Demonstration of full tensor current density imaging using ultra-low field MRI
Demonstration of full tensor current density imaging using ultra-low field MRI
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DOI：
10.1016/j.mri.2019.03.010
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发表时间：
2019-07-01
影响因子：
2.5
通讯作者：
Koerber, R.
中科院分区：
文献类型：
--
作者：
Hoemmen, P.;Storm, J-H;Koerber, R.
头部内外加直流电流的直接成像可以提供有价值的电导率信息，可能改善电磁神经成像。在μ T拉莫尔场的超低场磁共振成像（ULF MRI）可用于电流密度成像（CDI）。这里，使用专门的序列探测由外加电流密度J生成的磁场B-J对MR信号的可测量的影响。与高场MRI相比，由于序列设计的灵活性，B-J的全张量可以在扫描仪中不旋转的情况下导出，我们提出了一种基于超导量子干涉器件（SQUID）的ULF MRI装置，该装置工作在380 aT Hz（-1/2）的噪声水平下，能够在脉冲序列内切换所有成像场。因此，该系统能够实现零场编码，其中在没有其他磁场的情况下探测B-J的全张量。在具有不同几何形状的体模上演示了3D CDI，该体模承载约2 mA的电流，对应于0.45和8 A/m（2）之间的电流密度。通过与体内采集的头部图像进行比较，我们提供了对信噪比的必要改进的见解。
Direct imaging of impressed dc currents inside the head can provide valuable conductivity information, possibly improving electro-magnetic neuroimaging. Ultra-low field magnetic resonance imaging (ULF MRI) at mu T Larmor fields can be utilized for current density imaging (CDI). Here, a measurable impact of the magnetic field B-J, generated by the impressed current density J, on the MR signal is probed using specialized sequences. In contrast to high-field MRI, the full tensor of B-J can be derived without rotation of the subject in the scanner, due to a larger flexibility in the sequence design.We present an ULF MRI setup based on a superconducting quantum interference device (SQUID), which is operating at a noise level of 380 aT Hz(-1/2) and capable of switching all imaging fields within a pulse sequence. Thereby, the system enables zero-field encoding, where the full tensor of B-J is probed in the absence of other magnetic fields. 3D CDI is demonstrated on phantoms with different geometries carrying currents of approximately 2 mA corresponding to current densities between 0.45 and 8 A/m(2). By comparison to an in vivo acquired head image, we provide insights to necessary improvements in signal-to-noise ratio.