2D simulations based on the general time dependent reciprocal relation and initial experiments for LFEIT /

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2014
Karadaş, Mürsel
In this study, the new imaging modality Lorentz Field Electrical Impedance Tomography (LFEIT) is investigated. In LFEIT, the main aim is finding the conductivity distribution of different tissues. This method is based on the development of the current density distribution in the conductive medium. To develop the current density, the object is located in a static magnetic field and pressure wave due to an ultrasonic transducer develops particle movements inside the body. As a result, a velocity current distribution is created in the conductive medium via Lorentz force. An induction coil sensor placed around the body is utilized to measure the change in the magnetic flux density due to the velocity current distribution. To simulate the new technique, multiphysics solution is required which couples acoustic and electromagnetic equations. These equations in the conductive medium are reviewed and the numerical tools such as Finite Element Method (FEM) and Finite Difference Time Domain (FDTD) are used for their solution. To relate the conductive perturbation to the measurement, general time dependence reciprocal relation is used. The continuous forward problem is linearized and discretized to obtain a linear system of equations. The sensitivity matrix is obtained for different coil configurations and ultrasound transducer positions and its characteristics are analyzed. Thereafter, the image reconstruction algorithms and regularization methods are evaluated by means of the simulation data. The results show that, the imaging system provides high resolution for conductivity perturbation. Moreover, an initial experimental study is given to demonstrate the proof of the concept.