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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.
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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
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Adverse reactions to radiographic contrast material
KUBŮ, Štěpán
The main topic of this bachelor thesis are adverse reactions to radiographic contrast material. The theoretical part of the thesis defines the concept of contrast agents, history and their properties. The theoretical part also defines the concept of pharmacovigilance. I also present the division of individual contrast material according to diagnostic methods, adverse reactions after the application of contrast material in individual diagnostic methods, first aid in the case of an allergic reaction to contrast material and the reporting of suspected adverse reactions. The theoretical part is processed from professional publications, articles and websites in the form of literary review. The aim of my work was to map the occurrence of the most common reactions to specific contrast material. This aim was supported by two research questions: "Which are the most common types of reactions? Which controst material most often cause an adverse reaction? How do staff deal with side effects? " The aim and research question was fullfilled with questionary survey, the survey was attended by 33 responders (radiological assistants). The questionnaire included questions related to the occurrence of the most common adverse reactions of contrast agents, first aid for adverse reactions and other information related to adverse reactions of contrast agents.
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Trivalent and tetravalent metal complexes for radiodiagnostics
Hacaperková, Eliška ; Kubíček, Vojtěch (advisor) ; Drahoš, Bohuslav (referee) ; Polášek, Miloslav (referee)
Fluorine-18 is the most utilized nucleus for positron emission tomography (PET). In 2009, incorporation of fluorine-18 to the coordination sphere of Al(III) was introduced as a new alternative for commonly employed compounds with F-C bond. Such a radiotracer consists of two parts: a metal complex with a fluoride and a peptide or a small/part of biomolecule. Shortly after that, first clinical studies showed a promising potential of such com- pounds for clinical use. Despite a great number of papers dealing with this issue, the research is mostly application-driven and focused on the peptide part of the molecule responsible for specific accumulation within the organism. Studies oriented on a sta- bility of metal-ligand-fluorine ternary system are rather rare and only very little is known about such a three-component system from a chemical point of view in gen- eral. However, stability of F-Al bond strongly dependents on the chemical structure of other ligands in the coordination sphere. Pendant arms of a hexadentate ligand (usually used for Al(III) complexation, e.g., H3NOTA) can compete with fluoride and cause its release which leads to unspecific radioactivity accumulation. Lower ligand denticity should increase the F-Al bond stability, but can decrease the stability of the whole complex at the...
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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
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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.
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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.
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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.
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Use the Contrast-Enhanced Ultrasoun in the Morning of the Effect of Liver Tumors Treatment by Radiofrequency ablation
Korčáková, Eva ; Mírka, Hynek (advisor) ; Mechl, Marek (referee) ; Čtvrtlík, Filip (referee)
Use the contrast-enhanced ultrasound in the monitoring of the effect of liver tumors treatment by radiofrequency ablation. Summary High quality imaging is crucial for the treatment of liver tumors by the percutaneous radiofrequency ablation. Imaging methods are used for planning, navigation of the intervention and monitoring after treatment. An early detection of residual tumor tissue or recurrence affect significantly the quality of life and life expectancy of the patients. Contrast enhanced ultrasound (CEUS) seems to be a suitable method for monitoring the locoregional treatment mainly because zero radiation impact on patient and allows the highly accurate real-time assessment of vascularization. The aim of my work was to verify the ability of CEUS to detect residual tumor tissue or tumor recurrence in the field of changes after radiofrequency ablation. We evaluated the group of 73 patients, who were treated by radiofrequency ablation (RFA) for liver cancer. CEUS reached in our group the overal sensitivity 77.27 %, and in the group of colorectal cancer metastases 83.33 %. We compared CEUS with results of computed tomography (CT), which is the most commonly used method for monitoring the treatment. CEUS and CT results are similar. Based on this study, the CEUS appears to be a suitable method for monitoring...
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