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Evaluation of magnetohydrodynamic effects in magnetic resonance electrical impedance tomography at ultra‐high magnetic fields
Author(s) -
Minhas Atul S.,
Chauhan Munish,
Fu Fanrui,
Sadleir Rosalind
Publication year - 2019
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.27534
Subject(s) - magnetohydrodynamic drive , magnetohydrodynamics , lorentz force , electrical impedance tomography , physics , magnetic field , spin echo , nuclear magnetic resonance , laminar flow , phase (matter) , magnetic resonance imaging , mechanics , tomography , computational physics , optics , radiology , medicine , quantum mechanics
Purpose Artifacts observed in experimental magnetic resonance electrical impedance tomography images were hypothesized to be because of magnetohydrodynamic (MHD) effects. Theory and Methods Simulations of MREIT acquisition in the presence of MHD and electrical current flow were performed to confirm findings. Laminar flow and (electrostatic) electrical conduction equations were bidirectionally coupled via Lorentz force equations, and finite element simulations were performed to predict flow velocity as a function of time. Gradient sequences used in spin‐echo and gradient echo acquisitions were used to calculate overall effects on MR phase images for different electrical current application or phase‐encoding directions. Results Calculated and experimental phase images agreed relatively well, both qualitatively and quantitatively, with some exceptions. Refocusing pulses in spin echo sequences did not appear to affect experimental phase images. Conclusion MHD effects were confirmed as the cause of observed experimental phase changes in MREIT images obtained at high fields. These findings may have implications for quantitative measurement of viscosity using MRI techniques. Methods developed here may be also important in studies of safety and in vivo artifacts observed in high field MRI systems.