1,720,964 research outputs found
Machbarkeit und Unsicherheiten der 4D-Dosissimulation zur retrospektiven Qualitätssicherung in der Strahlentherapie bewegter Ziele
No full textQuality assurance in 4D radiotherapy is an essential process to verify that the dose delivered to a patient is sufficient to achieve pre-treatment defined goals, which are typically the total tumor eradication and optimal sparing of healthy tissue and organs. However, there are currently no appropriate tools available to account for the dynamical nature of free patient breathing in combination with complex dose delivery techniques. The focus of the present thesis lies therefore within a specific clinical context application: the development of a framework for retrospective quality assurance in 4D radiotherapy of lung and liver metastases treated by volumetric modulated arc therapy (VMAT).Achieving this requires following key steps to be taken: (1) Development of a patient-specific image- and model-based 4D (3D + time) dose accumulation framework for the highly dynamic VMAT dose delivery technique. (2) Application of respective framework to real patient data in order to investigate the correlation of during-treatment motion, its interplay with VMAT dose delivery dynamics and observed local recurrence of lung/liver metastases after treatment. (3) Investigation of simulation robustness, accuracy and potential uncertainty sources and implementation of uncertainty propagation.
The basis of step (1) is combining the modeling of the dynamic VMAT dose delivery, which employs the variation of gantry speed, dose rate and collimator leaf positions, and the patient-specific internal structure motion. However, internal structure motion information is routinely not acquired during dose delivery. Thus, a dedicated modeling approach has to be utilized to estimate the internal patient motion, enabling the simulation of motion-affected dose distributions. For step (2), the patient-specific 4D-simulated dose distributions are computed and compared to pre-treatment planned (reference-)dose distributions. The estimated deviations (underdosages) are analyzed and correlated to information about the clinical outcome. A potential linkage is found, which to some extent demonstrate the dose simulation to be reliable. Despite this result, dose simulation uncertainties and impacting parameters as well as the general accuracy are extensively investigated in step (3).
Limitations encountered during phantom-based verification measurements motivated to further improve the 4D dose simulation framework by introducing an uncertainty propagation scheme and re-implementing the actual dose calculation utilizing gold standard Monte Carlo dose simulations. It is concluded that the consideration of individual patient motion variability during dose delivery in combination with VMAT dose accumulation for quality assurance in 4D radiotherapy is feasible.Die Qualitätssicherung (QS) in der 4D-Strahlentherapie stellt sicher, dass vor der Patientenbehandlung definierte Ziele, d.h. typischerweise die irreparable Tumorschädigung und die optimale Schonung von gesundem Gewebe und Organen, erreichbar sind. Eine Berücksichtigung der freien Patientenatmungsdynamik während einer Behandlung mit komplexer Bestrahlungstechnik im Sinne einer QS ist jedoch mit zurzeit verfügbaren Methoden nicht möglich. Der Schwerpunkt dieser Arbeit liegt daher auf einer spezifischen klinischen Anwendung: die Entwicklung eines Frameworks für die retrospektive QS in der 4D-Strahlentherapie von Lungen- und Lebermetastasen, behandelt durch volumetrisch modulierte Bogenbestrahlung (VMAT). Folgende Arbeitsschritte sind nötig: (1) Entwicklung eines patientenspezifischen bild- und modellbasierten 4D (3D + Zeit)-Dosisakkumulationsframeworks für die dynamische VMAT-Bestrahlungstechnik. (2) Anwendung des entsprechenden Frameworks auf reale Patientendaten sowie die Untersuchung der Korrelation zwischen Bewegung während der Behandlung, ihr Zusammenspiel mit der VMAT-Bestrahlungsdynamik und das lokale Wiederauftreten von Lungen-/Lebermetastasen nach der Behandlung. (3) Analyse von Simulationsrobustheit, -genauigkeit und potenziellen Unsicherheitsquellen sowie Implementierung einer Unsicherheitsfortpflanzung.
Die Grundlage von Schritt (1) ist die Kombination aus der Modellierung der dynamischen VMAT-Technik (variierende Gantry-Geschwindigkeit, Dosisleistung und Kollimatorlamellenposition) und Informationen über die patientenspezifische interne Bewegung. Allerdings wird diese während der Dosisapplikation routinemäßig nicht erfasst. Ein spezieller Modellierungsansatz ist daher für die interne Schätzung der Bewegung nötig, um eine Simulation von bewegungsbeeinflussten Dosisverteilungen zu ermöglichen. Für Schritt (2) werden die patientenspezifischen 4D-simulierten Dosisverteilungen mit den vor der Behandlung geplanten (Referenz-)Dosisverteilungen verglichen. Die resultierenden Abweichungen werden analysiert und mit Informationen über den klinischen Ausgang korreliert. Die festgestellte Korrelation demonstriert zumindest zum Teil die Zuverlässigkeit der Dosissimulation. Trotz dieses Ergebnisses werden in Schritt (3) die Unsicherheiten der Dosissimulation und mögliche Einflussgrößen sowie die allgemeine Simulationsgenauigkeit untersucht.
Bei phantombasierten Verifikationsmessungen identifizierte Limitierungen motivierten, das 4D-Dosissimulationframework durch die Einführung einer Unsicherheitsfortpflanzung und die Implementierung einer eigenständigen Dosisberechnung (Goldstandard Monte Carlo-Simulation) zu verbessern. Die Resultate belegen die prinzipielle Möglichkeit der Berücksichtigung von der individuellen Bewegungsvariabilität in einer VMAT-Dosisakkumulation zur QS in der 4D-Strahlentherapie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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