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Observations of seismicity prior to large earthquakes show that the slope of a Gutenberg-Richter magnitude-frequency relation, referred to as a b-value, sometimes decreases with time to the mainshock. Yet, underlying physical processes associated with the temporal change of a b-value remain unclear. Here we utilize continuum models of fully dynamic earthquake cycles with fault frictional heterogeneities and aim to simulate the temporal variation of a b-value. We first identify a parameter regime in which the model gives rise to an active and accelerating foreshock behavior prior to the mainshock. We then focus on the spatio-temporal pattern of the simulated foreshocks and analyze their statistics. We find that the b-value of simulated foreshocks decreases with time prior to the mainshock. A marked decrease in the resulting b-value occurs over the duration of less than a few percent of the mainshock recurrence interval, broadly consistent with foreshock behaviors and b-value changes as observed in nature and laboratory, rock-friction experiments. In this model, increased shear stresses on creeping (or velocity-strengthening) fault patches resulting from numerous foreshocks make these creeping patches more susceptible to future coseismic slip, increasing the likelihood of large ruptures and leading to a smaller b-value with time. This mechanism differs from a widely invoked idea that the decrease of a b-value is caused by a rapid increase in shear stress that promotes micro-crack growth, and offers a new interpretation of b-value changes prior to a large earthquake.

[EN] Ionospheric anomalies have been shown to occur a few days before several large earthquakes. The published works normally address examples limited in time (a single event or few of them) or space (a particular geographic area), so that a clear method based on these anomalies which consistently yields the place and magnitude of the forthcoming earthquake, anytime and anywhere on earth, has not been presented so far. The current research is aimed at prediction of large earthquakes, that is with magnitude M-w 7 or higher. It uses as data bank all significant earthquakes occurred worldwide in the period from January 1, 2011 to December 31, 2018. The first purpose of the research is to improve the use of ionospheric anomalies in the form of TEC grids for earthquake prediction. A space-time TEC variation estimator especially designed for earthquake prediction will show the advantages with respect to the use of simple TEC values. Further, taking advantage of the well-known predictive abilities of the Gutenberg-Richter law's b-value, a combined estimator based on both TEC anomalies and b-values will be designed and shown to improve prediction performance even more.

In the present paper, three of the main seismic parameters, maximum magnitude -Mmax, b-value, and annual rate -AR, have been studied for the Pyrenees range in southwest Europe by a Geographic Information System (GIS). The main aim of this work is to calculate, represent continuously, and analyze some of the most crucial seismic indicators for this belt. To this end, an updated and homogenized Poissonian earthquake catalog has been generated, where the National Geographic Institute of Spain earthquake catalog has been considered as a starting point. Herein, the details about the catalog compilation, the magnitude homogenization, the declustering of the catalog, and the analysis of the completeness, are exposed. When the catalog has been produced, a GIS tool has been used to drive the parameters’ calculations and representations properly. Different grids (0.5 × 0.5° and 1 × 1°) have been created to depict a continuous map of these parameters. The b-value and AR have been obtained that take into account different pairs of magnitude–year of completeness. Mmax has been discretely obtained (by cells). The analysis of the results shows that the Central Pyrenees (mainly from Arudy to Bagnères de Bigorre) present the most pronounced seismicity in the range.

Catalogs of microseismicity are routinely compiled at geothermal reservoirs and provide valuable insights into reservoir structure and fluid movement. Hypocentral locations are typically used to infer the orientations of structures and constrain the extent of the permeable reservoir. However, frequency-magnitude distributions may contain additional, and underused, information about the distribution of pressure. Here, we present a four-year catalog of seismicity for the Rotokawa geothermal field in the central Taupō Volcanic Zone, New Zealand starting two years after the commissioning of the 140 MWe Nga Awa Purua power station. Using waveform-correlation-based signal detection we double the size of the previous earthquake catalog, refine the location and orientation of two reservoir faults and identify a new structure. We find the rate of seismicity to be insensitive to major changes in injection strategy during the study period, including the injectivity decline and shift of injection away from the dominant injector, RK24. We also map the spatial distribution of the earthquake frequency-magnitude distribution, or b-value, and show that it increases from ∼1.0 to ∼1.5 with increasing depth below the reservoir. As has been proposed at other reservoirs, we infer that these spatial variations reflect the distribution of pressure in the reservoir, where areas of high b-value correspond to areas of high pore-fluid pressure and a broad distribution of activated fractures. This analysis is not routinely conducted by geothermal operators but shows promise for using earthquake b-value as an additional tool for reservoir monitoring and management.

Context: Stressed rocks produce acoustic emission signals. Acoustic emission and seismic information are complementary in their applications as well as on their theoretical basis. Thus, studying characteristic frequencies in acoustic emission signals is relevant to understanding the seismic wave propagation on the Earth. Method: A uniaxial compression test was performed on cylindrical samples of andesite rock, which were stressed up to breakage. Acoustic emission signals were recorded during the test. Frequency analysis in these signals may be carried in the context of an elementary seismic focus model. This model describes the fracture advance and propagation during brittle material fracture. The corner frequency is obtained from the Fourier spectrum of the signals, conveniently represented in log scale. This parameter accounts for the size of fissures as damage progresses when the material is stressed. Results: The corner frequency was determined on a first analysis. On a second analysis, the signals were filtered on different bands with the Wavelet Transform and the corresponding wavelet energy b-value was obtained. Conclusions: Studying the evolution of the wavelet energy b-value in different frequency bands allowed the determination of characteristic frequencies which can be associated with different fracture regimes in rocks., Contexto: En las rocas sometidas a esfuerzos se producen señales de emisión acústica (EA). Esta y la información sísmica son complementarias tanto en sus aplicaciones como en su base teórica. Por ende, el estudio de frecuencias características en las señales de emisión acústica tiene relevancia para comprender la propagación de ondas sísmicas en la Tierra. Método: Se realizó un ensayo de compresión uniaxial en probetas cilíndricas de roca andesita, llevadas hasta la rotura. Se registraron las señales de EA obtenidas durante el ensayo. Un análisis de las frecuencias de estas señales cabe en el contexto de un modelo elemental de foco sísmico, el cual describe el avance y la propagación de ondas durante la fractura de un material frágil. A partir de los espectros de Fourier de las señales, convenientemente representados en escala logarítmica, se obtiene la frecuencia esquina. Este parámetro da cuenta del tamaño de las fisuras durante el avance del daño en el material sometido a esfuerzo. Resultados: En un primer análisis se determinó la frecuencia esquina. En un segundo análisis, se filtraron las señales para distintas bandas de frecuencias con transformada Wavelet y se obtuvo el Wavelet Energy b-value (bWE) correspondiente. Conclusiones: El estudio de la evolución del bWE para las distintas bandas de frecuencia permitió determinar frecuencias características que se pueden asociar a distintos mecanismos de fracturas en las rocas.

Catalogue-based studies are of central importance in seismological research, to investigate the temporal, spatial and size distribution of earthquakes in specified study areas. Methods for estimating the fundamental catalogue parameters like the Gutenberg–Richter (G-R) b-value and the completeness magnitude (Mc) are well established and routinely applied. However, the magnitudes reported in seismicity catalogues contain measurement uncertainties which may significantly distort the estimation of the derived parameters. In this study, we use numerical simulations of synthetic data sets to assess the reliability of different methods for determining b-value and Mc, assuming the G-R law validity. After contaminating the synthetic catalogues with Gaussian noise (with selected standard deviations), the analysis is performed for numerous data sets of different sample size (N). The noise introduced to the data generally leads to a systematic overestimation of magnitudes close to and above Mc. This fact causes an increase of the average number of events above Mc, which in turn leads to an apparent decrease of the b-value. This may result to a significant overestimation of seismicity rate even well above the actual completeness level. The b-value can in general be reliably estimated even for relatively small data sets (N < 1000) when only magnitudes higher than the actual completeness level are used. Nevertheless, a correction of the total number of events belonging in each magnitude class (i.e. 0.1 unit) should be considered, to deal with the magnitude uncertainty effect. Because magnitude uncertainties (here with the form of Gaussian noise) are inevitable in all instrumental catalogues, this finding is fundamental for seismicity rate and seismic hazard assessment analyses. Also important is that for some data analyses significant bias cannot necessarily be avoided by choosing a high Mc value for analysis. In such cases, there may be a risk of severe miscalculation of seis

Despite the key advantages of Fiber Reinforced Polymer (FRP) composites, they are susceptible to Barely Visible Impact Damage (BVID) under transverse loadings. This study investigates BVID in two quasi-isotropic carbon/epoxy laminates under quasi-static indentation and Low-Velocity Impact (LVI) loadings using Acoustic Emission (AE). First, the evolution of interlaminar and intralaminar damages is studied by analyzing the AE signals of the indentation test using b-value and sentry function methods. Then, the specimens are subjected to the LVI loading and the induced damages are compared with the indentation test and the percentage of each damage mechanism is calculated using Wavelet Packet Transform (WPT). In consistent with the mechanical data, ultrasonic C-scan and digital camera images of the specimens, the AE results show a considerable similarity between the induced BVID under quasi-static indentation and LVI tests. Finally, the obtained results show that AE is a powerful tool to study BVID in laminated composites under quasi-static and dynamic transverse loadings., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Structural Integrity & Composites

We investigated the foreshock activity characteristics using the Japan Meteorological Agency Unified Earthquake Catalog for the last 20 years. Using the nearest-neighbor distance approach, we systematically and objectively classified the earthquakes into clustered and background seismicity. We further categorized the clustered events into foreshocks, mainshocks, and aftershocks and analyzed their statistical features such as the b-value of the frequency–magnitude distribution. We found that the b-values of the foreshocks are lower than those of the aftershocks. This b-value difference suggested that not only the stochastic cascade effect but also the stress changes/aseismic processes may contribute to the mainshock-triggering process. However, forecasting the mainshock based on b-value analysis may be difficult. In addition, the rate of foreshock occurrence in all clusters (with two or more events) was nearly constant (30–40%) over a wide magnitude range. The difference in the magnitude, time, and epicentral distance between the mainshock and largest foreshock followed a power law. We inferred that the distinctive characteristics of foreshocks can be better revealed using the improved catalog, which includes the micro-earthquake information.

A detailed statistical investigation of the seismicity occurred at El Hierro volcano (Canary Islands) from 2011 to 2014 has been performed by analysing the time variation of four parameters: the Gutenberg-Richter b-value, the local coefficient of variation, the scaling exponent of the magnitude distribution and the main periodicity of the earthquake sequence calculated by using the Schuster's test. These four parameters are good descriptors of the time and magnitude distributions of the seismic sequence, and their variation indicate dynamical changes in the volcanic system. These variations can be attributed to the causes and types of seismicity, thus allowing to distinguish between different host-rock fracturing processes caused by intrusions of magma at different depths and overpressures. The statistical patterns observed among the studied unrest episodes and between them and the eruptive episode of 2011-2012 indicate that the response of the host rock to the deformation imposed by magma intrusion did not differ significantly from one episode to the other, thus suggesting that no significant local stress changes induced by magma intrusion occurred when comparing between all them. Therefore, despite the studied unrest episodes were caused by intrusions of magma at different depths and locations below El Hierro island, the mechanical response of the lithosphere was similar in all cases. This suggests that the reason why the first unrest culminated in an eruption while the other did not, may be related to the role of the regional/local tectonics acting at that moment, rather than to the forceful of magma intrusion.

The potential of temporal b-value variations as an intermediate-term (weeks to months) earthquake precursor was investigated in the western portion of the North Anatolian Fault Zone (NAFZ), between January 1982 to December 2004. The focus of the study is on the devastating, 1999 earthquake, near Izmit. Lists of events were provided from two teleseismic catalogues, ISC and NEIC, which are complete for threshold magnitude 3.7, comprising 287 and 224 events, respectively. To determine b-values, a technique of sliding overlapping time-windows was applied, using a fixed number of events in each window. Deduced b-values reveal large temporal variations in a broad range, 0.75-1.7 (ISC) and 0.5-1.6 (NEIC). There are statistically significant drops in b-value observed for both catalogues, preceding the occurrence of the Izmit earthquake. Also, present results reveal promising b(t)-characteristics of another large earthquake that occurred in the vicinity of Duzce, about 3 months after the Izmit shock. The stability of results is examined using different threshold magnitudes, different window sizes and step increments, declustering and a test through magnitude conversion. Observed correlation between low b and the occurrence of large earthquakes suggests that b(t) has a potential to act as an intermediate-term precursor in earthquake predictions., Potentialen av temporala variationer i b-värde som en indikator och förelöpare till jordbävningar har undersökts i västra delen av den Norra Anatoliska förkastningen, under perioden januari 1982 till december 2004. Studien fokuserar på den förödande jordbävningen som ägde rum i närheten av Izmit den 17 augusti 1999. Data för undersökningen har tillhandahållits från två teleseismiska kataloger, ISC och NEIC, som är kompletta för en tröskelmagnitud 3.7 och omfattar 287 och 224 skalv, respektive. För att beräkna b-värde som en funktion av tid har en teknik av glidande överlappande tidsfönster tillämpats, baserat på ett fixt antal skalv i varje fönster (40 skalv) som successivt flyttas i steg om 4 skalv. Resultaten visar stora temporala variationer i b-värdet som är jämförbara mellan de två katalogerna, 0.75-1.7 (ISC) och 0.5-1.6 (NEIC), och påvisar att en signifikant minskning av b-värdet äger rum innan Izmit jordbävningen sker. Erhållna resultat visar också lovande b(t)-egenskaper för ytterligare ett stort skalv som ägde rum i närheten av Duzce, omkring 3 månader efter Izmit jordbävningen. Stabiliteten av resultat har undersökts med hjälp av olika tröskelmagnituder, olika fönsterstorlekar och tidssteg, elimination av potentiella efterskalv samt genom ett test med magnitudomvandling. Denna studie påvisar att temporala förändringar i b-värde har potential att andvändas för jordskalvsförutsägelser och ger indikationer på veckor upp till månader för stora skalv (M >7).

Two aftershock series following the December 26, 2004 (M-w = 9.0) and the March 28, 2005 (M-w = 8.6) earthquakes off coast of NW Sumatra are studied. Deduced space heterogeneity of b-values, in the Gutenberg-Richter formula, and p-values, in the Omori law, show significant variations. General agreement is found between areas of high b and areas of significant slip predicted by different source models presented by other workers. Correlation with high p-values does exist, however, is less pronounced. The largest aftershocks occur during or near time periods when b-values reach their local minima. To examine the stability of results, two global earthquake catalogues (ISC and NEIC), different threshold magnitudes, moving-window lengths and moving steps were employed. The presented b- and p-distributions exhibit high confidence levels.

Fifteen largest earthquakes, M-w >= 7, occurring between 2000 and 2010 in the Andaman-Sumatra region are studied. The available USGS list of events used is complete for a threshold magnitude M-c = 4.5 and contains 6973 shocks. Spatial and temporal variation of b-values, in the Gutenberg-Richter formula log N = a - bM, was investigated in six selected epicentral regions. The technique of moving spatial- and time-windows was applied. Deduced b-values show large variations from 0.55 to 2.40. The 15 largest events all took place within regions of low b and were preceded by significant drops in b-values. Observed correspondence between low b and the occurrence of large earthquakes suggests that b(t) has a potential which could be employed in a medium term (months, years) earthquake prediction.

We report a case of heat stroke in which detection of brain injury was improved by high b-value diffusion-weighted imaging (DWI). High b-value DWI revealed moderate to marked hyperintensity at/around bilateral dentate nuclei and part of thalami. Apparent diffusion coefficient (ADC) maps revealed ADC decrease of the dentate lesions. Routine DWI showed only mild hyperintensity of part of dentate lesions. High b-value DWI could be valuable for improved detection of heat stroke-induced brain injury.

The present thesis collects results of research applying theory and methods of statistical seismology to the seismicity of Central America, a region with a complex tectonic setting controlled by the interaction of four major plates, namely the Caribbean, Cocos, Nazca and North American plates. Three different earthquake catalogues were used for studies focused on stress in a tectonic volume, seismic hazard maps and seismicity patterns (precursors), covering the region 94ºW to 81ºW and 5ºN to 20ºN. Variations in the b-value, the parameter in Gutenberg & Richter’s equation LogN=a-bM, as a function of depth in the subduction zone were investigated. High b-values were identified in the upper part of the slab at depths of 80-110km beneath Guatemala-El Salvador and at depths 130-170km beneath Nicaragua. These anomalies may be related to the generation of volcanism occurring above them. Time dependence of the b-value was also studied. Five case studies were selected (events with MS ≥7.2) for a detailed analysis. In three out of five cases, it was possible to link b-value minima to the time of occurrence of corresponding large events. Seismic quiescence was mapped as a function of time and space by a griding technique. The characteristics of the quiescence were calculated using the statistics Z and ß and for Time Window lengths between 1 and 5 years. Five positive anomalies were found, which can be associated with large earthquakes (MS≥7.2). Finally, a Monte Carlo approach was utilized to evaluate the ground motion hazard and its uncertainties in northern Central America. A set of new seismic hazard maps exhibiting probabilistic values of peak ground acceleration (PGA) with 50%, 10%, and 5% probabilities of exceedance (PE) in 50 years is presented for a large area of northern Central America, including El Salvador and Guatemala.

We analyze the spatio-temporal distribution of b-value in the frequency-magnitude relation of earthquakes, for the 1998-1999 Hida Mountain earthquake swarms. We found a b-value that varies from 0.8 to 1.5-1.7 when depth is increasing from 4 to 6km. The high b-value is located in a crustal region that is characterized, according to some previous studies, by low-velocity and low-density. The results suggest that the b-value can be a useful toolfor mapping such "anomalous" areas, possibly associated with magma movements. Our study confirms other similar investigations in volcanic areas.

The Vrancea seismic region contains an isolated cluster of events beneath the Carpathian Arc Bend in Romania, dipping down to about 200 km depth. Seismic activity mainly belongs to intermediate depths (h≧60 km). This paper aims at identifying the so called man-made changes in seismicity, included in the studied catalogue, to reveal possible real changes of seismicity. The magnitude of completeness of the catalog is found to vary significantly from 3 to 3.8, for the time period studied (1978-1998). However, taking the minimum magnitude as 3.7, the two big earthquakes which occurred in this period show possible premonitory patterns of quiescence and b-value changes.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.

Tato bakalářská práce se zabývá koregistrací difuzně vážených dat magnetické rezonance s vysokými b-hodnotami. Cílem je porovnat vybrané metody koregistrace na reálných datech a kvantifikovat kvalitu výstupu. V teoretické části je popsán princip difuzního zobrazování, vliv b-hodnoty na obraz a různé metody předzpracování dat se zaměřením na možnosti koregistrace obrazů s různým kontrastem. Dále jsou prezentovány dostupné softwarové nástroje a metody hodnocení kvality koregistrace. V praktické části je provedeno předzpracování difuzních dat, včetně koregistrace vybranými metodami, a analyzována kvalita pomocí statistických metod., This bachelor thesis deals with the coregistration of diffusion-weighted MRI data with high b-values. The aim is to compare selected coregistration methods on real data and to quantify the quality of the output. The theoretical part presents the principle of diffusion imaging, the effect of b-value on the image and different methods of data preprocessing with a focus on the possibilities of coregistration of images with varying contrast. In addition, available software tools and methods for assessing the quality of coregistration are introduced. In the practical portion of the paper, preprocessing of diffusion data, including coregistration by the selected methods, is performed and the quality is analyzed using statistical measures.

Tato semestrální práce se zabývá různými možnostmi registrace medicínských obrazů. Na začátku jsou uvedeny základní vlastnosti DKI dat. V dalších kapitolách je zaměřena na metody, které odstraňují pohybové artefakty a geometrické nepřesnosti. Těmito metodami jsou převzorkování, vyhlazování transformace a optimalizace. V práci je dále popsán software provádějící samotnou registraci. Na konci se věnuje metodami srovnávající úspěšnost registrací., This semestral thesis deals with several options of medical images registration. Basic properties of DKI data are presented in the begining. In the following chapters it is focused on methods, which are removing motion distortion and geometrical inaccuracies. These methods are oversampling, transformation smoothing and optimalization. Software doing registration itself is also covered in this thesis. Methods of comparing registration success rates are described in the end.