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Current‐induced alternating reversed dual‐echo‐steady‐state for joint estimation of tissue relaxation and electrical properties
Author(s) -
Lee Hyunyeol,
Sohn ChulHo,
Park Jaeseok
Publication year - 2017
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.26350
Subject(s) - steady state free precession imaging , relaxation (psychology) , nuclear magnetic resonance , steady state (chemistry) , alternating current , magnetic resonance imaging , current (fluid) , signal (programming language) , electrical impedance , eddy current , noise (video) , sensitivity (control systems) , conductivity , materials science , physics , chemistry , computer science , electronic engineering , voltage , medicine , quantum mechanics , artificial intelligence , engineering , image (mathematics) , radiology , programming language , thermodynamics
Purpose To develop a current‐induced, alternating reversed dual‐echo‐steady‐state‐based magnetic resonance electrical impedance tomography for joint estimation of tissue relaxation and electrical properties. Methods The proposed method reverses the readout gradient configuration of conventional, in which steady‐state‐free‐precession (SSFP)‐ECHO is produced earlier than SSFP‐free‐induction‐decay (FID) while alternating current pulses are applied in between the two SSFPs to secure high sensitivity of SSFP‐FID to injection current. Additionally, alternating reversed dual‐echo‐steady‐state signals are modulated by employing variable flip angles over two orthogonal injections of current pulses. Ratiometric signal models are analytically constructed, from which T 1 , T 2 , and current‐induced B z are jointly estimated by solving a nonlinear inverse problem for conductivity reconstruction. Numerical simulations and experimental studies are performed to investigate the feasibility of the proposed method in estimating relaxation parameters and conductivity. Results The proposed method, if compared with conventional magnetic resonance electrical impedance tomography, enables rapid data acquisition and simultaneous estimation of T 1 , T 2 , and current‐induced B z , yielding a comparable level of signal‐to‐noise ratio in the parameter estimates while retaining a relative conductivity contrast. Conclusion We successfully demonstrated the feasibility of the proposed method in jointly estimating tissue relaxation parameters as well as conductivity distributions. It can be a promising, rapid imaging strategy for quantitative conductivity estimation. Magn Reson Med 78:107–120, 2017. © 2016 International Society for Magnetic Resonance in Medicine