Myelin Water Atlas: A Template for Myelin Distribution in the Brain

Liu, Hanwen; Rubino, Cristina; Dvorak, Adam; Jarrett, Michael; Ljungberg, Emil; Vavasour, Irene M.; Lee, Lisa Eunyoung; Kolind, Shannon; MacMillan, Erin L.; Traboulsee, Anthony; Lang, Donna J.; Rauscher, Alexander; Li, David K.B.; MacKay, Alexander L.; Boyd, Lara A.; Kramer, John L. K.; Laule, Cornelia

doi:10.1111/jon.12657

Cited by 39 publications

(50 citation statements)

References 62 publications

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“…The mcDESPOT‐derived myelin volume fraction (VF m ) values were consistently much higher (30‐250%) than the T 2 ‐based MWF values, as has been previously reported 75 . We found an increase in MWF moving from anterior to posterior of the corpus callosum, matching the variation in MWF measured in adults 54 . In contrast, Geeraert et al.…”

Section: Discussionsupporting

confidence: 84%

“…Average mean and standard deviation of MWF, FA, MD, RD, and AD in each ROI was calculated from the atlases (Table 1). The same ROIs which had been applied to the pediatric maps were used to analyze adult MWF from an atlas created using a 32‐echo 3D GRASE acquisition protocol collected on the same scanner from 50 healthy adults (mean age: 25 years, range: 17‐42 years, 25 females) 54 . Two‐tailed paired t ‐tests were performed to compare pediatric MWF with adult MWF.…”

Section: Methodsmentioning

confidence: 99%

“…The same ROIs which had been applied to the pediatric maps were used to analyze adult MWF from an atlas created using a 32-echo 3D GRASE acquisition protocol collected on the same scanner from 50 healthy adults (mean age: 25 years, range: 17-42 years, 25 females). 54 Two-tailed paired t-tests were performed to compare pediatric MWF with adult MWF. DTI data were not available from this adult sample and so pediatric DTI metrics were not compared to adult values.…”

Section: Roi and Statistical Analysismentioning

confidence: 99%

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Brain Myelin Water Fraction and Diffusion Tensor Imaging Atlases for 9‐10 Year‐Old Children

Morris

Holmes

Dvorak

et al. 2020

Journal of Neuroimaging

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BACKGROUND AND PURPOSE Myelin water imaging (MWI) and diffusion tensor imaging (DTI) provide information about myelin and axon‐related brain microstructure, which can be useful for investigating normal brain development and many childhood brain disorders. While pediatric DTI atlases exist, there are no pediatric MWI atlases available for the 9‐10 years old age group. As myelination and structural development occurs throughout childhood and adolescence, studies of pediatric brain pathologies must use age‐specific MWI and DTI healthy control data. We created atlases of myelin water fraction (MWF) and DTI metrics for healthy children aged 9‐10 years for use as normative data in pediatric neuroimaging studies. METHODS 3D‐T1, DTI, and MWI scans were acquired from 20 healthy children (mean age: 9.6 years, range: 9.2‐10.3 years, 4 females). ANTs and FSL registration were used to create quantitative MWF and DTI atlases. Region of interest (ROI) analysis in nine white matter regions was used to compare pediatric MWF with adult MWF values from a recent study and to investigate the correlation between pediatric MWF and DTI metrics. RESULTS Adults had significantly higher MWF than the pediatric cohort in seven of the nine white matter ROIs, but not in the genu of the corpus callosum or the cingulum. In the pediatric data, MWF correlated significantly with mean diffusivity, but not with axial diffusivity, radial diffusivity, or fractional anisotropy. CONCLUSIONS Normative MWF and DTI metrics from a group of 9‐10 year old healthy children provide a resource for comparison to pathologies. The age‐specific atlases are ready for use in pediatric neuroimaging research and can be accessed: https://sourceforge.net/projects/pediatric-mri-myelin-diffusion/.

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Section: Discussionsupporting

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Roi and Statistical Analysismentioning

confidence: 99%

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Brain Myelin Water Fraction and Diffusion Tensor Imaging Atlases for 9‐10 Year‐Old Children

Morris

Holmes

Dvorak

et al. 2020

Journal of Neuroimaging

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“…Our findings suggest that, when comparing MWF of individual subjects to a myelin water atlas (58,59), these atlases have to be updated with DTI data. In particular, fiber tracts at angles between 10 • and 40 • , where MWI is most sensitive to changes in tissue orientation, may exhibit paradoxical results if their orientation differs from the average orientation of the tract in the atlas.…”

Section: Discussionmentioning

confidence: 99%

Myelin water imaging depends on white matter fiber orientation in the human brain

Birkl

Doucette

Fan

et al. 2020

Preprint

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The multiexponential T 2 decay of the magnetic resonance imaging (MRI) signal from cerebral white matter can be separated into short components sensitive to myelin water and long components related to intra-and extracellular water. In this study we investigated to what degree the myelin water fraction (MWF) depends on the angle between white matter fibers and the main magnetic filed. Maps of MWF were acquired using multi echo CPMG and GRASE sequences. The CPMG sequence was acquired with a TR of 1073 ms, 1500 ms and 2000 ms. The fiber orientation was mapped with diffusion tensor imaging. By angle-wise pooling the voxels across the brain's white matter, an orientation dependent MWF curve was generated. We found that MWF varied between 25% and 35% across different fiber orientations. The orientation dependency of the MWF is characterized by a dipole-dipole interaction model. Furthermore, the selection of the TR influences the orientation dependent and global white matter MWF. White matter fiber orientation induces a strong systematic bias on the estimation of MWF. This finding has important implications for future research and the interpretation of MWI results in previously published studies.myelin water imaging | fiber orientation | white matter | magic angle | brain | quantitative MRI MethodsEight healthy volunteers (3 female, 5 male) with a mean age of 26 years (age range = 21 -33 years) and without any history of neurological disorder participated in this study, which was approved by the University of British Columbia Clinical Research Ethics Board. All volunteers gave written informed consent. MR imaging was performed on a 3 T MR system (Ingenia Elition, Philips Medical Systems, Best, The Netherlands) using a 32-channel SENSE head coil. MRI acquisition.A 3D T1 weighted sequence with echo time (TE) = 4.9 ms, TR = 9.8 ms, flip angle = 8°, a resolution of 0.8 x 0.8 x 0.8 mm 3 , a compressed SENSE (CS) factor of 3.6 and acquisition time of 5:50 min was acquired for anatomical overview. CS is a combination of compressed sensing (35,36) and SENSE (37). For the calculation of fiber orientation a DTI sequence with TE = 60 ms, TR = 4111 ms, b-value = 700 s/mm 2 , 60 diffusion directions, a resolution of 2.3 x 2.3 x 2.4 mm 3 , multi band factor 2 (38), SENSE factor 2.1 and

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“…Fortuitously, myelin displays multiple physical properties that give rise to contrast in Magnetic Resonance (MR) images. Tissue containing myelinated axons has lower longitudinal and transverse relaxation times 1 , 2 , lower susceptibility 3 , increased Magnetization Transfer (MT) effects 4 , and reduced diffusion 5 , compared to non-myelinated tissue. However, while all of these MR parameters are sensitive to myelination, they are not specific, as other biological processes demonstrate the same effects 6 .…”

Section: Introductionmentioning

confidence: 99%

Silent myelin-weighted magnetic resonance imaging

et al. 2020

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Background: Inhomogeneous Magnetization Transfer (ihMT) is an emerging, uniquely myelin-specific magnetic resonance imaging (MRI) contrast. Current ihMT acquisitions utilise fast Gradient Echo sequences which are among the most acoustically noisy MRI sequences, reducing patient comfort during acquisition. We sought to address this by modifying a near silent MRI sequence to include ihMT contrast. Methods: A Magnetization Transfer preparation module was incorporated into a radial Zero Echo-Time sequence. Repeatability of the ihMT ratio and inverse ihMT ratio were assessed in a cohort of healthy subjects. We also investigated how head orientation affects ihMT across subjects, as a previous study in a single subject suggests this as a potential confound. Results: We demonstrated that ihMT ratios comparable to existing, acoustically loud, implementations could be obtained with the silent sequence. We observed a small but significant effect of head orientation on inverse ihMTR. Conclusions: Silent ihMT imaging is a comparable alternative to conventional, noisy, alternatives. For all future ihMT studies we recommend careful positioning of the subject within the scanner.

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Myelin Water Atlas: A Template for Myelin Distribution in the Brain

Cited by 39 publications

References 62 publications

Brain Myelin Water Fraction and Diffusion Tensor Imaging Atlases for 9‐10 Year‐Old Children

Brain Myelin Water Fraction and Diffusion Tensor Imaging Atlases for 9‐10 Year‐Old Children

Myelin water imaging depends on white matter fiber orientation in the human brain

Silent myelin-weighted magnetic resonance imaging

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