Dissertationen zum Thema „Diffusion CT“

Cancer is one of the major causes of worldwide mortality. Imaging plays a vital role in the staging, follow-up, and evaluation of therapeutic response in cancer patients. Whole-body (WB) magnetic resonance imaging (MRI), as a non-ionizing imaging technique, is a promising procedure to assess tumor spreading in a single examination. New MRI technological developments now enable the application of diffusion-weighted imaging (DWI) of the entire body. DWI reflects the random motion of water molecules and provides functional information of body tissues. DWI can be quantified with the use of the apparent diffusion coefficient (ADC). The aim of this dissertation was to demonstrate the value of WB MRI including DWI in cancer patients. WB MRI including DWI, 18F-NaF PET/CT, and bone scintigraphy was performed on 49 patients with newly diagnosed, high-risk prostate cancer, for the purpose of detecting bone metastases. WB DWI showed higher specificity, but lower sensitivity compared to 18F-NaF PET/CT. In addition, WB MRI including DWI, and CT of the chest and abdomen was performed in 23 patients with malignant melanoma. We concluded that WB MRI could not completely supplant CT for the staging of malignant melanoma, especially with respect to the detection of lesions in the chest region. In this study, WB MRI and DWI were able to detect more bone lesions compared to CT, and showed several lesions outside the CT field of view, reinforcing the advantage of whole-body examination. WB MRI, including DWI, was performed in 71 patients with testicular cancer. This modality demonstrated its feasibility for use in the follow-up of such patients. WB MRI, including DWI, and 18F-FDG PET-CT, were carried out in 50 patients with malignant lymphoma. Both these imaging modalities proved to be promising approaches for predicting clinical outcomes and discriminating between different subtypes of lymphomas. In conclusion, WB MRI, including DWI, is an evolving technique that is continuing to undergo technical refinement. Standardization of image acquisition and analysis will be invaluable, allowing for more accurate comparison between studies, and widespread application of this technique in clinical practice. Both WB MRI, including DWI and PET/CT, have their particular strengths and weaknesses in the evaluation of metastatic disease. DWI and PET/CT are different functional techniques, so that combinations of these techniques may provide complementary and more comprehensive information of tumor tissue.

A high-resolution, three-dimensional (3D) image of the interior of the sedimentary rock was obtained by means of nano-focus X-ray computer tomography (X-ray CT). Using computational methods to analyze the 3D microstructure of the rock, we presented the tortuosity and geometrical constrictivity. We also presented results on the tritiated water (HTO) diffusion tests and a mercury intrusion porosimetry (MIP) test performed on the rock. We have compared these results to understand the dominant parameters that control diffusion of HTO in the present system. These results suggest that the dominant parameters in the present system are not the constrictivity but the tortuosity and the diffusion-accessible porosity. The material considered in this study is the siliceous mudstones sampled from 500 m in depth at the Wakkanai formation around Horonobe underground research center in Hokkaido, Japan.

Ce travail de thèse s'est consacré à la comparaison de l'anatomie et de la fonction cardiaques à partir d'images médicales. La première partie de la thèse se concentre sur l'anatomie cardiaque avec une étude statistique de l'architecture des fibres musculaires du cœur à partir d'imagerie par résonance magnétique du tenseur de diffusion (IRM-TD). Dans la deuxième partie est proposée une comparaison conjointe de l'anatomie et de la fonction cardiaque par le recalage non-linéaire spatiotemporel de deux séquences 4D CT de différents patients ou du même patient à différents instants. L'architecture des fibres cardiaques, un arrangement spatial complexe des fibres localement liées les une aux autres pour former des plans appelés feuillets, joue un rôle essentiel dans le comportement électrique et mécanique du cœur, et donc de la fonction cardiaque. Nous avons proposé un cadre algorithmique pour réaliser une analyse statistique de l'architecture des fibres cardiaques à partir d'IRM-TD. La nouveauté de cette approche repose sur une analyse statistiques du premier et second ordre calculées directement sur les tenseurs de diffusion (matrices symétriques définies positives) utilisant la métrique Log-Euclidienne. La variabilité de l'orientation des fibres et feuillets au sein d'une population est ensuite extraite de la matrice de covariance des tenseurs de diffusion. Ce cadre algorithmique est appliqué à des données d'IRM-TD de cœurs chiens acquis ex vivo. Cette comparaison statistique inter-espèce fournit non seulement un modèle moyen (ou atlas) de l'architecture des fibres, mais révèle aussi une cohérence de l'orientation des fibres et une divergence de l'orientation des feuillets au sein de cette population de cœurs. L'atlas canin résultant est ensuite comparée à une donnée humaine rare d'IRM-TD acquise ex vivo et un modèle synthétique utilisé pour des simulations électromécaniques ou de l'analyse d'images. Cette comparaison inter-espèce préliminaire a révélé une bien meilleure similarité de l'orientation des fibres que des feuillets entre les cœurs humains et canins. Comparé à l'atlas canin, le modèle synthétique s'est quant a lui révélé limité pour une description complète et fidèle de l'architecture des fibres. L'acquisition de séquences d'images cardiaques permet d'observer le mouvement cardiaque et donc sa fonction, en plus de son anatomie. Afin de comparer cette fonction cardiaque, nous avons proposé un nouvel algorithme de recalage non-linéaire spatiotemporel de séquences d'images. Ce recalage spatiotemporal est découplé en un recalage temporel qui met en correspondance des événements physiologiques et en un recalage spatial qui quant à lui met en correspondance des points anatomiques tout en assurant une cohérence avec leurs mouvements respectifs. Cette cohérence est assurée par la définition de «contraintes de trajectoires» liant les transformations intra-séquences décrivant le mouvement cardiaque aux transformations inter-séquences décrivant les différences anatomiques à différents instants physiologiques. Sous ces contraintes de trajectoires, le problème de recalage spatial 4D est simplifié en un problème de recalage multicanal 3D résolu avec une nouvelle version des «Démons Diffeomorphes», appelée «Démons Diffeomorphes Multicanaux». Cette nouvelle méthode de recalage est appliquée au recalage inter-sujet de séquences 4D CT pour évaluation. Comparée à d'autres méthodes existantes, elle s'est révélée le meilleur compromis en terme de précision, de régularité spatiale et temporelle, ainsi que de temps de calcul. Un exemple d'application clinique possible du recalage non-linéaire spatiotemporal est proposé pour comparer l'anatomie et la fonction cardiaques avant et après thérapie. Pour cela, nous avons proposé d'étudier l'évolution au cours du cycle cardiaque des déformations des transformations inter-sujets que nous avons appelées «Déformations de Remodelage». Ces nouveaux indices cardiaques permettent notamment d'expliquer et de quantifier le remodelage ayant lieu après thérapie
In 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

Ce travail de thèse s'est consacré à la comparaison de l'anatomie et de la fonction cardiaques à partir d'images médicales. Une première partie se concentre sur l'anatomie cardiaque avec une étude statistique de l'architecture des bres musculaires du c÷ur à partir d'IRM de tenseur de di usion. Dans la deuxième partie est proposée une comparaison la fonction cardiaque de di érents patients ou du même patient a di érents instants par le recalage spatiotemporel de séquences 4D CT. La complexe organisation des bres musculaires cardiaques a un rôle très important dans le comportement électrique et mécanique du c÷ur. Pour étudier cette architecture des bres, nous avons proposé de nouveaux outils algorithmiques d'analyse statistique d'IRM de tenseurs de di usion. La nouveauté de cette approche est de réaliser cette analyse statistique directement sur les tenseurs de di usion l'a où la plupart des études statistiques se font sur des vecteurs ou angles d'orientation décrivant les directions des bres et des feuillets. La variabilité de l'orientation des bres et des feuillets est ensuite directement donnée par la matrice de covariance des tenseurs de di usion de laquelle sont extraites les variabilités des vecteurs propres. L'application de ces outils a une base de données d'IRM de tenseur de di usion de c÷urs de chiens acquis ex vivo a permis d'obtenir un atlas de l'architecture des bres mais aussi de révééler une cohérence de l'orientation des bres et une plus grande variabilité de l'orientation des feuillets. Ensuite, nous avons comparé l'atlas de c÷urs de chien à un c÷ur humain et un modèle synthétique couramment utilisé pour des simulations électromé- caniques ou l'analyse d'images cardiaques. Le c÷ur humain s'est révélé plus proche des c÷urs de chien au niveau de l'orientation des bres que de celle des feuillets. Le modèle synthétique quant à lui s'est montré trop simple pour décrire en détails la complexité de l'architecture des bres. L'acquisition de séquences d'images cardiaques permet d'observer le mouvement cardiaque et donc sa fonction. Nous avons proposé un nouvel algorithme de recalage nonlin éaire spatiotemporel de séquences d'images qui permet de comparer cette fonction cardiaque. Le recalage temporel assure la mise en correspondance d'instants physiologiques similaires. Le recalage spatial quant à lui doit assure une cohérence entre le mouvement des points physiques intra-séquence et leur mise en correspondance inter-séquence. Cette cohérence est assurée par les contraintes de trajectoires liant les transformations intras équences décrivant le mouvement cardiaque aux transformations inter-séquences décrivant les di érences anatomiques au cours du temps. Sous ces contraintes de trajectoires, le recalage spatial 4D est simpli é en un recalage multicanal 3D résolu avec une nouvelle version des Demons Di eomorphes Multicanaux. Cette méthode de recalage spatiotemporel est appliquée au recalage inter-sujet de séquences 4D CT pour évaluation. Comparée a d'autres techniques existantes, cette technique de recalage s'est révélée le meilleur compromis en terme de précision, de régularité spatiale et temporelle, mais aussi de temps de calcul. Un exemple d'application possible du recalage spatiotemporal est proposé avec la comparaison de l'anatomie et de la fonction cardiaques avant et après thérapie.

The effect of partially saturated conditions on aqueous diffusion was investigated on the Upper Ordovician Queenston Formation shale from the Michigan Basin of southwest Ontario, Canada. Effective diffusion coefficients (De) were determined for iodide tracer on duplicate cm-scale samples from a core segment. Partially saturated conditions were created with a new gas-ingrowth method that takes advantage of the variability of N2 solubility with pressure. The method is designed to create partially saturated pores, quantify the level of partial gas/brine saturation within the tracer-accessible pore space, and measure De under fully porewater-saturated and partially gas-saturated conditions for the same sample. X-ray radiography is used with an iodide tracer for quantifying the degree of partial saturation and measuring De. The saturated De values range from 2.8 x 10-12 to 3.1 x 10-12 m2/s. Following generation of a gas phase in the pores (average gas saturations of 4 to 6.7 %), De values decrease by 20 to 22 % relative to the porewater-saturated condition, indicating that the tortuosity factor (ratio of constrictivity to tortuosity) is sensitive to saturation. Suggesting that a small volume of the pore fraction is responsible for majority of the transport. The gas-ingrowth method was successful for generating partial gas saturation, but the distribution of the gas phase is non-uniform, with relatively high gas saturations near boundaries and lower saturations in the interior of the samples.

Objectives: To compare 64-slice contrast-enhanced computed tomography (CT) with 3-Tesla magnetic resonance imaging (MRI) using Gd-EOB-DTPA for the diagnosis of hepatocellular carcinoma (HCC) and evaluate the utility of diffusion-weighted imaging (DWI) in this setting. Methods: 3-phase-liver-CT was performed in fifty patients (42 male, 8 female) with suspected or proven HCC. The patients were subjected to a 3-Tesla-MRI-examination with Gd-EOB-DTPA and diffusion weighted imaging (DWI) at b-values of 0, 50 and 400 s/mm2. The apparent diffusion coefficient (ADC)-value was determined for each lesion detected in DWI. The histopathological report after resection or biopsy of a lesion served as the gold standard, and a surrogate of follow-up or complementary imaging techniques in combination with clinical and paraclinical parameters was used in unresected lesions. Diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were evaluated for each technique. Results: MRI detected slightly more lesions that were considered suspicious for HCC per patient compared to CT (2.7 versus 2.3, respectively). ADC-measurements in HCC showed notably heterogeneous values with a median of 1.2±0.5×10−3 mm2/s (range from 0.07±0.1 to 3.0±0.1×10−3 mm2/s). MRI showed similar diagnostic accuracy, sensitivity, and positive and negative predictive values compared to CT (AUC 0.837, sensitivity 92%, PPV 80% and NPV 90% for MRI vs. AUC 0.798, sensitivity 85%, PPV 79% and NPV 82% for CT; not significant). Specificity was 75% for both techniques. Conclusions: Our study did not show a statistically significant difference in detection in detection of HCC between MRI and CT. Gd-EOB-DTPA-enhanced MRI tended to detect more lesions per patient compared to contrast-enhanced CT; therefore, we would recommend this modality as the first-choice imaging method for the detection of HCC and therapeutic decisions. However, contrast-enhanced CT was not inferior in our study, so that it can be a useful image modality for follow-up examinations.

Background To investigate vascular-related pathophysiological characteristics of two human lung cancers with modifiable vascularisation using MRI and CT. Methods Tumour xenografts with modifiable vascularisation were established in 71 rats (approval by the Animal Care Committee was obtained) by subcutaneous transplantation of two human non-small-cell lung cancer (NSCLC) cells (A549, H1299) either alone or co-transplanted with vascular growth promoters. The vascularity of the tumours was assessed noninvasively by MRI diffusion-weighted-imaging (DWI), T2-weighted, and time-of-flight (TOF) sequences) as well as contrast-enhanced CT (CE-CT), using clinical scanners. As a reference standard, histological examinations (CD-31, fluorescent beads) were done after explantation. Results Microvessel density (MVD) was higher in co-transplanted tumours (171 ± 19 number/mm2) than in non-co-transplanted tumours (111 ± 11 number/mm2; p = 0.002). Co-transplanted tumours showed higher growth rates and larger tumour vessels at TOF-MRI as well as larger necrotic areas at CE-CT. In co-transplanted tumours, DWI revealed higher cellularity (lower minimal ADCdiff 166 ± 15 versus 346 ± 27 mm2/s × 10−6; p < 0.001), highly necrotic areas (higher maximal ADCdiff 1695 ± 65 versus 1320 ± 59 mm2/s × 10−6; p < 0.001), and better-perfused tumour stroma (higher ADCperf 723 ± 36 versus 636 ± 51 mm2/s × 10−6; p = 0.005). Significant correlations were found using qualitative and quantitative parameters: maximal ADCperf and MVD (r = 0.326); maximal ADCdiff and relative necrotic volume on CE-CT (r = 0.551); minimal ADCdiff and MVD (r = −0.395). Conclusions Pathophysiological differences related to vascular supply in two human lung cancer cell lines with modifiable vascularity are quantifiable with clinical imaging techniques. Imaging parameters of vascularisation correlated with the results of histology. DWI was able to characterise both the extent of necrosis and the level of perfusion.

Les changements thérapeutiques durant la dernière décennie ont contribué à une amélioration de la survie du Myélome Multiple (MM). Cela s’est accompagné de l’utilisation de nouveaux outils d’imagerie corps-entier, tels que la TEP-TDM au 18-FDG (TEP-FDG) et l’IRM, remplaçant les radiographies standards, à des fins diagnostiques mais également d’évaluation thérapeutique. Chacune de ces modalités présente cependant ses limites. L’imagerie de diffusion en IRM, l’analyse de l’hétérogénéité tumorale aidée des techniques d’intelligence artificielle (IA) ainsi que le développement de nouveaux radiotraceurs TEP sont trois voies d’explorations importantes pouvant contribuer à une meilleure prise en charge du MM. L’objectif général de ce travail a été d’évaluer l’apport de ces nouvelles approches lors du diagnostic initial du MM ainsi que lors de l’évaluation thérapeutique. La première partie de ce travail a été de comparer prospectivement dans une population de myélomes multiples de novo la détection des lésions osseuses focales par TEP-FDG et IRM de diffusion corps-entier (DW-MRI). La deuxième partie de travail a été d’évaluer l’apport de la Radiomique couplée à pour le diagnostic de l’atteinte ostéo-médullaire diffuse en TEP-FDG. La troisième partie de ce travail a été consacré à la comparaison prospective des valeurs pronostiques de la TEP-FDG et de la DW-MRI lors de l’évaluation thérapeutique du MM éligible à une autogreffe de cellules souches hématopoïétiques (ASCT). La dernière partie décrit le protocole comparant les performances de la TEP-TDM à la 18F-Fluorocholine (FCH) à la TEP-TDM au 18-FDG dans le bilan initial du myélome multiple
Therapeutic 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

Orientador: Osvair Vidal Trevisan
Dissertação (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

En oncologie ORL, l'imagerie multiparamétrique est utilisée par un nombre grandissant d'équipes. Parmi les bio-marqueurs, la captation normalisée du fluoro-désoxyglucose (SUV-FDG) en tomoscintigraphie par émission de positons (TEP) et la restriction de la diffusion en IRM (DWI-MRI) sont les plus utilisées.L'IRM couplée à la TEP (TEP/IRM) est une nouveauté qui permet une diminution très significative des doses d'irradiation délivrées par rapport à la TEP/TDM. Nous adressons notre première expérience concernant l'aspect en diffusion et en TEP/IRM dans la surveillance des patients après radio-chimiothérapie. A la question de l'interchangeabilité du FDG-PET et de la DWI-MRI, nous avons tenté d'identifier un lien en imagerie entre la cellularité tumorale et sa consommation glucidique. La cellularité tumorale est approchée en IRM par la mesure du coefficient apparent de diffusion (ADC) et son métabolisme glucidique est approché en TEP en utilisant le 18F-desoxyglucose (FDG) par la mesure de la valeur de fixation normalisée (SUV). Dans une série appariée de 33 patients, nous avons analysé la reproductibilité des mesures de l'ADC et de SUV. Puis nous avons évalué l'indépendance statistique de ces biomarqueurs. Nous avons ensuite voulu comparer les résultats de la TEP obtenus à partir de la TEP/TDM et de la TEP/IRM. Dans une série prospective appariée chez 32 patients explorés en FDG-TEP, nous avons évalué qualitativement les images obtenues par la fusion des images recalées en TEP/IRM et TEP/TDM. Nous avons ensuite comparé la pertinence clinique des deux techniques. Et enfin nous avons comparé les valeurs quantitatives de SUV obtenues du tissu sain et du tissu pathologique
Multiparametric 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)

Suite à l'allongement de la survie des patients atteints de la mucoviscidose (CF), des études ont montré la présence d'une perte osseuse chez les patients CF. Dans ce travail de thèse, une étude de l'évolution de la densité minérale osseuse chez des souris atteintes de mucoviscidose a été effectuée en utilisant un système de micro-tomodensitométrie X. Afin d'améliorer les précisions des mesure, deux méthodes de correction de deux phénomènes physiques ont été appliquées. La première méthode est une correction du durcissement de faisceau X et basée sur une segmentation de l'objet reconstruit après une première reconstruction et en utilisant des courbes d'atténuations précalculées. La deuxième méthode est une méthode de correction de la diffusion des rayons dans l'animal basée sur l'estimation des projections des diffusés en utilisant des noyaux de diffusion précalculées. Des améliorations au niveau de la qualité de l'image et les mesures de densité osseuses ont été obtenues.

Field compaction of asphalt mixtures is an important process that influences performance of asphalt pavements; however there is very little effort devoted to evaluate the influence of compaction on the uniformity and properties of asphalt mixtures. The first part of this study evaluated relationships between different field compaction patterns and the uniformity of air void distribution in asphalt pavements. A number of projects with different asphalt mixture types were compacted, and cores were taken at different locations from these projects. The X-ray Computed Tomography (X-ray CT) system was used to capture the air void distributions in these cores. The analysis results have revealed that the uniformity of air void distribution is highly related to the compaction pattern and the sequence of different compaction equipment. More importantly, the efficiency of compaction (reducing air voids) at a point was found to be a function of the location of this point with respect to the compaction roller width. The results in this study supported the development of the "Compaction Index (CI)," which quantifies the degree of field compaction. The CI is a function of the number of passes at a point and the position of the point with respect to the compaction roller width. This index was found to correlate reasonably well with percent air voids in the pavement. The CI calculated from field compaction was also related to the slope of the compaction curve obtained from the Superpave gyratory compactor. This relationship offers the opportunity to predict field compactability based on laboratory measurements. The compaction of longitudinal joints was investigated, and recommendations were put forward to improve joint compaction. The air void distributions in gyratory specimens were related to the mixture mechanical properties measured using the Overlay and Hamburg tests. The second part of this study focused on studying the relationship between air void distribution and moisture diffusion. A laboratory test protocol was developed to measure the diffusion coefficient of asphalt mixtures. This important property has not measured before. The results revealed that the air void phase within the asphalt mixtures controls the rate of moisture diffusion. The measured diffusion coefficients correlated well with the percent and size of connected air voids. The measured diffusion coefficient is a necessary parameter in modeling moisture transport and predicting moisture damage in asphalt mixtures. The last part of this study investigated the resistance of asphalt mixtures with different percent air voids to moisture damage by using experimental methods and a fracture mechanics approach that accounts for fundamental material properties.

Indiana University-Purdue University Indianapolis (IUPUI)
Computational 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.

STUDIO 1 I pazienti affetti da fibrosi cistica (FC) sviluppano frequentemente quadri di rinosinusite cronica con necessità di ricorso alla chirurgia endoscopica (FESS). La conoscenza pre-chirurgica dell’esatta anatomia dei seni paranasali è fondamentale per ridurre al minimo le complicanze intra-operatorie. Lo scopo dello studio è stato valutare l’incidenza di varianti anatomiche all'immaging di Tomografia Computerizzata nei pazienti affetti da FC che possono influire sull’incidenza di complicanze maggiori durante FESS. I risultati hanno dimostrato che, nonostante la maggiore complessità anatomica, l’incidenza di complicanze operatorie maggiori nei pazienti affetti da FC è stata simile a quella dei pazienti non affetti da FC. STUDIO 2 Sono stati reclutati 37 pazienti con diagnosi di carcinoma rino-orofaringeo sottoposti a trattamento RT-CHT ed a follow-up per almeno 12 mesi al fine di valutare la capacità della Risonanza Magnetica (RM) con sequenze di diffusione (DWI) e perfusione (DCE-PWI) nel distinguere le alterazioni tessutali post-trattamento dalla persistenza/recidiva di malattia. I primi risultati hanno dimostrato che l’imaging RM DWI e DCE-PWI è stato in grado di aggiungere significative informazioni nel distinguere le alterazioni tessutali indotte dal trattamento RT-CHT dalla presenza di residuo tumorale. STUDY 1 Patients with cystic fibrosis (CF) frequently develop chronic rhino-sinusitis with need for endoscopic surgery (FESS). Pre-surgical knowledge of the exact anatomy of the paranasal sinuses is essential to minimize intra-operative complications. The purpose of the study was to evaluate the incidence of anatomical variants in Computed Tomography imaging in patients with CF that can affect the incidence of major complications during FESS. The results showed that, despite the greater anatomical complexity, the incidence of major surgical complications in patients with CF was similar to that of patients with chronic rhino-sinusitis without CF. STUDY 2 We recruited 37 patients diagnosed with naso-oropharyngeal carcinoma undergoing radio-chemotherapy (RT-CHT) treatment and follow-up for at least 12 months in order to evaluate the ability of magnetic resonance imaging (MRI) with sequences of diffusion (DWI) and perfusion (DCE -PWI) in distinguishing post-treatment tissue alterations from disease persistence/relapse. The first results showed that MRI with DWI and DCE-PWI imaging was able to add significant information in distinguishing the tissue alterations induced by RT-CHT treatment from the presence of residual tumour.

Traumatic spinal cord injury (SCI) is a devastating condition for which there is no effective clinical treatment. Neuroprotective molecules that minimize tissue loss have shown promising results; however systemic delivery may limit in vivo benefits due to short systemic half-life and minimal passage across the blood-spinal cord barrier. To overcome these limitations, an injectable intrathecal delivery vehicle comprised of hyaluronan and methylcellulose (HAMC) was developed, and previously demonstrated to be safe and biocompatible intrathecally. Here, HAMC was determined to persist in the intrathecal space for between 4-7 d in vivo, indicating it as an optimal delivery system for neuroprotective agents to reduce tissue degeneration after SCI. HAMC was then investigated as an in vivo delivery system for two neuroprotective proteins: erythropoietin (EPO) and fibroblast growth factor 2 (FGF2). Both proteins demonstrated a diffusive release profile in vitro and maintained significant bioactivity during release. When EPO was delivered intrathecally with HAMC to the injured spinal cord, reduced cavitation in the tissue and significantly improved neuron counts were observed relative to the conventional delivery strategies of intraperitoneal and intrathecal bolus. When FGF2 was delivered intrathecally from HAMC, therapeutic concentrations penetrated into the injured spinal cord tissue for up to 6 h. Poly(ethylene glycol) modification of FGF2 significantly increased the amount of protein that diffused into the tissue when delivered similarly. Because FGF2 is a known angiogenic agent, dynamic computed tomography was developed for small animal serial assessment of spinal cord hemodynamics. Following SCI and treatment with FGF2 from HAMC, moderate improvement of spinal cord blood flow and a reduction in permeability were observed up to 7 d post-injury, suggesting that early delivery of neuroprotective agents can have lasting effects on tissue recovery. Importantly, the entirety of this work demonstrates that HAMC is an effective short-term delivery system for neuroprotective agents by improving tissue outcomes following traumatic SCI.