Identification of “Premyelination” by Diffusion-Weighted MRI

Wimberger, D.; Roberts, T.P.L.; Barkovich, A. James; Prayer, L.; Moseley, Michael E.; Kucharczyk, John

doi:10.1097/00004728-199501000-00005

Cited by 312 publications

(177 citation statements)

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“…In the term brain, the high fractional constant is present within the internal capsule (IC) but not in the corpus callosum (CC). Wimberger et al, 1995), before the development of myelin layers. Further increases in anisotropy occur upon myelination (Huppi et al, 1998;Neil et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Diffusion MR imaging characteristics of the developing primate brain

et al. 2005

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Diffusion-based magnetic resonance imaging holds the potential to noninvasively demonstrate cellular-scale structural properties of brain. This method was applied to fixed baboon brains ranging from 90 to 185 days gestational age to characterize the changes in diffusion properties associated with brain development. Within each image voxel, a probability-theory-based approach was employed to choose, from a group of analytic equations, the one that best expressed water displacements. The resulting expressions contain eight or fewer adjustable parameters, indicating that relatively simple expressions are sufficient to obtain a complete description of the diffusion MRI signal in developing brain. The measured diffusion parameters changed systematically with gestational age, reflecting the rich underlying microstructural changes that take place during this developmental period. These changes closely parallel those of live, developing human brain. The information obtained from this primate model of cerebral microstructure is directly applicable to studies of human development. D 2004 Elsevier Inc. All rights reserved.Keywords: Magnetic resonance imaging; Diffusion anisotropy; Baboon brains; Brain development IntroductionMagnetic resonance imaging (MRI) is increasingly utilized in human and animal studies to provide information relating to cerebral injury and development in the newborn. Diffusion MRI, in particular, is being applied to assess brain development (Huppi et al., 1998;Neil et al., 2002;Partridge et al., 2004;Rutherford et al., 2004). Diffusion MRI provides information about the directional dependence of water displacements due to diffusion. This, in turn, reflects underlying tissue microstructure. In white matter, for example, water moving parallel to myelinated fibers can move within or between myelin layers, without crossing membranes. Water moving orthogonal to fibers, on the other hand, must either cross myelin layers or go around them. As a result, water displacements are smaller when measured orthogonal to myelinated fibers than when measured parallel to them. Thus, water diffusion in myelinated white matter is anisotropic. The regional changes in diffusion anisotropy within the developing white matter of the newborn brain have been well appreciated for some time (Huppi et al., 1998;Neil et al., 1998).Diffusion anisotropy has also been described within cerebral cortical gray matter in the developing human brain. Anisotropy is high early in development, with the preferred displacement direction oriented radially with respect to the cortical surface (Maas et al., 2004;Mori et al., 2001;Neil et al., 1998). This has been attributed to the orientation of radial glial fibers and the apical dendrites of pyramidal cells. As the brain matures, the magnitude of cortical diffusion anisotropy decreases (McKinstry et al., 2002;Mori et al., 2001), reflecting a loss in orientational coherence of cortical structures that restrict diffusion. This may be due to the elaboration of pyramidal cell basal dendrites, additio...

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Section: Discussionmentioning

confidence: 99%

Diffusion MR imaging characteristics of the developing primate brain

et al. 2005

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“…In the central nervous system (CNS), diffusion anisotropy is not simply caused by myelin in white matter, since several studies have shown that, even before myelin is deposited, diffusion anisotropy can be measured using MRI. [93][94][95][96] Thus, despite the fact that increases in myelin are temporally correlated with increases in diffusion anisotropy, structures other than the myelin sheath must be contributing to diffusion anisotropy. 97 This is an important point, because there is a common misconception that the degree of diffusion anisotropy can be used as a quantitative measure or 'stain' of myelin content, when in reality no such simple relationship exists.…”

Section: Other Complexitiesmentioning

confidence: 99%

Diffusion‐tensor MRI: theory, experimental design and data analysis – a technical review

2002

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This article treats the theoretical underpinnings of diffusion-tensor magnetic resonance imaging (DT-MRI), as well as experimental design and data analysis issues. We review the mathematical model underlying DT-MRI, discuss the quantitative parameters that are derived from the measured effective diffusion tensor, and describe artifacts thet arise in typical DT-MRI acquisitions. We also discuss difficulties in identifying appropriate models to describe water diffusion in heterogeneous tissues, as well as in interpreting experimental data obtained in such issues. Finally, we describe new statistical methods that have been developed to analyse DT-MRI data, and their potential uses in clinical and multi-site studies.

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“…Diffusion gradients were applied along the anterior -posterior direction with δ = 5 ms, Δ = 15 ms, and a gradient strength of 30 G/cm. This diffusion-weighted imaging sequence provides imporved gray/white matter contrast in these early-aged premyelinated brains compared to standard T 2 -or T 2 * -weighted imaging methods (Wimberger et al, 1995). MRM data sets were acquired with a 256 × 128 × 128 matrix size and zero-filled yielding a final resolution of 33 μm × 66 μm × 66 μm.…”

Section: P4-p4mentioning

confidence: 99%

Disruption of Foxg1 expression by knock-in of Cre recombinase: Effects on the development of the mouse telencephalon

et al. 2007

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The Cre/loxP system is used routinely to manipulate gene expression in the mouse nervous system. In order to delete genes specifically from the telencephalon, the Foxg1-cre line was created previously by replacing the intron-less Foxg1 coding region with cre, resulting in a Foxg1 heterozygous mouse. As the telencephalon of heterozygous Foxg1 mice was reported to be normal, this genotype often has been used as the control in subsequent analyses. Here we describe substantial disruption of forebrain development of heterozygous mice in the Foxg1-cre line, maintained on the C57BL/6J background. High resolution magnetic resonance microscopy reveals a significant reduction in the volume of the neocortex, hippocampus and striatum. The alteration in the neocortex results, in part, from a decrease in its tangential dimension, although gross patterning of the cortical sheet appears normal. This decrease is observed in three different Foxg1 heterozygous mouse lines, independent of the method of achieving deletion of the Foxg1 gene. Although Foxg1 is not expressed in the diencephalon, three-dimensional magnetic resonance microscopy revealed that thalamic volume in the adult is reduced. In contrast, at postnatal day 4, thalamic volume is normal, suggesting that interactions between cortex and dorsal thalamus postnatally produce the final adult thalamic phenotype. In the Foxg1-cre line maintained on the C57BL/6J background, the radial domain of the cerebral cortex also is disrupted substantially, particularly in supragranular layers. However, neither Foxg1 heterozygous mice of the Foxg1-tet line, nor those of the Foxg1-lacZ and Foxg1-cre lines maintained on a mixed background, displayed a reduced cortical thickness. Thus Cre recombinase contributes to the radial phenotype, although only in the context of the congenic C57BL/6J background. These observations highlight an important role for Foxg1 in cortical development, reveal noteworthy complexity in the invocation of specific mechanisms underlying phenotypes expressed following genetic manipulations and stress the importance of including appropriate controls of all genotypes. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Development of the cerebral cortex relies on extracellular cues and intrinsic signals that instruct the proliferation, differentiation and migration of neuronal precursors. The duration and location of these cues are critical to producing the final cortical architecture (FukuchiShimogori and Grove, 2001, Parnavelas et al., 2002, Rakic, 2002, Shimogori et al., 2004, Rash and Grove, 2006, Storm et al., 2006. The...

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Identification of “Premyelination” by Diffusion-Weighted MRI

Cited by 312 publications

References 0 publications

Diffusion MR imaging characteristics of the developing primate brain

Diffusion MR imaging characteristics of the developing primate brain

Diffusion‐tensor MRI: theory, experimental design and data analysis – a technical review

Disruption of Foxg1 expression by knock-in of Cre recombinase: Effects on the development of the mouse telencephalon

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