Optimization of multiply acquired magnetic flux densityB_zusing ICNE-Multiecho train in MREIT

Abstract

The aim of magnetic resonance electrical impedance tomography (MREIT) is to visualize the electrical properties, conductivity or current density of an object by injection of current. Recently, the prolonged data acquisition time when using the injected current nonlinear encoding (ICNE) method has been advantageous for measurement of magnetic flux density data, Bz, for MREIT in the signal-to-noise ratio (SNR). However, the ICNE method results in undesirable side artifacts, such as blurring, chemical shift and phase artifacts, due to the long data acquisition under an inhomogeneous static field. In this paper, we apply the ICNE method to a gradient and spin echo (GRASE) multi-echo train pulse sequence in order to provide the multiple k-space lines during a single RF pulse period. We analyze the SNR of the measured multiple B(z) data using the proposed ICNE-Multiecho MR pulse sequence. By determining a weighting factor for B(z) data in each of the echoes, an optimized inversion formula for the magnetic flux density data is proposed for the ICNE-Multiecho MR sequence. Using the ICNE-Multiecho method, the quality of the measured magnetic flux density is considerably increased by the injection of a long current through the echo train length and by optimization of the voxel-by-voxel noise level of the B(z) value. Agarose-gel phantom experiments have demonstrated fewer artifacts and a better SNR using the ICNE-Multiecho method. Experimenting with the brain of an anesthetized dog, we collected valuable echoes by taking into account the noise level of each of the echoes and determined B(z) data by determining optimized weighting factors for the multiply acquired magnetic flux density data.

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

“…The collected B z signals were optimized to reduce noise effects by combining them with the appropriate weight factor. 13 In the next step, we performed brain DTI imaging at the same slice position, using a conventional single-shot spin-echo echo-planner-imaging (SS-SE-EPI) sequence with a b-value of 1000 sec/mm 2 . Diffusion-weighting gradients were applied in 32 non-collinear diffusion pulses with a TR/TE values of 2000/60 msec.…”

Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

“…4(e) were optimized by determining the weighting factors of the multiple echoes depending on the MR image magnitude and the injection current pulse width. 35 Fig. 6(a) shows the optimized B ' z ; ' ¼ 1; 2 obtained as the weighted combination of the multiple B z data in Fig.…”

In vivo magnetic resonance electrical impedance tomography of canine brain: Disease model study of ischemia and abscess

“…In this paper, we address this issue and describe our recent in vivo animal imaging studies. Adopting all the latest methodological improvements such as carbon-hydrogel electrodes [16], low-noise constant current source [17] and multi-echo pulse sequence [18,19], we have performed in vivo animal imaging studies to investigate any change of electrical conductivity due to brain ischemia and abscess. We describe details of the imaging method and present conductivity images of canine brains without and with such disease models.…”