1,720,961 research outputs found
Quantification of I-131 Activity from Gamma Camera Images of Thyroid Cancer Patients
No full textBACKGROUND: Radioiodine (131I) has been used in thyroid cancer treatments for many years, and has demonstrated good results with regards to disease management. Radioiodine therapy is however partially empirical, as not very much is known concerning radiation dosimetry. At Skåne University Hospital, the number of treatments has been growing steadily over the past couple of years, resulting in an increased demand for dosimetry. The aim of this thesis was to develop a method for patient-specific 131I activity quantifications, and thereby provide a foundation for patient-specific dosimetry at Skåne University Hospital. METHOD: Planar measurements were performed to evaluate the degradation from penetration and scatter, and assess the effectiveness of two different window based scatter corrections (namely a DEW and a TEW correction). Calibration factors were established for planar and SPECT acquisitions, and the NEMA Body Phantom was used to study partial volume effects. Lastly, an anthropomorphic phantom study was carried through to test the quantification method and thereby assess potential quantification errors in patient imaging. RESULTS: For spherical structures, quantifications errors of up to 40% were obtained for planar images, while SPECT quantification errors were generally below 10%. For non-spherical structures, the error was significantly increased. In the planar studies of scatter and penetration, a TEW scatter correction was shown to be most effective. However, in quantifications, the scatter correction appeared to have little impact on the accuracy of the results. Instead, the quantification error seem to majorly depend on size and shape of the lesion, as well as the overall attenuation properties of the examined object. CONCLUSIONS: With the developed method, accurate SPECT quantifications are feasible. However, a varying patient geometry can potentially induce significant errors, as a window based scatter correction alone cannot compensate for large variations in the level of attenuation. Hence, the accuracy of the calibration is crucial. Object shape effects appear to be significant, as applying a sphere-based recovery coefficient to a non-spherical structure will not recover all of the activity, and errors remain large. Planar quantifications are generally associated with large errors, and accurate planar quantifications would be difficult to achieve in patient imaging. Additional work is needed to improve the accuracy of the method. Nonspherical recovery coefficient needs to be established, and effects of variations in patient geometry and 131I uptake should be examined more thoroughly. Furthermore, the reconstruction protocol should be optimized. In order for dosimetry to be performed, methods of mass determination would need to be explored. Also, methods of determining the effective half-life would need assessment.Jod är ett grundämne som är livsnödvändigt för människan. Det finns att hitta i bland annat fisk, skaldjur ägg och mejeriprodukter. Många av oss har även jodberikat salt på middagsbordet. En del av det jod vi får i oss via kosten kommer att ansamlas i sköldkörteln - ett organ som sitter under struphuvudet, på halsens nedre del. Sköldkörteln har i uppgift att producera hormoner. Dessa hormoner utsöndras i blodet, och tas upp av kroppens alla vävnader, där de hjälper cellerna att reglera sin ämnesomsättning. Sköldkörteln påverkar därmed många av kroppens viktiga funktioner. För att produktionen av sköldkörtelhormoner skall fungera normalt krävs jod. Det jod som finns i vårt hushållssalt har en syster – det radioaktiva jodet. Kroppen ser ingen skillnad på dessa två. Om radioaktivt jod tillförs kroppen kommer detta omsättas på samma sätt som vanligt jod, men med en viktig skillnad – det strålar! Denna egenskap utnyttjar man för att behandla sjukdomar i sköldkörteln, däribland sköldkörtelcancer. Radioaktivt jod tas upp av cancercellerna, vilka därmed strålas sönder. Vidare kan man, genom att detektera strålningen i en så kallad gammakamera, avbilda jodets fördelning i kroppen, och på så sätt få en bild av sjukdomens utbredning. Vid bildtagning med gammakameran genereras tvådimensionella bilder av det radioaktiva läkemedlet i patienten. Vidare kan man genom att låta kameran rotera runt patienten kan man även framkalla tredimensionella bilder – en metod som kallas Single Photon Emssion Computed Tomography (SPECT). Syftet med detta examensarbete är att, utifrån nuklearmedicinska bilder av patienter som genomgått terapi med radioaktivt jod, utveckla en metod för att bestämma mängden jod som tagits upp av en cancertumör. För att göra detta krävs vetskap om de processer som äger rum, från dess att strålningen skickas ut, till dess att den färdiga bilden har framställts. Vidare måste man ha metoder för att kompensera för den försämring i bildkvalité som vissa av dessa processer kan föra med sig. Detta arbete fokuserar på just detta; hur gör man för att kvantifiera mängden jod i en tumör, och hur skall man förhålla sig till de faktorer som försvårar beräkningarna? Det långsiktiga målet med arbetet är att göra det möjligt att bestämma vilken stråldos en patient erhåller i samband med en cancerbehandling med radioaktivt jod, och därigenom potentiellt lägga grunden för en förbättrad framtida behandling
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
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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