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Liu F, Block WF, Kijowski R, Samsonov A. Rapid multicomponent relaxometry in steady state with correction of magnetization transfer effects. Magn Reson Med 2016; 75:1423-33. [PMID: 25959974 PMCID: PMC4637271 DOI: 10.1002/mrm.25672] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 01/26/2015] [Accepted: 02/06/2015] [Indexed: 11/07/2022]
Abstract
PURPOSE To study the effects of magnetization transfer (MT) on multicomponent T2 parameters obtained using mcDESPOT in macromolecule-rich tissues and to propose a new method called mcRISE to correct MT-induced biases. METHODS The two-pool mcDESPOT model was modified by the addition of an exchanging macromolecule proton pool to model the MT effect in cartilage. The mcRISE acquisition scheme was developed to provide sensitivity to all pools. An incremental fitting was applied to estimate MT and relaxometry parameters with minimized coupling. The interaction between MT and relaxometry parameters, efficacy of MT correction, and feasibility of mcRISE in vivo were investigated in simulations and in healthy volunteers. RESULTS The MT effect caused significant errors in multicomponent T1/T2 values and in fast-relaxing water fraction fF , which is consistent with previous experimental observations. fF increased significantly with macromolecule content if MT was ignored. mcRISE resulted in a multifold reduction of MT biases and yielded decoupled multicomponent T1/T2 relaxometry and quantitative MT parameters. CONCLUSION mcRISE is an efficient approach for correcting MT biases in multicomponent relaxometry based on steady state sequences. Improved specificity of mcRISE may help to elucidate the sources of the previously described high sensitivity of noncorrected mcDESPOT parameters to disease-related changes in cartilage and the brain.
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Affiliation(s)
- Fang Liu
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Walter F Block
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Richard Kijowski
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Alexey Samsonov
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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52
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Xu J, Li H, Li K, Harkins KD, Jiang X, Xie J, Kang H, Dortch RD, Anderson AW, Does MD, Gore JC. Fast and simplified mapping of mean axon diameter using temporal diffusion spectroscopy. NMR IN BIOMEDICINE 2016; 29:400-410. [PMID: 27077155 PMCID: PMC4832578 DOI: 10.1002/nbm.3484] [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] [Indexed: 05/29/2023]
Abstract
Mapping axon diameter is of interest for the potential diagnosis and monitoring of various neuronal pathologies. Advanced diffusion-weighted MRI methods have been developed to measure mean axon diameters non-invasively, but suffer major drawbacks that prevent their direct translation into clinical practice, such as complex non-linear data fitting and, more importantly, long scanning times that are usually not tolerable for most human subjects. In the current study, temporal diffusion spectroscopy using oscillating diffusion gradients was used to measure mean axon diameters with high sensitivity to small axons in the central nervous system. Axon diameters have been found to be correlated with a novel metric, DDR⊥ (the rate of dispersion of the perpendicular diffusion coefficient with gradient frequency), which is a model-free quantity that does not require complex data analyses and can be obtained from two diffusion coefficient measurements in clinically relevant times with conventional MRI machines. A comprehensive investigation including computer simulations and animal experiments ex vivo showed that measurements of DDR⊥ agree closely with histological data. In humans in vivo, DDR⊥ was also found to correlate well with reported mean axon diameters in human corpus callosum, and the total scan time was only about 8 min. In conclusion, DDR⊥ may have potential to serve as a fast, simple and model-free approach to map the mean axon diameter of white matter in clinics for assessing axon diameter changes.
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Affiliation(s)
- Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.
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53
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Mulas G, Anedda R, Longo D, Roggio T, Uzzau S. An MRI method for monitoring the ripening of Grana Padano cheese. Int Dairy J 2016. [DOI: 10.1016/j.idairyj.2015.08.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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54
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Barta R, Kalantari S, Laule C, Vavasour IM, MacKay AL, Michal CA. Modeling T(1) and T(2) relaxation in bovine white matter. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:56-67. [PMID: 26295169 DOI: 10.1016/j.jmr.2015.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 07/31/2015] [Accepted: 08/03/2015] [Indexed: 06/04/2023]
Abstract
The fundamental basis of T1 and T2 contrast in brain MRI is not well understood; recent literature contains conflicting views on the nature of relaxation in white matter (WM). We investigated the effects of inversion pulse bandwidth on measurements of T1 and T2 in WM. Hybrid inversion-recovery/Carr-Purcell-Meiboom-Gill experiments with broad or narrow bandwidth inversion pulses were applied to bovine WM in vitro. Data were analysed with the commonly used 1D-non-negative least squares (NNLS) algorithm, a 2D-NNLS algorithm, and a four-pool model which was based upon microscopically distinguishable WM compartments (myelin non-aqueous protons, myelin water, non-myelin non-aqueous protons and intra/extracellular water) and incorporated magnetization exchange between adjacent compartments. 1D-NNLS showed that different T2 components had different T1 behaviours and yielded dissimilar results for the two inversion conditions. 2D-NNLS revealed significantly more complicated T1/T2 distributions for narrow bandwidth than for broad bandwidth inversion pulses. The four-pool model fits allow physical interpretation of the parameters, fit better than the NNLS techniques, and fits results from both inversion conditions using the same parameters. The results demonstrate that exchange cannot be neglected when analysing experimental inversion recovery data from WM, in part because it can introduce exponential components having negative amplitude coefficients that cannot be correctly modeled with nonnegative fitting techniques. While assignment of an individual T1 to one particular pool is not possible, the results suggest that under carefully controlled experimental conditions the amplitude of an apparent short T1 component might be used to quantify myelin water.
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Affiliation(s)
- R Barta
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - S Kalantari
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - C Laule
- Department of Radiology, University of British Columbia, Vancouver, BC, Canada; Department of Pathology & Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada; International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada
| | - I M Vavasour
- Department of Radiology, University of British Columbia, Vancouver, BC, Canada
| | - A L MacKay
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada; Department of Radiology, University of British Columbia, Vancouver, BC, Canada
| | - C A Michal
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada.
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55
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Lin M, He H, Schifitto G, Zhong J. Simulation of changes in diffusion related to different pathologies at cellular level after traumatic brain injury. Magn Reson Med 2015; 76:290-300. [PMID: 26256558 DOI: 10.1002/mrm.25816] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 05/26/2015] [Indexed: 11/05/2022]
Abstract
PURPOSE The goal of the current study was to investigate tissue pathology at the cellular level in traumatic brain injury (TBI) as revealed by Monte Carlo simulation of diffusion tensor imaging (DTI)-derived parameters and elucidate the possible sources of conflicting findings of DTI abnormalities as reported in the TBI literature. METHODS A model with three compartments separated by permeable membranes was employed to represent the diffusion environment of water molecules in brain white matter. The dynamic diffusion process was simulated with a Monte Carlo method using adjustable parameters of intra-axonal diffusivity, axon separation, glial cell volume fraction, and myelin sheath permeability. The effects of tissue pathology on DTI parameters were investigated by adjusting the parameters of the model corresponding to different stages of brain injury. RESULTS The results suggest that the model is appropriate and the DTI-derived parameters simulate the predominant cellular pathology after TBI. Our results further indicate that when edema is not prevalent, axial and radial diffusivity have better sensitivity to axonal injury and demyelination than other DTI parameters. CONCLUSION DTI is a promising biomarker to detect and stage tissue injury after TBI. The observed inconsistencies among previous studies are likely due to scanning at different stages of tissue injury after TBI. Magn Reson Med 76:290-300, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Mu Lin
- Center for Brain Imaging Science and Technology, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hongjian He
- Center for Brain Imaging Science and Technology, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China
| | - Giovanni Schifitto
- Department of Neurology, University of Rochester Medical Center, Rochester, New York, USA.,Department of Imaging Sciences, University of Rochester Medical Center, Rochester, New York, USA
| | - Jianhui Zhong
- Center for Brain Imaging Science and Technology, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China.,Department of Imaging Sciences, University of Rochester Medical Center, Rochester, New York, USA
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56
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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: 40] [Impact Index Per Article: 4.4] [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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57
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Harkins KD, Xu J, Dula AN, Li K, Valentine WM, Gochberg DF, Gore JC, Does MD. The microstructural correlates of T1 in white matter. Magn Reson Med 2015; 75:1341-5. [PMID: 25920491 DOI: 10.1002/mrm.25709] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 02/11/2015] [Accepted: 03/05/2015] [Indexed: 12/14/2022]
Abstract
PURPOSE Several studies have shown strong correlations between myelin content and T1 within the brain, and have even suggested that T1 can be used to estimate myelin content. However, other micro-anatomical features such as compartment size are known to affect longitudinal relaxation rates, similar to compartment size effects in porous media. METHODS T1 measurements were compared with measured or otherwise published axon size measurements in white matter tracts of the rat spinal cord, rat brain, and human brain. RESULTS In both ex vivo and in vivo studies, correlations were present between the relaxation rate 1/T1 and axon size across regions of rat spinal cord with nearly equal myelin content. CONCLUSION While myelination is likely the dominant determinant of T1 in white matter, variations in white matter microstructure, independent of myelin volume fraction, may also be reflected in T1 differences between regions or subjects.
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Affiliation(s)
- Kevin D Harkins
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
| | - Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Adrienne N Dula
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Ke Li
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
| | | | - Daniel F Gochberg
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
| | - John C Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Mark D Does
- Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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58
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Xu J, Li H, Harkins KD, Jiang X, Xie J, Kang H, Does MD, Gore JC. Mapping mean axon diameter and axonal volume fraction by MRI using temporal diffusion spectroscopy. Neuroimage 2014; 103:10-19. [PMID: 25225002 PMCID: PMC4312203 DOI: 10.1016/j.neuroimage.2014.09.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 02/01/2023] Open
Abstract
Mapping mean axon diameter and intra-axonal volume fraction may have significant clinical potential because nerve conduction velocity is directly dependent on axon diameter, and several neurodegenerative diseases affect axons of specific sizes and alter axon counts. Diffusion-weighted MRI methods based on the pulsed gradient spin echo (PGSE) sequence have been reported to be able to assess axon diameter and volume fraction non-invasively. However, due to the relatively long diffusion times used, e.g. >20ms, the sensitivity to small axons (diameter<2μm) is low, and the derived mean axon diameter has been reported to be overestimated. In the current study, oscillating gradient spin echo (OGSE) diffusion sequences with variable frequency gradients were used to assess rat spinal white matter tracts with relatively short effective diffusion times (1-5ms). In contrast to previous PGSE-based methods, the extra-axonal diffusion cannot be modeled as hindered (Gaussian) diffusion when short diffusion times are used. Appropriate frequency-dependent rates are therefore incorporated into our analysis and validated by histology-based computer simulation of water diffusion. OGSE data were analyzed to derive mean axon diameters and intra-axonal volume fractions of rat spinal white matter tracts (mean axon diameter of ~1.27-5.54μm). The estimated values were in good agreement with histology, including the small axon diameters (<2.5μm). This study establishes a framework for the quantification of nerve morphology using the OGSE method with high sensitivity to small axons.
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Affiliation(s)
- Junzhong Xu
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA.
| | - Hua Li
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA
| | - Kevin D Harkins
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA
| | - Xiaoyu Jiang
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Jingping Xie
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Hakmook Kang
- Department of Biostatistics, Vanderbilt University, Nashville, TN 37203, USA
| | - Mark D Does
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA
| | - John C Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
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59
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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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60
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Piędzia W, Jasiński K, Kalita K, Tomanek B, Węglarz WP. White and gray matter contrast enhancement in MR images of the mouse brain in vivo using IR UTE with a cryo-coil at 9.4T. J Neurosci Methods 2014; 232:30-5. [DOI: 10.1016/j.jneumeth.2014.04.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 04/12/2014] [Accepted: 04/14/2014] [Indexed: 11/30/2022]
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61
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Alonso-Ortiz E, Levesque IR, Pike GB. MRI-based myelin water imaging: A technical review. Magn Reson Med 2014; 73:70-81. [PMID: 24604728 DOI: 10.1002/mrm.25198] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/11/2014] [Accepted: 02/12/2014] [Indexed: 12/19/2022]
Abstract
Multiexponential T2 relaxation time measurement in the central nervous system shows a component that originates from water trapped between the lipid bilayers of myelin. This myelin water component is of significant interest as it provides a myelin-specific MRI signal of value in assessing myelin changes in cerebral white matter in vivo. In this article, the various acquisition and analysis strategies proposed to date for myelin water imaging are reviewed and research conducted into their validity and clinical applicability is presented. Comparisons between the imaging methods are made with a discussion regarding potential difficulties and model limitations.
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Affiliation(s)
- Eva Alonso-Ortiz
- Medical Physics Unit, McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, 3801 University Street, room WB 321, Montreal, Quebec, Canada, H3A 2B4
| | - Ives R Levesque
- Department of Oncology, McGill University and Research Institute of the MUHC, 1650 Cedar Avenue, room L5-212.3, Montreal, Quebec, Canada, H3A 2G4
| | - G Bruce Pike
- Department of Radiology and Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada, T2N 4N1
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62
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Kozlowski P, Rosicka P, Liu J, Yung AC, Tetzlaff W. In vivo longitudinal Myelin Water Imaging in rat spinal cord following dorsal column transection injury. Magn Reson Imaging 2013; 32:250-8. [PMID: 24462106 DOI: 10.1016/j.mri.2013.12.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 10/15/2013] [Accepted: 12/01/2013] [Indexed: 11/29/2022]
Abstract
Longitudinal Myelin Water Imaging was carried out in vivo to characterize white matter damage following dorsal column transection (DC Tx) injury at the lumbar level L1 of rat spinal cords. A transmit-receive implantable coil system was used to acquire multiple spin-echo (MSE) quantitative T2 data from the lumbar spinal cords of 16 rats at one week pre-injury as well as 3 and 8weeks post-injury (117 microns in-plane resolution and 1.5mm slice thickness). In addition, ex vivo MSE and DTI data were acquired from cords fixed and excised at 3 or 8weeks post injury using a solenoid coil. The MSE data were used to generate Myelin Water Fractions (MWFs) as a surrogate measure of myelin content, while DTI data were acquired to study damage to the axons. Myelin damage was assessed histologically with Eriochrome cyanine (EC) and Myelin Basic Protein in degenerated myelin (dgen-MBP) staining, and axonal damage was assessed by neurofilament-H in combination with neuron specific beta-III-tubulin (NF/Tub) staining. These MRI and histological measures of injury were studied in the dorsal column at 5mm cranial and 5mm caudal to injury epicenter. MWF increased significantly at 3weeks post-injury at both the cranial and caudal sites, relative to baseline. The values on the cranial side of injury returned to baseline at 8weeks post-injury but remained elevated on the caudal side. This trend was found in both in vivo and ex vivo data. This MWF increase was likely due to the presence of myelin debris, which were cleared by 8 weeks on the cranial, but not the caudal, side. Both EC and dgen-MBP stains displayed similar trends. MWF showed significant correlation with EC staining (R=0.63, p=0.005 in vivo and R=0.74, p=0.0001 ex vivo). MWF also correlated strongly with the dgen-MBP stain, but only on the cranial side (R=0.64, p=0.05 in vivo; R=0.63, p=0.038 ex vivo). This study demonstrates that longitudinal MWI in vivo can accurately characterize white matter damage in DC Tx model of injury in the rat spinal cord.
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Affiliation(s)
- Piotr Kozlowski
- Univeristy of British Columbia, Departments of Radiology and Urologic Sciences, Vancouver British Columbia, Canada; UBC MRI Research Centre, Vancouver, British Columbia, Canada; ICORD, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada.
| | - Paulina Rosicka
- Institute of Nuclear Physics, Department of Magnetic Resonance Imaging, Krakow, Poland; UBC MRI Research Centre, Vancouver, British Columbia, Canada
| | - Jie Liu
- ICORD, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada
| | - Andrew C Yung
- UBC MRI Research Centre, Vancouver, British Columbia, Canada
| | - Wolfram Tetzlaff
- University of British Columbia, Departments of Zoology and Surgery, Vancouver, British Columbia, Canada; ICORD, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada
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63
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Thiessen JD, Zhang Y, Zhang H, Wang L, Buist R, Del Bigio MR, Kong J, Li XM, Martin M. Quantitative MRI and ultrastructural examination of the cuprizone mouse model of demyelination. NMR IN BIOMEDICINE 2013; 26:1562-1581. [PMID: 23943390 DOI: 10.1002/nbm.2992] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 05/23/2013] [Accepted: 05/24/2013] [Indexed: 06/02/2023]
Abstract
The cuprizone mouse model of demyelination was used to investigate the influence that white matter changes have on different magnetic resonance imaging results. In vivo T2 -weighted and magnetization transfer images (MTIs) were acquired weekly in control (n = 5) and cuprizone-fed (n = 5) mice, with significant increases in signal intensity in T2 -weighted images (p < 0.001) and lower magnetization transfer ratio (p < 0.001) in the corpus callosum of the cuprizone-fed mice starting at 3 weeks and peaking at 4 and 5 weeks, respectively. Diffusion tensor imaging (DTI), quantitative MTI (qMTI), and T1/T2 measurements were used to analyze freshly excised tissue after 6 weeks of cuprizone administration. In multicomponent T2 analysis with 10 ms echo spacing, there was no visible myelin water component associated with the short T2 value. Quantitative MTI metrics showed significant differences in the corpus callosum and external capsule of the cuprizone-fed mice, similar to previous studies of multiple sclerosis in humans and animal models of demyelination. Fractional anisotropy was significantly lower and mean, axial, and radial diffusivity were significantly higher in the cuprizone-fed mice. Cellular distributions measured in electron micrographs of the corpus callosum correlated strongly to several different quantitative MRI metrics. The largest Spearman correlation coefficient varied depending on cellular type: T1 versus the myelinated axon fraction (ρ = -0.90), the bound pool fraction (ƒ) versus the myelin sheath fraction (ρ = 0.93), and axial diffusivity versus the non-myelinated cell fraction (ρ = 0.92). Using Pearson's correlation coefficient, ƒ was strongly correlated to the myelin sheath fraction (r = 0.98) with a linear equation predicting myelin content (5.37ƒ - 0.25). Of the calculated MRI metrics, ƒ was the strongest indicator of myelin content, while longitudinal relaxation rates and diffusivity measurements were the strongest indicators of changes in tissue structure.
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Affiliation(s)
- Jonathan D Thiessen
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada
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Harkins KD, Valentine WM, Gochberg DF, Does MD. In-vivo multi-exponential T2, magnetization transfer and quantitative histology in a rat model of intramyelinic edema. NEUROIMAGE-CLINICAL 2013; 2:810-7. [PMID: 24179832 PMCID: PMC3777678 DOI: 10.1016/j.nicl.2013.06.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 06/10/2013] [Accepted: 06/12/2013] [Indexed: 11/26/2022]
Abstract
Two MRI methods, multi-exponential analysis of transverse relaxation (MET2) and quantitative magnetization transfer (qMT), were used along with quantitative evaluation of histology in a study of intra-myelinic edema in rat spinal white matter. The results showed a strong linear correlation between a distinct long-T2 signal from MET2 analysis and the edema water volume fraction as measured by histology, although this analysis overestimated the edema water content by ≈ 100% relative to quantitative histological measurements. This overestimation was reasoned to result from the effects of inter-compartmental water exchange on observed transverse relaxation. Commonly studied MRI markers for myelin, the myelin water fraction (from MET2 analysis) and the macromolecular pool size ratio (from qMT analysis) produced results that could not be explained purely by changes in myelin content. The results demonstrate the potential for MET2 analysis as well as the limits of putative myelin markers for characterizing white matter abnormalities involving intra-myelinic edema. We studied a rat model of intra-myelinic edema induced by hexachlorophene ingestion. We used multi-exponential T2 (MET2) and quantitative magnetization transfer MRI. Histology was quantitatively evaluated to measure edema volume and myelin content. MET2 provides a measure that correlates but overestimates with edema volume fraction. MET2 measure of edema is affected by microscopic water dynamics.
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Duyn J. MR susceptibility imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 229:198-207. [PMID: 23273840 PMCID: PMC3602381 DOI: 10.1016/j.jmr.2012.11.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 11/14/2012] [Accepted: 11/15/2012] [Indexed: 05/23/2023]
Abstract
This work reviews recent developments in the use of magnetic susceptibility contrast for human MRI, with a focus on the study of brain anatomy. The increase in susceptibility contrast with modern high field scanners has led to novel applications and insights into the sources and mechanism contributing to this contrast in brain tissues. Dedicated experiments have demonstrated that in most of healthy brain, iron and myelin dominate tissue susceptibility variations, although their relative contribution varies substantially. Local variations in these compounds can affect both amplitude and frequency of the MRI signal. In white matter, the myelin sheath introduces an anisotropic susceptibility that has distinct effects on the water compartments inside the axons, between the myelin sheath, and the axonal space, and renders their signals dependent on the angle between the axon and the magnetic field. This offers opportunities to derive tissue properties specific to these cellular compartments.
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Affiliation(s)
- Jeff Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
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66
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What causes the hyperintense T2-weighting and increased short T2 signal in the corticospinal tract? Magn Reson Imaging 2013; 31:329-35. [DOI: 10.1016/j.mri.2012.07.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 06/30/2012] [Accepted: 07/08/2012] [Indexed: 11/23/2022]
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67
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Sati P, van Gelderen P, Silva AC, Reich DS, Merkle H, de Zwart JA, Duyn JH. Micro-compartment specific T2* relaxation in the brain. Neuroimage 2013; 77:268-78. [PMID: 23528924 DOI: 10.1016/j.neuroimage.2013.03.005] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 01/29/2013] [Accepted: 03/05/2013] [Indexed: 12/12/2022] Open
Abstract
MRI at high field can be sensitized to the magnetic properties of tissues, which introduces a signal dependence on the orientation of white matter (WM) fiber bundles relative to the magnetic field. In addition, study of the NMR relaxation properties of this signal has indicated contributions from compartmentalized water environments inside and outside the myelin sheath that may be separable. Here we further investigated the effects of water compartmentalization on the MRI signal with the goal of extracting compartment-specific information. By comparing MRI measurements of human and marmoset brain at 7T with magnetic field modeling, we show that: (1) water between the myelin lipid bilayers, in the axonal, and in the interstitial space each experience characteristic magnetic field effects that depend on fiber orientation (2) these field effects result in characteristic relaxation properties and frequency shifts for these compartments; and (3) compartmental contributions may be separated by multi-component fitting of the MRI signal relaxation (i.e. decay) curve. We further show the potential application of these findings to the direct mapping of myelin content and assessment of WM fiber integrity with high field MRI.
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Affiliation(s)
- Pascal Sati
- Translational Neuroradiology Unit, Neuroimmunology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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68
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Dortch RD, Harkins KD, Juttukonda MR, Gore JC, Does MD. Characterizing inter-compartmental water exchange in myelinated tissue using relaxation exchange spectroscopy. Magn Reson Med 2012; 70:1450-9. [PMID: 23233414 DOI: 10.1002/mrm.24571] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 10/16/2012] [Accepted: 10/30/2012] [Indexed: 12/20/2022]
Abstract
PURPOSE To investigate inter-compartmental water exchange in two model myelinated tissues ex vivo using relaxation exchange spectroscopy. METHODS Building upon a previously developed theoretical framework, a three-compartment (myelin, intra-axonal, and extra-axonal water) model of the inversion-recovery prepared relaxation exchange spectroscopy signal was applied in excised rat optic nerve and frog sciatic nerve samples to estimate the water residence time constants in myelin (τmyelin ). RESULTS In the rat optic nerve samples, τmyelin = 138 ± 15 ms (mean ± standard deviation) was estimated. In sciatic nerve, which possesses thicker myelin sheaths than optic nerve, a much longer τmyelin = 2046 ± 140 ms was observed. CONCLUSION Consistent with previous studies in rat spinal cord, the extrapolation of exchange rates in optic nerve to in vivo conditions indicates that τmyelin < 100 ms. This suggests that there is a significant effect of inter-compartmental water exchange on the transverse relaxation of water protons in white matter. The much longer τmyelin values in sciatic nerve supports the postulate that the inter-compartmental water exchange rate is mediated by myelin thickness. Together, these findings point to the potential for MRI methods to probe variations in myelin thickness in white matter.
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Affiliation(s)
- Richard D Dortch
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
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69
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Brown RA, Narayanan S, Arnold DL. Segmentation of magnetization transfer ratio lesions for longitudinal analysis of demyelination and remyelination in multiple sclerosis. Neuroimage 2012; 66:103-9. [PMID: 23110887 DOI: 10.1016/j.neuroimage.2012.10.059] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 09/25/2012] [Accepted: 10/05/2012] [Indexed: 11/29/2022] Open
Abstract
We demonstrate a new technique to quantify longitudinal changes in magnetization transfer ratio (MTR) magnetic resonance imaging (MRI). These changes are indicative of demyelination and remyelination. This technique comprises a definition of ΔMTR lesions, which are identified directly from the MTR images, and an automatic procedure for segmenting these lesions. We used this technique to analyze MTR changes in lesions of subjects with rapidly progressing multiple sclerosis before and after treatment with immunoablation and autologous stem cell transplant. Subjects who experienced clinical improvement after treatment showed significantly improved MTR recovery in lesions that were recovering during treatment (p<0.0001) while those who were clinically stable after treatment showed significantly poorer MTR recovery (p=0.002). The statistical power of this technique to detect treatment effects on MTR recovery was shown to be considerably better than previous methods. These results suggest that longitudinal measurements of MTR in ΔMTR lesions may be an important technique for the assessment of treatment effects on remyelination in clinical trials.
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Affiliation(s)
- Robert A Brown
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, 3801 Rue University, Montreal, Canada H3A 2B4.
| | - Sridar Narayanan
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, 3801 Rue University, Montreal, Canada H3A 2B4.
| | - Douglas L Arnold
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, 3801 Rue University, Montreal, Canada H3A 2B4.
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Fiber orientation-dependent white matter contrast in gradient echo MRI. Proc Natl Acad Sci U S A 2012; 109:18559-64. [PMID: 23091011 DOI: 10.1073/pnas.1211075109] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent studies have shown that there is a direct link between the orientation of the nerve fibers in white matter (WM) and the contrast observed in magnitude and phase images acquired using gradient echo MRI. Understanding the origin of this link is of great interest because it could offer access to a new diagnostic tool for investigating tissue microstructure. Since it has been suggested that myelin is the dominant source of this contrast, creating an accurate model for characterizing the effect of the myelin sheath on the evolution of the NMR signal is an essential step toward fully understanding WM contrast. In this study, we show by comparison of the results of simulations and experiments carried out on human subjects at 7T, that the magnitude and phase of signals acquired from WM in vivo can be accurately characterized by (i) modeling the myelin sheath as a hollow cylinder composed of material having an anisotropic magnetic susceptibility that is described by a tensor with a radially oriented principal axis, and (ii) adopting a two-pool model in which the water in the sheath has a reduced T(2) relaxation time and spin density relative to its surroundings, and also undergoes exchange. The accuracy and intrinsic simplicity of the hollow cylinder model provides a versatile framework for future exploitation of the effect of WM microstructure on gradient echo contrast in clinical MRI.
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71
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Lankford CL, Does MD. On the inherent precision of mcDESPOT. Magn Reson Med 2012; 69:127-36. [PMID: 22411784 DOI: 10.1002/mrm.24241] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 01/28/2012] [Accepted: 02/14/2012] [Indexed: 11/07/2022]
Abstract
A statistical analysis of the mcDESPOT protocol for characterizing two exchanging water proton pools--a seven-dimensional problem that fits to multiple flip angle measurements of both spoiled and refocused gradient echoes--is presented. Theoretical calculations of the Cramér-Rao lower bounds of the variance of fitted model parameters were made using a variety of model system parameters, meant to mimic those expected in human white matter. The results, validated by Monte Carlo simulations, indicated that mcDESPOT signals acquired at feasibly attainable signal-to-noise ratios cannot provide parameter estimates with useful levels of precision. Precision can be greatly improved by constraining solutions with a priori model information, although this will generally lead to biased parameter estimates with less specificity. These results indicate that previous, apparently successful applications of mcDESPOT to human white matter may have used data fitting methods that implicitly constrained parameter solutions, or that the two-pool model of white matter may not be sufficient to describe the observed water proton signal in mcDESPOT acquisitions. In either case, mcDESPOT-derived estimates of two-pool model parameters cannot yet be unambiguously related to specific tissue characteristics.
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