title: Multishot echo-planar MREIT for fast imaging of conductivity, current density, and electric field distributions.
abstract: OBJECTIVE
  Magnetic resonance electrical impedance tomography (MREIT) sequences typically use conventional spin or gradient echo-based acquisition methods for reconstruction of conductivity and current density maps. Use of MREIT in functional and electroporation studies requires higher temporal resolution and faster sequences. Here, single and multishot echo planar imaging (EPI) based MREIT sequences were evaluated to see whether high-quality MREIT phase data could be obtained for rapid reconstruction of current density, conductivity, and electric fields.
  
  
  METHODS
  A gel phantom with an insulating inclusion was used as a test object. Ghost artifact, geometric distortion, and MREIT correction algorithms were applied to the data. The EPI-MREIT-derived phase-projected current density and conductivity images were compared with simulations and spin-echo images as a function of EPI shot number.
  
  
  RESULTS
  Good agreement among measures in simulated, spin echo, and EPI data was achieved. Current density errors were stable and below 9% as the shot number decreased from 64 to 2, but increased for single-shot images. Conductivity reconstruction relative contrast ratios were stable as the shot number decreased. The derived electric fields also agreed with the simulated data.
  
  
  CONCLUSIONS
  The EPI methods can be combined successfully with MREIT reconstruction algorithms to achieve fast imaging of current density, conductivity, and electric field. Magn Reson Med 79:71-82, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
authors.forename: Munish
authors.initials: M
authors.lastname: Chauhan
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
authors.forename: Rohini
authors.initials: R
authors.lastname: Vidya Shankar
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
authors.forename: Neeta
authors.initials: N
authors.lastname: Ashok Kumar
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
authors.forename: Vikram D
authors.initials: VD
authors.lastname: Kodibagkar
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Sadleir
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D017352:Echo-Planar Imaging / Q000379:methods; D004553:Electric Conductivity; D017097:Electric Impedance; D004566:Electrodes; D004574:Electromagnetic Fields; D018274:Electroporation; D004867:Equipment Design; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007717:Knee / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D014054:Tomography / Q000379:methods*
keywords: EPI; MREIT; conductivity imaging; current density imaging; functional imaging