Experimental studies for LFEIT with magnetic field measurements

Tetik, Ahmet Önder
Lorentz Force Electrical Impedance Tomography based on magnetic field measurements (LFEIT) is a hybrid imaging modality to image the electrical impedance of body tissues. In this modality, ultrasound pressure waves applied to the body tissues under static magnetic fields induce Lorentz currents. Magnetic flux density due to these currents is measured using receiver coils. The main aim of this thesis is to develop an experimental setup and a data acquisition system to obtain LFEIT sig nals from phantoms. Moreover, conductivity contrast images are formed using the measured LFEIT signals. For the data acquisition system, custom made contactless receiver coils in Helmholtz configuration are utilized and a two-stage cascaded amplifier is designed to obtain LFEIT signals. A magnetic field generator is built with permanent magnets to apply 0.56 T static magnetic field to phantoms in the experimental setup. In addition, 16-element Linear Phased Array (LPA) Transducer is used to steer ultrasound waves in the phantoms. Two different phantoms are prepared for experiments. In the first experiment, a conductive inhomogenity with 3 S/m conductivity is detected at 92 mm from the transducer surface. The last experiment is conducted with a phantom including sunflower oil and agar-gel having a cavity filled with 58 S/m solution. The transducer steers ultrasound waves from -20◦ to 20◦ with 1◦ step angle in the phantom. At each angle, data acquisition system records LFEIT signals. With this system, 58 S/m cavity with 15.15 mm height, 30 mm width and 20 mm length dimensions is detected at a depth of 75 mm. As a result, conductivity contrast image of this phantom is formed using LFEIT signals. 3 S/m is the lowest conductivity detected by this technique compared to the previous studies reported in the literature.


Data acquisition system for Lorentz force electrical impedance tomography using magnetic field measurements
Kaboutari, Keivan; Gençer, Nevzat Güneri; Department of Electrical and Electronics Engineering (2017)
Lorentz Force Electrical Impedance Tomography (LFEIT) is a novel imaging modality to image electrical conductivity properties of biological tissues. This modality is recently proposed for early stage diagnosis of cancerous tissues. The main aim of this thesis study is to develop a data acquisition system for LFEIT. Design of contactless receiver sensor, static magnetic field generation (0.56 T is generated by permanent neodymium magnets), amplification of received signals and experimental studies using vari...
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In magnetic resonance-electrical impedance tomography, magnetic flux density due to current injection is the measured quantity. Different conductivity distributions create different magnetic flux density distributions. Distinguishability for MR-EIT is defined using this fact. The definition is general and valid for 2D as well as 3D structures of any shape. It is not always possible to find an analytic expression for distinguishability. However, when a 2D cylindrical body with concentric inhomogeneity is con...
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Magnetic Resonance Electrical Impedance Tomography (MREIT) is a medical imaging method that provides images of electrical conductivity at low frequencies (0-1 kHz). In MREIT, electrical current is applied to the body via surface electrodes and corresponding magnetic flux density is measured by means of Magnetic Resonance (MR) phase imaging techniques. By utilizing the magnetic flux density measurements and surface potential measurements images of true conductivity distribution can be reconstructed. In order...
Citation Formats
A. Ö. Tetik, “Experimental studies for LFEIT with magnetic field measurements,” M.S. - Master of Science, Middle East Technical University, 2018.