Abstract
Measuring the z-component of magnetic flux density B = (Bx, By, Bz) induced by transversally injected current, magnetic resonance electrical impedance tomography (MREIT) aims to visualize electrical property (current density and/or conductivity distribution) in a three-dimensional imaging object. For practical implementations of MREIT technique, it is critical to reduce injection of current pulse within safety requirements. With the goal of minimizing the noise level in measured Bz data, we propose a new method to enhance the measure Bz data using steady-state coherent gradient multi-echo (SSC-GME) MR pulse sequence combining with injection current nonlinear encoding (ICNE) method in MREIT, where the ICNE technique injects current during a readout gradient to maximize the signal intensity of phase signal including Bz. The total phase offset in SSC-GME includes additional magnetic flux density due to the injected current, which is different from the phase signal for the conventional spoiled MR pulse sequence. We decompose the magnetization precession phase from the total phase offset including Bz and optimize Bz data using the steady-state equilibrium signal. Results from a real phantom experiment including different kinds of anomalies demonstrated that the proposed method enhanced Bz comparing to a conventional spoiled pulse sequence.
Highlights
Measuring the z-component of magnetic flux density B = (Bx, By, Bz) induced by transversally injected current, magnetic resonance electrical impedance tomography (MREIT) aims to visualize electrical property in a three-dimensional imaging object
With the goal of minimizing the noise level in measured Bz data, we propose a new method to enhance the measure Bz data using steady-state coherent gradient multi-echo (SSC-GME) MR pulse sequence combining with injection current nonlinear encoding (ICNE) method in MREIT, where the ICNE technique injects current during a readout gradient to maximize the signal intensity of phase signal including Bz
The total phase offset in SSC-GME includes additional magnetic flux density due to the injected current, which is different from the phase signal for the conventional spoiled MR pulse sequence
Summary
Since the steady-state magnetization by injecting current depends on the field inhomogeneity and the magnetic flux density by the injected current-induced resonance offset, the magnetization precession phase, which denotes the accumulated phase in the transverse plane during previous free precession periods, includes information of Bz. We performed a phantom experiment using a 3 T MRI scanner (Philips Achieva 3.0 T) with a multi-channel RF coil (SENSE-Head-8ch). The steady-state magnetization using SSC-GME pulse sequence by injecting currents I± from the end of first RF pulse to the end of reading gradient can be represented as a total phase offset βTR during each repetition time TR βT±R(r) = φ0(∆B(r), G⃗ ,TR) ± φ1(Bz(r),TR). Comparing to the conventional spoiled pulse sequences, the total precession angle of the steadystate transverse magnetization components depends on the static, gradient field inhomogeneity and the phase shift by the injected current. Using the identity (5), we have the following over-determined system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
