1,720,956 research outputs found
Current CT practice in Germany: Results and implications of a nationwide survey
No full textPurpose: To assess patient doses and relative frequencies of standard CT examinations performed in Germany in 2013/14 as well as the effect of modern CT technology on patient exposure. Methods: All known CT facilities in Germany were requested to complete a questionnaire on the frequency of 34 examinations and the respective parameter settings used. Taking into account type-specific properties of each scanner, effective doses were estimated for each reported examination. The mean and the percentiles of the CT dose index, scan length, dose length product, and effective dose were determined for each type of examination. Results: According to the data provided for about 11% of all medical CT scanners operated in 2013/14, the effective dose was 4.6/5.9 mSv per scan/examination. The effective dose was significantly reduced by about 15% compared to the CT practice before 2010. Modern CT technology, such as tube current modulation and iterative image reconstruction reduced the effective dose significantly by 6% and 13%, respectively. The mean effective dose applied at scanners produced by different manufacturers differed by 25%, at maximum. Conclusion: Patient exposure was reduced substantially in recent years. There is, however, still a considerable potential for further dose reduction by adapting scan protocols to the medical purpose and by a consequent exploitation of modern CT technologies. (C) 2017 Elsevier B.V. All rights reserved.German Roentgen Society (DRG); Association of German Radiologists (BDR
International survey on diagnostic reference levels based on clinical indications in plain radiography
No full textAbstract Purpose To collect and analyze radiation dose-related data as part of international cooperation; to define diagnostic reference levels (DRL) for 24 X-ray projections in plain radiography (DX) considering anatomical region, clinical task, and procedural technique; and to harmonize the exposure practice across country borders. Methods A multicenter study was performed in Austria, Germany, Italy, and Switzerland in 2022–23 to provide dose-related data. Healthcare facilities were asked to provide processed data from their dose management systems. A 5%-level was used for assessing the statistical significance of dose differences between various groups. Results Dose-related data from 85 radiographic systems in academic and non-academic, public, and private healthcare facilities were analyzed. Dose-related parameters differed significantly for many projections with different clinical tasks and techniques. Dose-related data of the procedures varied by a maximum factor of 16 for the same system, and median dose values also differed between hospitals by a maximum factor of 31. A fifth of the surveyed systems exhibit doses above more than half of the new DRLs defined in this study. Apart from the three reference procedures, no significant dose differences were observed between X-ray systems of different ages, from different manufacturers, or from different countries. Conclusions This is the first survey in which exposure practices were investigated in institutions in different central European countries by establishing clinical DRLs for radiography. The observed dose variations could be explained by different reasons, such as non-optimized dose protocols. The new DRLs help to harmonize the exposure practice across country borders. Key Points Question What is the exposure practice for plain radiography procedures for which no clinical diagnostic reference levels (DRLs) have been defined? Are there differences between countries? Findings The dose for the same clinical task and technique can vary considerably among institutions but, on average, do not significantly differ between neighboring countries in Europe. Clinical relevance In this international multicenter study, clinical DRLs were defined for 24 plain radiography projections to promote the optimization of the exposure practice, to reduce dose variations among institutions even across national borders, and to strengthen international cooperation among users
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
Struktur- und Staubentwicklung in zirkumstellaren Scheiben um TTauri-Sterne - Analyse und Modellierung hochauflösender Beobachtungen in verschiedenen Wellenlängenbereichen
No full textIm Zentrum dieser Doktorarbeit steht die Untersuchung der inneren Strukturen zirkumstellarer Scheiben um TTauri-Sterne sowie die Analyse zirkumstellarer Staub- und Eisteilchen und ihres Einflusses auf die Scheibenstruktur. Unter Zuhilfenahme von theoretisch berechneten Vergleichsspektren gibt der Verlauf der 10um-Emissionsbande in den Spektren junger stellarer Objekte Hinweise auf den Entwicklungsgrad von Silikatstaub. Die Silikatbanden von 27 TTauri-Objekten werden analysiert, um nach potentiell vorliegenden Korrelationen zwischen der Silikatstaubzusammensetzung und den stellaren Eigenschaften zu suchen. Analog erlaubt das Absorptionsband bei 3um, das dem Wassereis zugeschrieben wird, eine Untersuchung der Entwicklung von Eiskörnern in jungen stellaren Objekten. Erstmals ist es gelungen, kristallines Wassereis im Spektrum eines TTauri-Objektes nachzuweisen. Unser wichtigstes Hilfsmittel zur Analyse der Temperatur- und Dichtestrukturen zirkumstellarer Scheiben ist ein Monte-Carlo-Strahlungstransportprogramm. In einem erweiterten Modellansatz wird die Dichtestruktur der Scheibe in Abhängigkeit von deren Temperaturverteilung selbstkonsistent, mit Hilfe der hydrostatischen Gleichgewichtsbeziehung ermittelt. Die korrekte numerische Umsetzung wird in einer Vergleichsstudie verifiziert. Interferometrische Beobachtungen von 14 TTauri-Objekten im mittleren und nahen infraroten Wellenlängenbereich liefern Informationen über die räumliche Verteilung von warmem und heißem Staub. Ebenfalls sind Aussagen über die radiale Abhängigkeit des Entwicklungsgrades von Silikatstaub in den zirkumstellaren Scheiben um TTauri-Sterne möglich. Zur Modellierung interferometrischer Messungen und gleichzeitig der spektralen Energieverteilungen der beobachteten Objekte wird der Ansatz der passiven Scheibe bzw. der aktiven Scheibe mit oder ohne zirkumstellarer Hülle herangezogen. Mit Hilfe der interferometrischen Messungen kann die Anzahl der Modelle, die allein die spektrale Energieverteilung reproduzieren können, verringert werden
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
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