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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Investigation of gradient echo MRI for blood vessel imaging and susceptibility-weighted imaging in the human brain

Eissa, Amir Unknown Date
No description available.
172

Serum lipoprotein(a) in relation to ischemic heart disease and associated risk factors

Slunga, Lisbeth January 1993 (has links)
Lipoprotein(a) (Lp(a)) consists of an LDL-like particle and the specific protein apo(a), which is very similar to plasminogen. Apo(a) contains repeated kringle structures and a serine protease domain, which cannot be activated by t-PA. Lp(a) is considered to be a predictor for atherosclerotic disease. It has been found incorporated in atherosclerotic plaques and inhibits in vitro fibrinolysis. Lp(a) was determined in 1527 randomly selected individuals participating in the Northern Sweden WHO-MONICA project. A weak but significant relation between Lp(a) and increasing age was found. Menopausal status was the strongest independent predictor of Lp(a) level in women. Fibrinogen was independently related to Lp(a) in both sexes. Only a minor fraction of Lp(a) variance could be explained for in a multiple regression model, which is in agreement with the contention that Lp(a) is highly genetically determined. Lp(a) was determined in 1571 patients investigated with coronary angiography because of suspected severe coronary artery disease (CAD). Patients with proven CAD at elective angiography had significantly higher Lp(a) than patients without significant CAD or healthy controls. Lp(a) was found to be an independent discriminator of CAD in both sexes. HLA-DR genotype 13 or 17 was found more frequently in 30 male patients with angiographic CAD at young age (&lt; 50 years) than in 30 age matched controls. These genotypes were common in patients with high Lp(a) levels, which indicates that Lp(a) may be related to immunological processes. The reaction of Lp(a) was investigated in 32 patients with acute myocardial infarction (AMI). Lp(a) increased during the first week, but the response was comparatively weak. Individual Lp(a) responses were heterogeneous and no correlations to infarct size or changes in the acute phase proteins were found. In a randomized cross-over study on 36 hypercholesterolaemic patients treated with simvastatin/placebo during 12+12 weeks Lp(a) did not change significantly, but patients with high Lp(a) levels at baseline tended to develop further increased Lp(a). To conclude, Lp(a) was found to be an independent predictor of angiographic CAD in both men and women. Lp(a) levels are primarily genetically determined and only a small fraction of Lp(a) variance could be explained by other factors in this study. Lp(a) may be related to HLA DR types and immunological processes involved in atherosclerotic disease. Lp(a) increased slightly during the first week of AMI, but was not related to changes in the acute-phase proteins. The effective LDL-lowering agent simvastatin did not influence Lp(a) significantly. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 5 uppsatser.</p> / digitalisering@umu
173

Assessment of aortic stenosis with special reference to Doppler ultrasound

Teien, Dag January 1986 (has links)
<p>Härtill 5 uppsatser</p> / digitalisering@umu
174

Eine Phantomstudie zur Strahlenexposition des Untersuchers bei Rotationsaquisitionen mit einer Flachdetektor-Angiographie-Anlage / A phantom-study about the radiation exposure to the examiner at rotational acquisitions using a flat-panel detector angiographic system

Friedrichs, Tatiana 24 July 2014 (has links)
Neben der konventionellen Digitalen Subtraktions-Angiografie (DSA) werden insbesondere seit Einführung der Angiografiesysteme mit Flachdetektor-Technologie zunehmend auch Rotationsangiografien und DYNA-CTs durchgeführt. Ziel der Studie ist die Bestimmung der Strahlenexposition für den Untersucher bei DSA-Serien im Vergleich zu Rotationsangiografien an einem biplanen Angiografiesystem unter Berücksichtigung gerätetechnischer Strahlenschutzvorrichtungen. Die Untersuchung erfolgte an einem biplanen Angiographiesystem mit Flachdetektor-Technologie (AxiomArtis dBA, Siemens). Die Strahlenexposition wurde als Ortsdosis in Höhe der Augen, Schilddrüse und Gonaden eines stehenden Untersuchers mit dem Dosimeter UMO LB 123 (Berthold) bestimmt. Alle Messungen wurden sowohl mit als auch ohne deckengeführtes Strahlenschutzschild und Unterkörperschutz mit Aufsatz durchgeführt. Die Messorte wurden in unterschiedlichen Abständen und Winkeln zum Isozentrum gewählt. Der Patient wurde durch ein Alderson-Phantom simuliert. Die Messergebnisse ergaben eine 90%ige Reduzierung der Strahlenexposition des Untersuchers durch die Strahlenschutzvorrichtung am Tisch. Für einen wirksamen Gonadenschutz ist der Aufsatz zum Unterkörperschutz unverzichtbar. Die optimale Schutzwirkung ist nur an der Position des Untersuchers nachweisbar; Personal direkt neben dem Untersucher ist einer bis zu 10mal größeren Strahlenexposition ausgesetzt. Die Strahlenexposition des Untersuchers ist bei der Durchführung einer Rotationsangiografie (8s DS H) auch unter Berücksichtigung aller gerätetechnischen Strahlenschutzvorrichtungen 9 bis 10fach höher, verglichen zu einer DSA-Serie in Standardprojektionen (6s, 3 Bilder/s). Die Strahlenexposition des Untersuchers an einem biplanen Angiografiesystem kann durch gerätetechnische Strahlenschutzvorrichtungen erheblich reduziert werden. Hochdosisprotokolle für Rotationsangiografien sollten auf ihre Notwendigkeit überprüft werden.
175

Filtering of thin objects : applications to vascular image analysis

Tankyevych, Olena 19 October 2010 (has links) (PDF)
The motivation of this work is filtering of elongated curvilinear objects in digital images. Their narrowness presents difficulties for their detection. In addition, they are prone to disconnections due to noise, image acquisition artefacts and occlusions by other objects. This work is focused on thin objects detection and linkage. For these purposes, a hybrid second-order derivative-based and morphological linear filtering method is proposed within the framework of scale-space theory. The theory of spatially-variant morphological filters is discussed and efficient algorithms are presented. From the application point of view, our work is motivated by the diagnosis, treatment planning and follow-up of vascular diseases. The first application is aimed at the assessment of arteriovenous malformations (AVM) of cerebral vasculature. The small size and the complexity of the vascular structures, coupled to noise, image acquisition artefacts, and blood signal heterogeneity make the analysis of such data a challenging task. This work is focused on cerebral angiographic image enhancement, segmentation and vascular network analysis with the final purpose to further assist the study of cerebral AVM. The second medical application concerns the processing of low dose X-ray images used in interventional radiology therapies observing insertion of guide-wires in the vascular system of patients. Such procedures are used in aneurysm treatment, tumour embolization and other clinical procedures. Due to low signal-to-noise ratio of such data, guide-wire detection is needed for their visualization and reconstruction. Here, we compare the performance of several line detection algorithms. The purpose of this work is to select a few of the most promising line detection methods for this medical application
176

Malignant Profile Detected by CT Angiographic Information Predicts Poor Prognosis despite Thrombolysis within Three Hours from Symptom Onset

Pütz, Volker, Dzialowski, Imanuel, Hill, Michael D., Steffenhagen, Nikolai, Coutts, Shelagh B., O’Reilly, Christine, Demchuk, Andrew M. 26 February 2014 (has links) (PDF)
Objective: A malignant profile of early brain ischemia has been demonstrated in the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) trial. Patients with a malignant profile had a low chance for an independent functional outcome despite thrombolysis within 3–6 h. We sought to determine whether CT angiography (CTA) could identify a malignant imaging profile within 3 h from symptom onset. Methods: We studied consecutive patients (04/02–09/07) with anterior circulation stroke who received CTA before intravenous thrombolysis within 3 h. We assessed the Alberta Stroke Program Early CT Score (ASPECTS) on CTA source images (CTASI). Intracranial thrombus burden on CTA was assessed with a novel 10-point clot burden score (CBS). We analyzed percentages independent (modified Rankin Scale score ≤2) and fatal outcome at 3 months and parenchymal hematoma rates across categorized combined CTASI-ASPECTS + CBS score groups where 20 is best and 0 is worst. Results: We identified 114 patients (median age 73 years [interquartile range 61–80], onset-to-tPA time 129 min [95–152]). Among 24 patients (21%) with extensive hypoattenuation on CTASI and extensive thrombus burden (combined score ≤10), only 4% (1/24) were functionally independent whereas mortality was 50% (12/24). In contrast, 57% (51/90) of patients with less affected scores (combined score 11–20) were functionally independent and mortality was 10% (9/90; p < 0.001). Parenchymal hematoma rates were 30% (7/23) vs. 8% (7/88), respectively (p = 0.008). Conclusion: CTA identifies a large hyperacute stroke population with high mortality and low likelihood for independent functional outcome despite early thrombolysis. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
177

Assessment of atherosclerosis by whole-body magnetic resonance angiography /

Hansen, Tomas, January 2007 (has links)
Diss. (sammanfattning) Uppsala : Univ., 2007. / Härtill 4 uppsatser.
178

Interactions between neural retina, retinal epithelium and choroid /

Ivert, Lena, January 2006 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 6 uppsatser.
179

Associação entre periodontite crônica, perda dentária e marcador inflamatório de doenças cardiovasculares

Zanella, Silvia Maria January 2017 (has links)
Periodontite crônica e perda dentária tornaram-se ferramentas úteis para estudar a hipótese de que a infecção/inflamação aumenta o risco de doenças cardiovasculares. Tem se demonstrado que a periodontite e suas consequências (perdas dentárias) têm o poder de elevar os marcadores inflamatórios sistêmicos, incluindo a proteína C-reativa, a qual é uma proteína aguda plasmática que é reconhecida como um preditor de infarto e se encontra aumentada em infecções. Com base no entendimento que o processo inflamatório sistêmico é o fator ligante entre as duas condições, o objetivo deste estudo foi analisar a associação entre edentulismo, perda dentária e parâmetros clínicos de periodontite crônica com inflamação sistêmica medida através de níveis de proteína C-reativa. Este estudo transversal controlado faz parte de um macro-projeto do Instituto de Cardiologia do Rio Grande do Sul que num estudo tipo consórcio incluiu 130 pacientes que receberam indicação para realizar cineangiocoronariografia. Os pacientes selecionados foram examinados entre dezembro de 2016 e outubro de 2017 e passaram por exame periodontal completo constando de índice de placa visível (IPV), sangramento à sondagem (SS), perda de inserção (PI), profundidade de sondagem (PS) em todos os dentes presentes nos seis sítios e também coletado o número de dentes perdidos e coleta de exames sanguíneos. A amostra foi dividida em 2 grupos: edêntulos (24,6%) e dentados (75,3%), sendo que maioria era homens (67,7%), com idade média de 63,30(±10,7) brancos (80%), com educação fundamental (70%), sedentários (62%), diabéticos (52%), hipertensos (74%) e com pelo menos um evento cardiovascular anterior (52%). As médias ± desvio-padrão de PS foram de 3,36±1,25; para PIos valores foram de 5,42±1,85; IPV médio de 0,39±0,25; e SS médio de 0,34±0,23, com uma média de 13,44±7,95 dentes. No modelo de regressão logística observou-se o efeito independente da perda dentária após ajustada para fumo e sexo. Conclui-se que a perda dentária está associada a incremento do risco cardíaco medido por inflamação sistêmica. / Chronic periodontitis and tooth loss have become useful tools for studying the hypothesis that infection/inflammation increases the risk of cardiovascular disease. It has been shown that periodontitis and its consequences (tooth loss) have the power to elevate systemic inflammatory markers; one of these markers is C-reactive protein is an acute plasma protein that is recognized as a predictor of myocardial infarction and is increased in infections. Based on the understanding that the systemic inflammatory process is the linking factor between the two conditions the objective of this study was to analyze the association between edentulism, tooth loss and clinical parameters of chronic periodontitis with systemic inflammation measured through C-reactive protein levels. This controlled cross-sectional study is part of a macro-project of the Instituto de Cardiologia do Rio Grande do Sul, which in a consortium-type study included 130 patients who were indicated to perform coronary angiography. The selected patients were examined between December 2016 and October 2017 and underwent complete periodontal examination consisting of visible plaque index (VPI), bleeding on probing (BOP), probing depth (PD), clinical attachment loss (CAL), in six sites per tooth of all teeth present in addition to blood tests. The sample was divided into 2 groups: edentulous (24,6%) and dentate (75,3%)individuals. The majority were men (67.7%), with mean age of 63.30 (± 10.7) whites (80%), hypertensive (74%) and with at least one previous cardiovascular event (52%). The means and standard deviation of PD were 3.36 ±1.25; for CAL mean values of 5.42 ±1,85; Mean VPI was of 0.39 ± 0.25; and BOP presented 0.34 ± 0.23 as mean, with a mean of 13.44 ± 7.95 teeth present. In logistic regression model, we observed the independent effect of tooth loss after adjustment for smoking and sex. It is concluded that tooth loss is associated with increased cardiac risk as measured by systemic inflammation.
180

Embolização arterial no traumatismo de bacia / Arterial embolisation on pelvic trauma

Guilherme de Palma Abrão 17 October 2008 (has links)
O trauma pélvico apresenta alta morbi-mortalidade, especialmente nos casos de dupla ruptura do anel pélvico (AP), devido à hemorragia. O objetivo deste trabalho é observar o tempo transcorrido até a realização do tratamento endovascular (TE), a sua eficácia e a estratégia de exames complementares empregado. 53 pacientes com fratura de bacia póstraumática foram submetidos a embolização arterial num estudo retro e prospectivo, realizado no período de janeiro de 2000 e dezembro de 2005. A idade dos pacientes variou entre 93 e 17 anos, com média de 37,5 anos. Houve predomínio do sexo masculino, com cerca de 62,2%. A causa do trauma mais freqüente foi o acidente de moto em 36% dos casos. Predominaram as fraturas com dupla ruptura do AP em 71,6 % dos casos. 49 pacientes apresentavam instabilidade hemodinâmica, e desses, todos receberam derivados sanguíneos previamente à realização do TE. Neste estudo 38,7% (n = 19) dos pacientes instáveis foram submetidos ao exame de tomografia computadorizada (TC) antes do TE, o tempo médio desse grupo para atingir a sala de radiologia vascular foi de 230,45 minutos. Nos pacientes enviados diretamente à arteriografia com intenção terapêutica, o tempo médio até início da realização do tratamento foi de 146,77 minutos. A diferença entre as taxas de mortalidade precoce nos grupos de pacientes submetidos ou não a TC previamente ao TE foi de 5,63%. O choque hemorrágico foi à causa de óbito em 63,33% dos pacientes que apresentaram mortalidade precoce. Na conduta inicial desses pacientes preconiza-se realizar o menor número de intervenções até o controle da hemorragia. O tempo transcorrido até a chegada na sala de radiologia vascular é fator importante no prognóstico dos pacientes com fraturas hemorrágicas da bacia. O TE precoce é uma importante ferramenta nos pacientes hemodinamicamente instáveis inicialmente / Pelvic trauma presents high morbi-mortality specially in cases of double rupture of pelvic ring due to hemorrhages. The objective of this work is to observe the time period since the rupture till the execution of endovascular treatment (ET) as well as the effectiveness and strategy for the used complementary exam. 53 patients with pos-traumatic pelvic fracture were submitted to arterial embolization during retro and prospective study. Such study was executed during the period of January 2000 to December 2005. The age of the patients varied between 17 and 93 years old, average 37.5 year old and predominantly men at about 62.2% of the cases. The most frequent cause of the traumas, 36%, was motorcycle accident. Predominantly fractures with double rupture of the pelvic ring, that is 71.6% of the cases. 49 patients presented hemodynamic instability, all of them received blood derivatives previously to the ET execution. In this study 38.7% (n=19) of the unstable patients were submitted to computerized tomography exam (CT) before the ET. The average period of time for this group to reach the room of vascular radiology was 230.45 min. For patients sent straight to arteriography with therapeutic intention, the average period time was 146.77 min. The difference, between the early mortality rate of the group undertaken or not to the CT previously to the ET, was 5.63%. The hemorrhagic shock was the cause of death in 63.33% patients, who presented early mortality. For the initial on going study of these patients, we recommend to accomplish the least number of interventions until hemorrhage is controlled. The elapsed time till the arrival at the vascular radiology room is an important factor to make prognosis about patients with hemorrhagic pelvic fractures. The early ET is an important tool for patients with hemodynamic instability

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