HIGH FIELD CURRENT DENSITY IMAGING

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。当我们向像人体这样的导电对象注入电流时，它会产生电压、电流密度和磁通密度分布。这些分布由受试者的几何形状、电极配置和电导率分布决定。有关电导率和电流密度分布的信息在许多生物医学应用中都是非常重要的，如生物电学中的组织建模、电刺激过程中电流分布的估计、生理功能的监测和损伤检测等。自20世纪80年代初以来，电导率图像重建一直是电阻抗断层成像(EIT)的活跃研究目标。EIT利用边界上测量的电流-电压数据来提供电导率分布的横截面图像。对这一成像问题的数学分析表明，由于相应反问题的病态性质，它具有根本的局限性。磁共振电阻抗断层成像(MREIT)被提出用来克服EIT中图像重建问题的不适定性。其核心思想是利用核磁共振扫描仪测量的内部磁通密度数据来产生电导率和电流密度分布的横断面图像。最近，已经开发了几种图像重建算法，该算法基于仅测量磁通量密度的一个分量，而不在MRI扫描仪内旋转对象。在讨论了mREIT的测量技术之后，我们将给出实验数据和重建的电导率和电流密度图像。总结mREIT的最新研究成果，提出未来的研究方向，使mREIT成为一种新的临床应用的电导和电流密度成像技术。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. When we inject current into an electrically conducting subject such as the human body, it induces voltage, current density, and magnetic flux density distributions. These distributions are determined by the geometry, electrode configuration, and conductivity distribution of the subject. Information about the conductivity and current density distribution is of significant importance in many biomedical applications, such as modeling of tissues in bioelectricity, estimation of current distributions during electrical stimulations, monitoring of physiological functions, lesion detections, and so on. Conductivity image reconstruction has been the active research goal of Electrical Impedance Tomography (EIT) since early 1980s. EIT utilizes the measured current-voltage data on the boundary to provide cross-sectional images of a conductivity distribution. Mathematical analysis of this imaging problem indicates that it has fundamental limitations due to the ill-posed nature of the corresponding inverse problem. Magnetic Resonance Electrical Impedance Tomography (MREIT) has been suggested to overcome this ill-posedness of the image reconstruction problem in EIT. The key idea is to utilize the internal magnetic flux density data measured by an MRI scanner to produce cross-sectional images of conductivity and current density distributions. Lately, several image reconstruction algorithms have been developed based on the measurement of only one component of the magnetic flux density without rotating the subject within the MRI scanner. After discussing the measurement techniques in MREIT, we will present experimental data and reconstructed conductivity and current density images. Summarizing latest outcomes of the MREIT research, we will present future research directions to make MREIT a new clinically applicable conductivity and current density imaging technique.