The molecular basis for gray and white matter contrast in phase imaging

Zhong, Kai; Leupold, Jochen; Elverfeldt, Dominik von; Speck, Oliver

doi:10.1016/j.neuroimage.2008.01.061

Cited by 119 publications

(152 citation statements)

References 36 publications

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“…Several candidate mechanisms have been suggested and investigated as sources for this frequency contrast (1,(5)(6)(7)(8). A primary candidate is an altered bulk magnetic susceptibility due to such compounds as ferritin, myelin, and deoxyhemoglobin, all of which are found throughout brain tissue.…”

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confidence: 99%

“…Strong support for this mechanism comes from postmortem tissue analysis (9), and from the observation that the phase distribution within and between gray and white matter is consistent with calculations from susceptibility models. † An additional contribution to MRI resonance frequency may come from the exchange processes between protons in water and in amide groups on proteins or other exchangeable sites (8). The frequency shifts arising from these mechanisms may provide important information about the chemical composition of brain tissues in vivo.…”

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confidence: 99%

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Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Lee

Shmueli²,

Fukunaga³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

247

316

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Recent advances in high-field (≥7 T) MRI have made it possible to study the fine structure of the human brain at the level of fiber bundles and cortical layers. In particular, techniques aimed at detecting MRI resonance frequency shifts originating from local variation in magnetic susceptibility and other sources have greatly improved the visualization of these structures. A recent theoretical study [He X, Yablonskiy DA (2009) Proc Natl Acad Sci USA 106:13558–13563] suggests that MRI resonance frequency may report not only on tissue composition, but also on microscopic compartmentalization of susceptibility inclusions and their orientation relative to the magnetic field. The proposed sensitivity to tissue structure may greatly expand the information available with conventional MRI techniques. To investigate this possibility, we studied postmortem tissue samples from human corpus callosum with an experimental design that allowed separation of microstructural effects from confounding macrostructural effects. The results show that MRI resonance frequency does depend on microstructural orientation. Furthermore, the spatial distribution of the resonance frequency shift suggests an origin related to anisotropic susceptibility effects rather than microscopic compartmentalization. This anisotropy, which has been shown to depend on molecular ordering, may provide valuable information about tissue molecular structure.

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confidence: 99%

mentioning

confidence: 99%

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Lee

Shmueli²,

Fukunaga³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

247

316

View full text Add to dashboard Cite

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“…So far the chemical shift contribution towards phase imaging has only been proposed as an isotropic effect (Luo et al, 2010;Shmueli et al, 2011;Zhong et al, 2008) and therefore could not be responsible for the observed polarity change between the ac and the cc in the absence of myelin. It could be hypothesized that chemical shift could have a contribution that is structure orientation dependent (macromolecules can be arranged in an ordered fashion resulting phases depending on the orientation of the underlying structures) and such an anisotropic mechanism could not be differentiated (in our data) from the effect described by He et al (He and Yablonskiy, 2009).…”

Section: Discussionmentioning

confidence: 99%

In vivo assessment of myelination by phase imaging at high magnetic field

et al. 2012

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The present study evaluated the potential of using the phase of T 2 * weighted MR images to characterize myelination during brain development and pathology in rodents at 9.4 T. Phase contrast correlated with myelin content assessed by histology and suggests that most contrast between white and cortical gray matter is modulated by myelin. Ex vivo experiments showed that gray-white matter phase contrast remains unchanged after iron extraction. In dysmyelinated shiverer mice, phase imaging correlated strongly with myelin staining, showing reduced contrast between white and gray matter when compared to healthy controls. We conclude that highresolution phase images, acquired at high field, allow assessment of myelination and dysmyelination.© 2011 Elsevier Inc. All rights reserved. IntroductionThe assessment of myelination in healthy subjects and following injury in humans and in animal models is one of the ways to determine the degree of cerebral integrity or the degree of injury in case of white matter disease like multiple sclerosis. In newborns, myelination of the posterior limb of the internal capsule, when assessed at term equivalent, has been shown to be a very robust predictor of motor impairment (Cowan and de Vries, 2005). A simple technique that would access the degree of myelination of white matter would be very useful in mature animal models of white matter injury such as multiple sclerosis and in immature animal models of white matter injury such as periventricular leukomalacia as well as in human studies. There are various methods available: one approach consists of quantification of myelin bond and free water fractions by a multiexponential analysis of the T 2 decay (Beaulieu et al., 1998;MacKay et al., 1994;Whittall and MacKay, 1989;Lancaster et al., 2003). This is generally performed using a CarrPurcell-Meiboom-Gill (CPMG) or a Turbo Spin-Echo sequences with multiple echo times (Beaulieu et al., 1998). Due to specific absorption rate (SAR) (especially at high fields) and timing constraints, the T 2 decay curve is often not fully sampled for an accurate quantification. Recently, it has been shown that myelin water fraction can also be measured using a multi-exponential analysis of the T 2 * decay in multislice multiple echo gradient echo sequence (Du et al., 2007;Hwang et al., 2010). The resulting myelin water fractions are highly dependent on the constraints introduced on the multi-exponential fitting procedure (Hwang et al., 2010) and suffer from significant inaccuracies in regions close to air-tissue interfaces. An alternative approach of a multicomponent relaxation analysis using multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) (Deoni et al., 2008) was applied successfully on infants from 3 to 11 months to quantify myelination (Deoni et al., 2011). Magnetization transfer represents an alternative approach to quantify myelin with new approaches refining its modelization by characterizing individually the relaxation and exchange rates of the free water and macromolec...

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“…Low signal on MAG images comes from changes induced by local susceptibility to both paramagnetic substances, such as iron, and diamagnetic substances, such as myelin. 1 High signal on PHA images comes mainly from local positive phase caused by iron, 7,11,12,[27][28][29] water-macromolecule exchange, 16,30 anisotropic microscopic tissue architecture, and fiber orientation within the main magnetic field, 31-33 whereas low signal on PHA images comes from local negative phase in response to such diamagnetic substances as myelin. Nevertheless, it has to be noted that diamagnetic substances do not always show low signal on phase images; when considering the relative susceptibilities of substances to water susceptibility, substances less diamagnetic than water (such as lipids) might cause a quasi-paramagnetic effect and show high signal on PHA images.…”

Section: Discussionmentioning

confidence: 99%

“…15 Water-macromolecule exchange has been reported as another cause of contrast on PHA images. 16 A combination of the above-mentioned mechanisms might contribute to the final SWI contrast.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Susceptibility-Weighted Images of Cortico-Medullary Junction

et al. 2014

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Objective: We qualitatively evaluated the differences among susceptibility-weighted (SWI), magnitude (MAG), and high pass filtered phase (PHA) images in depicting interlobar differences in the appearance of the signal of the corticomedullary junction (CMJ). We conducted quantitative evaluation to validate the qualitative results.Materials and Methods: We obtained SWI images from 25 preoperative brain tumor patients (12 men, 13 women, aged 19 to 82 years, mean, 52 years). Two trained neuroradiologists evaluated MAG, PHA, and SWI images. Qualitative evaluation of the CMJ signal and quantitative calculation of the relative signal ratio (RSR) percentages between the CMJ and deep white matter (WM) were conducted at 3 different slice levels of the brain independently for 4 different lobes (frontal, parietal, temporal, and occipital) and compared among MAG, PHA, and SWI. The extent of the area of the CMJ signal was graded on a 4-point scale (Grade 3, >75%; Grade 2, 50 to 75%; Grade 1, 25 to 50%; Grade 0, <25%). Data were statistically analyzed using a nonparametric Friedman test.Results: The Kappa coefficients between the qualitative and quantitative grades were 0.002 for MAG, 0.0047 for PHA, and 0.050 for SWI. Qualitatively, on the PHA images and SWI, grades of the occipital lobes were significantly higher than those of the other lobes (P < 0.005). Quantitatively, PHA images showed statistically significant interlobar differences in RSR percentage values of the CMJ (P = 0.025).Conclusion: Qualitatively, the appearance of the CMJ differed significantly among the different lobes of the brain on SWI and underlying PHA images but not on MAG images. Quantitatively, only PHA images showed significant interlobar differences in the RSR. PHA images are most sensitive to the CMJ signal contrast due to local paramagnetic iron content.

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The molecular basis for gray and white matter contrast in phase imaging

Cited by 119 publications

References 36 publications

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

In vivo assessment of myelination by phase imaging at high magnetic field

Analysis of Susceptibility-Weighted Images of Cortico-Medullary Junction

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