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A torque balance measurement of anisotropy of the magnetic susceptibility in white matter
Author(s) -
van Gelderen Peter,
Mandelkow Hendrik,
de Zwart Jacco A.,
Duyn Jeff H.
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25524
Subject(s) - anisotropy , nuclear magnetic resonance , white matter , magnetic resonance imaging , magnetic field , torque , physics , optics , medicine , radiology , quantum mechanics , thermodynamics
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.