|
|
Hydrogen quantification by electron spectroscopy
Endstrasser, Zdeněk ; Polčák, Josef (referee) ; Čechal, Jan (advisor)
The absence of hydrogen in the photoelectron spectrum remains one of the greatest limitations of X-ray photoelectron spectroscopy. The main aim of this work is therefore to determine the concentration of hydrogen atoms in the near surface region of a sample. The REELS electron spectroscopic method based on quasi-elastic electron scattering is used for this purpose. The choice of this method was given mainly by the fact that the photoelectron spectrometers has an electron source in the basic equipment, so there is no requirement to purchase additional equipment. In our case, measurements were realized using the AXIS Supra photoelectron spectrometer in CEITEC laboratories. We were primarily focused on the study of polymer samples in this work. The gus cluster ion source was used for sputter cleaning of the sample surface. Then the XPS and REELS measurements were performed on such cleaned samples. The obtained data were subsequently evaluated, and the results discussed. The most important output of this work was to develop the methodology of detection and quantification of hydrogen atoms. However, the theoretical description of the methods used, and the appreciation of critical aspects associated with the use of the REELS method are also embraced. In particular, the effect of sample charging and electron dose on measurement results is discussed.
|
|
|
Advanced Methods of Perfusion Analysis in MRI
Macíček, Ondřej ; Frollo, Ivan (referee) ; Mikl, Michal (referee) ; Jiřík, Radovan (advisor)
This dissertation deals with quantitative perfusion analysis of MRI contrast-enhanced image time sequences. It focuses on two so far separately used methods -- Dynamic contrast-enhanced MRI (DCE-MRI) and Dynamic susceptibility contrast MRI (DSC-MRI). The common problem of such perfusion analyses is the unreliability of perfusion parameters estimation. This penalizes usage of these unique techniques on a regular basis. The presented methods are intended to improve these drawbacks, especially the problems with quantification in DSC in case of contrast agent extravasation and instability of the deconvolution process in DCE using advanced pharmacokinetic models. There are a few approaches in literature combining DCE and DSC to estimate new parameters of the examined tissue, namely the relaxivity of the vascular and of the interstitial space. Originally, in this scheme, the 2CXM DCE model was used. Here various models for DCE analysis are tested keeping in mind the DCE-DSC combination. The ATH model was found to perform better in this setting compared to 2CXM. Finally, the ATH model was used in alternating DCE-DSC optimization algorithm and then in a truly fully simultaneous DCE-DSC. The processing was tested using simulated and in-vivo data. According to the results, the proposed simultaneous algorithm performs better in comparison with sequential DCE-DSC, unleashing full potential of perfusion analysis using MRI.
|
|
| |
|
|
Classification of marked cells migration in tissue
Solař, Jan ; Skopalík, Josef (referee) ; Čmiel, Vratislav (advisor)
This diploma thesis deals with analysing of modern methods for cell detection, visualization and quantification in 3D space. The first section deals with optical methods for cells detection. There is detailed discussion about cell labeling and detection on confocal microscopy. There is also description about developed algorithm for whole cell volume quantification from microscopy images. This could made a comparsion of fluorescence signal according to time of cell labeling and according to cell shapes. There was also optimalization of handmade tissue phantoms visualization. It could be compared a possibilities of cell detections in these phantoms by confocal microscopy and OCT. It was also implemented algorithm for quantification of cells from OCT images. Besides confocal microscopy and OCT cells are also analyzed by other methods. The last part is the Conclusion of results and comparison of used methods.
|
|
|
MRI of Rats - Quantification of T1 in Myocardium
Vitouš, Jiří ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This thesis focuses on cardiac imaging and quantification of T1 relaxation time in rat hearts. Its main focus is to investigate available methods for such quantification and their application in the development of quantification tools. The large impact is given to methods of acquisition synchronization, mainly with respect to cardiac motion and breathing using retrospective gating, where the navigator signal is obtained solely from the acquired data, so without any external equipment such as the ECG or respiratory sensors. This paper takes into account situations where steady-state has been reached and also those where it has not, by means of contrast agent injection or by inversion pulses.
|
|
|
Quantification of Perfusion using MRI ASL Methods
Kolajová, Martina ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This bachelor thesis deals with quantification of perfusion using a contrast-free MRI technique called „Arterial Spin Labeling“ (ASL). Firstly, the physical principle of magnetic resonance imaging and the concept of perfusion will be described for better understanding of the subject. The next chapters will focus on the ASL method itself and perfusion quantification using mathematical models, namely T1 perfusion and Standard. The algorithm for preprocessing and analysis of selected datasets, designed in the thesis, is implemented using the program MATLAB. Program BASIL was used for further processing. The outputs in the form of perfusion and ATT maps and model fitting processes using various models from both programs are compared and evaluated.
|
|
|
Non-contrast MRI perfusion imaging
Kruml, Ondřej ; Jiřík, Radovan (referee) ; Krátká, Lucie (advisor)
This bachelor paper is focused on the magnetic resonance perfusion imaging technic without the usage of an external contrast media. This paper contains a look at the basic functional principle of the magnetic resonance. The focus is then set set on the Arterial Spin Labeling (ASL) technic. The basic principle of ASL uses protons from the water mocelules in arterial blood as an endogenous contrast agent. This technic can be used for obtaining a perfusion map of any tissue without the usage of invasiont echnics or contrast agents. The quantification of perusion was done applying the FAIR-RARE scheme, which belongs to the large family pulsed ASL.
|
|
|
Quantitative analysis of matrix elements using SIMS and LEIS methods
Staněk, Jan ; Šik, Ondřej (referee) ; Bábor, Petr (advisor)
This thesis studies comparison and connection of two spectrometric methods – low energy ion scattering spektrometry (LEIS) and secondary ion mass spectrometry (SIMS). SIMS method, despite its many positive qualities, suffers of so called matrix effect, which makes quantifiaction of data very difficult. LEIS method on the other hand is immune to this effect and so it’s suitable completion of SIMS method. As a convenient sample have been chosen AlGaN samples with various concentration of gallium and aluminium. In the first part of thesis is introduced physical essence of SIMS and LEIS method, experimental details and studied samples. In second part of the thesis there’s a description of measurements and comparison of data gained by each method.
|
|
|
Quantification of Relaxation Time T1 in DCE-MRI
Vitouš, Jiří ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This bachelor thesis deals with methods of T1 relaxation time quantification and B1 magnetic field inhomogeneities corrections. For purposes of the required measurements, the phantom was created using a 3D printer. Firstly the thesis presents information about a given theme, then it hands out the results of measurements taken using standard quantification methods. These methods are consequently analyzed and compared. Next part of the bachelor thesis deals with the fast method based on a variable flip angle (VFA), which needs a magnetic field B1 correction maps to give reasonable T1 estimates. For this purpose, two methods of B1 correction are presented. The first method is a double angle method and second is based on mapping magnetic field B1 using a reference T1 map. To decide which T1 map of which method should be used as a reference, a simple simulation is proposed, which describes the impact of unfavorable effects, such as B1 itself, on the T1 estimate of standard methods. In the end, the conclusions are made and the results of VFA methods are compared with standard methods of quantification.
|
|
|
The usage of the "Ethanol as internal standard" method for the SPME-GC/FID analysis of volatile compounds in alcoholic products
Zavoralová, Lucie ; Korban, Anton (advisor) ; Sobotníková, Jana (referee)
This bachelor thesis dealt with the optimization of a method for the determination of 10 volatile compounds occurring as minor components in alcoholic products. The quantification was performed by the internal standard method, comparing the results using 1-pentanol and ethanol as classical and proposed internal standards, respectively. In the case of ethanol usage, better repeatability and accuracy of the results were expected as this method does not require any sample pre-treatment. The optimized measurement method was monitored for both internal standards, while following these parameters - repeatability, recovery, linearity and limits of detection and quantification. It was found out that, as expected, the method of the proposed ethanol internal standard gives more accurate results for the analysis of real alcoholic beverage samples. However, it did not outperform the classical internal standard method in all parameters. That one gave better results for repeatability and linearity for the set of calibration solutions measured, despite the fact that each sample had to be pre-treated. It was also found that samples with a high ethanol or other volatile content were not suitable for SPME analysis, because the fibre then loses its ability to sorb these substances in the same proportions and...
|
guest ::
