Tesis sobre el tema "Diffusion CT"
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Mosavi, Firas. "Whole-Body MRI including Diffusion-Weighted Imaging in Oncology". Doctoral thesis, Uppsala universitet, Enheten för radiologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-209777.
Texto completoTakahashi, Hiroaki, Yoshimi Seida y Mikazu Yui. "3D X-ray CT and diffusion measurements to assess tortuosity and constrictivity in a sedimentary rock". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191088.
Texto completoTakahashi, Hiroaki, Yoshimi Seida y Mikazu Yui. "3D X-ray CT and diffusion measurements to assess tortuosity and constrictivity in a sedimentary rock". Diffusion fundamentals 11 (2009) 89, S. 1-11, 2009. https://ul.qucosa.de/id/qucosa%3A14061.
Texto completoPeyrat, Jean-Marc. "Comparison of cardiac anatomy and function : statistics on fibre architecture form DT-MRI and registration of 4D CT images". Nice, 2009. http://www.theses.fr/2009NICE4053.
Texto completoIn this thesis, we address the problem of comparing cardiac anatomy and function from medical images. The first part focuses on cardiac anatomy with a statistical study of cardiac fibre architecture from diffusion tensor magnetic resonance imaging (DT-MRI). The second part focuses on a joint comparison of cardiac anatomy and function with the nonlinear spatiotemporal registration of two 4D computed tomography (CT) sequences of different patients or of the same patient at different times. Cardiac fiber architecture, a complex spatial arrangement of myofibres locally bounded to each other to form planes called laminar sheets, plays an essential role in defining the electrical and mechanical behaviour of the heart, and thus in cardiac function. We propose a unified computational framework to perform a statistical analysis of cardiac fibre architecture from DT-MRI. The novelty of this framework lies on first- and second-order statistics directly computed on diffusion tensors (symmetric definite positive matrices) based on the Log-Euclidean metric. The variability of fibre and laminar sheet orientations among a population is then extracted from the covariance matrix of diffusion tensors. This computational framework is applied to a dataset of canine DT-MRI acquired ex vivo. This intra-species statistical comparison does not only provide an average model (or atlas) of cardiac fibre architecture, but also shows consistency of fibre orientation and discrepancies of laminar sheet orientation among this population of hearts. The resulting canine atlas is then compared to a rare single human DT-MRI acquisition ex vivo and a synthetic model used for electromechanical simulations or image analysis. This preliminary inter-species comparison shows a much better consistency of fibre orientation than laminar sheet orientation between human and canine hearts. Compared to the canine atlas, the synthetic model has showed to be limited for a complete and accurate description of cardiac fibre architecture. The acquisition of time-series of cardiac images gives the opportunity to observe cardiac motion and thus its function in addition to its anatomy. In order to compare this cardiac function, we propose a novel nonlinear spatiotemporal registration algorithm of time-series of images. The spatiotemporal registration is decoupled into a temporal registration that aims at mapping corresponding physiological events and into a spatial registration that aims at mapping corresponding anatomical points ensuring a consistency with their respective motion. This consistency is ensured by defining «trajectory constraints» linking intra-sequence transformations describing cardiac motion to inter-sequence transformations describing anatomical differences at different physiological times. Under these trajectory constraints, the 4D spatial registration problem is simplified to 3D multichannel registration problem solved using a new version of the «Diffeomorphic Demons», called the «Multichannel Diffeomorphic Demons». This new registration method is applied to the inter-subject registration of 4D cardiac CT sequences for evaluation. Its comparison to other existing methods shows that it is the best compromise between accuracy, spatial and temporal regularization, and computation times. A possible clinical application of the spatiotemporal nonlinear registration is then proposed to compare cardiac anatomy and function before and after therapy. We propose to study over a cardiac cycle the evolution of strains of inter-sequence transformations that we called «Remodeling Strains». These new cardiac indices can be used to explain and quantify remodeling processes after therapy
Peyrat, Jean-Marc. "Comparaison de l'Anatomie et de la Fonction Cardiaque : Statistiques sur l'Architecture des Fibres et Recalage d'Images 4D CT". Phd thesis, Université de Nice Sophia-Antipolis, 2009. http://tel.archives-ouvertes.fr/tel-00635292.
Texto completoNunn, Jacob. "Investigations of Partial Gas Saturation on Diffusion in Low-permeability Sedimentary Rocks". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38396.
Texto completoGu, Jing y 谷静. "Multiparametric imaging using diffusion and dynamic-contrast enhanced MRI, and 18F-FDG PET/CT in the evaluation of primary rectal cancer andmalignant lymphoma". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47027174.
Texto completoFabien, Aurélie Jessica. "Etude du couplage comportement hydromécanique – durabilité dans le béton de la structure : application à la maquette MAREVA". Nantes, 2012. http://www.theses.fr/2012NANT2090.
Texto completoMaiwald, Bettina, Donald Lobsien, Thomas Kahn y Patrick Stumpp. "Is 3-Tesla Gd-EOB-DTPA-enhanced MRI with diffusion-weighted imaging superior to 64-slice contrast-enhanced CT for the diagnosis of hepatocellular carcinoma?" Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-155190.
Texto completoCunningham, Dustin T. "Fusion of Multimodal Neuroimaging for Deep Brain Stimulation Studies". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337895443.
Texto completoMirus, Matthew M., Sergey V. Tokalov, Gerald Wolf, Jerilyn Heinold, V. Prochnow y Nasreddin Abolmaali. "Noninvasive assessment and quantification of tumour vascularisation using MRI and CT in a tumour model with modifiable angiogenesis – An animal experimental prospective cohort study". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-232305.
Texto completoMesguich, Charles. "Apport de l’imagerie fonctionnelle par TEP dans la prise en charge diagnostique et thérapeutique du myélome multiple et comparaison à l’IRM de diffusion". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0229.
Texto completoTherapeutic changes over the past decade have contributed to an improvement in the survival of Multiple Myeloma (MM). Newer whole-body imaging techniques, such as 18-FDG PET-CT (PET-FDG) and MRI, have replaced radiological surveys for diagnostic purposes but also therapeutic evaluation. However, each of these modalities has its limits. Diffusion-weighted MRI (DW-MRI), analysis of tumor heterogeneity with the help of artificial intelligence (AI) as well as the development of new PET radiotracers are three important ways that may contribute to improve MM patient’s management. The general objective of this work was to assess the contribution of these new approaches during the initial diagnosis of MM as well as during therapeutic evaluation.The first part of this work was to prospectively compare the detection of focal bone lesions by FDG-PET and DW-MRI in a population of newly diagnosed MM. The second part of this work was to assess the contribution of radiomics coupled to AI for the diagnosis of diffuse bone marrow disease in FDG-PET. The third part of this work was devoted to the prospective comparison of the prognostic values of FDG-PET and DW-MRI during the therapeutic evaluation of MM eligible to autologous stem cell transplantation. The last part describes the protocol that aims at comparing the performance of 18F-Fluorocholine PET-CT and FDG-PET in the initial work-up of MM
Araújo, Susana Vasconcelos 1984. "Diffusion and swelling of CO2/light oil mixtures using pressure decay and CT-scan = Difusão e inchamento de misturas de CO2/óleo leve usando as técnicas de queda de pressão e de tomografia computadorizada". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265948.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
Made available in DSpace on 2018-08-25T01:17:03Z (GMT). No. of bitstreams: 1 Araujo_SusanaVasconcelos_M.pdf: 2255387 bytes, checksum: dda0bb2a99db1fae70648bf6282ce8f6 (MD5) Previous issue date: 2014
Resumo: O CO2 utilizado na recuperação avançada em reservatórios de petróleo é um importante agente de injeção devido a suas características de miscibilidade e de inchamento. No que tange a miscibilidade, a difusão molecular é o processo que descreve a mistura natural de fluidos miscíveis, e seu principal parâmetro é o coeficiente de difusão molecular. O objetivo deste estudo é medir o coeficiente de difusão bem como o fator de inchamento do CO2 em óleos leves em diferentes condições experimentais envolvendo pressão, temperatura e composição do óleo. Com intuito de obter o coeficiente de difusão, duas técnicas experimentais foram realizadas em paralelo: uma primeira técnica conhecida como decaimento de pressão e outra chamada de tomografia computadorizada. Esta última, apesar de ainda estar em processo de investigação, permitiu também a obtenção do fator de inchamento nas condições experimentais selecionadas. O óleo estudado é um óleo leve proveniente dos reservatórios do pré-sal no Brasil. Os testes foram efetuados em uma célula para altas pressões especialmente desenvolvida para esses ensaios que envolvem tomografia computadorizada. As pressões e temperatura variaram de 2.76 MPa a 28.96 MPa a 293.15 K e somente 10.34 MPa a 341.15 K. A difusão molecular é considerada um mecanismo chave que controla a miscibilidade entre o óleo e o gás. Sabendo que o coeficiente de difusão determina a taxa de transferência de massa durante o processo, a difusão de solventes em óleo leve dentro de um meio poroso se tornou de grande importância na engenharia de petróleo. Em paralelo, o inchamento do óleo bruto com CO2 aumenta o fator de volume de formação do óleo a tal ponto que o óleo residual remanescente após a injeção de água é menor em volume nas condições de superfície. A extensão do aumento ou do inchamento é medida pelo fator de inchamento. Nos últimos anos a difusão do CO2 em óleo pesado tem atraído uma maior atenção, enquanto que a difusão em óleo leve tem sido pouco estudada na literatura. Com foco nos reservatórios do pré-sal no litoral brasileiro, onde o óleo tem entre 28 a 30 graus API e concentrações variadas de CO2, diferentes modelos de difusão envolvendo as condições de fronteira na interface e a termodinâmica do CO2-óleo volátil precisam ser levados em consideração. No presente trabalho, os coeficientes de difusão puderam ser obtidos somente através da técnica experimental de decaimento de pressão por meio do modelo de resistência na interface proposto por Etminan et al. (2013). Os coeficientes de difusão estavam dentro dos intervalos reportados previamente na literatura. Além disso, um outro parâmetro, o coeficiente de transferência de massa, permitiu identificar que a resistência à transferência de massa na interface era praticamente insignificante no óleo original. Apesar das limitações do método de tomografia computadorizada na obtenção das concentrações de CO2 no óleo, a investigação desse método ofereceu uma melhor compreensão do fenômeno da difusão do CO2 dentro da coluna de óleo. Em contrapartida, o inchamento pôde ser claramente observado e caracterizado através desse método
Abstract: CO2-EOR is an important injection agent in oil reservoir due to its miscibility and swelling effects. Concerning the miscibility effect, molecular diffusion is the process describing the natural mixture of miscible fluids, whose main modeling parameter is the molecular diffusion coefficient. The aim of this study is to measure the diffusion coefficient and swelling factor of CO2 in light crude oil under different experimental conditions concerning pressure, temperature and oil composition. In order to obtain the diffusion coefficient, two experimental techniques were run in parallel: the well-established and so-called pressure decay method and a CT scan method that was still under investigation. The later method was also used to obtain the swelling factor in the selected experimental conditions. The oil studied was light oil from Brazilian subsalt oil reservoirs. Tests were carried on a specially constructed vertical high pressure cell, from 2.76 MPa to 28.96 MPa (400 psi to 4200 psi) at 293.15 K (20oC) and just 10.34 MPa (1500 psi) at 341.15 K (65oC). Molecular diffusion is particularly important for miscible gas flooding processes, as diffusion is a key mechanism controlling the miscibility between oil and gas. The diffusion coefficient determines the rate of mass transfer during the diffusive process that will result in a miscible system. The diffusivity of solvents into light oil in porous media has become of great significance in petroleum engineering, since CO2 injection has been proposed more and more as the enhanced oil recovery method to be applied in the reserves of conventional oils. The swelling effect of crude oil with CO2 increases the oil formation volume factor so that residual oil after waterflooding is smaller in volume at surface conditions. The extent of the expansion or swelling is measured by the swelling factor. While diffusion in CO2-heavy oils systems has attracted some attention, the subject in light crude oils is scarcely described in the public literature. Such prospect needs therefore to be thoroughly investigated for the pre-salt reservoirs offshore Brazil, where oil has an API gravity between 28 and 30 and a variable contents of CO2. Due to such properties, differences in the models regarding boundary conditions at the interface and in the thermodynamics of the CO2-volatile oil must be taken into consideration. Diffusion coefficients were obtained using only the pressure decay technique throughout Etminan et al. (2013) interface resistance model. The obtained diffusion coefficients were within the ranges previously reported in the literature. Furthermore, another parameter obtained with the model, namely the mass transfer coefficient, allowed identifying that there was almost no mass transfer resistance in the interface in original oil. Despite the CT limitations to obtain CO2 concentration, CT investigation could offer an important insight on CO2 diffusion inside the oil column. In contrast the swelling effect could be clearly observed and characterized through this method
Mestrado
Reservatórios e Gestão
Mestra em Ciências e Engenharia de Petróleo
Varoquaux, Arthur Damien. "Evaluation clinique et expérimentale des nouvelles modalités d'imagerie dans la prise en charge des néoplasies ORL notamment par la TEP/IRM". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5058.
Texto completoMultiparametric imaging interest and clinical use is rising for head and neck carcinoma (HNC). Among these modalities, FDG in PET and DWI-MRI are the most studied. PET/MRI is a new modality that allows in a single examination of combined various biologic biomarkers.After an optimization process of PET/MRI, we applied our first experience concerning the aspects of DWI-MRI and PET-MRI after radiation therapy. Thereafter we studied the correlation of SUV and ADC in HNC. In this study SUV and ADC values were independent parameters in HNSCC. Measurements of these two biomarkers were reproducible with almost perfect observer agreements for both methods. Neither SUV nor ADC values were able to predict the histologic grade, although a trend towards higher SUV and lower ADC values was observed in poorly differentiated tumours. Secondly, we we studied detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MRI versus PET/CT in 32 consecutive HNSCC who underwent 18F-FDG PET/MRI and PET/CT. Attenuation correction sequence for PET/MRI and CT for PET/CT were used to caculate SUV. In results, PET/MRI coregistration and image fusion was feasible in all patients. There was no statistically significant difference between PET/MRI and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUV measured on PET/MRI and PET/CT. SUV measured on PET/MRI were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p <0.05)
Koubar, Khodor. "Amélioration du calcul de la masse osseuse par micro-tomodensitométrie X : prise en compte des phénomènes physiques". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01062827.
Texto completoKassem, Emad Abdel-Rahman Ahmed. "Compaction Effects on Uniformity, Moisture Diffusion, and Mechanical Properties of Asphalt Pavements". Thesis, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-242.
Texto completoLim, Cheol Woong. "Mathematical analysis of the lithium ion transport in lithium ion batteries using three dimensional reconstructed electrodes". 2012. http://hdl.handle.net/1805/3419.
Texto completoComputational analysis of lithium ion batteries has been improved since Newman and et al. suggested the porous electrode theory. It assumed the electrode as a simple structure of homogeneous spherical particles. Bruggeman relationship which characterizes porous material by a simple equation was adopted in the homogeneous electrode model instead of the electrode morphology. To improve the prediction of a cell performance, the numerical analysis requires the realistic microstructure of the cell. Based on the experimentally determined microstructure of the positive and negative electrodes of a lithium ion battery (LIB) using x-ray micro/nano-CT technology, three dimensional (3D) simulations have been presented in this research. Tortuosity of the microstructures has been calculated by a linear diffusion equation to characterize the 3D morphology. The obtained tortuosity and porosity results pointed out that the Bruggeman relationship is not sufficiently estimate the tortuosity by the porosity of electrodes. We studied the diffusion-induced stress numerically based on realistic morphology of reconstructed particles during the lithium ion intercalation process. Diffusion-induced stresses were simulated at different C rates under galvonostatic conditions and compared with spherical particles. The simulation results showed that the intercalation stresses of particles depend on their geometric characteristics. The highest von Mises stress and tresca stress in a real particle are several times higher than the stresses in a spherical particle with the same volume. With the reconstructed positive electrode structure, local effects in the LIB cathode electrode during galvanostatic discharge process have been studied. The simulation results reported that large current density usually occurs at the joints between cathode active material particles and in the small channels in electrolyte, which will generate high electric joule power. By using the 3D real image of a LIB cathode electrode, numerical simulation results revealed that the spatial distribution of variable fields such as concentration, voltage, reaction rate, overpotential, and etc. in the cathode electrode are complicated and non-uniform, especially at high discharge rates.
Pietragalla, Michele. "Role of both pre-treatment CT in the upper respiratory airways pathology of cystic fibrosis patients and MRI Diffusion (DwI) - perfusion (DCE-PwI) in diagnosis, predicting pre- treatment response and treatment monitoring in head and neck neoplasms". Doctoral thesis, 2022. http://hdl.handle.net/2158/1260674.
Texto completoKang, Catherine. "Neuroprotective Drug Delivery to the Injured Spinal Cord with Hyaluronan and Methylcellulose". Thesis, 2010. http://hdl.handle.net/1807/24777.
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