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Connecting macroscopic diffusion metrics of cardiac diffusion tensor imaging and microscopic myocardial structures based on simulation. Med Image Anal 2022; 77:102325. [DOI: 10.1016/j.media.2021.102325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/20/2022]
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Jeong KE, Lee SY, Yeom SK, Carlson N, Shah LM, Rose J, Jeong EK. Ultrahigh-b diffusion-weighted imaging for quantitative evaluation of myelination in shiverer mouse spinal cord. Magn Reson Med 2021; 87:179-192. [PMID: 34418157 DOI: 10.1002/mrm.28978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 07/22/2021] [Accepted: 07/30/2021] [Indexed: 12/12/2022]
Abstract
PURPOSE To perform a quantitative evaluation of myelination on WT and myelin-deficient (shiverer) mouse spinal cords using ultrahigh-b diffusion-weighted imaging (UHb-DWI). METHODS UHb-DWI of ex vivo on spinal cord specimens of two shiverer (C3HeB/FeJ-shiverer, homozygous genotype for MbPshi ) and six WT (Black Six, C3HeB/FeJ) mice were acquired using 3D multishot diffusion-weighted stimulated-echo EPI, a homemade RF coil, and a small-bore 7T MRI system. Imaging was performed in transaxial plane with 75 × 75 μm2 in-plane resolution, 1-mm-slice thickness, and radial DWI using bmax = 42,890 s/mm2 . Histological evaluation was performed on upper thoracic sections using optical and transmission electron microscopy. Numerical Monte Carlo simulations (MCSs) of water diffusion were performed to facilitate interpretation of UHb-DWI signal-b curves. RESULTS The white matter ultrahigh-b radial DWI (UHb-rDWI) signal-b curves of WT mouse cords behaved biexponentially with high-b diffusion coefficient DH < 0.020 × 10-3 mm2 /s. However, as expected with less myelination, the signal-b of shiverer mouse cords behaved monoexponentially with significantly greater DH = 0.162 × 10-3 , 0.142 × 10-3 , and 0.164 × 10-3 mm2 /s at anterodorsal, posterodorsal, and lateral columns, respectively. The axial DWI signals of all mouse cords behaved monoexponentially with D = (0.718-1.124) × 10-3 mm2 /s. MCS suggests that these elevated DH are mainly induced by increased water exchange at the myelin sheath. Microscopic results were consistent with the UHb-rDWI findings. CONCLUSION UHb-DWI provides quantitative differences in myelination of spinal cords from myelin-deficit shiverer and WT mice. UHb-DWI may become a powerful tool to evaluate myelination in demyelinating disease models that may translate to human diseases, including multiple sclerosis.
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Affiliation(s)
- Kyle E Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Sophie YouJung Lee
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Suk-Keu Yeom
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Korea University Ansan Medical Center, Ansan, Korea
| | - Noel Carlson
- Neuroimmunology Division, University of Utah, Salt Lake City, Utah, USA.,Neurobiology, University of Utah, Salt Lake City, Utah, USA.,GRECC, VA Salt Lake City Healthcare System, Salt Lake City, Utah, USA.,Neurovirology Research Laboratory, VA Salt Lake City Healthcare System, Salt Lake City, Utah, USA
| | - Lubdha M Shah
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - John Rose
- Neuroimmunology Division, University of Utah, Salt Lake City, Utah, USA.,Neurovirology Research Laboratory, VA Salt Lake City Healthcare System, Salt Lake City, Utah, USA
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
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Jeong K, Shah LM, Lee YJ, Thapa B, Sapkota N, Bisson E, Carlson NG, Jeong EK, Rose JW. High-b diffusivity of MS lesions in cervical spinal cord using ultrahigh-b DWI (UHb-DWI). Neuroimage Clin 2021; 30:102610. [PMID: 33752076 PMCID: PMC7985401 DOI: 10.1016/j.nicl.2021.102610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 02/11/2021] [Accepted: 02/18/2021] [Indexed: 12/27/2022]
Abstract
PURPOSE The purpose of this study was to investigate UHb-rDWI signal in white matter tracts of the cervical spinal cord (CSC) and compare quantitative values between healthy control WM with both MS NAWM and MS WM lesions. METHODS UHb-rDWI experiments were performed on (a) 7 MS patients with recently active or chronic lesions in CSC and on (b) 7 healthy control of similar age range and gender distribution to MS subjects. All MRI data were acquired using clinical 3T MRI system. Axial high-b diffusion images were acquired using 2D single-shot DW stimulated EPI with reduced FOV and a CSC-dedicated 8 channel array coil. High-b diffusion coefficient DH was estimated by fitting the signal-b curve to a double or single-exponential function. RESULTS The high-b diffusivity DH values were measured as (0.767 ± 0.297) × 10-3 mm2/s in the posterior column lesions, averaged over 6 MS patients, and 0.587 × 10-3 mm2/s in the corticospinal tract for another patient. The averaged DH values of the 7 healthy volunteers from the posterior and lateral column were (0.0312 ± 0.0306) × 10-3 and (0.0505 ± 0.0205) × 10-3 mm2/s, respectively. UHb-rDWI signal-b curves of the MS patients revealed to noticeably behave differently to that of the healthy controls. The patient signal-b curves decayed with greater high-b decay constants to reach lower signal intensities relative to signal-b curves of the healthy controls. CONCLUSION UHb-DWI of the CSC reveals a marked difference in signal-b-curves and DH values in MS lesions compared to NAWM and healthy control WM. Based on physical principles, we interpret these altered observations of quantitative diffusion values to be indicative of demyelination. Further studies in animal models will be required to fully interpret UHb-DWI quantitative diffusion values during demyelination and remyelination.
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Affiliation(s)
- Kyle Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Utah, USA
| | - Lubdha M Shah
- Department of Radiology and Imaging Sciences, University of Utah, Utah, USA
| | - You-Jung Lee
- Utah Center for Advanced Imaging Research, University of Utah, Utah, USA
| | - Bijaya Thapa
- Utah Center for Advanced Imaging Research, University of Utah, Utah, USA
| | - Nabraj Sapkota
- Utah Center for Advanced Imaging Research, University of Utah, Utah, USA
| | - Erica Bisson
- Department of Neurosurgery, University of Utah, Utah, USA
| | - Noel G Carlson
- Neuroimmunology and Neurovirology Division, Department of Neurology, University of Utah, Utah, USA; GRECC, VA Salt Lake City Health Care System, Utah, USA; Department of Neurobiology, University of Utah, Utah, USA
| | - E K Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Utah, USA; Department of Radiology and Imaging Sciences, University of Utah, Utah, USA
| | - John W Rose
- Neuroimmunology and Neurovirology Division, Department of Neurology, University of Utah, Utah, USA; Neurology Service, VA Salt Lake City Health Care System, Utah, USA.
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Brusini L, Menegaz G, Nilsson M. Monte Carlo Simulations of Water Exchange Through Myelin Wraps: Implications for Diffusion MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:1438-1445. [PMID: 30835213 DOI: 10.1109/tmi.2019.2894398] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Diffusion magnetic resonance imaging (dMRI) yields parameters sensitive to brain tissue microstructure. A structurally important aspect of this microstructure is the myelin wrapping around the axons. This paper investigated the forward problem concerning whether water exchange via the spiraling structure of the myelin can meaningfully contribute to the signal in dMRI. Monte Carlo simulations were performed in a system with intra-axonal, myelin, and extra-axonal compartments. Diffusion in the myelin was simulated as a spiral wrapping the axon, with a custom number of wraps. Exchange (or intra-axonal residence) times were analyzed for various number of wraps and axon diameters. Pulsed gradient sequences were employed to simulate the dMRI signal, which was analyzed using different methods. Diffusional kurtosis imaging analysis yielded the radial diffusivity (RD) and radial kurtosis (RK), while the two-compartment Kärger model yielded estimates the intra-axonal volume fraction ( ν ic ) and exchange time ( τ ). Results showed that τ was on the sub-second level for geometries with axon diameters below 1.0 μ m and less than eight wraps. Otherwise, exchange was negligible compared to typical experimental durations, with τ of seconds or longer. In situations where exchange influenced the signal, estimates of RK and ν ic increased with the number of wraps, while RD decreased. τ estimates from simulated signals were in agreement with predicted ones. In conclusion, exchange through spiraling myelin permits sub-second τ for small diameters and low number of wraps. Such conditions may arise in the developing brain or in neurodegenerative disease, and thus the results could aid the interpretation of dMRI studies.
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Thapa B, Sapkota N, Lee Y, Jeong K, Rose J, Shah LM, Bisson E, Jeong EK. Ultra-high-b radial diffusion-weighted imaging (UHb-rDWI) of human cervical spinal cord. J Magn Reson Imaging 2018; 49:204-211. [PMID: 29707845 DOI: 10.1002/jmri.26169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Accepted: 04/05/2018] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Injury in the cervical spinal cord (CSC) can lead to varying degrees of neurologic deficit and persistent disability. Diffusion tensor imaging (DTI) is a promising method to evaluate white matter integrity and pathology. However, the conventional DTI results are limited with respect to the specific details of neuropathology and microstructural architecture. In this study we used ultrahigh-b radial-DWI (UHb-rDWI) with b-values ranging from 0 to ∼7500 s/mm2 and calculated decay constant (DH ) at the high b-values, which gives much deeper insight about the microscopic environment of CSC white matter. PURPOSE To evaluate a novel diffusion MRI, UHb-rDWI technique for imaging of the CSC. STUDY TYPE Longitudinal. SUBJECTS Four healthy controls, each scanned twice. FIELD STRENGTH/SEQUENCE 3T/2D single shot diffusion-weighted stimulated echo planar imaging with reduced field of view. ASSESSMENT The signal from each pixel of b0 (b = 0) and b-value (b ≠ 0) images were fitted to a biexponential function and normalized. The signal-b curve is obtained by dividing the latter curve by the former. DH was obtained from the curve at b >4000 s/mm2 . A Monte-Carlo Simulation (MCS) was performed to investigate how DH changes upon the increased water-exchange at the CSC. RESULTS The signal-b curves plotted at multiple levels of healthy CSC are almost identical on two successive scans and show a biexponential decay behavior: fast exponential decay at lower b-values and much slower decay at UHb-values. The mean values of DH were measured as (0.0607 ± 0.02531) ×10-3 and (0.0357 ± 0.02072) ×10-3 s/mm2 at the lateral funiculus and posterior column, respectively. MCS of diffusion MRI shows that the DH is elevated by increased water exchange between the intra- and extraaxonal spaces. DATA CONCLUSION UHb-rDWI signal-b plots of the normal CSC were highly reproducible on successive scans and their biexponential decay behavior can be used to characterize normal spinal white matter. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:204-211.
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Affiliation(s)
- Bijaya Thapa
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, USA
| | - Nabraj Sapkota
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, USA
| | - YouJung Lee
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Kyle Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA
| | | | - Lubdha M Shah
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Erica Bisson
- Department of Neurosurgery, University of Utah, Salt Lake City, Utah, USA
| | - Eun-Kee Jeong
- Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
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