Conductivity and current density image reconstruction using harmonic Bz algorithm in magnetic resonance electrical impedance tomography
Conductivity and current density image reconstruction using harmonic Bz algorithm in magnetic resonance electrical impedance tomography
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DOI：
10.1088/0031-9155/48/19/001
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发表时间：
2003-10-07
影响因子：
3.5
通讯作者：
Seo, JK
中科院分区：
文献类型：
--
作者：
Oh, SH;Lee, BI;Seo, JK
磁共振电阻抗断层扫描（MREIT）是提供一个对象的电导率分布的横截面图像。当向受试者注入电流时，我们使用MRI扫描仪测量感应磁通密度B = (B-x, B-y, B-z)的一个分量B。谐波B-z算法基于del(2)B(z)与delsigma之间的关系，利用多个成像切片测量的B-z数据重建sigma图像。在得到σ后，我们可以重建任意给定电流注入方法的电流密度分布图像。在描述谐波B-z算法的基础上，本文通过计算机模拟和模拟实验，利用4个嵌入电极注入6种不同的26 mA电流，重建了电导率和电流密度图像。为了获得实验结果，我们使用了一个三维盐水模体，里面有两个聚丙烯酰胺物体。我们使用0.3 T（特斯拉）实验MRI扫描仪测量诱导的B-z。使用谐波B-z算法，我们可以重建82 x 82像素的电导率和电流密度图像。像素尺寸为0.6 x 0.6 mm(2)。当相应MR量级图像的信噪比约为30时，重构图像的相对L-2误差在13.8% ~ 21.5%之间。结果表明，体外和体内动物实验研究是可行的。需要进一步的研究将注射电流的量降低到低于1 mA的人类受试者。
Magnetic resonance electrical impedance tomography (MREIT) is to provide cross-sectional images of the conductivity distribution sigma of a Subject. While injecting current into the subject, we measure one component B, of the induced magnetic flux density B = (B-x, B-y, B-z) using an MRI scanner. Based on the relation between del(2)B(z) and delsigma, the harmonic B-z algorithm reconstructs an image of sigma using the measured B-z data from multiple imaging slices. After we obtain sigma, we can reconstruct images of current density distributions for any given current injection method. Following the description of the harmonic B-z, algorithm, this paper presents reconstructed conductivity and current density images from computer simulations and phantom experiments using four recessed electrodes injecting six different currents of 26 mA. For experimental results, we used a three-dimensional saline phantom with two polyacrylamide objects inside. We used our 0.3 T (tesla) experimental MRI scanner to measure the induced B-z. Using the harmonic B-z algorithm, we could reconstruct conductivity and current density images with 82 x 82 pixels. The pixel size was 0.6 x 0.6 mm(2). The relative L-2 errors of the reconstructed images were between 13.8 and 21.5% when the signal-to-noise ratio (SNR) of the corresponding MR magnitude images was about 30. The results suggest that in vitro and in vivo experimental studies with animal subjects are feasible. Further studies are requested to reduce the amount of injection current down to less than 1 mA for human subjects.