Výpočetní tomografie je nástroj pro nedestruktivní inspekci vzorků, který je běžně používán v mnoha oblastech průmyslu a výzkumu. Některé tomografické přístroje umožňují snímání obrazů s prostorovým rozlišením pod jeden mikrometr. Zorné pole takovýchto přístrojů bývá malé, v rozsahu jednotek milimetrů či méně. Tím jsou omezeny rozměry vzorků, což je značně limitující. Toto omezení lze překonat pomocí různých technik pro rozšíření zorného pole. Jedna takováto dříve publikovaná metoda byla v této práci upravena a implementována pro přístroj Rigaku Nano3DX. Tato technika téměř zdvojnásobuje zorné pole přístroje bez nutnosti většího detektoru. Implementovaný přístup byl testován pomocí umělých i skutečných dat, a jeho účinnost byla zhodnocena subjektivně i objektivně, pomocí vizuální kontroly a metrik kvality obrazu. Hodnocení je převážně založeno na srovnání obrazů rekonstruovaných pomocí této metody s obrazy získanými pomocí většího detektoru. Implementovaná technika rozšíření zorného pole poskytuje věrné rekonstrukce vzorku, srovnatelné se zmíněnými protějšky.

In this thesis, we present ProxiSART, a flexible proximal framework for robust 3D cone beam tomographic reconstruction based on the Simultaneous Algebraic Reconstruction Technique (SART). We derive the proximal operator for the SART algorithm and use it for minimizing the data term in a proximal algorithm. We show the flexibility of the framework by plugging in different powerful regularizers, and show its robustness in achieving better reconstruction results in the presence of noise and using fewer projections. We compare our framework to state-of-the-art methods and existing popular software tomography reconstruction packages, on both synthetic and real datasets, and show superior reconstruction quality, especially from noisy data and a small number of projections.

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The first part of the Master´s thesis describes physical principles of ultrasound and fundamental variables of ultrasound field. It also deals with mathematical description of finite element method and outlines basic principles of ultrasound computed tomography. The second part introduces finite elements generator GMSH. This part focuses on the process of ultrasound field simulation and presents software that can be used for field simulation. The last part contains examples of models.

The graduation thesis is engaged in the design of computed tomography (CT). It is a piece of medical equipment which helps to define the diagnosis of a patient. The first part of the project is a research into contemporary stage and production of CT systems. Consequently the new design of computed tomography is designed in a way to maximise ergonomical, technical and aesthetic quality.

The area of clinical biomechanics is a rapidly growing engineering discipline in the world of today. This master's thesis is concerned with the stress-strain analysis of human femoral neck. In the first place it emphasizes the creation of computational model, especially the model of bone material, because of its high level of inhomogeneity. The creation of the computational model has been tested using several software packages, which are often mentioned in connection with the biomechanical tasks. The latter part of the thesis contains finite element method analysis for several material models, which are based on extensive analysis of relations used to transfer the information from computed tomography data to material model properties. Subsequently, the realization of experimental measurement is described. The final part of the thesis contains evaluated results obtained from the FEM analysis, which are also compared with the experiment.

L’emphysème pulmonaire est, avec la bronchite chronique à laquelle il est généralement associé, une bronchopathie chronique obstructive (BPCO). Ce groupe de maladie a été la sixième cause de mortalité au monde en 1990 et pourrait devenir la troisième en 2020.L’emphysème pulmonaire est défini par un élargissement anormal et permanent des espaces aériens en amont des bronchioles terminales avec destruction des parois alvéolaires sans fibrose évidente. Compte tenu de cette définition, son diagnostic devrait idéalement être basé sur l’histopathologie. Cependant, en pratique clinique, si les EFR sont à la base de la définition de la BPCO, elles ne suffisent pas au diagnostic de l’emphysème pulmonaire.<p><p>La tomodensitométrie (TDM) est une méthode diagnostique d’obtention in vivo de coupes anatomiques qui, formées de milliers de pixels, en font la méthode morphologique la plus précise pour investiguer la structure pulmonaire. Si la juxtaposition de ces pixels – dont la tonalité de gris est fonction de l’atténuation – est à la base de l’image TDM, la même information peut être représentée par la distribution de fréquence de ces atténuations. En présence d’emphysème, la destruction du tissu pulmonaire (et la plus grande proportion d’air) déterminent le déplacement de cette distribution vers les atténuations plus négatives. Plusieurs index TDM dérivés de cette distribution – notamment l’atténuation moyenne, la surface pulmonaire occupée par des valeurs d’atténuation inférieures à un seuil, un percentile particulier de la distribution – sont de possibles mesures de l’étendue de l’emphysème pulmonaire. L’émergence de la technique hélicoïdale, permettant notamment d’explorer tout le parenchyme pulmonaire en une seule apnée, justifie de déterminer les seuils et percentiles adéquats par comparaison à une mesure histologique de référence.<p><p>Au cours de nos études, nous avons montré que les index TDM dérivés de la distribution de fréquence d’atténuation tels que les surfaces relatives de poumon occupées par les coefficients d’atténuation inférieures à -960 UH (RA960) ou -970 UH (RA970) et le premier percentile (p1) sont les index les plus appropriés. En revanche, toujours sur base de comparaisons histo-morphométriques, d’autre index qui reflètent la géométrie des espaces emphysémateux – tels que la distribution de la taille des groupes de pixels adjacents occupés par des coefficients d’atténuation inférieurs à un seuil ou à un percentile – ne sont pas des index valables.<p><p>La dose d’irradiation peut être abaissée à 20 mAs effectifs. Cette réduction est particulièrement appropriée dans une pathologie susceptible de concerner des patients jeunes et l’objet d’examens répétés. Cependant, la dose d’irradiation influençant ces index, elle doit être maintenue constante au cours de suivis longitudinaux.<p><p>En TDM multi-coupes, ces index sont les plus appropriés quelque soit l’épaisseur des coupes. Cependant, cette épaisseur influençant ces index, elle doit aussi être maintenue constante au cours de suivis longitudinaux.<p><p>L’inspiration incomplète induit une sous-estimation statistiquement significative mais cliniquement insignifiante de l’étendue de l’emphysème pulmonaire. La destruction du tissu pulmonaire et l’hyperinflation ont des influences séparées sur les index TDM, faisant recommander leur ajustement aux valeurs prédites de la CPT.<p><p> / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

Purpose: The aim of the first part of this work was to evaluate the trend of the number of head CT examinations in patients with minor head injury in emergency service and to find out whether it has objective causes. The aim of the second part was to assess patients' knowledge regarding the CT examination, its risks, the source of their information and to evaluate the effect of providing information about the CT examination in a printed form. Method: In the first part of the work, we extracted data from the radiological module of the hospital information system. We searched for head CT scans in patients with minor head injury and their input characteristics and findings on CT. Further data were obtained from the hospital, the Institute of Health Information and Statistics and the Czech Statistical Office. Trends of regression curves were compared by F-test, correlation of trends was expressed using Spearman's coefficient. The second part of the work was based on a questionnaire for patients scheduled for CT scan of the body. The questionnaire included demographic data as well as items assessing patients' awareness of the risks of radiation exposure, intravenous contrast media, their sources of information and their fear of the examination. On the second page, Zung's Anxiety Scale was printed. On...

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Sex and ancestry are most commonly estimated by anthropologists using the skull. Typically, measurements and observations are taken on the skull itself, but for the purpose of convenience, computed tomography (CT) scans are increasingly used in place of skulls in research and forensic casework. Researchers work under the assumption that the dry skull-to-CT scan ratio is one-to-one; however, research on the accuracy of CT scans is sparse. In this study, eight skulls from the Boston University Donated Skeletal Collection were scored for sex and ancestral morphological traits following Buikstra and Ubelaker (1994) and Hefner and Ousley (2014), and measured using standard cranial measurements according to Langley et al. (2016). CT scans were then taken of the eight skulls and the same morphological observations and measurements were taken using the RadiAnt 5.5.1 CT viewer. Additionally, the measurements of each skull and scan were entered into FORDISC 3.1, a software program that provides discriminant functions for the processes of sex and ancestry estimation. The measurements for each dry skull-CT scan pairing were then analyzed for variance and mean differences. The results of the morphological and metric analyses indicate that the majority of the data gathered from dry skulls did not vary significantly from the measurements taken on the CT scans. The morphological sex estimation resulted in the same estimation for each skull-to-CT scan pairing; however, the morphological ancestry estimation results indicated that skeletal information lost in CT scans can make full visualization and therefore assessment of the facial region difficult. The FORDISC 3.1 results generally support the indication that there is not a significant difference between skull and CT scan measurements, with consistent sex estimation results for each dry skull-to-CT scan pairing and consistent ancestry estimation results for the majority of the pairings. However, the sex and ancestry estimations were not always accurate considering the true ancestral backgrounds of the individuals. Based on these outcomes, it is evident that CT scans can be used to obtain reliable morphological assessments and measurements of a skull, which can then be used to estimate sex using FORDISC 3.1. However, to ensure accuracy of the sex and ancestry estimations, other methods should be used in conjunction with FORDISC 3.1.