Department of Biomedical Engineering, Kyung Hee University, Korea.
Magn Reson Med. 2014 Jan;71(1):200-8. doi: 10.1002/mrm.24642. Epub 2013 Feb 8.
To propose a single magnetic resonance scan conductivity imaging technique providing dual-frequency characteristics of tissue conductivity.
Using a modified spin-echo pulse sequence, the magnetic flux density induced by externally injected currents and the B1+ phase map with injected current effects removed were acquired simultaneously. The low-frequency conductivity was reconstructed from the measured magnetic flux density by the projected current density method, while the high-frequency conductivity was reconstructed using the B1+ maps. Three different conductivity phantoms were used to demonstrate low- and high-frequency conductivity characteristics.
A conductivity spectrum at two frequencies was successfully acquired with the proposed scheme. Magnetic resonance electrical impedance tomography is advantageous for seeing an anomaly itself wrapped with a thin insulating membrane. In addition, if the membrane is porous, the membrane property can be quantitatively visualized with magnetic resonance electrical impedance tomography. Magnetic resonance electrical properties tomography does not detect such membranes, which enable it to probe things inside an insulating membrane.
Considering these pros and cons and also the fact that the conductivity of biological tissue changes with frequency, a dual-frequency conductivity imaging incorporating both magnetic resonance electrical impedance tomography and magnetic resonance electrical properties tomography in future animal and human experiments is suggested.
提出一种单磁共振扫描电导率成像技术，提供组织电导率的双频特性。
使用改进的自旋回波脉冲序列，同时获取外部注入电流引起的磁通密度和去除注入电流影响的 B1+相位图。通过投影电流密度法从测量的磁通密度重建低频电导率，而通过 B1+图重建高频电导率。使用三个不同的电导率体模来演示低频和高频电导率特性。
该方案成功地获得了两个频率的电导率谱。磁共振电阻抗断层成像有利于观察本身被薄绝缘膜包裹的异常。此外，如果膜是多孔的，则可以用磁共振电阻抗断层成像定量可视化膜的性质。磁共振电特性断层成像无法检测到这些膜，这使其能够探测绝缘膜内部的物体。
考虑到这些优缺点，以及生物组织电导率随频率变化的事实，建议在未来的动物和人体实验中结合磁共振电阻抗断层成像和磁共振电特性断层成像进行双频电导率成像。
