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...
Experimental results for 2D magnetic resonance electrical impedance tomography (MR-EIT) using magnetic flux density in one direction
Birgul, O; Eyüboğlu, Behçet Murat; Ider, YZ (IOP Publishing, 2003-11-07)
Magnetic resonance electrical impedance tomography (MR-EIT) is an emerging imaging technique that reconstructs conductivity images using magnetic flux density measurements acquired employing MRI together with conventional EIT measurements. In this study, experimental MR-EIT images from phantoms with conducting and insulator objects are presented. The technique is implemented using the 0.15 T Middle East Technical University MRI system. The dc current method used in magnetic resonance current density imaging...
Induced Current Magnetic Resonance Electrical Impedance Tomography with z-Gradient Coil
Eroglu, Hasan H.; Eyuboglu, Murat (2014-08-30)
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...
Anisotropic Conductivity Imaging with MREIT Using J-substitution and Hybrid J-substitution Algorithms
Degirmenci, E.; Eyüboğlu, Behçet Murat (2009-09-12)
Magnetic Resonance Electrical Impedance Tomography (MREIT) is a tomographical imaging technique which uses measurements of magnetic flux density induced by a probing current to reconstruct electrical conductivity distribution within a conductor object with magnetic resonance active nuclei. In this study, two novel anisotropic conductivity reconstruction algorithms for MREIT are proposed. The technique is evaluated with simulated measurements.
2D Simulations Based on General Time-Dependent Reciprocal Relation for LFEIT
KARADAŞ, Mursel; Gençer, Nevzat Güneri (2015-08-29)
Lorentz field electrical impedance tomography (LFEIT) is a newly proposed technique for imaging the conductivity of the tissues by measuring the electromagnetic induction under the ultrasound pressure field. In this paper, the theory and numerical simulations of the LFEIT are reported based on the general time dependent formulation. In LFEIT, a phased array ultrasound probe is used to introduce a current distribution inside a conductive body. The velocity current occurs, due to the movement of the conductiv...
Citation Formats
A. Ö. Tetik, “Experimental studies for LFEIT with magnetic field measurements,” M.S. - Master of Science, Middle East Technical University, 2018.