1,721,080 research outputs found
Quantitation of global and regional left ventricular function by MRI
No full textMagnetic resonance imaging (MRI) provides several imaging strategies for assessing left ventricular function. As a three-dimensional imaging technique, all measurements can be performed without relying on geometrical assumptions. Global and regional function parameters can be derived from conventional or breath-hold cine MR imaging techniques. Velocity encoded cine MR imaging techniques can be applied during the same acquisition to provide quantitative information on flow velocity and volume in the heart and the greater arteries. Quantitative image analysis based on manual tracing of contours is a time consuming procedure and therefore not practical in routine clinical practice. This chapter describes the developments towards automated image analysis and contour detection techniques for cardiovascular MR imaging.</p
Quantitation of global and regional left ventricular function by MRI
No full textMagnetic resonance imaging (MRI) provides several imaging strategies for assessing left ventricular function. As a three-dimensional imaging technique, all measurements can be performed without relying on geometrical assumptions. Global and regional function parameters can be derived from conventional or breath-hold cine MR imaging techniques. Velocity encoded cine MR imaging techniques can be applied during the same acquisition to provide quantitative information on flow velocity and volume in the heart and the greater arteries. Quantitative image analysis based on manual tracing of contours is a time consuming procedure and therefore not practical in routine clinical practice. This chapter describes the developments towards automated image analysis and contour detection techniques for cardiovascular MR imaging.</p
Computer-aided Detection of Wall Motion Abnormalities in Cardiac MRI
No full textWith the increasing prevalence and hospitalization rate of ischaemic heart disease, an explosive growth of diagnostic imaging for ischaemia is ongoing. Clinical decision making on revascularization procedures requires reliable viability assessment to assure long-term patient survival and to elevate cost effectiveness of the therapy and treatment. As such, the demand is increasing for a computer-assisted diagnosis (CAD) method for ischaemic heart disease that supports clinicians with an objective analysis of infarct severity, a viability assessment or a prediction of potential functional improvement before performing revascularization. The goal of this thesis was to explore novel mechanisms that can be used for CAD in ischaemic heart disease, particularly through wall motion analysis from cardiac MR images. Existing diagnostic treatment of wall motion analysis from cardiac MR relies on visual wall motion scoring, which suffers from inter- and intra-observer variability. To minimize this variability, the automated method must contain essential knowledge on how the heart contracts normally. This enables automatic quantification of regional abnormal wall motion, detection of segments with contractile reserve and prediction of functional improvement in stress
Genetic factors in the progression of atherosclerosis and response to cholesterol lowering drugs
No full textGeneric factors play a role in the development of atherosclerosis. While some monogenetic disorders induce premature atherosclerosis, other genetic alterations cooperate in a polygenetic model, modifying the process of atherosclerosis. Genetic alterations can modify disease but can also modify the efficacy of treatment of the disease. An example of such a modifying gene is the deletion polymorphism in the 16th intron of the angiotensin converting enzyme (ACE) gene. This polymorphism is associated with higher ACE activities, and a broad variety of diseases. We assessed in a subset of the REgression GRowth Evaluation Statin Study (REGRESS) whether the ACE gene polymorphism modifies the beneficial effect of pravastatin on the atherosclerotic process. We found that the lipid lowering effect of pravastatin was similar to the three genotype groups. However, the effect of the lipid lowering drugs pravastatin on the progression of coronary at atherosclerosis was attenuated in the DID genotype group. This demonstrates that the ACE deletion genotype can modify the response to treatment. Therefore, involvement of generic alterations in modifying disease and therapy should reserve the treatment of cardiovascular disorders from a population and evidence-based approach, towards an individual-based intervention.</p
Genetic factors in the progression of atherosclerosis and response to cholesterol lowering drugs
No full textGeneric factors play a role in the development of atherosclerosis. While some monogenetic disorders induce premature atherosclerosis, other genetic alterations cooperate in a polygenetic model, modifying the process of atherosclerosis. Genetic alterations can modify disease but can also modify the efficacy of treatment of the disease. An example of such a modifying gene is the deletion polymorphism in the 16th intron of the angiotensin converting enzyme (ACE) gene. This polymorphism is associated with higher ACE activities, and a broad variety of diseases. We assessed in a subset of the REgression GRowth Evaluation Statin Study (REGRESS) whether the ACE gene polymorphism modifies the beneficial effect of pravastatin on the atherosclerotic process. We found that the lipid lowering effect of pravastatin was similar to the three genotype groups. However, the effect of the lipid lowering drugs pravastatin on the progression of coronary at atherosclerosis was attenuated in the DID genotype group. This demonstrates that the ACE deletion genotype can modify the response to treatment. Therefore, involvement of generic alterations in modifying disease and therapy should reserve the treatment of cardiovascular disorders from a population and evidence-based approach, towards an individual-based intervention.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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