National Repository of Grey Literature 89 records found  previous11 - 20nextend  jump to record: Search took 0.00 seconds. 
Image Deblurring in Demanding Conditions
Kotera, Jan ; Šroubek, Filip (advisor) ; Portilla, Javier (referee) ; Jiřík, Radovan (referee)
Title: Image Deblurring in Demanding Conditions Author: Jan Kotera Department: Institute of Information Theory and Automation, Czech Academy of Sciences Supervisor: Doc. Ing. Filip Šroubek, Ph.D., DSc., Institute of Information Theory and Automation, Czech Academy of Sciences Abstract: Image deblurring is a computer vision task consisting of removing blur from image, the objective is to recover the sharp image corresponding to the blurred input. If the nature and shape of the blur is unknown and must be estimated from the input image, image deblurring is called blind and naturally presents a more difficult problem. This thesis focuses on two primary topics related to blind image deblurring. In the first part we work with the standard image deblurring based on the common convolution blur model and present a method of increasing robustness of the deblur- ring to phenomena violating the linear acquisition model, such as for example inten- sity clipping caused by sensor saturation in overexposed pixels. If not properly taken care of, these effects significantly decrease accuracy of the blur estimation and visual quality of the restored image. Rather than tailoring the deblurring method explicitly for each particular type of acquisition model violation we present a general approach based on flexible automatic...
Advanced Moment-Based Methods for Image Analysis
Höschl, Cyril ; Flusser, Jan (advisor) ; Papakostas, George (referee) ; Jiřík, Radovan (referee)
The Thesis consists of an introduction and four papers that contribute to the research of image moments and moment invariants. The first two papers focus on rectangular decomposition algorithms that rapidly speed up the moment calculations. The other two papers present a design of new moment invariants. We present a comparative study of cutting edge methods for the decomposition of 2D binary images, including original implementations of all the methods. For 3D binary images, finding the optimal decomposition is an NP-complete problem, hence a polynomial-time heuristic needs to be developed. We propose a sub-optimal algorithm that outperforms other state of the art approximations. Additionally, we propose a new form of blur invariants that are derived by means of projection operators in a Fourier domain, which improves mainly the discrimination power of the features. Furthermore, we propose new moment-based features that are tolerant to additive Gaussian image noise and we show by extensive image retrieval experiments that the proposed features are robust and outperform other commonly used methods.
Zpracování digitálních snímků videokymografických záznamů jako podpůrný nástroj pro diagnostiku hlasivek
Hauzar, David ; Flusser, Jan (advisor) ; Jiřík, Radovan (referee)
Videokymography is a medical imaging method of revealing and diagnosing vocal cords vibrations in voice disorders. Manual data extraction is problematic while automatic extraction can facilitate and re ne the diagnostic process. However, automatic processing is hampered by signal noise and considerable variability in vocal cords vibrations of individual patients. The objective of the present study is to identify typical characteristics of vocal cords vibrations suitable for automatic extraction and diagnostic interpretation and to implement such automatic extraction. The automatic extraction tool that was implemented reects specifi c features of viodeokymographic images. The system for interpretation of automatic extraction results was developed and tested against manually extracted vibrations data and images. The tool can support kymographic diagnosis of vocal cords disorders.
Registration of MR Images and Histological Sections
Martinásková, Klára ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This bachelor’s thesis deals with methods of multimodal image registration. The work is focused specifically on the registration of histological sections and MR images, which various studies examine because of improving oncological diagnostics. A substantial part of the work is devoted to theories of registration - types of registration, geometric transformations, criterial functions, interpolation and methods of optimization. There is also an overview of tools, which can be used for multimodal image registration. MR images and histological sections were provided from three different sources. The program for image registration was created in software MATLAB 2020a with a graphical user interface and it includes a converter for editing images before the registration began. In conclusion, the results of registration were analyzed.
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.
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.
Image Deblurring in Demanding Conditions
Kotera, Jan ; Šroubek, Filip (advisor) ; Portilla, Javier (referee) ; Jiřík, Radovan (referee)
Title: Image Deblurring in Demanding Conditions Author: Jan Kotera Department: Institute of Information Theory and Automation, Czech Academy of Sciences Supervisor: Doc. Ing. Filip Šroubek, Ph.D., DSc., Institute of Information Theory and Automation, Czech Academy of Sciences Abstract: Image deblurring is a computer vision task consisting of removing blur from image, the objective is to recover the sharp image corresponding to the blurred input. If the nature and shape of the blur is unknown and must be estimated from the input image, image deblurring is called blind and naturally presents a more difficult problem. This thesis focuses on two primary topics related to blind image deblurring. In the first part we work with the standard image deblurring based on the common convolution blur model and present a method of increasing robustness of the deblur- ring to phenomena violating the linear acquisition model, such as for example inten- sity clipping caused by sensor saturation in overexposed pixels. If not properly taken care of, these effects significantly decrease accuracy of the blur estimation and visual quality of the restored image. Rather than tailoring the deblurring method explicitly for each particular type of acquisition model violation we present a general approach based on flexible automatic...
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.
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.
Comparison of Pharmacokinetic models for DCE-MRI
Bačovská, Kristýna ; Mézl, Martin (referee) ; Jiřík, Radovan (advisor)
This thesis deals with perfusion analysis using DCE-MRI (Dynamic contrast-enhanced magnetic resonance imaging). DCE-MRI is commonly used for microcirculation evaluation mainly in oncology and in recent years also in cardiology. The theoretical overview focuses on the issue of pharmacokinetic modeling and the estimation of perfusion parameters using selected models. The experimental part describes research software PerfLab and then it is aimed at the proposed program for synthetic data generation. Simulated data obtained under ideal conditions and in the presence of noise were used to compare models for the accuracy and reliability of DCE-MRI analysis.

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1 Jiřík, Rudolf
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