Quantitative susceptibility mapping for investigating subtle susceptibility variations in the human brain

Schweser, Ferdinand; Sommer, Karsten; Deistung, Andreas; Reichenbach, Jürgen R.

doi:10.1016/j.neuroimage.2012.05.067

Cited by 237 publications

(277 citation statements)

References 70 publications

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“…Currently, there is significant interest in using a combination of R p 2 and Δχ dipole to assess nonheme iron variations in human brain tissue (7,23,24). However, to date most studies have performed correlations between MRI susceptibility parameters in vivo and ex vivo iron concentrations derived from the literature (7).…”

Section: Resultsmentioning

confidence: 99%

“…One method for quantifying these microstructural changes is the mapping of the effective transverse relaxation rate (R p 2 ). Along with the longitudinal relaxation rate (R 1 ) and transverse relaxation rate (R 2 ), R p 2 has been viewed as a fundamental MRI tissue parameter, affected by several factors including myelin content (5,6), endogenous ferritin-based (Fe 3+ ) iron (7,8), tissue microstructure (6), and paramagnetic, blood deoxyhemoglobin (9). However, a number of recent studies have reported a somewhat surprising dependence of R p 2 on tissue orientation, at least in white matter (10)(11)(12).…”

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confidence: 99%

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Origins of R ₂ ^∗ orientation dependence in gray and white matter

Rudko

Klassen²,

Chickera³

et al. 2013

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

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Estimates of the apparent transverse relaxation rate (R 2 * ) can be used to quantify important properties of biological tissue. Surprisingly, the mechanism of R 2 * dependence on tissue orientation is not well understood. The primary goal of this paper was to characterize orientation dependence of R 2 * in gray and white matter and relate it to independent measurements of two other susceptibility based parameters: the local Larmor frequency shift (f L ) and quantitative volume magnetic susceptibility (Δχ ). Through this comparative analysis we calculated scaling relations quantifying R 2 ′ (reversible contribution to the transverse relaxation rate from local field inhomogeneities) in a voxel given measurements of the local Larmor frequency shift. R 2 ′ is a measure of both perturber geometry and density and is related to tissue microstructure. Additionally, two methods (the Generalized Lorentzian model and iterative dipole inversion) for calculating Δχ were compared in gray and white matter. The value of Δχ derived from fitting the Generalized Lorentzian model was then connected to the observed R 2 * orientation dependence using image-registered optical density measurements from histochemical staining. Our results demonstrate that the R 2 * and f L of white and cortical gray matter are well described by a sinusoidal dependence on the orientation of the tissue and a linear dependence on the volume fraction of myelin in the tissue. In deep brain gray matter structures, where there is no obvious symmetry axis, R 2 * and f L have no orientation dependence but retain a linear dependence on tissue iron concentration and hence Δχ .MRI contrast mechanisms | grey matter | cellular architecture | relaxation times I n many neurological diseases such as multiple sclerosis, Alzheimer's, and Parkinson, and in conditions following traumatic brain injury, microstructural changes occur in gray and white matter (1-4). One method for quantifying these microstructural changes is the mapping of the effective transverse relaxation rate (R p 2 ). Along with the longitudinal relaxation rate (R 1 ) and transverse relaxation rate (R 2 ), R p 2 has been viewed as a fundamental MRI tissue parameter, affected by several factors including myelin content (5, 6), endogenous ferritin-based (Fe 3+ ) iron (7,8), tissue microstructure (6), and paramagnetic, blood deoxyhemoglobin (9). However, a number of recent studies have reported a somewhat surprising dependence of R p 2 on tissue orientation, at least in white matter (10-12). The purpose of this paper was to investigate the mechanisms that could contribute to this orientation dependence of R p 2 in both gray and white matter. Because R p 2 is influenced by magnetic field perturbations, we examined the role of local Larmor frequency shift (f L ) and quantitative magnetic susceptibility (Δχ), parameters that relate field and frequency. Through this analysis we identified unique scaling relations that relate R 2 ′ to the local Larmor frequency shift calculated after removal of macroscopic field ...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Origins of R ₂ ^∗ orientation dependence in gray and white matter

Rudko

Klassen²,

Chickera³

et al. 2013

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

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“…The development of novel RSO-type algorithms optimized for more accurate and faster processing of QSMs is an active field of research and fQSM benefits directly from every improvement on this field, e.g. Schweser et al, 2012a;Schweser et al, 2012b;Wu et al, 2012). Thus, we suggest the implementation of the fQSM pipeline for SO datasets using DORK with SHARP spatio-temporal phase filtering and regularized QSM calculation algorithms using a priori information about edges in the object derived from the magnitude image.…”

Section: Alternative Fqsm Pipelinesmentioning

confidence: 99%

Functional quantitative susceptibility mapping (fQSM)

et al. 2014

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Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is a powerful technique, typically based on the statistical analysis of the magnitude component of the complex time-series. Here, we additionally interrogated the phase data of the fMRI time-series and used quantitative susceptibility mapping (QSM) in order to investigate the potential of functional QSM (fQSM) relative to standard magnitude BOLD fMRI. High spatial resolution data (1 mm isotropic) were acquired every 3 seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B0. Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM time-series and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatiotemporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data. Our results present the potential of fQSM as a quantitative method of mapping BOLD changes. We also critically discuss the technical challenges and issues linked to this intriguing new technique. seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B 0 . Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM timeseries and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatio-temporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data.

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“…In most studies involving GE phase imaging, it is assumed that the dominant source of phase contrast is the variation in isotropic magnetic susceptibility across different tissues (5). This assumption has led to the development of a plethora of sophisticated techniques for inverting phase measurements to yield three-dimensional (3D) maps of the isotropic magnetic susceptibility (6)(7)(8)(9)(10)(11)(12). These "quantitative susceptibility mapping" (QSM) methods take advantage of the simple, Fourier relationship connecting the underlying distribution of isotropic magnetic susceptibility to the induced dipolar magnetic fields whose effect can be measured in phase images (13,14).…”

Section: Introductionmentioning

confidence: 99%

Effects of white matter microstructure on phase and susceptibility maps

Wharton

Bowtell

2015

Magn. Reson. Med.

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Purpose: To investigate the effects on quantitative susceptibility mapping (QSM) and susceptibility tensor imaging (STI) of the frequency variation produced by the microstructure of white matter (WM). Methods: The frequency offsets in a WM tissue sample that are not explained by the effect of bulk isotropic or anisotropic magnetic susceptibility, but rather result from the local microstructure, were characterized for the first time. QSM and STI were then applied to simulated frequency maps that were calculated using a digitized whole-brain, WM model formed from anatomical and diffusion tensor imaging data acquired from a volunteer. In this model, the magnitudes of the frequency contributions due to anisotropy and microstructure were derived from the results of the tissue experiments. Results: The simulations suggest that the frequency contribution of microstructure is much larger than that due to bulk effects of anisotropic magnetic susceptibility. In QSM, the microstructure contribution introduced artificial WM heterogeneity. For the STI processing, the microstructure contribution caused the susceptibility anisotropy to be significantly overestimated. Conclusion: Microstructure-related phase offsets in WM yield artifacts in the calculated susceptibility maps. If susceptibility mapping is to become a robust MRI technique, further research should be carried out to reduce the confounding effects of microstructure-related frequency contributions.

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Quantitative susceptibility mapping for investigating subtle susceptibility variations in the human brain

Cited by 237 publications

References 70 publications

Origins of R ₂ ^∗ orientation dependence in gray and white matter

Origins of R ₂ ^∗ orientation dependence in gray and white matter

Functional quantitative susceptibility mapping (fQSM)

Effects of white matter microstructure on phase and susceptibility maps

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Quantitative susceptibility mapping for investigating subtle susceptibility variations in the human brain

Cited by 237 publications

References 70 publications

Origins of R 2 ∗ orientation dependence in gray and white matter

Origins of R 2 ∗ orientation dependence in gray and white matter

Functional quantitative susceptibility mapping (fQSM)

Effects of white matter microstructure on phase and susceptibility maps

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Origins of R ₂ ^∗ orientation dependence in gray and white matter

Origins of R ₂ ^∗ orientation dependence in gray and white matter