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Diffussion measurement by NMR
Vanko, Filip ; Gescheidtová, Eva (referee) ; Bartušek, Karel (advisor)
In Bachelor thesis is described the principle of MRI, the physical foundations of the phenomenon of magnetic resonance imaging, quantum and macroscopic model. Followed by a description of the mechanisms of relaxation of magnetic resonance phenomenon. In the following sections describes the basis of diffusion, each sequence for measuring diffusion NMR methods and the method of three measurements, which was used in experimental measurements. Last chapter deals with the practical. The results of measurements are evaluated in conclusion.
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Filtering methods for NMR measurements
Nezhyba, Jiří ; Mikulka, Jan (referee) ; Gescheidtová, Eva (advisor)
This master’s thesis deals with the wavelet transform and its use in processing and removing noise from images acquired by nuclear magnetic resonance. It defines fundamental terms for this work as mother wavelet or thresholding. Above all, it describes the principle of wavelet transform, thresholding techniques and criteria for evaluating the effectiveness of filtration. It describes the relation between wavelet transforms and digital filter banks. The experimental section describes the designed filtering method for removing noise from an image captured by the technique of nuclear magnetic resonance. We applied to different kinds of mother wavelets. Evaluation of the effectiveness of filtering was performed using the signal to noise ratio, relative contrast and the steepness of the intensity changes in signal intensity. It also discusses the comparison of properties of the image and selecting the mother wavelets based on image characteristics. Images were compared in terms of a histogram, cumulative histogram, k-space and the difference image.
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Measurement of diffusion coefitients by use of magnetic resonance
Král, Jakub ; Gescheidtová, Eva (referee) ; Bartušek, Karel (advisor)
This Bachelor thesis is focused on imaging techniques based on the principles of nuclear-magnetic resonance. These techniques are one of the most modern studies of physical, chemical and biological properties of substances. Introduction of this work is focused primarily on physical principles. Further in this work attention is given to the method of the PFG-SE but also to more modern multiinterval NMR methods, which removes the systematic measurement errors for heterogeneous materials. Part of the work is also devoted to b-factor calculations for various kinds of pulse sequences. In last part the work is devoted to data processing in Matlab and Marevisi. Selected method from the beginning of the work is than used to measure the diffusion and processing of tissue cultures.
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Image signal processing by wavelet
Slávik, Vladimír ; Gescheidtová, Eva (referee) ; Kubásek, Radek (advisor)
The first part of text introduces reader to basic theory of wavelet transform and its realization by filter banks. WT of two-dimensional signals is shown and a particular application of WT in this domain - signal denoising, is discussed. The second part describes the application for image denoising realized in MATLAB from both user's and programmer's viewpoint.
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MR image processing
Mrákava, Petr ; Smékal, Zdeněk (referee) ; Gescheidtová, Eva (advisor)
The subject of this bachelor's thesis is to become familiar with the methods of processing image acquired by techniques of nuclear magnetic resonance. It describes the gradual steps in the digitizing of the signal to the image data. But in the process a disturbing component is almost always created in the image, in particular noise, which causes image devaluation. Therefore, further work is focused mainly on eliminating present disturbing components. For the noise elimination, the widely used wavelet transformation is applied, which is implemented by banks of digital filters. The experimental part of this work deals with design of MR filtering method, optimal filtering parameters setting, decomposition of images into magnetic field map, and subsequent comparison of results obtained.
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Measurement of relaxation constants by use of magnetic resonance
Kořínek, Radim ; Bartušek, Karel (referee) ; Gescheidtová, Eva (advisor)
This bachelor’s thesis is dedicated to principles of magnetic resonance and measurement of relaxation times. At theoretical part all basics methods of measurement (SE-spin echo, GE-gradient echo, SR-saturation recovery, IR- inversion recovery) of relaxation times T1, T2 resp. T2* are shown. At practical part T1 and flip angles are carefully observed. In case of measurement of relaxation time T2, the FID signal acquisition after 90° RF pulse is sufficient. T2* time is set from absorbtion line. For measurement of transversal relaxation method SE (often called as Hahn spin echo –90° RF pulse is followed by next 180° RF pulse) can be used. With GE method, the T2* relaxation is observed. Measurement of relaxation time T1 using RF impulses and inclinable angles A, is described at chapter 3. Every magnetization components during RF impulses are deeply described by mathematical formulas. Other chapter of this bachelor thesis describes some functions from MATLAB and their fitness for approximation of signal. From every tested functions, the lsqcurvefit function would be the best. Iteration method is most fitting function for approximation of FID signal.
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Study of gel electrolytes properties by MR methods
Mrnka, Michal ; Gescheidtová, Eva (referee) ; Bartušek, Karel (advisor)
Theoretical part of the work deals with explanation of nuclear magnetic resonance phenomenon, relaxation processes in system of nuclear spins, basic techniques for measurement of relaxation times. There are described diffusion and techniques for diffusion coefficient measurement including method for suppressing the background gradient. Experimental part describes preparation of gel electrolytes samples and measurement of relaxation times. Sodium salt was used as a conductive agent. There is interpreted dependence of relaxation times on polymerization times and on concentration of conductive agent in gels.
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Measurement of selected samples relaxations by use of NMR
Kovalčík, Tomáš ; Gescheidtová, Eva (referee) ; Bartušek, Karel (advisor)
The work deals with nuclear magnetic resonance and principles of relaxation measurement and diffusion constants. Magnetic resonance is phenomenon, when energy in the form of RF pulse with Larmor frequency is added to this material in the magnetic field B0, the elements will be excited to a higher energy level. When you measure FID up to 90° RF pulse, from the absorption line, you will acquire . Further we can, for measurement of the transverse relaxation time T2, use the Spin echo method, that makes use of the 90° RF pulse and the series of 180° RF pulses. From measured values, the T2 relaxation time is directly acquired (inhomogeneity will prevent existence).
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RF coil for MR systém
Vojtíšek, Miloš ; Kořínek, Radim (referee) ; Gescheidtová, Eva (advisor)
The bachelor thesis is focused on radio frequency coils for magnetic resonance imaging systems. Magnetic resonance is used for imaging of many objects, especially human body in medicine, plants and many other different objects. For obtaining optimal results it is essential to use a special suitable coil for every single application. In the first part of this work, the short overview of principles of magnetic resonance imaging is described followed by a look at hardware used in MRI. The main aim of the work is design of several different types of RF coils used in MRI. Finally two suitable designs have been chosen for the purpose. Coils have been realized, tested in experiments. Results were analyzed, maps of generated magnetic field were calculated and homogeneity was determined.
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Filtering methods for NMR measurements
Zvěřina, Lukáš ; Rajmic, Pavel (referee) ; Gescheidtová, Eva (advisor)
The subject of this thesis is the principle of modern filtering techniques of signals acquired by nuclear magnetic resonance technique. In the NMR images a disturbing element is almost always present, especially noise, which causes useful signal and image degradation. The noise is a random signal, related to the errors of measurement and evaluation. The noise brings no information about the behaviour of the signal and it is unwanted signal component. The bachelor thesis is therefore focused mainly on the removal of the interfering parts of the signals. It exploits the fact that the nowadays widely expanding wavelet transform is closely connected with the banks of the digital filters. The subsequent section deals with experimental filtering of signals by implementation the wavelet transform in Matlab.
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