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1
An, Li. "Water-fat imaging and general chemical shift imaging with spectrum modeling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0032/NQ38848.pdf.
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Huang, Fangping. "Water and Fat Image Reconstruction in Magnetic Resonance Imaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1309791802.
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Aru, Jim. "Abdominal fat distribution, measured by magnetic resonance imaging, and insulin resistance." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ54444.pdf.
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Narayan, Sreenath Prativadi. "Magnetic Resonance Imaging of Hepatic Fat Content Measurements at 7 Tesla." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1341869672.
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Huang, Hui. "Non-destructive detection of pork intramuscular fat content using hyperspectral imaging." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119675.
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Intramuscular fat levels of pork affect the flavor of pork meat. In the pork industry, two quality attributes namely intramuscular fat (IMF) content and marbling score (MS) are used to represent intramuscular fat levels of pork meat. Conventional determination methods are not suitable for the current requirements of the pork industry as they are either destructive or subjective. This study investigated the use of hyperspectral imaging in evaluating intramuscular fat content and marbling score of pork. Intramuscular fat distribution along the longissmus muscle and the influences of freezing, thawing, and image pattern analysis on prediction capacity were also considered. Near infrared (NIR) hyperspectral imaging technique from 900 to 1700 nm was used for prediction of IMF content and MS. Fresh pork at the 3rd/4th last rib was imaged. Pattern analysis techniques of Gabor filter, wide line detector (WLD), and an improved grey-level co-occurrence matrix (GLCM) were studied and different image features, i.e. spectral, texture, and line features, were extracted. Key wavelengths were identified. Multiple linear regression (MLR) was used to develop prediction models. For determination of marbling score, the MLR model, using the first derivative of Gabor filtered mean spectra, performed best with a prediction accuracy of 0.90 at wavelengths of 961, 1186 and 1220 nm. For intramuscular fat content, prediction accuracy of 0.85 was obtained using the raw mean spectra at 1207 and 1279 nm. The distribution map of IMF content in pork was developed. The results showed the possibility of rapid and non-destructive evaluation of intramuscular fat level of pork using NIR images. Regarding marbling as a visual index, a method for objective evaluation of pork marbling score using red-green-blue (RGB) images was developed by applying WLD-based linear models. The possibility of non-destructive prediction of IMF content and MS using frozen and frozen-thawed pork was studied. Prediction accuracy of 0.90 for MS was achieved for frozen pork. Prediction accuracy of 0.82 for IMF content and accuracy of 0.91 for MS were realized by frozen-thawed pork. The potential of frozen and frozen-thawed pork for assessment of marbling score and frozen-thawed pork for the assessment of intramuscular fat content were demonstrated. Besides the effects of freezing and thawing, the variation of IMF content and MS across the last seven thoracic longissmus muscle was studied. Relationships between IMF content and MS at the last rib and the corresponding attribute at other ribs and the whole section of the loin were determined. The relationship between NIR images of rib end and the IMF level of pork at the six last thoracic ribs was investigated. Close relationships were indicated, especially between the images of rib end and IMF levels at the 2nd/3rd last ribs and the 2nd last/last ribs.La teneur en matières grasses du porc affecte la saveur de la viande de porc. Dans l'industrie porcine, la graisse intramusculaire (GIM) et la cote de persillage (CP) sont deux propriétés qui déterminent la teneur en gras du porc. Les méthodes conventionnelles de détermination ne sont pas adaptées aux besoins actuels de l'industrie car elles sont destructrices ou subjectives. Cette étude porte sur l'utilisation de l'imagerie hyperspectrale dans l'évaluation de la teneur en graisse intramusculaire et du persillage du porc. Les effets de la répartition de la graisse intramusculaire le long du muscle Longissmus, de la congélation, du dégel et de l'analyse de la forme pour le traitement de l'image ont été pris en compte. Une technique d'imagerie hyperspectrale proche infrarouge (IR) allant de 900 à 1700 nm a été utilisée pour prédire le GIM ou la CP. La viande fraîche au niveau de la 3ème/4ème côte du porc a été utilisée pour recueillir les images hyperspectrales. Des analyses de la forme fondée sur les techniques du filtre de Gabor, du détecteur linéaire à large spectre (WLD) et de la matrice de cooccurrence de niveau gris améliorée (GLCM) ont été étudiées et les propriétés de l'image, i.e spectre, texture et propriétés des lignes, ont été extraites. La régression linéaire multiple (RLM) a été utilisée pour développer des modèles de prédiction. Pour la cote persillage, le modèle de RLM utilisant la moyenne de spectre filtrée pour la première dérivée de Gabor a le mieux performé avec une précision de calibration de 0,90 aux longueurs d'onde de 961, 1186 et 1220 nm. Pour le GIM, une précision de calibration de 0.85 a été obtenue avec un spectre moyen de base à 1207 et 1279 nm. La distribution du contenu de GIM a été illustrée. Les résultats démontrent la possibilité d'utiliser les images hyperspectralces proche IR pour évaluer rapidement et de façon non-destructive le taux de gras intramusculaire du porc. En ce qui concerne le persillage en tant qu'indice visuel, une méthode objective d'évaluation de la cote persillage utilisant des images rouge-vert-bleu (RGB) a été développée en appliquant un WLD basé sur un model linéaire au canal vert. La possibilité d'un contrôle non-destructif du GIM et de la CP utilisant du porc congelé et décongelé a été étudiée. Une précision de la prédiction de 0.90 pour la CP a été réalisée avec du porc congelé. Une précision de la prédiction de 0.82 pour le GIM découle du porc décongelé. Le potentiel du porc congelé et décongelé pour l'évaluation de la cote de persillage et du porc décongelé pour l'évaluation de la teneur en gras intramusculaire a été démontré. Outre l'effet du gel et du dégel, la variation du GIM et de la CP à travers les sept derniers muscles thoraciques Longissmus a été étudiée. Les relations entre le GIM et la CP à la dernière côte et les propriétés correspondantes aux autres côtes et au filet ont été déterminées avec précision. La relation entre les images de proche IR à l'extrémité et le niveau de GIM du porc six dernières côtes thoraciques a été étudiée. Des relations étroite ont été déterminées, en particulier entre les images de l'extrémité de la côte et les taux de GIM aux 2eme/3eme dernières côtes et la 2eme dernière côte.
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Mehemed, Taha Mohamed M. "Fat-Water Interface on Susceptibility-Weighted Imaging and Gradient-Echo Imaging: Comparison of Phantoms to Intracranial Lipomas." Kyoto University, 2014. http://hdl.handle.net/2433/193572.
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Groll, Emily D. "Comparison of anthropometric and DXA measurements of regional body fat." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1398712.
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Purpose: The primary purpose of this research study was to assess the degree of agreement between simple anthropometric measurements (i.e. body mass index, waist circumference, hip circumference, and waist-to-hip ratio) and the measures of regional adiposity, with a primary focus on the androidlgynoid ratio, assessed using dual energy x-ray absorptiometry (DXA). This secondary purpose of the study was to identify any significant correlations between the measures of regional adiposity, physical activity, and cardiovascular risk factors. Methods: Forty-eight subjects, 19 males (48.7 ± 16.9 years) and 29 females (43.6 ± 16.2 years), volunteered to participate in this study. Subjects underwent laboratory testing compromised of resting blood pressure, blood lipid analysis, waist & hip circumference, total body DXA scan, and a one week physical activity assessment. Results: Significant correlations were observed between body mass index and region body fat % (r = 0.84, 0.79), waist circumference and android fat % (r = 0.79, 0.75), and waist-to-hip ratio and androidlgynoid ratio (r = 0.72, 0.61) for men and women, respectively. Fasting insulin was correlated with region body fat %, android body fat %, trunk body fat %, and the android/gynoid ratio. The android/gynoid ratio was correlated with high density lipoproteins, very low density lipoproteins, triglycerides, and fasting glucose. There was a statistically significant negative relationship observed between average steps per day and body mass index, waist circumference, hip circumference, region body fat %, android body fat %, and trunk body fat %. Conclusions: This study found that there are strong relationships between simple anthropometric measures and regional body fat measures from the DXA. According to the data in the present study, body mass index, waist circumference, and waist-to-hip ratio provide simple yet sensitive methods for the estimation of regional body fat in Caucasian males and females. In addition, this study found significant correlations between measures of the blood lipid profile, physical activity, and both simple anthropometric and DXA measures of regional body fat. Key words: android fat, body mass index, dual-energy x-ray absorptiometry, gynoid fat, obesity, waist circumference.School of Physical Education, Sport, and Exercise Science
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Hussein, Mahamoud Omar. "Magnetic resonance imaging and spectroscopy of fat emulsions in the gastrointestinal tract." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13582/.
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The relationship between meal structure and composition can modulate gastrointestinal processing and the resulting sense of satiety. This applies also to the fat component of meals and particularly to the surface area available for digestion. The main hypothesis underpinning this thesis work was that fat emulsion droplet size has a profound effect on fat digestion and, in turn, on the gastrointestinal and satiety responses. To test this hypothesis two fat emulsion meal systems were used. They had exactly the same composition but a small (termed the Fine emulsion, with a droplet size of 400 nm) or a large (termed the Coarse emulsion, with a droplet size of 8 μm) emulsified fat droplet size. The two fat emulsion systems were manufactured and characterised using a range of bench techniques, in vitro digestion models and MRI techniques in vitro. The difference in microstructure caused different temporal creaming characteristics for the emulsions and different percentage hydrolysis profiles in a gastric digestion model in vitro. The Fine emulsion showed initial rapid hydrolysis whilst the Coarse emulsion showed an initial slow hydrolysis phase with the hydrolysis rate increasing at later stages. This indicated that there was indeed a droplet size effect on fat hydrolysis whereby the smaller droplet size with a larger surface area hydrolysed faster than a larger droplet size. The emulsions’ performance was finally tested in vivo in healthy volunteers using MRI in a series of pilot studies leading to a main physiological study. Creaming differences in the gastric lumen were addressed by redesigning the meals using a locust bean gum (LBG) thickener that made them stable throughout the gastric emptying process. A main three-way physiological and satiety study in healthy volunteers showed that a highly emulsified, intragastrically stable emulsion delayed gastric emptying, increased small bowel water content and reduced consumption of food at the end of the study day. Finally, magnetic resonance imaging, relaxometry and spectroscopy were further evaluated to assess fat emulsion parameters in vitro and in vivo in the gastric lumen. Main static magnetic field and droplet size effects on T2 relaxation times of the Fine and the Coarse emulsions were observed. There was reasonable correlation between m-DIXON and spectroscopy methods to quantify fat fraction both in vitro and in vivo. Differences in T2 relaxation times for different droplet sizes of 20% fat emulsions were detected in vitro. These changes were however difficult to separate from creaming effects in vivo with a view of drawing meaningful inferences on droplet sizes. The main conclusion from this work was that manipulating food microstructure especially intragastric stability and fat emulsion droplet size can influence human gastrointestinal physiology and satiety responses and that MRI and MRS provide unique non invasive insights into these processes. This improved knowledge could help designing foods with desired health-promoting characteristics which could help to fight the rising tide of obesity.
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Costa, Yuri Ajala da. "A proposal for full-range fat fraction estimation using magnitude MR imaging." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-01102018-083519/.
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Current methods for estimation of proton density fat fraction (PDFF) of the liver using magnitude magnetic resonance (MR) imaging face the challenge of correctly estimating it when fat is the dominant molecule, i.e. PDFF is more than 50%. Therefore, the accuracy of the methods is limited to half-range operation. We introduce a method based on neural networks for regression capable of estimating over the full range of fat fractions. We built a neural network based on the angles and distances between the data in the discrete MR signal (ADALIFE), using these as features associated to different PDFFs and as input for the network. Tests were performed assessing ADALIFE against dual echo, triple echo, and especially Multi-interference, a state-of-the-art method to estimate PDFFs, with simulated signals at various signal-to-noise (SNR) values. Results were compared in order to verify repeatability and agreement using regression analysis, Bland-Altman and REC curves. Results for Multi-interference were similar to its in-vivo literature, showing the relevance of a simulation. ADALIFE was able to correctly estimate fat fractions up to 100%, breaking the current paradigm for full-range estimation using only off-line post processing. Within half-range, our method outperformed Multi-interference in repeatability and agreement, with narrower limits of agreement and lower expected error at any SNR.Os métodos atuais para estimação de gordura hepática por densidade de prótons (PDFF) utilizando imagem de magnitude de ressonância magnética (RM) enfrentam o desafio de estimar corretamente quando a gordura é a molécula dominante, ou seja, PDFF é maior que 50%. Assim, a acurácia desses métodos é limitada a meio intervalo de operação. Apresentamos aqui um método baseado em redes neurais para regressão capaz de estimar pelo intervalo completo de frações de gordura. Construímos uma rede neural baseada nos ângulos e distâncias entre os dados do sinal discreto da imagem de RM (ADALIFE), usando esses atributos associados a diferentes valores de PDFF, com sinais simulados considerando diferentes relações sinal-ruído (SNR). Resultados foram comparados para verificar a repetibilidade e concordância através de análise de regressão, Bland- Altman e curvas de característica de erro de regressão (REC). Resultados para o método Multi-interferência (estado-da-arte) foram similares aos relatados in vivo pela literatura, ressaltando a relevância das simulações. ADALIFE foi capaz de estimar corretamente frações de gordura até 100%, quebrando o paradigma para intervalo completo de operação utilizando apenas processamento posterior à aquisição de imagens ou sinais. Considerando meio intervalo, nosso método superou o estado-da-arte em termos de repetibilidade e concordância, com limites mais estreitos e menor erro esperado em qualquer SNR.
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Sigar, Joseph Aduol. "Visible hyperspectral imaging for predicting intra-muscular fat content from sheep carcasses." Thesis, Sigar, Joseph Aduol (2020) Visible hyperspectral imaging for predicting intra-muscular fat content from sheep carcasses. Honours thesis, Murdoch University, 2020. https://researchrepository.murdoch.edu.au/id/eprint/54744/.
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Intramuscular fat (IMF) content plays a key role in the quality attributes of meat, such as sensory properties and health considerations. The tenderness, flavour and juiciness of meat are examples of sensory attributes influenced by IMF content. Traditionally, IMF content in meat was determined using destructive, time consuming and at times unsuitable methods in industry applications. However, with recent advancement of technology, there has been an interest in exlporing ways to ascertain meat quality without damage. Hyperspectral imaging analysis is an emerging technology that combines the use of spectroscopy and computer imaging analysis to obtain both the spectral and spatial information of objects of interest. Hyperspectral imaging was initially developed for remote sensing, but has recently emerged as powerful tool for non-destructive analysis of quality in the food industry and has had very accurate results in the prediction of meat qualities such as IMF content. In this thesis, we use a data set of 101 hyperspectral images of sheep carcasses to investigate the ability of multivariate statistical methods to accurately predict IMF content.
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Bookwalter, Candice Anne. "CONTINUOUS SAMPLING IN MAGNETIC RESONANCE IMAGING." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1194049081.
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Berglund, Johan. "Separation of Water and Fat Signal in Magnetic Resonance Imaging : Advances in Methods Based on Chemical Shift." Doctoral thesis, Uppsala universitet, Enheten för radiologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158111.
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Magnetic resonance imaging (MRI) is one of the most important diagnostic tools of modern healthcare. The signal in medical MRI predominantly originates from water and fat molecules. Separation of the two components into water-only and fat-only images can improve diagnosis, and is the premier non-invasive method for measuring the amount and distribution of fatty tissue. Fat-water imaging (FWI) enables fast fat/water separation by model-based estimation from chemical shift encoded data, such as multi-echo acquisitions. Qualitative FWI is sufficient for visual separation of the components, while quantitative FWI also offers reliable estimates of the fat percentage in each pixel. The major problems of current FWI methods are long acquisition times, long reconstruction times, and reconstruction errors that degrade image quality. In this thesis, existing FWI methods were reviewed, and novel fully automatic methods were developed and evaluated, with a focus on fast 3D image reconstruction. All MRI data was acquired on standard clinical scanners. A triple-echo qualitative FWI method was developed for the specific application of 3D whole-body imaging. The method was compared with two reference methods, and demonstrated superior image quality when evaluated in 39 volunteers. The problem of qualitative FWI by dual-echo data with unconstrained echo times was solved, allowing faster and more flexible image acquisition than conventional FWI. Feasibility of the method was demonstrated in three volunteers and the noise performance was evaluated. Further, a quantitative multi-echo FWI method was developed. The signal separation was based on discrete whole-image optimization. Fast 3D image reconstruction with few reconstruction errors was demonstrated by abdominal imaging of ten volunteers. Lastly, a method was proposed for quantitative mapping of average fatty acid chain length and degree of saturation. The method was validated by imaging different oils, using gas-liquid chromatography (GLC) as the reference. The degree of saturation agreed well with GLC, and feasibility of the method was demonstrated in the thigh of a volunteer. The developed methods have applications in clinical settings, and are already being used in several research projects, including studies of obesity, dietary intervention, and the metabolic syndrome.
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Salvati, Roberto. "Development of Magnetic Resonance Imaging (MRI) methods for in vivo quantification of lipids in preclinical models." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1B026/document.
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L'obésité est associée à une augmentation de la morbidité et de la mortalité liée à de nombreuses maladies, y compris le diabète de type 2, l'hypertension et des pathologies hépatiques menant à une surcharge lipidique d’origine non alcoolique. Récemment, l’imagerie par résonance magnétique (IRM) est devenue la méthode de choix pour la quantification non invasive de la graisse. Dans cette thèse, les méthodes d'IRM ont été étudiées sur un scanner préclinique de 4.7T in vitro (fantômes MR) et in vivo (souris). Deux algorithmes de quantifications de la graisse -la méthode de Dixon et l’algorithme IDEAL- ont été considérés. Les performances de l'algorithme IDEAL ont été analysées en fonction de propriétés des tissus (T2*, fraction de graisse et modèle spectral de la graisse), de paramètres d'acquisition IRM (temps d’écho, nombre d'échos) et de paramètres expérimentaux (SNR et carte de champ). Sur les fantômes, l'approche standard single-T2* IDEAL a montré certaines limites qui pourraient être surmontées en optimisant le nombre d'échos. Une nouvelle méthode, pour déterminer les valeurs de vérité terrain pour T2* de l'eau et pour T2* de la graisse, a été proposée. Pour les mesures in vivo, différentes analyses ont été effectuées en utilisant l'algorithme IDEAL sur le foie et les muscles. L'analyse statistique sur les mesures de ROI a montré que le choix optimal du nombre d'échos est égal à trois pour la quantification de la graisse et six ou plus pour la quantification du T2*. Les valeurs de la fraction de graisse, calculées avec l'algorithme IDEAL, étaient statistiquement comparables aux valeurs obtenues avec la méthode de Dixon. Enfin, un procédé pour générer des signaux de référence mimant les systèmes eau-graisse (Fat Virtual Phantom MRI), sans l'aide d'objets physiques, a été proposé. Ces fantômes virtuels, qui présentent des caractéristiques de bruit réalistes, représentent une alternative intéressante aux fantômes physiques pour fournir un signal de référence dans les mesures IRMObesity is associated with increased morbidity and mortality linked to many diseases, including type 2 diabetes, hypertension and disease nonalcoholic fatty liver. Recently, 1H magnetic resonance imaging (MRI) has emerged as the method of choice for non-invasive fat quantification. In this thesis, MRI methodologies were investigated for in vitro (MR phantoms) and in vivo (mice) measurements on a 4.7T preclinical scanner. Two algorithms of fat quantifications – the Dixon’s method and IDEAL algorithm – were considered. The performances of the IDEAL algorithm were analyzed as a function of tissue properties (T2*, fat fraction and fat spectral model), MRI acquisition parameters (echo times, number of echoes) and experimental parameters (SNR and field map). In phantoms, the standard approach of single-T2* IDEAL showed some limitations that could be overcome by optimizing the number of echoes. A novel method to determine the ground truth values of T2* of water and T2* of fat was here proposed. For in vivo measurements, different analyses were performed using the IDEAL algorithm in liver and muscle. Statistical analysis on ROI measurements showed that the optimal choice of the number of echoes was equal to three for fat quantification and six or more for T2* quantification. The fat fraction values, calculated with IDEAL algorithm, were statistically similar to the values obtained with Dixon’s method. Finally, a method for generating reference signals mimicking fat-water systems (Fat Virtual Phantom MRI), without using physical objects, was proposed. These virtual phantoms, which display realistic noise characteristics, represent an attractive alternative to physical phantoms for providing a reference signal in MRI measurements
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Coe, Peter. "Validation and early qualification of pancreatic fat deposition as an imaging biomarker of pancreatic cancer risk." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/validation-and-early-qualification-of-pancreatic-fat-deposition-as-an-imaging-biomarker-of-pancreatic-cancer-risk(ff38a95b-f135-4bfe-b901-80d79c388974).html.
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Introduction: Pancreatic cancer is the 10th most common cause of cancer in the United Kingdom (UK) yet the 5th most common cause of cancer related death. Although excess adiposity, measured as body mass index (BMI), is a risk factor for the development of pancreatic cancer the increase in relative risk is modest. Animal models suggest that the intra-organ deposition of lipids may be more specific to disease risk than anthropometric measurements. There is therefore a need to develop non-invasive methods to quantify intra-pancreatic fat deposition as a potential biomarker for pancreatic cancer predisposition. Cancer Research UK (CRUK) sets out clear guidelines for biomarker discovery and development. Potential biomarkers must go through a process of discovery and assay development followed by qualification. Methods Three streams of research: (i) Stage-one of the PanORAMA project. Assessment of accuracy through comparison of CS-MR and MRS quantified intra-pancreatic fat with histologically quantified intra-pancreatic fat in 12 patients undergoing pancreatic surgery. (ii) Stage-two of the PanORAMA study. Assessment of precision (reproducibility) and comparison with other anthropometric markers of excess adiposity in healthy volunteers (n=15). Refinement of MRS protocols and repeated assessment of precision in healthy volunteers (n=10). (iii) The Breast Risk Reduction Intermittent Dietary Evaluation 2 (BRRIDE-2) trial. Comparison of the effects of Intermittent Energy Restriction (IER) with Daily Energy Restriction (DER) on intra-pancreatic and intra-hepatic fat stores and metabolic markers of disease risk (n=26). Results (i) CS-MR and MRS had agreement with histological assessment of intra-pancreatic fat, but correlations were only moderate to good (rho 0.672 and 0.781 respectively). (ii) CS-MR, and after refinement, MRS, have clinically acceptable precision. This study tested this principle in intra-pancreatic fat in healthy volunteers with a range of intra-pancreatic fat consistent with the literature on the healthy population. (iii) I found no differences in reduction in intra-hepatic or intra-pancreatic fat when comparing IER with DER. Overall, I found that significant reductions (mean: 6.5%) in both of these ectopic fat stores could be achieved with eight-weeks of dietary intervention. Discussion More recent hypotheses on the link between excess adiposity and cancer have focused on the importance of within organ local ectopic fat as an abnormal micro-environment favouring cancer development and progression. Importantly, this hypothesis explains the specificity of epidemiological associations between excess adiposity and cancer risk. The observations that within a given individual, in the presence of short-term weight reduction, there are differential changes in local within organ fats – hepatic fat and pancreatic fat – support the specificity hypothesis. This thesis has put us in position to scale-up and explore the importance of intra-organ fats using non-invasive imaging techniques.
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Nakatsu, Masashi. "Comparison of Short Inversion Time Inversion Recovery(STIR)and Fat-Saturated(chemsat)Techniques for Background fat Intensity Suppression in Cervical and Thoracic MR Imaging." Kyoto University, 2001. http://hdl.handle.net/2433/150168.
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Breda, Vriesman Adriaan Cornelius van. "Infarction and idiopathic inflammation of intraperitoneal fat implications of diagnostic imaging of the acute abdomen /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/74362.
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Sun, Ling. "3D Mellisa : a new three dimensional fat/water image acquisition technique for magnetic resonance imaging /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487854314873059.
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Shibahara, Eriko, Hiroshi Fukatsu, Shinji Naganawa, Tokiko Ito, Eriko Iwayama, Takeo Ishigaki, Toru Segawa, and Waguo Zhang. "Water fat separation using the single acquisition "sandwich" type 3-point Dixon method to optimize knee joint scans." Nagoya University School of Medicine, 2000. http://hdl.handle.net/2237/5354.
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Johnson, David Herbert. "Phenotyping Rodent Models of Obesity Using Magnetic Resonance Imaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1250086728.
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Peng, Qi. "Novel chemically selective rapid magnetic resonance imaging techniques and the clinical applications." Access to abstract only; dissertation is embargoed until after 12/20/2006, 2005. http://www4.utsouthwestern.edu/library/ETD/etdDetails.cfm?etdID=136.
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Alexander, Heather. "An evaluation of B mode ultrasound in the measurement of subcutaneous fat and muscle in lean and obese subjects." Thesis, Queensland University of Technology, 1991. https://eprints.qut.edu.au/35974/1/35974_Alexander_1991.pdf.
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The measurement of subcutaneous fat thickness is widely
used to calculate the percentage of body mass that is fat and
also to estimate the distribution of that fat. Skinfold
calipers are used in both research and clinical practice, but
assumptions underlying the calculations of total body fat
from caliper measurements have been shown to be incorrect.
Calipers cause variable compression of fat between sites and
individuals, and cannot measure fat folds over 40mm. The
variance of caliper measurements tends to increase with
increasing fat thickness.
Ultrasound has the potential to be a useful measure of
fat at any body site. It can measure any depth of fat; it
does not compress fat; test-retest variance does not vary
significantly with the thickness of the fatfold; it can
simultaneously measure underlying muscle; and it has recently
been applied to the measurement of internal fat as well as
subcutaneous fat at the abdominal site.
There are methodological differences in published
studies using B mode ultrasound to measure fat and muscle.
The first study of this thesis investigated these
differences, and established a protocol for using B mode
ultrasound in lean subjects. The test-retest reliability of
ultrasound measurements of fat was comparable to that of
skinfold calipers. The test-retest reliability of ultrasound
muscle measurements was less than for the fat measurements,
and the protocol may need revision. B mode ultrasound was
used to develop new methods for the measurement of lower
abdominal subcutaneous fat, and to investigate fascial planes
within the subcutaneous fat layer,
Few studies have reported reliability of
ultrasound in obese subjects, or its use to measure body
composition changes with weight change. The second study of
this thesis addressed these issues, and confirmed that the
reliability of ultrasound measurements of subcutaneous fat
was the same in both lean and obese female subjects. A clear
fascial plane was observed in the subcutaneous fat at the
triceps and abdominal sites in this group. The superficial
and deep fat layers showed different correlations with the
body mass index. This study compared longitudinal data on
ultrasound and caliper measurements in obese subjects
undergoing weight change.
The site for abdominal measurements was developed
during this project, but the relationship between the
subcutaneous fat at this site to indices of adiposity varied
from results of published studies. Computed tomography
abdominal scans in a group of male and female subjects,
confirmed results of the ultrasound measurements.
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Mendoza, Michael A. "Water Fat Separation with Multiple-Acquisition Balanced Steady-State Free Precession MRI." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4304.
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Magnetic resonance imaging (MRI) is an important medical imaging technique for visualizing soft tissue structures in the body. It has the advantages of being noninvasive and, unlike x-ray, does not rely on ionizing radiation for imaging. In traditional hydrogen-based MRI, the strongest measured signals are generated from the hydrogen nuclei contained in water and fat molecules.Reliable and uniform water fat separation can be used to improve medical diagnosis. In many applications the water component is the primary signal of interest, while the fat component represents a signal which can obscure the underlying pathology or other features of interest. In other applications the fat signal is the signal of interest. There currently exist many techniques for water fat separation. Dixon reconstruction techniques take multiple images acquired at select echo times with specific phase properties. Linear combinations of these images produce separate water and fat images. In MR imaging, images with high signal-to-noise ratio (SNR), that can be generated in a short time, are desired. Balanced steady-state free precession (bSSFP) MRI is a technique capable of producing images with high SNR in a short imaging time but suffers from signal voids or banding artifacts due to magnetic field inhomogeneity and susceptibly variations. These signal voids degrade image quality. Several methods have been developed to remove these banding effects. The simplest methods combine images across multiple bSSFP image acquisitions. This thesis describes a technique in water fat separation I developed which combines the advantages of bSSFP with Dixon reconstruction in order to produce robust water fat decomposition with high SNR in a short imaging time, while simultaneously reducing banding artifacts which traditionally degrade image quality. This algorithm utilizes four phased-cycled bSSFP acquisitions at specific echo times. Phase sensitive post-processing and a field map are used to prepare the data and reduce the effects of field inhomogeneities. Dixon reconstruction is then used to generate separate water and fat images.
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Knight, Caroline L. "Antenatal characterisation and postnatal validation of fetal nutritional status using novel fetal imaging methods, neonatal body composition data, and anthropometry." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:11107be6-35ea-4d6d-9161-ddee4cde1b3e.
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Background: Fetal growth restricted (FGR) infants have increased perinatal morbidity and mortality risks. Standard fetal biometry may identify some FGR babies; amniotic fluid measurement and Doppler assessment of blood vessels provide additional, functional assessments, but are often normal in babies with late-onset FGR who are difficult to diagnose. A marker reflecting nutritional status should help to identify FGR fetuses, enabling effective intervention: increased monitoring or delivery and neonatal management. Arm and/or thigh measurements have previously shown potential in 2D and 3D. Limb fat volume has never been measured and could provide an in utero marker of fetal nutritional status. Aims: 1. To develop an ultrasound scanning protocol to acquire 2D images and 3D volumes of fetal arms and thighs. 2. To develop method(s), suitable for use in clinical practice, to measure fat in these images and volumes. 3. To assess the reproducibility of these methods. 4. To assess the validity of these methods by comparing them with MRI images of fetal limb fat. 5. To use these methods in a healthy population to develop reference ranges. 6. To correlate these methods with validated neonatal measurements, to assess whether the antenatal methods reflect neonatal body composition. 7. To apply these methods to longitudinal prospective ultrasound images from multiple countries to assess SGA fetuses. Method: Ultrasound imaging protocols were developed to obtain accurate images and volumes of fetal arms and thighs. Segmentation tools were designed with biomedical engineers to measure fat, lean and limb compartments, and applied to 2D images and 3D volumes (n=500), with calculation of reference centiles in optimally healthy women (INTERGROWTH-21st study) and MRI validation of the ultrasound measurements. Additional methods were assessed: a two-ellipse method, and a three-thickness Fetal Fat Index (FFI). Reproducibility was assessed using Bland-Altman plots and ICCs. Fetal measurements were correlated with neonatal body composition data and anthropometry. Third trimester fetal thigh fat volumes were compared in sub-cohorts of AGA and SGA fetuses. Results: Reference centiles were calculated for novel fractional arm and leg volumes (fat and lean), from 16 to 41 weeks. 2D reference ranges were also calculated. The FFI technique - quick, simple, 2D - correlated well with fat area and fat volume. DXA analyses showed a strong correlation between neonatal limb and whole body fat. Correlation analyses showed that infants with above- and below-average arm circumferences have significantly different amounts of arm fat as early as 30-35 weeks. The strength of correlation between antenatal limb fat and neonatal PEA POD whole body fat increased with increasing gestational age. Scans at 30-34 weeks showed a significant difference in fractional thigh fat between those who would be born SGA compared with AGA. Conclusion: This thesis explores, in detail, the measurement of fetal arm and thigh fat using 2D and 3D ultrasound, and demonstrates that it is correlated to neonatal body composition thus allowing 'fetal body composition' to be established as a research tool; the ultimate aim is to be able to distinguish growth-restricted fetuses from those of normal nutritional status. Novel measurements have been developed, acquisition protocols described, reproducibility assessed, and reference centiles calculated in an optimally healthy population: 2D Fetal Fat Index, 3D fractional limb fat and lean volumes, and limb fat (2D and 3D) as a percentage.
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Belbaisi, Adham. "Deep Learning-Based Skeleton Segmentation for Analysis of Bone Marrow and Cortical Bone in Water-Fat Magnetic Resonance Imaging." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297528.
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A major health concern for subjects with diabetes is weaker bones and increased fracture risk. Current clinical assessment of the bone strength is performed by measuring Bone Mineral Density (BMD), where low BMD-values are associated with an increased risk of fracture. However, subjects with Type 2 Diabetes (T2D) have been shown to have normal or higher BMD-levels compared to healthy controls, which does not reflect the recognized bone fragility among diabetics. Thus, there is need for more research about diabetes-related bone fragility to find other factors of impaired bone health. One potential biomarker that has recently been studied is Bone Marrow Fat (BMF). The data in this project consisted of whole-body water-fat Magnetic Resonance Imaging (MRI) volumes from the UK Biobank Imaging study (UKBB). Each subject in this data has a water volume and a fat volume, allowing for a quantitative assessment of water and fat content in the body. To analyze and perform quantitative measurements of the bones specifically, a Deep Learning (DL) model was trained, validated, and tested for performing fully automated and objective skeleton segmentation, where six different bones were segmented: spine, femur, pelvis, scapula, clavicle and humerus. The model was trained and validated on 120 subjects with 6-fold cross-validation and tested on eight subjects. All ground-truth segmentations of the training and test data were generated using two semi-automatic pipelines. The model was evaluated for each bone separately as well as the overall skeleton segmentation and achieved varying accuracy, performing better on larger bones than on smaller ones. The final trained model was applied on a larger dataset of 9562 subjects (16% type 2 diabetics) and the BMF, as well as bone marrow volume (BMV) and cortical bone volume (CBV), were measured in the segmented bones of each subject. The results of the quantified biomarkers were compared between T2D and healthy subjects. The comparison revealed possible differences between healthy and diabetic subjects, suggesting a potential for new findings related to diabetes and associated bone fragility.
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Palosaari, K. (Kari). "Quantitative and semiquantitative imaging techniques in detecting joint inflammation in patients with rheumatoid arthritis:phase-shift water-fat MRI method for fat suppression at 0.23 T, contrast-enhanced dynamic and static MRI, and quantitative 99mTc-nanocolloid scintigraphy." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514288623.
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Abstract
The purpose of this study was to evaluate the value of 0.23T low-field magnetic resonance imaging (MRI) and nanocolloid (NC) scintigraphy in assessing joint pathology associated with rheumatoid arthritis (RA).
Fat suppression methods combined with contrast media enhancement aid in distinguishing enhancing inflamed tissue from the surrounding fat, especially in the imaging of arthritic joints. The feasibility and image quality of a phase-shift water-fat MRI method for fat suppression at low-field 0.23T open configuration MR scanner was evaluated. The technique was combined with contrast-enhanced imaging to assess the conspicuity of synovial hypertrophy in the joints of 30 RA patients. Improved conspicuity and delineation of synovitis was detected with this method. However, because of a great amount of manual post processing, future development is needed to make this method more feasible.
Contrast-enhanced MRI and NC scintigraphy may provide objective and quantitative information about the inflammatory activity in arthritic joints. The value of quantitative and semiquantitative measures of inflammation derived from NC scintigraphy and low-field MRI of the wrist joint of 28 early RA patients was evaluated. Furthermore, it was investigated whether these parameters have predictive value of further erosive development during two years of follow-up.
Strong correlations were detected between the NC scintigraphy and MRI measures, and these parameters were associated with laboratory markers of inflammation. During the two-year follow-up, the initial MRI and NC scintigraphy measures were closely related with the progression of wrist joint erosions.
Small erosive-like bone defects can occasionally be found in wrist MRI of patients without clinically overt arthritis. The prevalence of these lesions was studied in bilateral wrist MRI examinations of 31 healthy persons. Small lesions resembling erosions were detected in 14 out of 31 subjects. Altogether 24 of the 930 wrist bones evaluated showed such lesions (3%). Thus small changes resembling erosions can be found in the wrist MRI of healthy subjects; the significance of these findings must always be interpreted with reference to the clinical picture.
In conclusion, early RA patients with high local inflammatory activity, as detected by NC scintigraphy and MRI are at risk of developing further bone damage. Furthermore, in the follow-up of early RA patients, if clinically sustained response is not achieved, these methods help to identify patients who need more intensive drug treatment.
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Dowdy, Regina Alma Evelyn. "Using Computed Tomography to Predict Difficult Tracheal Intubation." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586195479987532.
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Rakoczy, Ryan J. "Measuring the Effects of High-Fat Diet on Breathing and Oxygen-Sensitivity of the Carotid Body Type I Cell." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1505728876488752.
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Salomão, Heloise Zanelatto Neves. "Seguimento mamográfico após reconstrução imediata com lipoenxertia em pacientes submetidas a cirurgia conservadora de mama e radioterapia." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/150714.
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Introdução: Os enxertos de gordura autóloga (lipoenxertia) são utilizados há muito tempo como material de preenchimento para correção de defeitos de tecido mole, sendo inicialmente utilizados para correção de defeitos faciais. Nos últimos anos, houve um crescente interesse no uso da lipoenxertia em mamas, tanto como método de reconstrução em pacientes submetidas a cirurgias por câncer de mama quanto em procedimentos estéticos. A gordura é considerada um material de preenchimento ideal em decorrência da facilidade de obtenção e da baixa reação imunogênica e alérgica, além de se tratar de material autólogo. Os principais problemas da lipoenxertia são as taxas de reabsorção imprevisíveis do material enxertado (40-60%), a preocupação quanto a sua segurança, principalmente pela hipótese de a gordura estimular o crescimento de células cancerígenas e o fato da necrose do material enxertado poder produzir fibrose, calcificações ou cistos oleosos na mama, os quais poderiam interferir na interpretação das imagens mamográficas. A partir da técnica desenvolvida por Coleman, diversos estudos surgiram mostrando a eficácia e a segurança da lipoenxertia, já que a mesma não parece interferir nas imagens radiológicas, demonstrando que alterações mamográficas após a lipoenxertia são facilmente interpretadas como alterações benignas por radiologistas experientes. Objetivo: Analisar se a lipoenxertia realizada durante a cirurgia conservadora por câncer de mama e posteriormente seguida de radioterapia causa modificações mamográficas. Método: Foi realizado seguimento de 171 pacientes com diagnóstico de câncer inicial submetidas a tratamento conservador e radioterapia no Hospital de Clínicas de Porto Alegre, no período de junho de 2010 a junho de 2013. Trinta e oito dessas pacientes foram submetidas a reconstrução imediata com lipoenxerto segundo a técnica de Coleman. Resultados: A média da idade das pacientes foi de 58,9 anos para as pacientes sem lipoenxerto e 52,5 anos para as com lipoenxerto, e a média do volume enxertado foi de 125 mL. Foram analisadas as alterações mamográficas dessas pacientes 6, 12, 18 e 24 meses após a radioterapia. Constatou-se uma maior incidência de alterações benignas, como cistos oleosos e esteatonecrose, nas pacientes submetidas a lipoenxertia. Não se detectou no presente estudo diferenças quanto a frequência de nódulos, achados suspeitos ou na classificação BI-RADS entre as pacientes com e sem lipoenxerto. Conclusão: Conclui-se, portanto, que a lipoenxertia causa alterações mamográficas facilmente percebidas como benignas, sem elevar a incidência de achados inconclusivos ou suspeitos. Trata-se de um estudo inédito, pois a reconstrução mamária com gordura é realizada no momento da cirurgia conservadora.Background: Fat grafts have been used for a long time as a filling material for correction of soft tissue defects. There is growing interest in the use of fat grafting as a method of breast reconstruction in patients undergoing surgery for breast cancer. Fat is considered an ideal filler material due to its easy availability and low immunogenic and allergic reaction and because it is an autologous material. However, fat grafts often have high rates of reabsorption and replacement by fibrous scar tissue, calcifications or oily cysts, which can generate sequels and difficulties in the interpretation of radiological images of the breast. Based on the technique developed by Coleman, several studies have emerged showing the efficacy of fat grafting and that it does not seem to interfere with the early diagnosis of breast cancer. Studies have shown that the incidence of mammographic changes after fat grafting does not differ from other surgical procedures of the breast and that they are easily interpreted as benign changes by experienced radiologists in breast imaging. Aim: Analyze mammographic changes in fat grafting performed during conservative surgery for breast cancer and subsequently followed by radiotherapy. Methods: A total of 171 patients diagnosed with early-stage cancer who received conservative treatment and radiotherapy at the Hospital de Clínicas de Porto Alegre from June 2010 to July 2013 were followed in the present study. Thirty-eight of these also underwent immediate reconstruction with fat grafting, as described by Coleman. Results: Mean patient age was 58.9 years for those not exposed to lipomodeling, and 52.5 years in the remainder of the sample. The mean graft volume was 125 ml. In the present study, oncological follow-ups at 6, 12, 18 and 24 months revealed a higher incidence of benign mammographic findings, such as oil cysts and steatonecrosis, in women who had undergone lipomodeling. However, no between-group differences were identified on any other radiological parameter, including scarring, nodules, suspicious findings and BI-RADS categories. Conclusion: These findings suggest that the mammography alterations caused by lipomodeling are easily identified as benign, and that this procedure is not associated with an increased incidence of inconclusive or suspicious findings. This is a unique study because breast reconstruction with fat is conducted at the time of conservative surgery.
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Anderl, Ines. "Activation of the Cellular Immune Response in Drosophila melanogaster Larvae." Doctoral thesis, Umeå universitet, Institutionen för molekylärbiologi (Medicinska fakulteten), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-106981.
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During the last 40 years, Drosophila melanogaster has become an invaluable tool in understanding innate immunity. The innate immune system of Drosophila consists of a humoral and a cellular component. While many details are known about the humoral immune system, our knowledge about the cellular immune system is comparatively small. Blood cells or hemocytes constitute the cellular immune system. Three blood types have been described for Drosophila larvae. Plasmatocytes are phagocytes with a plethora of functions. Crystal cells mediate melanization and contribute to wound healing. Plasmatocytes and crystal cells constitute the blood cell repertoire of a healthy larva, whereas lamellocytes are induced in a demand-adapted manner after infection with parasitoid wasp eggs. They are involved in the melanotic encapsulation response against parasites and form melanotic nodules that are also referred to as tumors. In my thesis, I focused on unraveling the mechanisms of how the immune system orchestrates the cellular immune response. In particular, I was interested in the hematopoiesis of lamellocytes. In Article I, we were able to show that ectopic expression of key components of a number of signaling pathways in blood cells induced the development of lamellocytes, led to a proliferative response of plasmatocytes, or to a combination of lamellocyte activation and plasmatocyte proliferation. In Article II, I combined newly developed fluorescent enhancer-reporter constructs specific for plasmatocytes and lamellocytes and developed a “dual reporter system” that was used in live microscopy of fly larvae. In addition, we established flow cytometry as a tool to count total blood cell numbers and to distinguish between different blood cell types. The “dual reporter system” enabled us to differentiate between six blood cell types and established proliferation as a central feature of the cellular immune response. The combination flow cytometry and live imaging increased our understanding of the tempo-spatial events leading to the cellular immune reaction. In Article III, I developed a genetic modifier screen to find genes involved in the hematopoiesis of lamellocytes. I took advantage of the gain-of-function phenotype of the Tl10b mutation characterized by an activated cellular immune system, which induced the formation blood cell tumors. We screened the right arm of chromosome 3 for enhancers and suppressors of this mutation and uncovered ird1. Finally in Article IV, we showed that the activity of the Toll signaling pathway in the fat body, the homolog of the liver, is necessary to activate the cellular immune system and induce lamellocyte hematopoiesis.
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Olhager, Elisabeth. "Studies on adipose tissue, body fat, body water and energy expenditure during the first four months of infancy using magnetic resonance imaging, skinfold measurements and the doubly labelled water method /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/med798s.pdf.
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Bianchini, Mariaelvy [Verfasser], and Sabine [Akademischer Betreuer] Steffens. "Imaging hematopoietic cells in their native environments : application of TPLSM to study HSCs and monocyte biology in Bone Marrow and Fat-Associated Lymphoid Clusters / Mariaelvy Bianchini ; Betreuer: Sabine Steffens." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1221061917/34.
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MURTAJ, VALENTINA. "GENDER, AGE AND METABOLIC DYSFUNCTION AS RISK FACTOR FOR NEUROINFLAMMATORY DISEASES." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/306486.
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L'elevata prevalenza di disturbi metabolici e cognitivi rappresenta uno dei maggiori problemi della salute umana. Recenti scoperte indicano che l'obesità può influenzare le funzioni cerebrali, tuttavia l'effetto di una dieta ricca di grassi sul sistema nervoso centrale non è ancora completamente compreso. Lo scopo di questo studio è la valutazione dell'influenza della dieta grassa sulla neuro infiammazione e sulla funzione cerebrale regionale in un modello murino di insulino-resistenza, con particolare attenzione alle differenze dipendenti dal sesso.
I topi maschi e femmine C57BL/6J sono stati nutriti con dieta standard o dieta grassa (due tenori: 45% / 60% di grassi) per 35 settimane. Gli animali sono stati monitorati settimanalmente per analizzare le variazioni di peso corporeo, analisi ematochimiche (glucosio circolante, colesterolo totale, ALT e AST) e test di tolleranza al glucosio. Gli studi di imaging con tomografia a emissione di positroni (PET) sono stati eseguiti longitudinalmente utilizzando [18F] -FDG e [18F] -VC701 come radio-traccianti, per misurare rispettivamente il consumo di glucosio e l'attivazione di microglia / macrofagi all'interno del cervello. La risonanza magnetica (RM) e la spettroscopia a risonanza magnetica (SRM) sono state utilizzate per misurare gli effetti della dieta sul contenuto lipidico epatico e sull'accumulo di grasso peri addominale. Infine, l'analisi della trascrittomica post-mortem è stata applicata alla corteccia anteriore al fine di rivelare potenziali modifiche nell'espressione genica.
La dieta grassa introduce in modo significativo un aumento del peso corporeo, della tolleranza al glucosio e dei parametri ematochimici che variano in base al sesso. Anche l'accumulo di grasso peri addominale nel maschio e il contenuto di lipidi nel fegato, come rivelato alla spettroscopia RM, sono stati osservati in tale modello. Quest'ultimo effetto è stato particolarmente evidente nelle femmine. La PET [18F]-FDG ha mostrato un aumento relativo del metabolismo del glucosio nella regione anteriore del cervello, inclusi i bulbi olfattivi sia nei topi maschi che in quelli femmine, mentre l'aumento osservato nella corteccia anteriore è stato riscontrato solamente nei topi maschi alimentati con il 60% di dieta grassa. Inoltre, l'analisi della correlazione tra l'assorbimento del glucosio cerebrale e i diversi biomarcatori metabolici ha rivelato, principalmente nei topi maschi, modificazioni metaboliche cerebrali regionali associate a valori di BMI e parametri ematochimici. Lo studio PET condotto con il tracciante [18F]-VC701 ha mostrato una tendenza generale verso un aumento dell'assorbimento del tracciante in tutto il cervello dopo il consumo di dieta grassa nei topi maschi e femmine. L'analisi della trascrittomica nella corteccia anteriore ha mostrato una comune de-regolazione dei geni associati allo sviluppo del sistema nervoso, ma anche modificazioni specifiche legate al sesso.
Il nostro studio suggerisce che l'obesità indotta da regime alimentare di dieta grassa nei topi adulti, causa un deterioramento metabolico generale non confinato alla periferia ma che coinvolge anche regioni cerebrali selezionate. L'aumento del segnale del tracciante per la proteina TSPO suggerisce che l'obesità può indurre una reazione neuro-infiammatoria diffusa nel cervello dei topi di entrambi i sessi. La tecnica di imaging PET è stata usata per identificare la presenza di squilibrio metabolico e risposta neuro-infiammatoria del cervello di topo sotto regime alimentare di dieta grassa. Questo dato è rilevante poiché il nostro modello riproduce le alterazioni metaboliche periferiche tipiche della sindrome di insulino resistenza e del diabete di tipo 2.The high prevalence of metabolic and cognitive disorders represents one of the major issues of health systems. Recent findings indicate that obesity may affect brain functions however the effect of a high-fat diet (HFD) on the central nervous system is not fully understood. The aim of this study is the evaluation of the influence of HFD on neuroinflammation and regional brain function in a mouse model of Insulin Resistance (IR) focusing on sex-dependent differences induced by peripheral metabolic impairment. C57BL/6J male and female mice were fed with standard chow or HFD (45%/60%) for 35 weeks. Animals were monitored weekly for body weight, haemato-chemical analysis (circulating glucose, total cholesterol, ALT, and AST), and glucose tolerance test (GTT). Positron Emission Tomography (PET) imaging studies were performed longitudinally using [18F]-FDG and [18F]-VC701 as radiotracers, to measure respectively glucose consumption and microglia/macrophages activation within the brain. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) was used to measure the effects of diet on hepatic lipid content and peri abdominal fat accumulation. Finally, post-mortem transcriptome analysis was applied to the anterior cortex to reveal potential modification in gene expression. HFD induced a significant increase in body weight, glucose tolerance, and haemato-chemical parameter in a sex dependent manner. HFD diet increased peri abdominal fat accumulation in male and lipid content in the liver as revealed at MR spectroscopy. This last effect was particularly evident in females. PET [18F]-FDG showed a relative increase in glucose metabolism in the anterior region of the brain including the olfactory bulbs in both male and female mice while an increase in the anterior cortex was found in males mice fed with 60% HFD. Moreover, correlation analysis between glucose uptake and different metabolic biomarkers revealed, mainly in male mice, regional brain metabolic modifications associated with BMI values and haemato-chemical parameters. [18F]-VC701-PET showed a general trend toward an increase of tracer uptake all over the brain after diet consumption in both male and female HFD mice. Anterior cortex transcriptome analysis showed a common de-regulation of genes related to nervous system development but also sex-specific modifications. Our finding suggests that HFD induced obesity in adult mice causes a general metabolic impairment not confined in the periphery but involving also selected brain regions. The increased binding of the activated microglia associated with TSPO radioligand suggests that obesity can induce a diffuse neuro-inflammatory reaction in mice's brains. PET imaging technique is permitted to identify the presence of metabolic derangement and the neuro-inflammatory response of mice brain induced by HFD. This finding is relevant since our model reproduces the peripheral metabolic modification typical of IR and type 2 diabetes.
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Daudé, Pierre. "Quantification du tissu adipeux épicardique à haut champ par IRM-Dixon, pour le phénotypage de la cardiomyopathie diabétique." Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0333.
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L’amélioration de la prise en charge des complications cardiaques dans les maladies métaboliques, obésité et diabète, est un enjeu majeur de notre société. La mesure du tissu adipeux épicardique (TAE), dépôt de graisse attaché au cœur, est un élément diagnostique émergent et prometteur pour identifier les patients à risque. Nous avons développé l’automatisation de cette mesure sur des images IRM de routine par apprentissage profond. Puis, une technique IRM innovante a été proposée pour mesurer et caractériser le TAE en 3D, réunissant : une acquisition en respiration libre, une reconstruction des images robuste au mouvement cardio-respiratoire et aux imperfections de l’IRM, un algorithme de caractérisation de la graisse optimisé et validé et la connaissance de la composition d’échantillons ex-vivo de TAE. L’ensemble permet la caractérisation in vivo et non-invasive du TAE, élément diagnostique novateur du risque cardio-métaboliqueImproving the management of cardiac complications in metabolic diseases, obesity and diabetes, is a major challenge for our society. The measurement of epicardial adipose tissue (EAT), a fat depot attached to the heart, is an emerging and promising diagnosis to identify patients at risk. We developed the automation of this measurement on routine MRI images by deep learning. Then, an innovative MRI technique was proposed to measure and characterize the EAT in 3D, combining: a free-breathing acquisition, an image reconstruction robust to cardio-respiratory motion and MRI imperfections, an optimized and validated fat characterization algorithm and the knowledge of the composition of ex-vivo EAT samples. Together, this allows for in vivo, non-invasive characterization of EAT, a novel diagnosis for cardiometabolic risk
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Ruschke, Stefan Albert [Verfasser], Dimitrios [Akademischer Betreuer] Karampinos, Dimitrios [Gutachter] Karampinos, Axel [Gutachter] Haase, and Marion I. [Gutachter] Menzel. "Quantification of Proton Density Fat Fraction and Fatty Acid Composition of Triglycerides in Musculoskeletal Tissues using Magnetic Resonance Imaging and Spectroscopy / Stefan Albert Ruschke ; Gutachter: Dimitrios Karampinos, Axel Haase, Marion I. Menzel ; Betreuer: Dimitrios Karampinos." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/116879854X/34.
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Dieckmeyer, Michael [Verfasser], Thomas [Akademischer Betreuer] Baum, Dimitrios C. [Gutachter] Karampinos, Jan S. [Gutachter] Kirschke, and Thomas [Gutachter] Baum. "Quantitative Magnetic Resonance Imaging and Spectroscopy of Vertebral Bone Marrow: Addressing Confounding Effects in the Measurement of Fat Fraction and Apparent Diffusion Coefficient / Michael Dieckmeyer ; Gutachter: Dimitrios C. Karampinos, Jan S. Kirschke, Thomas Baum ; Betreuer: Thomas Baum." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1201086248/34.
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Harvey, P. R. "Hyper-fast NMR imaging." Thesis, University of Nottingham, 1991. http://eprints.nottingham.ac.uk/13753/.
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The work presented in this thesis was carried out in the Physics Department at the University of Nottingham between October 1988 and October 1991. It is the original work of the author except where indicated by reference. This thesis describes the continuation of the development of Echo Volumar Imaging (EVI) to facilitate snapshot imaging of a volume within the human body. Variants of the technique which have also been investigated include a spin echo version, SE-EVI, and a zoomed version ZEVI. All formats acquired data in a modulus fashion in times ranging from 64 ms to 120 ms. Hardware limitations have restricted the image matrix size to 64 x 32 x 8 voxels and prompted the employment of more efficient gradient driver circuitry. A multi-mode resonant gradient circuit is described for use in both Echo Planar Imaging (EPI) and EVI. The circuit behaves in an overall resonant manner but at a fixed number of discrete frequencies. By choosing the number of resonant modes, the circuit can be used to generate approximations to a square wave or trapezoidal waveform. Because of the energy conserving nature of the circuit design much faster current rise times can be achieved with a given amplifier and gradient coil. The multi-mode gradient driver circuit was utilized both for planar imaging and to investigate the effect of rapidly modulated magnetic fields on the human body. A simple neural stimulation model is used to evaluate the stimulation threshold current density for a variety of magnetically induced waveforms and for sinusoidal stimulation as a function of frequency. Experimental results correlate well with the model showing that for short times, contrary to the widely held view, neural stimulation is independent of the magnetic field switching rate dB / dt, but depends on the final magnetic field value.
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Lee, Kuan Jin. "Fast magnetic resonance imaging." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397487.
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Fleming, Matthew James. "Far-field resolution imaging." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497730.
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Wave based imaging methods aim to build an accurate reconstruction of the physical properties of an object by recording the scattered field caused by illumination from multiple directions. Classically the minimum distance between the characteristics of the object that can be resolved by an imaging method is limited by the wavelength, λ, of the interrogating field. In order to improve the resolution shorter wavelengths can be propagated; however, due to material absorption, this limits the penetration depth of the wave which consequently reduces the potential imaging range. Any imaging technique which can overcome the resolution limit is of great practical and academic interest and represents the subject of this thesis. Subwavelength characterisation has become well established in the field of Near- field Scanning Optical Microscopy which requires part of the probing system to be within λ of the object being illuminated (near field), in order to detect the nonpropagating evanescent waves. The super-oscillatory properties of the evanescent waves are subsequently used to achieve subwavelength resolution. However, access to the near field of an object is not always feasible and since evanescent waves decay exponentially they cannot be directly detected in the far field (greater than λ from the object). The aim of this thesis is to define and investigate an imaging strategy that will allow super resolution to be achieved from the far field. Conventional imaging techniques, which are constrained by the resolution limit, neglect the distortion of the scattered field caused by the internal structure of the object. This thesis will show that a more accurate description of the interaction of the incident field with the object, which includes the multiple scattering of evanescent waves, can lead to subwavelength resolution from the far field.
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Tu, Ning. "Fast imaging with surface-related multiples." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54592.
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Surface-related multiples, which are waves that bounce more than once between the water surface and the subsurface reflectors, constitute a significant part of the data acquired in marine seismic surveys. If left untreated, they can lead to misplaced phantom reflectors in the image, and result in erroneous interpretations of the subsurface structure. As a result, these multiples are removed before the imaging procedure in conventional seismic data processing. However, because they interact more with the subsurface medium, they may carry extra information that is not present in the primaries. Therefore instead of removing these multiples, a more desirable alternative is to make active use of them. We derive from the well- established "Surface-Related Multiple Elimination" relation, and arrive at a linearized expression of the wave-equation based modelling that incorporates the surface- related multiples. We then present a computationally efficient approach to iteratively invert this expression to obtain an image of the subsurface from data that contain multiples. We achieve the computational efficiency inside each iteration by (i) using the wave-equation solver to implicitly carry out the expensive multiple prediction; and (ii) reducing the number of wave-equation solves during data simulation by subsampling the monochromatic source experiments. We show that, compared with directly applying the cross-correlation/deconvolutional imaging conditions, the presented approach can suppress the coherent imaging artifacts from multiples more effectively. We also show that, by curvelet-domain sparsity promoting and occasionally drawing new data samples during the inversion, the proposed inversion method gains improved robustness to velocity errors in the background model, as well as modelling errors incurred during linearization of the wave-equation. To combine the information encoded in both the primaries and the multiples, we then propose a highly accurate source estimation method to jointly invert the total upgoing wavefield. We show with field data examples that we can reap benefits from both the relative noise-free primaries and the extra illumination coverage of the multiples. We also demonstrate that the inclusion of multiples help mitigate the amplitude ambiguity during source estimation. We conclude the thesis with an outlook for future research directions, as well as potential extensions of the proposed work.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Aletras, Anthony Homer. "Ultra-Fast Imaging with Echo Planar Techniques /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933245538532.
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Bueno, Lucian Soares. "Aquisição rápida de imagens com técnicas tipo Echo Planar Imaging - Implementação das sequências EPI e SEPI." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-12112007-092645/.
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O objetivo deste trabalho é o desenvolvimento e implementação de metodologias de imagens por Ressonância Magnética Nuclear, para diminuição do tempo de aquisição, já que nos exames clínicos convencionais esse tempo é muito superior ao utilizado nessas seqüências, que é da ordem de T_ 2 , essas seqüências são baseadas na varredura única do espaço-k, convencionalmente denominada Echo Planar Imaging. Os propósitos de utilização dessa metodologia compreendem desde exames clínicos convencionais, em que se pretende analisar, em projetos futuros, eventos não periódicos de curta duração e a dinâmica dos sistemas biológicos estudados, até imagens de cavidades utilizando gases hiperpolarizados. As técnicas implementadas em comparação com as inicialmente propostas por Masfield apresentam uma diferença que é a inexistência do pulso de RF de inversão e, com isso, o tempo de duração das seqüências implementadas é ainda menor. Apenas não se deve esperar muito da qualidade das imagens sem o pós-processamento, uma vez que esse trabalho já está em andamento.The objective of this work is the development and implementation of methodologies of images for Nuclear Magnetic Resonance, for reduction of the time of acquisition, since in the conventional clinical examinations this time is very superior to the used one in these sequences, that are of the order of T_ 2 , these sequences is based on the only sweepings of the space-k, conventionally called Echo Planar Imaging. The intentions of use of this methodology understand since conventional clinical examinations, where if it intends to analyze, in future projects, not periodic events of short duration and the dynamics of the biological systems studied, until socket images using hiperpolarizados gases. The techniques implemented in comparison with initially the proposals for Masfield present a difference that is the inexistence of the pulse of RF of inversion and, with this, the time of duration of the implemented sequences are still lesser. But if it does not have to wait very of the quality of the images without the after-processing, a time that this work already is in progress.
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Darkazanli, Ammar. "Magnetic resonance imaging modeling and applications to fast imaging and guidance of ultrasound surgery." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186252.
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Magnetic Resonance Imaging (MRI) is the only known radiological modality that provides a diagnostic cross sectional images non-invasively in virtually any orientation without patient repositioning. The principles of MRI are based on Bloch's equations, which describe the behavior of proton molecules in the presence of a magnetic field. There are many interesting areas where MRI has contributed, such as perfusion and diffusion studies, MR angiography, cardiac studies as weIl as therapeutic applications in cancer treatment. In this dissertation two MRI related topics were investigated. First, a computer program was developed to simulate virtually any MRI pulse sequence. The phase encoding gradient pulses are also included which has proved to be very useful in predicting image artifacts and contrast behavior. The second is the application of MRI in guiding ultrasound surgery. A detailed study was performed on the sensitivity of MRI parameters to temperature changes. In-vivo studies were also performed on seven Greyhound dogs and twenty five rabbits. Temperature elevations were successfully depicted using MRI. Computer simulations were also used to study the effects of changing temperature during image acquisition.
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Zhang, Li 1969. "Coded aperture imaging for fast neautron activation analysis." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41018.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 107-111).
by Li Zhang.
M.S.
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Zhu, Danyi. "Imaging Fast Neural Activities with Electrical Impedance Tomography." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23477.
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In this thesis we show impedance imaging may be used to measure neuronal activity at various stages of the visual system. Electrical Impedance Tomography (EIT) is a medical imaging technique that reconstructs conductivity distribution of an object using impedance measurement. EIT enables neuronal depolarisation to be imaged at high spatial-temporal resolution in rat cerebral cortex and sciatic nerve. Moreover it holds therapeutic potentials of localising epileptic foci and detecting cortical stroke in clinical diagnosis. The overall aim of this work is to image fast neural activities in visual system using EIT. In the course of the investigation, a computational model of retinal stimulation and impedance measurement was developed to characterise the mechanism of neuronal impedance change in retinal ganglion cells. Base on the results derived from mathematical modelling, we set up experiment paradigm of recording impedance change from isolated mouse retina. Furthermore, we developed finite element model to evaluated feasibility of imaging visual thalamic bodies with EIT by incorporating realistic mesh and electrophysiological recording from marmoset. The outcome was encouraging as we observed light evoked spike trains and impedance changes in dark adapted retina, which in agreement with our simulated prediction. The result presented in this dissertation was the first attempt of acquiring neural impedance recording from retinal tissue to our knowledge, which may inspire EIT into sub-millimetre imaging at cellular level. This study implies EIT has the possibility of yielding novel approaches to image neuronal activities in visual neuroscience.
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Pine, Kerrin J. "Localized fast field-cycling NMR relaxometry." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215228.
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Conventional MRI relies on a strong fixed magnetic field B0 which is stable during the imaging process. By contrast, field-cycling MRI switches the strength of B0 up or down during an experiment. In this way, field-cycling provides access to endogenous information not accessible to standard MRI, such as enhanced T1 relaxation at certain NMR frequencies due to interactions between hydrogen and nitrogen nuclei in proteins. However, biomedical research of T1 dispersion is limited by the unavailability of equipment and rapid software methods. Strategies are presented to address these deficiencies. A removable electromagnet was designed and implemented for use with a 59-mT vertical-field, permanent-magnet based imager. The resistive magnet locally offsets the primary field over a small projected region to enable field-cycling relaxometry on an otherwise-conventional imager. Radiofrequency coils were constructed to suit the electromagnet’s configuration. T1 dispersion measurements were demonstrated for, separately, the finger joints and forearm of a human volunteer. Prior to this work, producing graphs of T1 dispersion from a volume of interest required lengthy T1 mapping at each field strength step. A new pulse sequence combining SR/IR T1 determination with field-cycling and point-resolved spectroscopy localization enables the measurement of dispersion curves of a volume selected from a pilot image. Its advantages include less partial voluming than whole-sample relaxometry, as well as better SNR and faster acquisition times than image-based techniques. The sequence’s sensitivity is sufficient to reveal distinctive ‘quadrupole dips’ in dispersion curves. To the author’s knowledge, it is the first pulse sequence to enable the relationship between T1 and field strength to be examined in times which are feasible for clinical investigations. Used together as presented in this thesis, the hardware and software developed represent a step towards field-cycling being used to reveal useful diagnostic information inaccessible to conventional MRI.
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Silva, Luciana Tabajara Parreiras e. "Influência do tecido adiposo, adiposidade da medula óssea e das incretinas sobre a densidade mineral óssea de pacientes com síndrome do intestino curto." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/17/17138/tde-20072018-100203/.
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A Síndrome do Intestino Curto (SIC) é uma doença complexa que ocorre após extensa ressecção do intestino delgado, levando a uma má absorção de nutrientes e fluidos, uma condição que pode causar diarreia, desnutrição e perda de peso graves com alto risco para o desenvolvimento da osteoporose. Estudos recentes mostram existir ampla interação fisiológica do esqueleto com os diversos sistemas, incluindo o metabolismo energético e o trato digestório. Peptídeos originados não só no tecido adiposo, mas também no intestino como as incretinas [GIP (polipeptídeo trópico insulínico dependente de glicose) e GLP1 (peptídeo 1 tipo glucagon)] modulam a atividade de remodelação óssea. O objetivo principal do atual estudo foi avaliar a relação entre os tecidos adiposos subcutâneo (TAS), visceral (TAV), lipídeos intra-hepáticos (LIH), tecido adiposo da medula óssea (TAMO), bem como do GIP, GLP1, e grelina com a densidade mineral óssea (DMO) em pacientes com SIC. Tratase de um estudo observacional prospectivo composto por dois grupos experimentais pareados por altura, idade e sexo: a) o grupo controle (GC) (n = 18; 9M,9F) e b) o grupo de pacientes com SIC, o qual foi avaliado em 2 ocasiões, com intervalo de um ano entre as análises, sendo denominados SIC0 (n = 14; 7M,7F) e SIC1 (n = 11; 6M,5F). Em comparação com o GC, pacientes com SIC ao longo do estudo apresentaram menor DMO e maior LIH e GIP (p< 0,05). Os valores de TAMO, GLP1 e grelina foram similares entre os grupos. O TAMO teve correlação negativa e significativa com DMO de L3 no GC (r= -0,6; p< 0,05), porém, no grupo SIC esta correlação foi positiva, mas sem significância estatística ao longo do estudo: SIC0 (r= 0,45; p= 0,13) e SIC1 (r= 0,45; p= 0,17). LIH associou-se negativamente com DMO do colo do fêmur (R²= 0,16; p< 0,05) e quadril total (R²= 0,27; p< 0,05). Existe alta prevalência de osteoporose em pacientes com SIC. No entanto, não se observou nem expansão de TAMO e nem relação negativa da DMO com o TAMO. O acesso a calorias parece afetar positivamente a relação entre TAMO e massa óssea. A deposição hepática de lipídeos parece afetar negativamente a massa óssea de pacientes com SIC.Short bowel syndrome (SBS) is a complex disease that occurs after extensive resection of the small intestine leading to malabsorption of nutrients and fluids, a condition that can cause severe watery diarrhea, dehydration and acute weight loss, developing high risk for the appearance of osteometabolic disease. Studies have shown the progress on the physiological interaction of the skeleton with the various systems, including energetic metabolism and the gastrointestinal tract. Peptides originated not only in adipose tissue but also in the intestine such as incretin [GIP (Glucose-dependent insulinotropic polypeptide) and GLP1 (glucagonlike peptide 1) modulate bone remodeling activity. The main objective of the current study was to evaluate the influence of subcutaneous (SAT), visceral (VAT) adipose tissue, intrahepatic lipids (IHL), bone marrow fat adipose tissue (MAT), as well as the influence of GIP, GLP1, and ghrelin on the bone mineral density (BMD) of SBS patients. It is a prospective observational study composed by two experimental groups matched by height, age and sex: a) the control group (CG) (n = 18; 9M,9F) and b) the SBS group which were evaluated in two occasions with a period between analyzes of one year: named SBS0 (n = 14; 7M,7F) and SBS1 (n = 11; 6M,5F). Compared to CG, SBS patients throughout the study had significantly lower BMD and elevated IHL and GIP (p< 0.05). Values of MAT, GLP1 and ghrelin were similar between groups. MAT was negatively and significantly correlated with L3 BMD in the CG (r = -0.6; p< 0.05) and positively correlated, but not significant with L3 BMD in the SBS group throughout the study: SBS0 (r= 0.45; p= 0.13) and SBS1 (r= 0.45; p= 0.17). IHL was negatively and significantly associated with femoral neck BMD (R²= 0.16; p< 0.05) and total hip BMD (R²= 0.27; p< 0.05). The occurrence of osteoporosis is frequent in SBS patients, but MAT is not increased in these patients and had positive correlation with BMD, although not significant. Access to calories seems to positively affect the relationship between MAT and bone mass. IHL appear to negatively affect bone mass in SBS patients.
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Ross, Peter James. "Strategies for speeding up Fast Field-Cycling MRI." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230548.
Full textAbstract:
Fast field-cycling MRI (FFC-MRI) is a novel technique that promises to expand upon the diagnostic capabilities of conventional MRI by allowing the main magnetic field, B0, to be varied during the imaging pulse sequence. By doing this it is possible to gain access to information that is hidden to conventional scanners - namely the variation of the spin-lattice relaxation time, T1, with field strength, known as T1 dispersion. However, adding B0 as a new dimension to the imaging process necessitates a longer scan time which can limit the techniques application to clinical research. In this thesis, several methods are explored for reducing FFC-MRI scan times. A rapid imaging pulse sequence based on the well-known Fast Spin-Echo imaging sequence is presented, as well as an adaptation of the “keyhole” acquisition strategy. A method of determining T1 which requires significantly less data - and hence scan time - is also presented. When combined, these techniques are demonstrated to reduce total scan time from several hours to minutes without compromising access to T1 dispersion information. The techniques are demonstrated in phantom studies and in vivo results from volunteers are presented as proof of concept. The reduction in scan time demonstrated by these methods will significantly improve the applicability of FFC-MRI for clinical trials which are currently being worked towards.
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Huo, Donglai. "Quantitative Image Quality Evaluation of Fast Magnetic Resonance Imaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1155913518.
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Son, Jong Bum. "Fast and contrast-enhanced phase-sensitive magnetic resonance imaging." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1496.
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Da, Silva Marco Jose. "Impedance Sensors for Fast Multiphase Flow Measurement and Imaging." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1228836406821-31677.
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Multiphase flow denotes the simultaneous flow of two or more physically distinct and immiscible substances and it can be widely found in several engineering applications, for instance, power generation, chemical engineering and crude oil extraction and processing. In many of those applications, multiphase flows determine safety and efficiency aspects of processes and plants where they occur. Therefore, the measurement and imaging of multiphase flows has received much attention in recent years, largely driven by a need of many industry branches to accurately quantify, predict and control the flow of multiphase mixtures. Moreover, multiphase flow measurements also form the basis in which models and simulations can be developed and validated. In this work, the use of electrical impedance techniques for multiphase flow measurement has been investigated. Three different impedance sensor systems to quantify and monitor multiphase flows have been developed, implemented and metrologically evaluated. The first one is a complex permittivity needle probe which can detect the phases of a multiphase flow at its probe tip by simultaneous measurement of the electrical conductivity and permittivity at up to 20 kHz repetition rate. Two-dimensional images of the phase distribution in pipe cross section can be obtained by the newly developed capacitance wire-mesh sensor. The sensor is able to discriminate fluids with different relative permittivity (dielectric constant) values in a multiphase flow and achieves frame frequencies of up to 10 000 frames per second. The third sensor introduced in this thesis is a planar array sensor which can be employed to visualize fluid distributions along the surface of objects and near-wall flows. The planar sensor can be mounted onto the wall of pipes or vessels and thus has a minimal influence on the flow. It can be operated by a conductivity-based as well as permittivity-based electronics at imaging speeds of up to 10 000 frames/s. All three sensor modalities have been employed in different flow applications which are discussed in this thesis. The main contribution of this research work to the field of multiphase flow measurement technology is therefore the development, characterization and application of new sensors based on electrical impedance measurement. All sensors present high-speed capability and two of them allow for imaging phase fraction distributions. The sensors are furthermore very robust and can thus easily be employed in a number of multiphase flow applications in research and industry.