1,720,991 research outputs found
Advanced myocardial magnetic resonance imaging in patients with cardiac implantable electronic devices
No full textCardiac magnetic resonance imaging (CMR) is a gold standard technique for non-invasive assessment of cardiac structure, lesions, function, and tissue composition. However, in patients with cardiac implantable electronic devices (CIEDs), its diagnostic use remains limited due to severe device-related artefacts. With implantation rates increasing worldwide and the majority of patients expected to require a CMR during their lifetime, dedicated solutions are required to extend the benefits of CMR to this growing population.
The objective of this thesis was to develop and evaluate CMR methods using wideband radiofrequency pulses in patients with CIEDs in order to reduce device-related artefacts, improve the detection of myocardial lesions and improve diagnostic confidence compared to available reference techniques. Several complementary approaches were investigated and validated in phantoms, animals, healthy volunteers, and patients.
First, wideband black-blood late gadolinium enhancement (LGE) imaging was introduced to improve scar detection and reduce hyperintensity artefacts introduced by devices. Second, a free-breathing, motion-corrected implementation of wideband black-blood LGE was developed to facilitate imaging in patients unable to perform repeated breath-holds and to speed up the examination time. Third, a joint wideband bright- and black-blood technique (wideband SPOT) was proposed, combining improved scar-to-blood contrast with preserved anatomical reference to enable the localization of scars within the myocardial wall in the presence of CIEDs. Finally, wideband T2 mapping with advanced denoising was implemented to enable quantitative assessment of myocardial oedema and inflammation in the presence of CIEDs.
This work has established a more comprehensive framework of cardiac MRI techniques that are less prone to artefacts for the assessment of myocardial scar using LGE, and oedema and inflammation using T2 mapping in patients with implantable cardiac devices. These developments contribute to extending the role of CMR to a patient group that has long been excluded, with potential impact on diagnosis, risk stratification, and ablation guidance
Weiterentwickeltes Rekonstruktionsverfahren bei hochauflösenden Multi-Kontrast Kardio-Magnetresonanztomographie bei freier Atmung
No full textCardiovascular magnetic resonance (CMR) imaging is a valuable tool for high-resolution myocardial structure function and tissue assessment, providing essential information for clinical diagnosis and treatment decisions in cardiovascular disease. The unique ability of CMR to manipulate contrast and morphological information is however challenged by long scan time and physiological motion artifacts, and is strongly influenced by system imperfections leading to noisy acquisition and poor through-plane resolution.
In this thesis, we aim to bridge the gap between remote denoising and motion-correction approaches by developing efficient and reliable reconstruction techniques that jointly reconstruct high-resolution cardiac images free of motion and noise artifacts. Proposed techniques are applied in myocardial T1 mapping denoising, high-resolution 2D motion correction, and isotropic 3D MRI experiments, providing improved information and image quality to the cardiologist at no cost for assessing myocardial diseases.
In conclusion, the set of reconstruction methods described in this thesis, as well as their applications, address several challenges in typical image acquisitions that compose routine cardiac MR examinations. These new advances might enable the acceleration of MRI scan, reduction of motion and noise artifact, better visualization of cardiac images, and ultimately improve clinical diagnosis and patient comfort.Die kardiovaskuläre Magnetresonanz (CMR) -Bildgebung ist ein wertvolles Instrument für die hochauflösende myokardiale Strukturfunktion und die Gewebebewertung, die wesentliche Informationen für klinische Diagnose- und Therapieentscheidungen bei kardiovaskulären Erkrankungen liefert. Die einzigartige Fähigkeit von CMR, Kontrast und morphologische Informationen zu manipulieren, wird jedoch durch lange Abtastzeit und physiologische Bewegungsartefakte erkauft und wird stark durch Systemunvollkommenheiten beeinflusst, was zu einer lauten Akquisition und einer schlechten Zwischenschichtauflösung führt.
In dieser Arbeit wollen wir die Lücke zwischen Lämreduktions- und Bewegungskorrekturansätzen überbrücken, indem wir effiziente und zuverlässige Rekonstruktionstechniken entwickeln, die hochauflösende Bilder vom Herzen rekonstruieren, die frei von Bewegungs- und Rauschenartefakten sind. Vorgeschlagene Techniken werden in der myokardialen T1-Kartierung verwendet, die eine hochauflösende 2D-Bewegungskorrektur und isotrope 3D-MRI-Experimente ermöglicht und dem Kardiologen eine verbesserte Information und Bildqualität für die Beurteilung von Herzmuskelerkrankungen bietet.
Zusammenfassend lässt sich sagen, dass die in dieser Arbeit beschriebenen Rekonstruktionsmethoden, sowie ihre Anwendungen, einige Herausforderungen in typischen Bildakquisitionen angehen, die in routinemäßige kardiale MR-Untersuchungen entsehen. Diese neuen Fortschritte ermöglichen die Beschleunigung des MRT-Scans, die Verminderung von Bewegungs- und Rauschartefakten, eine bessere Visualisierung von Herzbildern und letztlich die Verbesserung der klinischen Diagnose und des Patientenkomforts
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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