1,720,961 research outputs found
A comparison of three-field and four-field techniques in different clinical target volumes in prostate cancer irradiation using dose volume histograms: a prospective three-dimensional analysis
No full textThe purpose of the current study was to quantitatively assess differences between irradiation techniques on normal tissue exposure in different clinical target volumes (CTVs) in irradiation of prostate cancer. 14 patients with prostate cancer undergoing external beam radiotherapy were investigated. The prostate and prostate + proximal/entire seminal vesicles were delineated as CTVs. A three-field and two different four-field plans were generated and compared concerning rectum, bladder and femoral head dose-volume histograms (DVHs). The exposure of the rectum exposed to 40-60 Gy was significantly lower for all CTVs with the three-field technique compared with both four-field techniques. The exposure of the rectum to 70 Gy was significantly lower for all CTVs with the weighted four-field technique compared with the unweighted four-field and three-field techniques. The weighted four-field technique was worst in bladder dose sparing for the three CTVs. Comparing the threefield and the unweighted four-field technique for irradiation of the prostate and prostate + entire seminal vesicles, no technique provided a clear advantage or disadvantage in bladder dose sparing. For irradiation of the prostate + proximal seminal vesicles the unweighted four-field technique provided the best bladder dose sparing. Concerning the exposure of the femoral heads, the three-field technique was significantly worse for the three CTVs compared with both four-field techniques. No difference was found between the unweighted and the weighted four-field techniques. in conclusion, none of the studied techniques consistently proved superior in different CTVs in prostate cancer irradiation with respect to sparing all organs at risk. The absolute differences between the three techniques were small and the clinical relevance of these findings is uncertain
A prospective three-dimensional analysis about the impact of differences in the clinical target volume in prostate cancer irradiation on normal-tissue exposure - A potential for increasing the benefit/risk ratio
No full textBackground and Purpose: Rectal toxicity following external-beam irradiation of prostate cancer correlates with the exposed percentage of rectal volume. Recently, it has been recommended to reduce the volume of the seminal vesicles that should be included in the clinical target volume (CTV). The purpose of this study was to quantitatively assess the impact of this CTV reduction on the expected rectal and bladder dose sparing. Patients and Methods: 14 patients with Localized prostate cancer undergoing external-beam radiotherapy were investigated. The prostate, the prostate + entire seminal vesicles, or the prostate + proximal seminal vesicles were delineated as CTV. Treatment plans were generated and compared concerning rectum and bladder dose-volume histograms (DVHs). Results: The exposure of rectum and bladder volume was significantly Lower in case of irradiation of the prostate only compared to inclusion of the proximal or entire seminal vesicles into the CTV. The reduction of the CTV from prostate + entire seminal vesicles to prostate + proximal seminal vesicles Led to a significant reduction of the rectal and bladder dose exposure. Conclusion: Reduction of the CTV to the prostate only, or to the prostate + proximal seminal vesicles Led to significant rectal and bladder dose sparing compared to irradiation of the prostate + entire seminal vesicles. In patients with a higher risk for seminal vesicles involvement, irradiation of the prostate + proximal seminal vesicles should be preferred. In case of a need for irradiation of the entire seminal vesicles, patients should be informed about a higher risk for chronic rectal toxicity and, possibly, for bladder complications
The impact of varying volumes in rectal balloons on rectal dose sparing in conformal radiation therapy of prostate cancer - A prospective three-dimension analysis
No full textBackground and Purpose: The use of a rectal balloon Leads to a protection of the posterior rectal wall in irradiation of prostate cancer. The purpose of this analysis was to quantitatively assess the optimal volume in rectal balloons concerning rectal dose sparing in different clinical target volumes (CTVs) in prostate cancer irradiation. Patients and Methods: 14 patients with localized prostate cancer undergoing external beam radiotherapy were investigated. The prostate, the entire and the proximal seminal vesicles were delineated as CTV. Treatment plans without a rectal balloon and with a rectal balloon inflated with 40 ml (six patients) or 60 ml air (eight patients) were generated for each CTV and compared concerning rectal dose volume histograms. Results: The use of a rectal balloon filled with 40 ml air Led to no significant advantage in radiation exposure of the rectal wall in all CTVs. The use of a rectal balloon filled with 60 ml air resulted in a significant decrease of the exposed rectal wall volume in all CTVs with a reduced estimated risk for chronic toxicity in case of inclusion of the proximal or entire seminal vesicles into the CTV. Conclusion: The use of a rectal balloon filled with 60 ml air Led to a significantly decreased proportion of the irradiated rectal wall for all CTVs. This volume filled in rectal balloons is therefore recommended for use. In case of irradiation of the prostate without the seminal vesicles, the use of a rectal balloon should be considered carefully concerning the patients' imaginable discomfort using a rectal balloon and a questionable advantage concerning the estimated risk for chronic toxicity
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
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