School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
Magn Reson Med. 2018 Jan;79(1):71-82. doi: 10.1002/mrm.26638. Epub 2017 Feb 16.
Magnetic resonance electrical impedance tomography (MREIT) sequences typically use conventional spin or gradient echo-based acquisition methods for reconstruction of conductivity and current density maps. Use of MREIT in functional and electroporation studies requires higher temporal resolution and faster sequences. Here, single and multishot echo planar imaging (EPI) based MREIT sequences were evaluated to see whether high-quality MREIT phase data could be obtained for rapid reconstruction of current density, conductivity, and electric fields.
A gel phantom with an insulating inclusion was used as a test object. Ghost artifact, geometric distortion, and MREIT correction algorithms were applied to the data. The EPI-MREIT-derived phase-projected current density and conductivity images were compared with simulations and spin-echo images as a function of EPI shot number.
Good agreement among measures in simulated, spin echo, and EPI data was achieved. Current density errors were stable and below 9% as the shot number decreased from 64 to 2, but increased for single-shot images. Conductivity reconstruction relative contrast ratios were stable as the shot number decreased. The derived electric fields also agreed with the simulated data.
The EPI methods can be combined successfully with MREIT reconstruction algorithms to achieve fast imaging of current density, conductivity, and electric field. Magn Reson Med 79:71-82, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
磁共振电阻抗断层成像（MREIT）序列通常使用传统的自旋或梯度回波采集方法来重建电导率和电流密度图。MREIT 在功能和电穿孔研究中的应用需要更高的时间分辨率和更快的序列。在这里，评估了基于单激发和多激发回波平面成像（EPI）的 MREIT 序列，以观察是否可以获得高质量的 MREIT 相位数据，以便快速重建电流密度、电导率和电场。
使用带有绝缘内含物的凝胶体模型作为测试对象。对数据应用了鬼影、几何变形和 MREIT 校正算法。将 EPI-MREIT 衍生的相位投影电流密度和电导率图像与模拟和自旋回波图像进行比较，作为 EPI 激发次数的函数。
模拟、自旋回波和 EPI 数据中的测量结果之间达成了良好的一致性。当激发次数从 64 减少到 2 时，电流密度误差稳定且低于 9%，但单激发图像的误差增加。随着激发次数的减少，电导率重建相对对比度比保持稳定。得出的电场也与模拟数据一致。
EPI 方法可以与 MREIT 重建算法成功结合，实现电流密度、电导率和电场的快速成像。磁共振医学 79:71-82, 2018。© 2017 国际磁共振学会。
