1,720,959 research outputs found
Accuracy of patient-specific dosimetry using hybrid planar-SPECT/CT imaging: a Monte Carlo study
No full textThesis (Ph.D.(Medical Physics))--University of the Free State, 2021Introduction: Theragnostics is a precision medical discipline aiming to individualise patient targeted treatment. It aims at treating cancer by the systemic administration of a therapeutic radiopharmaceutical, which targets specific cells based on the labelling molecule. With the renewed interest in radiopharmaceutical therapy, the importance of accurate image quantification using iodine-123 (I-123) and iodine-131 (I-131), for dosimetry purposes, has been re-emphasised. Monte Carlo (MC) modelling techniques have been used extensively in Nuclear Medicine (NM), playing an essential role in modelling gamma cameras for the assessment of activity quantification accuracy, which is vital for accurate dosimetry. This thesis aimed to assess the accuracy of patient-specific I-131 dosimetry using hybrid whole-body (WB) planar-SPECT/CT imaging. The study was based on MC simulations of voxel-based digital phantoms, using the SIMIND MC code emulating the Siemens SymbiaTM T16 gamma camera. To achieve the aim, the thesis was divided into four objectives, (i) validating the accuracy of an energy resolution (ER) model, (ii) verifying the SIMIND setup for simulation of static, WB planar and SPECT images for I-123 with a low energy high resolution (LEHR) and a medium energy (ME) collimator and for I-131 with a high energy (HE) collimator, (iii) evaluating SPECT quantification accuracy for the three radionuclide- collimator combinations and (iv) assessing the accuracy of I-131 absorbed dose calculations for tumours and organs at risk, based on hybrid WB planar-SPECT/CT imaging. Methodology: The proposed ER model was fit to measured ER values (between 27.0 and 637.0 keV) as a function of photon energy. Measured and simulated energy spectra (in-air, in-scatter and a voxel-based digital patient phantom) were compared. The SIMIND setup was validated by comparing measured and simulated static and WB planar (extrinsic energy spectra, system sensitivity and system spatial resolution in-air and in-scatter), as well as SPECT (simple geometry sensitivity) results. Quantification accuracy was assessed in voxel- based digital simple and patient phantoms, using optimised OS-EM iterative reconstruction updates, calibration factor and recovery curves. Finally, using the true and quantitative activity data from I-123 and I-131 voxel-based digital patient phantoms, full MC radiation transport was performed, to determine the accuracy of the absorbed dose for I-131-mIBG radiopharmaceutical therapy. Results: The fitted ER model better simulated the energy response of the gamma camera, especially for high energy photopeaks, (I-123: 528.9 keV and I-131: 636.9 keV). The measured and simulated system energy spectra (differences ≤ 4.6 keV), system sensitivity (differences ≤ 6.9%), system spatial resolution (differences ≤ 6.4%) and SPECT validation results (difference ≤ 3.6%) compared well. Quantification errors less than 6.0% were obtained when appropriate corrections were applied. I-123 LEHR and I-123 ME quantification accuracies compared well (when corrections for septal scatter and penetration are applied), which can be useful in departments that perform I-123 studies and may not have access to ME collimators. Average I-131 absorbed doses of 2.0 ± 0.4 mGy/MBq (liver), 20.1 ± 4.0 mGy/MBq (3.0 cm tumour) and 22.6 ± 4.2 mGy/MBq (5.0 cm tumour) were obtained in simulated patient studies. When using a novel method of replacing the reconstructed activity distribution with a uniform activity distribution, eliminating the Gibbs artefact, the dosimetry accuracy was within 10.5%. Conclusion: Using the proposed fitted ER model, SIMIND could be used to accurately simulate static and WB planar and SPECT projection images of the Siemens SymbiaTM T16 SPECT/CT for both I-123 and I-131 with their respective collimators. Accurate quantification resulted in absorbed dose accuracies within 10.5%. The hybrid WB planar-SPECT/CT dosimetry method proved effective for personalised treatment planning of I-131 radiopharmaceutical therapy, with either I-123 or I-131 diagnostic imaging
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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