|
|
Analysys of magnetic field homogenity at computer tomography
Hrach, Petr ; Drexler, Petr (referee) ; Hadinec, Michal (advisor)
The dissertation deals with nuclear magnetic resonance, its projection technologies, measurement of magnetic induction and evaluation of magnetic field homogenity by the help of measuring probe. Further, the methods of NMR measurements are being described. The dissertation concentrates on methods of spin and gradient echo. The experimental part describes measurement of magnetic field homogenity in tomography and subsequent projection of measured field map. Users application, created in terms of dissertation, has more save labour imagery magnetic fields.
|
|
|
Measurement of relaxation constants, using MR techniques
Pavlíček, Petr ; Chmelař, Milan (referee) ; Gescheidtová, Eva (advisor)
Bachelor‘s thesis deals with measuring methods of relaxation times T1 and T2 using nuclear magnetic resonance (NMR) and experimental measuring of conductive gels samples. In the theoretical part an analysis of the behavior of atoms placed in the magnetic field, basic principles of NMR functionality and commonly used measuring sequences for relaxation times detection are given. The experimental part is oriented to measuring both relaxation times of conductive gels samples, which were examined in terms of use in lithium-polymer (Li-Pol) accumulators. Relaxation times T1 were measured using Inversion Recovery (IR) method and relaxation time T2 using Hahn Echo and halfwidth methods.
|
|
|
Exploitng sparse signal representations in capturing and recovery of nuclear magnetic resonance data
Hrbáček, Radek ; Zátyik, Ján (referee) ; Rajmic, Pavel (advisor)
This thesis deals with the nuclear magnetic resonance field, especially spectroscopy and spectroscopy imaging, sparse signal representation and low-rank approximation approaches. Spectroscopy imaging methods are becoming very popular in clinical praxis, however, long measurement times and low resolution prevent them from their spreading. The goal of this thesis is to improve state of the art methods by using sparse signal representation and low-rank approximation approaches. The compressed sensing technique is demonstrated on the examples of magnetic resonance imaging speedup and hyperspectral imaging data saving. Then, a new spectroscopy imaging scheme based on compressed sensing is proposed. The thesis deals also with the in vivo spectrum quantitation problem by designing the MRSMP algorithm specifically for this purpose.
|
|
|
RF detection method of explosives and drugs - NQR
Motyčka, Lukáš ; ČR,, MBA - ÚPT AV (referee) ; Kratochvíl, Tomáš (advisor)
The thesis deals with RF spectroscopic methods, which are applicable for the detection of hazardous substances such as explosives or drugs. Particular attention is focused on promising method of nuclear quadrupole resonance. Abroad this method has recently been applied in the detection of energetic materials in hazardous locations. The cornerstone of the nuclear quadrupole resonance is to evaluate the interaction between electromagnetic radiation, in the range of medium to very short waves, and the researched substance. Observed parameter are the resonant frequencies of the substance. Spectral analysis of signal is used for their evaluation. Resonant frequencies are always typical for the crystalline structure, therefore every explosive or drug is clearly identifiable by this method.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
MR image data processing in study of tissue cultures
Bidman, Petr ; Šmirg, Ondřej (referee) ; Gescheidtová, Eva (advisor)
Techniques based on principle of nuclear magnetic resonance (NMR) belong to the most modern methods for studying physical, chemical and biological properties of materials [1]. Their universality predestinates them for application in a wide range of scientific disciplines, e.g. in medicine to study properties of tissues. Advantages of techniques utilizing principle of NMR consist in their noninvasiveness and thoughtfulness to human health or studied material. In addition, no undesirable effects of magnetic force field have been so far proved by research. Objectives of this Diploma Thesis are evaluation of MR images of tissue cultures and determination of protons amount included in them. Theoretic part of the Thesis is devoted to the bases of NMR and provides basic overview of MR methods. The spin echo method (SE) is described in more details, including the process of assessment of technique’s parameters, e.g. general magnetization. Practical part of Diploma Thesis is focused on determination of integral of image intensity of clusters of early somatic embryos. Intensity integrals characterizing number of protons in growing cluster were calculated from MR images of spruce embryos contaminated by lead. The intensity of an image weighted by spin density is proportionate to the number of proton nuclei in the chosen slice. The Thesis describes further evaluation of relaxation time T2 from MR images weighted by spin density. Following part is dealing with determination of diffusion from MR images with application of compensation methods, three-measurement arrangement and presentation of obtained results. Images were processed by use of MATLAB and MAREVISI programs.
|
|
|
Filtering methods for MR images processing
Pláněk, Jiří ; Smékal, Zdeněk (referee) ; Gescheidtová, Eva (advisor)
This master´s thesis deals with wavelet transformation and its signal and image noise reduction application method. Significant parameters problems as a wavelet type, a threshold technique selection, a threshold level and a level analysis selection for successful signal and noise image filtering are described. A relation between wavelet transformation and digital bank filter is used by anti-noise and sub-bandwidth filtration. A part of the master´s thesis is focused on nuclear magnetic resonation, where jaw-joint image is processed. Jaw joint image noise reduction filtration methods are used in experimental part of the master´s thesis. Consequently, filtration methods improve a jaw joint image quality, which helps a doctor with patient health state condition. Different types of wavelets were tested and in different application methods order. Filtration methods results were visually compared; therefore any conclusion comparison has subjective matter. Accordingly, only doctor is able to resolve which filtration method is convenient to use to determine patient health state.
|
|
| |
guest ::
