1,720,964 research outputs found
CyberKnife®; Imaging-dose evaluation during IGRT-SRSand IGRT-SBRT treatments
No full textIl sistema di radiochirurgia robotica CyberKnife® è utilizzato per trattamenti di radoiochirurgia e radioterapia stereotassica intra ed extracranica guidati dalle immagini (IGRT). I trattamenti di tumori localizzati vengono erogati in singole (radiochirurgia stereotassica SRS[8]) o poche sedute (radioterapia stereotassica SBRT[11]) con un’elevata dose di radiazioni ionizzanti. Per questa ragione è necessaria un’elevata accuratezza nella localizzazione del bersaglio, ottenuta con il sistema di imaging (TLS).
Il TLS consiste di due sorgenti ortogonali di raggi X diagnostici fissate al soffitto orientati verso due rivelatori integrati nel pavimento. Tale sistema richiede l’acquisizione di numerose coppie di radiografie allo scopo di localizzare la posizione del bersaglio. Tali immagini vengono effettuate con frequenza e dati espositivi decisi dal TSRM, per tutta la durata del trattamento.
Scopo di questo studio è la determinazione dell’Air Kerma relativo al TLS del sistema CyberKnife® presente presso l’Istituto Europeo di Oncologia (Milano – Italia) ed una valutazione della dose imaging-dipendente su una popolazione clinica di pazienti sottoposti a trattamenti radioterapici con CyberKnife®.
Tutte le misure sono state effettuate con una camera a ionizzazione posta al centro dell’imaging della sala di trattamento di CyberKnife®, nel punto di intersezione degli assi principali dei due fasci di raggi X. La camera è stata connessa ad un elettrometro e tutte le letture sono state corrette per condizioni ambientali (pressione atmosferica e temperatura della stanza) e per la costante di calibrazione. Sono stati ottenuti i valori di Air Kerma variando i parametri espositivi del sistema di imaging di CyberKnife® (differenza di potenziale e carica elettrica). Questi dati hanno permesso la costruzione di un’equazione con cui è possibile stimare realisticamente la dose aggiuntiva di radiazioni dovuta all’imaging; i valori misurati ed i valori calcolati per i medesimi punti sono stati confrontati per stimare l’accuratezza della nostra equazione. È stato poi effettuato un controllo dei parametri espositivi di un campione di popolazione clinica trattato presso il nostro centro per il quale abbiamo calcolato i valori di Air Kerma. Questi valori sono infine stati confrontati con i valori forniti dal software del sistema CyberKnife®.
I valori di Air Kerma da noi calcolati hanno mostrato, in media, una variazione pari a ±1.8%, con un massimo del ±4.4% quando confrontati con i valori misurati di Air Kerma. Infine l’analisi dei valori di Air Kerma del campione clinico ha mostrato una sottostima della dose dovuta all’imaging da parte del software del sistema CyberKnife® quando paragonata con la dose calcolata da noi.
L’Air Kerma dipende dai valori di differenza di potenziale e carica elettrica selezionati dal TSRM e dal numero complessivo di coppie di radiografie necessarie per un trattamento completo di SRS o SBRT.
La localizzazione di bersagli con il sistema 6D Skull richiede, in genere, un numero inferiore di immagini e valori inferiori di differenza di potenziale e carica elettrica rispetto a trattamenti con X-Sight Spine, tutto ciò porta ad una più bassa dose dovuta all’imaging per pazienti trattati con il sistema 6D Skull. In media, la dose aggiuntiva dovuta all’imaging per il nostro campione è stata stimata essere lo 0.1% (per 6D Skull) e 0.3% (per X-Sight Spine) della dose terapeutica.(IGRT) intra and extracranial stereotactic radiotherapy and radiosurgery. The treatments of localized tumors are performed in a single (stereotactic radiosurgery SRS[8]) or few sessions (stereotactic radiotherapy SBRT[11]) with a high ionizing radiation rate. For this reason a high level of accuracy on target localization, obtained by the imaging guided system (TLS), is necessary.
The TLS consists in two orthogonal diagnostic X-ray sources fixed to the ceiling and aimed towards two flat panel detectors integrated into the floor. This system requires the acquisition of several pairs of images in order to localize the target position. These images are performed with frequency and exposition data decided by the radiographer, during the entire treatment.
Aim of this study is the evaluation of TLS Air Kerma of CyberKnife system, installed at the European Institute of Oncology (Milan – Italy) and an evaluation of the imaging-dependant dose in a clinical patient population receiving CyberKnife radiotherapy treatment.
All the measurements were performed with an ionization chamber positioned at the center point of imaging of the CyberKnife® treatment room, in the point of intersection of the two main axes of X-ray beams. The chamber was connected to an electrometer and all the readings were corrected for environmental conditions (atmospheric pressure and room temperature) and calibration constant. A series of Air Kerma values were obtained by varying the exposure parameters of CyberKnife® imaging system (electric potential difference and electric charge). These permitted to create a polynomial equation that allows a realistic evaluation of the dose due to the imaging. The measured and calculated values for the same points were compared in order to estimate the accuracy of our equation. An overview of the exposure parameters in a sample of clinical population treated in our centre, were then performed. With these parameters we calculated the Air Kerma values. These values were then compared with the values provided by the software of the CyberKnife®.
The Air Kerma values we calculated showed a percentage variation value of ±1.8%, with a maximum of ±4.4% when compared with measured Air Kerma values. The analysis of the Air Kerma values of the clinical sample showed that the CyberKnife® software underestimate the dose of the imaging when compared with the dose we calculated.
The Air Kerma depends on electric potential difference and electric charge values choose by the radiographer and on the overall number of radiographic pairs, needed for a complete SRS or SBRT treatment.
In general the target localization with the 6D Skull system, needs a lower number of images and lower electric potential difference and electric charge values than X-Sight Spine, so the imaging-dependent dose is lower for patients when the 6D Skull tracking system is used.
In our clinical sample the estimated average dose added by the imaging is 0.1% (for 6D Skull) and 0.3% (for X-Sight Spine) of the therapeutic dose
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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