Atul S Minhas1, Munish Chauhan2, Fanrui Fu2, Rosalind Sadleir2. 1. Faculty of Science and Engineering, School of Engineering, Macquarie University, Sydney, NSW, Australia. 2. School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona.
Abstract
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.
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.
Authors: Rosalind J Sadleir; Fanrui Fu; Corey Falgas; Stephen Holland; May Boggess; Samuel C Grant; Eung Je Woo Journal: Neuroimage Date: 2017-08-14 Impact factor: 6.556
Authors: Mukund Balasubramanian; Robert V Mulkern; William M Wells; Padmavathi Sundaram; Darren B Orbach Journal: Magn Reson Med Date: 2014-10-01 Impact factor: 4.668
Authors: Munish Chauhan; Aprinda Indahlastari; Aditya K Kasinadhuni; Michael Schar; Thomas H Mareci; Rosalind J Sadleir Journal: IEEE Trans Med Imaging Date: 2018-04 Impact factor: 10.048