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Numerical modelling and measurement of the magnetic susceptibility in inhomogeneous materials by the NMR technics
Julínek, Michal ; Steinbauer, Miloslav (referee) ; Fiala, Pavel (advisor)
This bachelor work is concerned in magnetic susceptibility of specific object (glass cube filled with clay, with glass sphere in the centre). In the first part determining of magnetic susceptibility of object was carried out. Measuring was conducted on tomograph of ÚPT AV ČR. Method of gradient echo, which allows magnetic susceptibility determining of non-magnetic materials, was used. Distribution of magnetic field within the object was acquired (object was measured with and without sphere), the change of magnetic field (between object with and without sphere) was subsequently determined. In the second part, magnetic field simulation of the same object in the ANSYS software was performed. Calculation was conducted on 3D model by the finite element analysis. Distribution of magnetic field of object was acquired as a result of simulation. Results from simulation were compared with experimental findings.
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Metal detector for industrial use
Stehno, Rostislav ; Friedl, Martin (referee) ; Szabó, Zoltán (advisor)
The goal of this project is explore and study the ways of metal detecting and create a metal detector for industrial use. During a project development, the device size and user easy interface were the basic requirement. As a visual device was chosen LCD touch display, which is very important as a user-friendly interface. For math calculations and right function of device will be implemented microcontroller from Atmel corporation. As a data storage will be used a flash memory with 16MB of size. When the device were inventing, a lot of methods were studied and the impulse detect method were chosen which is the most perspective way of metal detecting. Device will communicate with PC trough a USB port. The device will have a battery which allows device to run for a few hours. The prototype of PCB were developed. Few mistakes has been discovered, while the device were constructed, but they were solved successfully.
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Numericalanalysis and measurement of the magnetic charakteristics in inhomogeneous materials by the NMR technics
Mrázek, Jiří ; Bartušek, Karel (referee) ; Fiala, Pavel (advisor)
This bachelor thesis is concerned in magnetic susceptibility of specific object (glass cube, with four sticks in the centre). In the first part determining of magnetic susceptibility of object was carried out. Measuring was conducted on tomograph of ÚPT AV ČR. Method of gradient echo, which allows magnetic susceptibility determining of non-magnetic materials, was used. Distribution of magnetic field within the object was acquired (object was measured with and without sticks), the change of magnetic field (between object with and without stick) was subsequently determined. In the second part, magnetic field simulation of the same object in the ANSYS software was performed. Calculation was conducted on 3D model by the finite element analysis. Distribution of magnetic field of object was acquired as a result of simulation. Results from simulation were compared with experimental findings.
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Metal detector for industrial use
Stehno, Rostislav ; Hrabina, Jan (referee) ; Szabó, Zoltán (advisor)
The goal of this project is explore and study the ways of metal detecting and create a metal detector for industrial use. When the device were inventing, a lot of methods were studied and the impulse detect method were chosen as the most perspective way of metal detecting, thanks to a huge electronics parts possibilities. After experiences with preceding device was necessary to redesign it. Main target of this thesis is to increase the computing power of detector. For this purpose will device need a new microcontroller. Device will communicate with PC trough a USB port. The device will have a battery which allows device to run for a few hours. Processing of measured data will be make even with DFT which will lead to better analyze of mass and type of conductor under device.
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Change of magnetic susceptibility during the germination of plants
Sedlář, Petr ; Fiala, Pavel (referee) ; Vlachová Hutová, Eliška (advisor)
The work examines the changes in the magnetic susceptibility during the early germination of the somatic embryo (RSE) of the Norway spruce. Susceptibility is in the physically view the property, which can be used to determine a variety of parameters and properties of the measured objects. The aim of this work was to create a automatic to evaluate the susceptibility of the tissue RSE and take measurements to prove or disprove the contrary of the accuracy of this assessment. This work contains the results obtained by modeling a script in Matlab, in which can be shown the correctness of the theoretical concepts.
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Parameter optimization of MR sequences for magnetic susceptibility measurement
Pinkava, Jan ; Bartušek, Karel (referee) ; Steinbauer, Miloslav (advisor)
The Bachelor thesis deals with measuring magnetic susceptibility by means of nuclear magnetic resonance. Magnetic field is affected and deformed by various materials. The range and the shape of the deformation is caused by susceptibility. The thesis contains a 2D numerical model of a sample in a magnetic field 4.7 T. The results are compared with values obtained by a tomographic measurement. The second part of the thesis contains a 3D numerical model of diamagnetic and paramagnetic material. Moreover, a comparison with values measured in reality is drawn.
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Analysis of Selected Artefacts in Diffusion-Based Magnetic Resonance Measurements
Marcoň, Petr ; Král, Bohumil (referee) ; Frollo, Ivan (referee) ; Bartušek, Karel (advisor)
The presented dissertation thesis analyses artefacts in diffusion-weighted images. In medical practice, the artefacts can impede the diagnostics of pathological tissues and, therefore, need to be eliminated. As the first step within the thesis, an analysis of the most frequent artefacts in diffusion-weighted images is performed, and the hitherto known approaches to artefact elimination are described. In order to facilitate the reduction of artefacts caused by the inhomogeneity of the static magnetic field and induced by eddy currents, a novel three-measurement method is shown. This technique will find application especially in measuring the diffusion coefficient of isotropic materials. At this point, it is important to note that a significant and commonly found problem is the magnetic susceptibility artefact; different magnetic susceptibility values at the boundary between two materials can cause magnetic field inhomogeneities and even complete loss of the signal. Therefore, we designed a novel method for the measurement of magnetic susceptibility in various samples of magnetically incompatible materials, which do not produce any MR signal. The technique was experimentally verified using a set of differently shaped diamagnetic and paramagnetic samples. In addition to the magnetic susceptibility problem, the thesis presents artefacts such as noise, motion-induced items, hardware limitations, chemical shift, and the dependence of the diffusion coefficient on the temperature. To enable precise measurement of the diffusion coefficient, we proposed a thermal system; in the experiment, it was determined that when the measurement error does not exceed 5%, the temperature change should not be higher than 0,1 °C. In the final sections of the thesis, practical application examples involving the designed methods are shown.
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Compatibility of selected dental alloys with magnetic resonance imaging
Linetskiy, Igor ; Hubálková, Hana (advisor) ; Suchánek, Jakub (referee) ; Dostálová, Taťjana (referee)
Magnetic resonance imaging (MRI) is one of the up-to-date and perspective methods of diagnostic medical imaging. It is highly valued for absence of ionizing radiation, non-invasiveness, acquiring of highly accurate images of hard and especially soft tissues in any plane. It is a method of choice in central nervous system imaging. Nowadays it is used in diagnostics of other diseases in the maxillofacial area. The major shortcoming of MRI is interaction of magnetic fields of MRI system with metallic objects present in human body. As a result, this may lead to their heating, movement, and also to imaging artifacts. Since different metallic constructions (fixed bridges, dental implants, splints, plates, orthodontic appliances, etc.) are often used in the contemporary dentistry, the problem of their compatibility with MRI is relevant. The aim of this study was to validate the compatibility of dental alloys with MRI, classify the materials according to the degree of compatibility and to establish the range of their possible negative impact on quality of MRI in head and neck area. In order to find dental metals and alloys, General Health Insurance Company code- list, catalogues of manufacturers' and Prague dental labs were used. Measurement methods of magnetic susceptibility (MS), electric conductivity...
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MRI mapping of brain iron deposition in patients with neurological diseases with a focus on multiple sclerosis and neuromyelitis optica
Pudlač, Adam ; Burgetová, Andrea (advisor) ; Lisý, Jiří (referee) ; Ryška, Pavel (referee)
Background: Neuromyelitis optica (NMO) and multiple sclerosis (MS) often manifest similar symptoms. However, the distinction between the two diseases is particularly important for different therapies. The aim of this study is to determine whether these diseases can be distinguished based on cerebral iron deposits in the deep grey matter and whether there is a correlation between iron deposits, local deep grey matter atrophy and clinical severity of the disease. Methods: 40 patients with relapsing-remitting MS (RRMS), 20 patients with NMO and 20 healthy subjects were examined at the MRI department of the 1st Faculty of Medicine of Charles University in Prague from December 2013 to March 2015. All patients with RRMS fulfilled the revised McDonald criteria, the diagnosis of NMO was based on Wingerchuk criteria. All 20 patients with NMO had positive AQP4-IgG. Quantitative susceptibility mapping (QSM) and volumometry of individual deep gray matter structures were performed. All patients with NMO and MS underwent simultaneous examination by a specialist in demyelinating diseases. Neurological disability was assessed by the Kurtzke Disability Status Scale (EDSS). Results: Patients with NMO have higher magnetic susceptibility values in the substantia nigra compared to healthy controls. Patients with RRMS...
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Low-field excitations in magnetite
Švindrych, Zdeněk ; Janů, Zdeněk (advisor) ; Novák, Pavel (referee) ; Svoboda, Pavel (referee)
We have performed detailed measurements of magnetic and dielectric properties of high quality magnetite (Fe3O4) single crystals in weak magnetic and electric fields. These measurements can reveal details of phase transitions and other features that are not yet fully understood. We focused not only at the Verwey transition - a well known phase transition taking place at about 120 K in stoichiometric samples - but we also explored and described new relaxation effects in magnetite at low temperatures. The low-temperature properties were also found to be exceptionally sensitive to sample quality, stoichiometry and homogeneity. The results presented in this thesis were acquired on sensitive non-commercial SQUID magnetometer complemented by four-probe dielectric spectroscopy and dc conductivity measurements.
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