|
|
Optimization of Contrast in MRI of Labeled Thrombi
Dohnalová, Petra ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This bachelor thesis deals with the general principle of molecular MRI, the formation, composition of trombi and their impact on the human body. It also deals with the contrast agents, to which molecules are they targeted and why, as well as the principle of interactions with these target molecules. The following are found values of native relaxation times for thrombi, blood, gray and white matter and relaxivities of contrast agents at different values of B0 magnetic field. The next part is dedicated to the program for simulations of T1- and T2- weighted MRI and searching for the optimal setting of acquisition parametersbased on the achieved contrast. Finally, the possibility of combining T1- and T2- weighted images to increase contrast is explored.
|
|
|
Evolution algorithms for ultrasound perfusion analysis
Kolářová, Jana ; Odstrčilík, Jan (referee) ; Mézl, Martin (advisor)
This master´s thesis is focused on the application of evolutionary algorithms for interleaving data obtained by ultrasound scanning of tissue. The interleaved curve serves to estimate perfusion parameters, thus allowing to detect possible pathophysiology in the scanned area. The theoretical introduction is devoted to perfusion and its parameters, contrast agents for ultrasonic application, ultrasonic modality scanning, optimization, evolutionary algorithms in general and two selected evolutionary algorithms - genetic algorithm and bee algorithm. These algorithms were tested on noisy data obtained from clinical images of mice with tumor. The final part summarizes the results of the practical part and provides suggestions and recommendations for further possible development.
|
|
|
Using multi-echo sequences in DSC-MRI
Černý, Štěpán ; Jiřík, Radovan (referee) ; Macíček, Ondřej (advisor)
The task of this thesis is to study the subject of perfusion analysis based on dynamic imaging with T2/T2* contrast. The focus was on the acquisition commonly used for DSC-MRI and especially in the acquisition pulse sequences that use images with different echo time, so called Multi-echo sequence. Principles of dynamic measurement by magnetic resonance imaging, the role of contrast agents and their influence on the relaxation times are described. It also describes the problems perfusion analysis, measurement and mathematical modeling parameters entering to the convolution dependency for getting perfusion parametersIn the experimental part is developed automatic algorithm to gain curves relaxation time T2 *. Next, the synthetic data are created and tested robustness estimate perfusion parameters against noise. In the next phase of work there are compared real scanned objects with using a conversion with T2 * and free of T2*. In the last phase of work is compared influence of length of used echo times on concentration curves and after perfusion analysis influence on resulting perfusion parameters.
|
|
|
Spectral computed tomography: comparison of real and virtual nativ images
Širůčková, Kateřina ; Bartušek, Karel (referee) ; Marcoň, Petr (advisor)
Advanced X-ray medical diagnostic methods massively increase the radiation exposure of patients. Therefore, it is necessary to focus on the reduction of radiation and its stochastic and deterministic effects. This project compares real native images TNC with virtual native images VNC. Virtual native images are acquired by spectral computed tomography method and it is suggested that VNC could potentially substitute real native images, thereby, the total radiation dose from multiphase spectral CT would decrease. A comparison was performed by defining certain parameters that represented the differentiation of the measured and calculated values in the images. The parameters were SNR, CNR, absolute difference, relative error and they were analysed by statistical tests using p-value and correlation analysis. Another output is a database of patients with compared parameters from real and virtual native images.
|
|
|
MRI Acquisition of Image Sequences for Preclinical Perfusion Imaging
Krátká, Lucie ; Bartoš, Michal (referee) ; Jiřík, Radovan (advisor)
The task of this thesis is to study methods for the acquisition perfusní imaging based on dynamic MR imaging with T1 contrast. It describes methods of measurement of T1 relaxation time and the possibility of evaluating the results. It further describes the phantoms and their use. And it is here mentioned for the dynamic acquisition protocol perfusní imaging. There is also described in detail created a program for automatic control of the NMR system. In the experimental measurements are performed on static and dynamic phantom, are also evaluated perfusion parameters from the Flash sequence.
|
|
|
Contrast MRI perfusion imaging
Šejnoha, Radim ; Harabiš, Vratislav (referee) ; Krátká, Lucie (advisor)
This semestral thesis is focused on contrast MRI perfusion imaging using method of Dynamic Contrast-Enhanced MRI. It describes basic principles of nuclear magnetic resonance and puls sequences used in DCE MRI. The thesis contains a part dedicated to dynamic contrast imaging of phantom with experimental NMR device located at the Institut of Scientific Instruments of the ASCR in Brno. Results of measurements are analyzed based on models and reached perfusion parameters are discussed.
|
|
| |
|
|
Contrast enhancement for tissue discrimination and contrast nanoparticle detection by MRI
Bačovský, Jaromír ; Macíček, Ondřej (referee) ; Starčuk, Zenon (advisor)
Magnetic resonance imaging is a routine and powerful diagnostic technique capable of providing detailed information about the structure and composition of the tissues. This diploma thesis is concerned with the mechanisms of contrast origin and contrast modifications by molecular and nanoparticle contrast agents. First sections of the thesis summarize basic knowledge about pulse sequences and it aims to provide an overview on MRI contrast agent with a special emphasis on paramagnetic gadolinium contrast agents and superparamagnetic nanoparticles. The main purpose of this study is to develop the software called MRICalc, which is able to optimize contrast in MRI images. Based on analysis of signal formula of typical pulse sequences, MRICalc is able to propose the parameters of the pulse sequence for compartment-specific enhancement of the contrast. User chooses from the list of the samples and after calculation he obtains the values of echo time, repetition time and flip angle, all of which simultaneously seem to create the appropriate setting to enhance the contrast. MRICalc also allows to plot contrast function with respect to the chosen parameter. Software, including its graphical user interface, is designed in Python. The sample consists from solution of CuSO4 and distilled water was designed to verify the correct function of MRICalc. Sulphate represents a contrast agent. Preclinical MR system Bruker BioSpec 94/30 USR located at Institute of Scientific Instruments of the ASCR, v.v.i was used to measure contrast curve of FLASH pulse sequence, which is a typical representative of gradient echo. Results of the measurement were compared to the theoretical model provided by MRICalc.
|
|
|
Contrast agents for 19F magnetic resonance imaging
Dobrovolná, Tereza ; Kotek, Jan (advisor) ; Vojtíšek, Pavel (referee)
Complexes of transition metal ions with ligands containing fluorine atoms represent an interesting group of 19 F MRI contrast agents that could facilitate the diagnosis of various diseases. The presence of a paramagnetic metal ion in the vicinity of the 19 F nucleus results in shorter relaxation times and the possibility to obtain more NMR spectra in a given time, leading to better resolution. This work deals with the synthesis of the fluorinated macrocyclic ligand H3NOTPtfe , the preparation of its complexes with transition metal ions, their characterization and study by methods suitable for assessing their applicability in 19 F MRI, i.e. relaxometric NMR measurements and electrochemistry. The results show that the chosen concept is promising for 19 F MRI. The prepared complexes are applicable as 19 F MRI contrast agents, some even as redox active 19 F MRI "smart" contrast agents. The best properties were observed for the complex [Co(NOTPtfe )]− . Keywords: heteronuclear MRI, contrast agent, fluorine, PRE effect, spin relaxation, magnetic resonance imaging, paramagnetic complexes
|
|
|
Transition metal ion complexes as potential 19F MRI contrast agents
Dobrovolná, Tereza ; Kotek, Jan (advisor) ; Blahut, Jan (referee)
Fluorinated coordination compounds having short nuclear spin relaxation times due to the presence of paramagnetic metal ions close to 19 F nuclei are suitable/potential contrast agents in 19 F MRI. This thesis deals with the preparation of a ligand based on 1,4,7-triazacyclononane (TACN) with pendant arms containing fluorine atoms. The coordination properties to transition metal ions were studied and prepared complexes were characterised. Measured values of longitudinal relaxation times of 19 F NMR signal indicate that the chosen concept is promising for further use in 19 F MRI, especially for the Co(II) complex. Keywords: 19 F MRI, contrast agent, trifluoroethyl phosphinic acid, TACN, paramagnetic ion, relaxation time, effective magnetic moment
|
guest ::
