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Sensitivity analysis of magnetic field measurements for magnetic resonance electrical impedance tomography (MREIT)
Author(s) -
Göksu Cihan,
Scheffler Klaus,
Ehses Philipp,
Hanson Lars G.,
Thielscher Axel
Publication year - 2018
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.26727
Subject(s) - imaging phantom , nuclear magnetic resonance , sensitivity (control systems) , spin echo , physics , relaxation (psychology) , magnetic resonance imaging , magnetic field , larmor precession , materials science , computational physics , optics , biology , medicine , quantum mechanics , electronic engineering , neuroscience , radiology , engineering
Purpose Clinical use of magnetic resonance electrical impedance tomography (MREIT) still requires significant sensitivity improvements. Here, the measurement of the current‐induced magnetic field (ΔB z,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 T 1 , T 2 , andT 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 ΔB z,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, ΔB z,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. Magn Reson Med 79:748–760, 2018. © 2017 International Society for Magnetic Resonance in Medicine.