Multi-frequency electrical conductivity imaging via contactless measurements

Download

index.pdf

Date

2006

Author

Özkan, Koray Özdal

Metadata

Show full item record

Item Usage Stats

182
views

102
downloads

A multi-frequency data acquisition system is realized for subsurface conductivity imaging of biological tissues. The measurement procedures of the system at different frequencies are same. The only difference between the single frequency experiments and the multi-frequency experiments is the hardware, i.e. the sensor and the power amplifier used in the single frequency experiments was different than that were used in the multi-frequency experiments. To avoid confusion the measurement system with which the single frequency experiments were performed is named as prototype system and the measurement system with which the multi-frequency experiments were performed is named as multi-frequency system. This system uses magnetic excitation (primary field) to induce eddy currents inside the conductive object and measures the resulting magnetic field due to eddy currents (secondary field). For this purpose, two differential-coil sensors are constructed; one is for the single frequency measurements and the other is for the multi-frequency measurements. Geometrically the coils are same, the only difference between them is the radius of the wires wound on them. The sensor consists of two differentially connected identical receiver coils employed to measure secondary field and in between the receiver coils is placed a transmitter coil, which creates the primary field. The coils are coaxial. In the prototype system the transmitter coil is driven by a sinusoidal current of 300 mA (peak) at 50 kHz. In the multi-frequency system the transmitter coil is driven by a sinusoidal current of 217 mA (peak), 318 mA (peak), 219 mA (peak) and 211 mA (peak) at 30 kHz, 50 kHz, 60 kHz and 90 kHz, respectively. A data acquisition card (DAcC) is designed and constructed on a printed circuit board (PCB) for phase sensitive detection (PSD). The equivalent input noise voltage of the card was found as

Subject Keywords

Electricity and magnetism.

URI

http://etd.lib.metu.edu.tr/upload/12607071/index.pdf
https://hdl.handle.net/11511/15798

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

A labview interface to integrate magnetic resonance imaging (MRI) simulator with system control and its application to regional magnetic resonance electrical impedance tomography (MREIT) reconstruction Topal, Tankut; Eyüboğlu, Behçet Murat; Department of Electrical and Electronics Engineering (2010) Magnetic resonance imaging (MRI) is a high resolution medical imaging technique based on distinguishing tissues according to their nuclear magnetic properties. Magnetic resonance electrical impedance tomography (MREIT) is a conductivity imaging technique which reconstructs images of electrical properties, based on their effect on induced magnetic flux density due to externally applied current flow. Both of these techniques are of interest for novel research and development. Simulators help researchers obser...
Microstructure development in nickel zinc ferrites Okatan, Mahmut Barış; Timuçin, Muharrem; Department of Metallurgical and Materials Engineering (2005) Nickel zinc ferrites (NZF) have been considered as one of the basic components in high frequency electromagnetic applications especially in the field of telecommunications. In the present study, the aim was to produce high quality nickel zinc ferrite ceramics at low soaking temperatures. For this purpose, conventional ceramic manufacturing method based on mixed oxide precursors was followed using calcium fluoride, CaF2, as sintering additive. During the sintering studies, it was noticed that both the micros...
Electrical and structural characterization of bismuth thin films Durkaya, Göksel; Parlak, Mehmet; Department of Physics (2005) Electrical and structural properties of Bismuth thin films were studied simultaneously. Electrical properties of the Bismuth thin films have been characterized by measuring temperature dependent conductivity and Hall effect. Structural analysis were carried out by X-ray diffraction technique and using a room temperature Atomic Force Microscope (RT-AFM).
Electrical conductivity imaging via contactless measurements Gençer, Nevzat Güneri (Institute of Electrical and Electronics Engineers (IEEE), 1999-07-01) A new imaging modality is introduced to image electrical conductivity of biological tissues via contactless measurements. This modality uses magnetic excitation to induce currents inside the body and measures the magnetic fields of the induced currents. In this study, the mathematical basis of the methodology is analyzed and numerical models are developed to simulate the imaging system. The induced currents are expressed using the (A) over right arrow-phi formulation of the electric field where (A) over rig...
Preparation and characterization of magnetite nanoparticles by thermal decomposition method for their potential use in tumor imaging Tatlıcı, Zehra; Volkan, Mürvet; Department of Chemistry (2010) In biomedical applications, magnetic nanoparticles have been used as they offer attractive possibilities. First, they have controllable sizes ranging from a few nanometers up to tens of nanometers and second, the nanoparticles are magnetic and magnetic fields can penetrate into human tissue which means that they can be manipulated by an external magnetic field gradient. In this study, Fe₃O₄ nanoparticles are synthesized by thermal decomposition method for their potential use in cancer diagnosis. Techniques ...

Citation Formats

K. Ö. Özkan, “Multi-frequency electrical conductivity imaging via contactless measurements,” M.S. - Master of Science, Middle East Technical University, 2006.