1,720,966 research outputs found
Adjuvant treatment of brain metastases
No full textWith an incidence of 15/10(5) in the general population, brain metastases constitute a serious, debilitating complication in cancer patients. The majority of those patients suffer from more than one metastasis, but up to 30% to 40% present with a solitary lesion. Whole-brain radiotherapy (WBRT) extends median survival from 1 to 2 months for treatment with steroids only, to 4 to 6 months in most series. However, long-term survival(>l-2 years) is observed in up to 10% of patients with favorable prognostic factors, such as solitary lesions, good Karnofsky performance status, and absence of extracranial disease. For those patients, individually optimized treatment is worthwhile. For good-prognosis patients with controlled extracranial disease, surgery in combination with postoperative WBRT should be considered, especially when fast relief of symptoms is mandated. For surgically inaccessible solitary lesions below a size threshold of approximately 30 ccm, stereotactic radiosurgery (RS), although never compared to surgery in a randomized fashion, seems to yield comparable results and is the treatment of choice for more than one lesion in appropriately selected patients. Nevertheless, a number of questions concerning the optimal treatment regimens for brain metastases remain. These mainly concern the radiation dose, need for a combination of RS and WBRT, relative timing of different treatment modalities, and maximum number of brain metastases that can reasonably be treated with RS when long-term progression-free survival is the peal. However, RS is definitely an excellent option for salvage and palliation in patients with short life expectancy, as it is simultaneously noninvasive and cost-effective, with short hospitalization times. (C) 2001 Wiley-Liss, Inc
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
Conformal radiotherapy of challenging paraspinal tumors using a multiple arc segment technique
No full textPurpose: Target volumes that wrap around the spinal cord are difficult to treat. We present and evaluate a refined multiple are segment (MAS) technique that is applicable with standard three-dimensional (3D) radiotherapy equipment and may be a solution for facilities that do not get have full access to intensity-modulated radiotherapy (IMRT). Methods and Materials: The presented technique consisted of 13 isocentric coplanar beam's eye view shaped fields,delivered as 20 degrees or 10 degrees are segments with an integrated multileaf collimator (MLC) using automatic sequential field delivery. Dose-volume histograms (DVH) for this technique were compared to a modified bar-are technique (MBA) modeled as 30 static fields and to an inverse planned IMRT technique using 7 coplanar, equispaced beams delivered with the same MLC. Results: Compared to the MBA technique, maximum dose and target coverage were similar when using 80% of the maximum dose as the reference dose. However, the MAS technique reduced the maximum doses (to greater than or equal to1% of the organs at risk [OAR]) by 9% for the spinal cord, 17% for the esophagus, and 25% for the trachea, as well as the mean doses. Although inverse planned IMRT could further reduce exposure of OAR except for the spinal cord and improve target coverage, our forward planned MAS technique seems to achieve clinically comparable results. Conclusion: Substituting a series of small split-field are segments for large static fields and using additional narrow paraspinal segments significantly improves the sparing of organs at risk for paraspinal targets, Although these results are not quite as good as those achieved with IMRT, for facilities not yet equipped with inverse treatment planning capability, the presented technique enables dose escalation for primary paraspinal tumors and retreatment of recurrent lesions, (C) 2000 Elsevier Science Inc
Comparison of intensity-modulated radiotherapy with conventional conformal radiotherapy for complex-shaped tumors
No full textPurpose: Conformal and intensity-modulated radiotherapy (IMRT) plans for 9 patients were compared based on characterization of plan quality and effects on the oncology department. Methods and Materials: These clinical cases, treated originally with conformal radiotherapy (CRT), required extraordinary effort to produce conformal treatment plans using nonmodulated, shaped noncoplanar fields with multileaf collimators (MLCs). IMRT plans created for comparison included rotational treatments with slit collimator, and fixed-field MLC treatments using equispaced coplanar, and noncoplanar fields. Plans were compared based upon target coverage, target conformality, dose homogeneity, monitor units (MU), user-interactive planning time, and treatment delivery time. The results were subjected to a statistical analysis. Results: IMRT increased target coverage an average of 36% and conformality by 10%. Where dose escalation was a goal, IMRT increased mean dose by 4-6 Gy and target coverage by 19% with the same degree of conformality. Rotational IMRT was slightly superior to fixed-field IMRT. All IMRT techniques increased integral dose and target dose heterogeneity. IMRT planning times were significantly less, whereas MU increased significantly; estimated delivery times were similar. Conclusion: IMRT techniques increase dose and target coverage while continuing to spare organs-at-risk, and can be delivered in a time frame comparable to other sophisticated techniques. (C) 2000 Elsevier Science Inc
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
Conformal three-dimensional photon radiotherapy for paranasal sinus tumors
No full textBackground: Tumors in the nasal cavity and paranasal sinus are difficult to treat with radiotherapy. Usually, in addition to a two- or three-field photon technique, an interorbital electron field is required. This may result, however, in severe over or underdosage, the latter being especially detrimental when occurring in the main tumor bulk. Methods and results: We present a conformal three-dimensional treatment technique that provides sufficient interorbital dose with photons only while sparing the eyes, optic nerves and chiasm, and may be considered for selected tumors in this region. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved
Radiosurgery alone or in combination with whole-brain radiotherapy for brain metastases
No full textPurpose: Evaluation of the treatment outcome after radiosurgery (RS) alone or in combination with whole-brain radiotherapy (WBRT) with special attention to prescribed dose and its influence on local control and survival. Patients and Methods: Between September 1984 and January 1997, 236 patients with 311 brain metastases treated with radiosurgery met the following inclusion criteria: one to three brain metastases per patient; no previous WBRT; and Karnofsky performance status (KPS) greater than or equal to 50%. One,hundred fifty-eight patients treated only with RS received a median dose of 20 Gy prescribed to the 80% isodose line; 78 patients received RS with a median dose of 15 Gy/80% and an additional course of WBRT. Results: For the entire series, overall median survival was 5.5 months, with control of CNS disease achieved in 92% of the treated brain metastases; the results were not significantly different between patients treated by RS with or without WBRT. However, in patients without evidence of extracranial disease, median survival wets increased for patients who received WBRT (15.4 vs 8.3 months; P = .08). Additionally, there was a suggestion that increased doses for patients treated with RS only resulted in improved outcome. Four lesions were suspicious for radiation necrosis by magnetic resonance imaging (MRI); in one of the four lesions, radiation necrosis was confirmed histologically. the incidence of transient low-grade toxicity was 18%; symptoms could be treated by the temporary administration of steroids. Conclusion: RS is an effective, noninvasive means of controlling brain metastases when used alone or in combination with WBRT. There is a trend for superior local control and especially in patients without extracranial disease for superior survival when RS is used in conjunction with WBRT. Randomized trials would seem to be warranted, comparing the benefit of RS with or without additional WBRT. (C) 1998 by American Society of Clinical Oncology
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
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