HIGH FIELD CURRENT DENSITY IMAGING

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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.