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摘要
PurposeTo develop a novel, current-controlled alternating steady-state free precession (SSFP)-based conductivity imaging method and corresponding MR signal models to estimate current-induced magnetic flux density (B-z) and conductivity distribution. MethodsIn the proposed method, an SSFP pulse sequence, which is in sync with alternating current pulses, produces dual oscillating steady states while yielding nonlinear relation between signal phase and B-z. A ratiometric signal model between the states was analytically derived using the Bloch equation, wherein B-z was estimated by solving a nonlinear inverse problem for conductivity estimation. A theoretical analysis on the signal-to-noise ratio of B-z was given. Numerical and experimental studies were performed using SSFP-FID and SSFP-ECHO with current pulses positioned either before or after signal encoding to investigate the feasibility of the proposed method in conductivity estimation. ResultsGiven all SSFP variants herein, SSFP-FID with alternating current pulses applied before signal encoding exhibits the highest B-z signal-to-noise ratio and conductivity contrast. Additionally, compared with conventional conductivity imaging, the proposed method benefits from rapid SSFP acquisition without apparent loss of conductivity contrast. ConclusionWe successfully demonstrated the feasibility of the proposed method in estimating current-induced B-z and conductivity distribution. It can be a promising, rapid imaging strategy for quantitative conductivity imaging. Magn Reson Med 75:2009-2019, 2016.
- 出版日期2016-5
