data acquisition to individual data processing steps. We also show preliminary results of several new concepts introduced in this review in an attempt to improve the quality and accuracy for certain steps. The uncertainties in estimating susceptibility differences using susceptibility maps, phase images, and T2* maps are analyzed and compared. Finally, example clinical applications are presented. We conclude that QSM holds great promise in quantifying iron and becoming a standard clinical tool.
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Affiliation(s)
- E Mark Haacke
- Department of Radiology, Wayne State University, Detroit, MI, USA; School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada; Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China.
| | - Saifeng Liu
- School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada
| | - Sagar Buch
- School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada
| | - Weili Zheng
- Department of Radiology, Wayne State University, Detroit, MI, USA
| | - Dongmei Wu
- Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai, China
| | - Yongquan Ye
- Department of Radiology, Wayne State University, Detroit, MI, USA
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148
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Ward RJ, Zucca FA, Duyn JH, Crichton RR, Zecca L. The role of iron in brain ageing and neurodegenerative disorders. Lancet Neurol 2014. [PMID: 25231526 DOI: 10.1016/s1474-4422(14)70117-6.(] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
In the CNS, iron in several proteins is involved in many important processes such as oxygen transportation, oxidative phosphorylation, myelin production, and the synthesis and metabolism of neurotransmitters. Abnormal iron homoeostasis can induce cellular damage through hydroxyl radical production, which can cause the oxidation and modification of lipids, proteins, carbohydrates, and DNA. During ageing, different iron complexes accumulate in brain regions associated with motor and cognitive impairment. In various neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, changes in iron homoeostasis result in altered cellular iron distribution and accumulation. MRI can often identify these changes, thus providing a potential diagnostic biomarker of neurodegenerative diseases. An important avenue to reduce iron accumulation is the use of iron chelators that are able to cross the blood-brain barrier, penetrate cells, and reduce excessive iron accumulation, thereby affording neuroprotection.
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Affiliation(s)
- Roberta J Ward
- Centre for Neuroinflammation and Neurodegeneration, Department of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK; Faculte de Science, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Fabio A Zucca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Robert R Crichton
- Faculte de Science, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Luigi Zecca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy.
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149
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Kim D, Lee HM, Oh SH, Lee J. Probing signal phase in direct visualization of short transverse relaxation time component (ViSTa). Magn Reson Med 2014; 74:499-505. [PMID: 25154599 DOI: 10.1002/mrm.25416] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 07/03/2014] [Accepted: 07/28/2014] [Indexed: 11/08/2022]
Abstract
PURPOSE To demonstrate the phase evolutions of direct visualization of short transverse relaxation time component (ViSTa) matches with those of myelin water. METHOD Myelin water imaging (MWI) measures short transverse signals and has been suggested as a biomarker for myelin. Recently, a new approach, ViSTa, has been proposed to acquire short T2* signals by suppressing long T1 signals. This method does not require any ill-conditioned data processing and therefore provides high-quality images. In this study, the phase of the ViSTa signal was compared with the phase of myelin water simulated by the magnetic susceptibility model of hollow cylinder. RESULTS The phase evolutions of the ViSTa signal were similar to the simulated myelin water phase evolutions. When fiber orientation was perpendicular relative to the main magnetic field, both the ViSTa and the simulated myelin water phase showed large positive frequency shifts, whereas the gradient echo phase showed a slightly negative frequency shift. Additionally, the myelin water phase map generated using diffusion tensor imaging (DTI) information revealed a good match with the ViSTa phase image. CONCLUSION The results of this study support the origin of ViSTa signal as myelin water. ViSTa phase may potentially provide sensitivity to demyelination.
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Affiliation(s)
- Daeun Kim
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Signal and Image Processing Institute, Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA
| | - Hyo Min Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Se-Hong Oh
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Imaging Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Jongho Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Electrical and Computer Engineering, School of Engineering, Seoul National University, Seoul, Korea
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150
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Li X, van Zijl PCM. Mean magnetic susceptibility regularized susceptibility tensor imaging (MMSR-STI) for estimating orientations of white matter fibers in human brain. Magn Reson Med 2014; 72:610-9. [PMID: 24974830 DOI: 10.1002/mrm.25322] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 05/24/2014] [Accepted: 05/26/2014] [Indexed: 12/16/2022]
Abstract
PURPOSE An increasing number of studies show that magnetic susceptibility in white matter fibers is anisotropic and may be described by a tensor. However, the limited head rotation possible for in vivo human studies leads to an ill-conditioned inverse problem in susceptibility tensor imaging (STI). Here we suggest the combined use of limiting the susceptibility anisotropy to white matter and imposing morphology constraints on the mean magnetic susceptibility (MMS) for regularizing the STI inverse problem. METHODS The proposed MMS regularized STI (MMSR-STI) method was tested using computer simulations and in vivo human data collected at 3T. The fiber orientation estimated from both the STI and MMSR-STI methods was compared to that from diffusion tensor imaging (DTI). RESULTS Computer simulations show that the MMSR-STI method provides a more accurate estimation of the susceptibility tensor than the conventional STI approach. Similarly, in vivo data show that use of the MMSR-STI method leads to a smaller difference between the fiber orientation estimated from STI and DTI for most selected white matter fibers. CONCLUSION The proposed regularization strategy for STI can improve estimation of the susceptibility tensor in white matter.
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Affiliation(s)
- Xu Li
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA; Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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