Volume 74, Issue 5 pp. 1388-1396
Full Paper

A torque balance measurement of anisotropy of the magnetic susceptibility in white matter

Peter van Gelderen

Corresponding Author

Peter van Gelderen

Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA

Correspondence to: Peter van Gelderen, Ph.D., AMRI, LFMI, NINDS, NIH, 10 Center Drive, Bldg. 10, Room B1D-725, Bethesda, MD 20892. E-mail: [email protected]Search for more papers by this author
Hendrik Mandelkow

Hendrik Mandelkow

Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA

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Jacco A. de Zwart

Jacco A. de Zwart

Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA

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Jeff H. Duyn

Jeff H. Duyn

Advanced MRI section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA

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First published: 14 November 2014
Citations: 20

Abstract

Purpose

Recent MRI studies have suggested that the magnetic susceptibility of white matter (WM) in the human brain is anisotropic, providing a new contrast mechanism for the visualization of fiber bundles and allowing the extraction of cellular compartment-specific information. This study provides an independent confirmation and quantification of this anisotropy.

Methods

Anisotropic magnetic susceptibility results in a torque exerted on WM when placed in a uniform magnetic field, tending to align the WM fibers with the field. To quantify the effect, excised spinal cord samples were placed in a torque balance inside the magnet of a 7 T MRI system and the magnetic torque was measured as function of orientation.

Results

All tissue samples (n = 5) showed orienting effects, confirming the presence of anisotropic susceptibility. Analysis of the magnetic torque resulted in reproducible values for the WM volume anisotropy that ranged from 13.6 to 19.2 ppb.

Conclusion

The independently determined anisotropy values confirm estimates inferred from MRI experiments and validate the use of anisotropy to extract novel information about brain fiber structure and myelination. Magn Reson Med 74:1388–1396, 2015. © 2014 Wiley Periodicals, Inc.

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