1,721,869 research outputs found
The impact of gross tumor volume (GTV) and clinical target volume (CTV) definition on the total accuracy in radiotherapy - Theoretical aspects and practical experiences
No full textAim: To evaluate the impact of interobserver variability in the contouring of gross tumor volumes (GTVs) and clinical target volumes (CTVs) on the global geometric accuracy in radiation therapy. Material and Methods: In a review of the currently available Literature, the magnitude of interobserver variability is analyzed, causes and consequences are discussed. Uncertainties due to inconsistencies in contouring are related to other sources of geometric errors, particularly patient positioning and organ motion. Results: Interobserver variability is a major-for some tumor Locations probably the Largest-factor contributing to geometric inaccuracy. Causes are multifactorial and include image- and observer-related factors, such as the subjective interpretation of image information. Conclusion: Consequences to reduce interobserver variability are proposed, among others the selection of adequate imaging modalities, intensified radiologic training, and the use of telecommunication tools
Comment by E. Weiss and C.F. Hess on G.M. Villeirs et al. Interobserver delineation variation using CT versus combined CT+MR in intensity-modulated radiotherapy for prostate cancer in: Strahlenther Onkol 2005;181 : 424-30
No full textDifferent maximal leaf-speeds and dose rates influencing the monitor unit and risk organ strain for dynamic IMRT
No full textGoing 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
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
Impact of a double belly board on the testis dose compared with a conventional belly board in the irradiation of patients with rectum cancer
No full textTest protection through application of a double-cavity board in radiation of patients with rectal cancer
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