Sensitivity analysis of magnetic field measurements for magnetic resonance electrical impedance tomography (MREIT)

Cihan Göksu, Klaus Scheffler, Philipp Ehses, Lars G. Hanson, Axel Thielscher*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Purpose: Clinical use of magnetic resonance electrical impedance tomography (MREIT) still requires significant sensitivity improvements. Here, the measurement of the current-induced magnetic field (DBz,c) is improved using systematic efficiency analyses and optimization of multi-echo spin echo (MESE) and steady-state free precession free induction decay (SSFP-FID) sequences. Theory and Methods: Considering T1, T2, and T 2 relaxation in the signal-to-noise ratios (SNRs) of the MR magnitude images, the efficiency of MESE and SSFP-FID MREIT experiments, and its dependence on the sequence parameters, are analytically analyzed and simulated. The theoretical results are experimentally validated in a saline-filled homogenous spherical phantom with relaxation parameters similar to brain tissue. Measurement of DBz,c is also performed in a cylindrical phantom with saline and chicken meat. Results: The efficiency simulations and experimental results are in good agreement. When using optimal parameters, DBz,c can be reliably measured in the phantom even at injected current strengths of 1 mA or lower for both sequence types. The importance of using proper crusher gradient selection on the phase evolution in a MESE experiment is also demonstrated. Conclusion: The efficiencies observed with the optimized sequence parameters will likely render in-vivo human brain MREIT feasible.
Original languageEnglish
JournalMagnetic Resonance in Medicine
Volume79
Issue number2
Pages (from-to)748–760
ISSN0740-3194
DOIs
Publication statusPublished - 2017

Keywords

  • Efficiency analysis
  • Magnetic resonance electrical impedance tomography
  • Multi-echo spin echo
  • Steady-state free precession
  • Sequence optimization

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