1,720,971 research outputs found
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
Optimierung der Anzahl an Daten für das Trainieren von GANs (Generative Adversarial Networks) für die automatisierte Segmentation in der Strahlentherapie
Full text linkPurpose : Radiation oncology relies on the accuracy of organ-at-risk (OAR) and target structure delineations for dose calculations and treatment planning. The effect of inaccurate structure localization is more pronounced in particle therapy due to higher dose gradients in comparison to photon therapy. Manual segmentation is the gold standard even though inter-observer-variability and temporal anatomical changes influence subsequent dose calculations. However, manual segmentation is a time-consuming task, which makes it unfeasible for adaptive radiotherapy (ART). The increased workload due to multiple replannings could, therefore, benefit from automated segmentation. In particular, deep learning methods have already been used with great success in segmentation tasks and are currently investigated for their use in medical applications. Discriminative classifiers are one such method that is typically used for image segmentation. However, they suffer from small data sets resulting in overfitting, and typical loss functions do not guarantee spatial consistency. Generative adversarial networks (GANs), on the other hand, have shown promise in tackling those issues. This thesis aimed to compare GANs with convolutional neural networks (CNNs) based on the popular U-net architecture, as a type of discriminative classifier, on different sized training data. This was done to determine a potential benefit of using GANs for segmentation in radiation oncology. Both network architectures were trained, validated, and tested on segmentations of a subset of OARs in prostate cancer patients. Methods and Materials: Data of 360 patients, who were treated for prostate cancer at the Department of Radiation Oncology at the Medical University of Vienna, was investigated. The OARs were bladder, rectum, and the femoral heads. The CNN, as well as the GAN architecture, were trained on different training data sets consisting of 1, 6, 11, 16, 21, 26, and 100 patients. An extensive hyperparameter search was performed to identify the best settings for all observed structures. The performance of the networks was evaluated using metrics such as Dice similarity coefficient (DSC), sensitivity, precision, Hausdorff distance (HD), mean squared error (MSE), and root mean squared error (RMSE).Results: No significant difference could be observed for small training data set sizes between GAN and CNN when measured with the DSC. For sensitivity and precision, the networks did perform differently for certain data set sizes and OARs. The precision score of the GAN was higher for 6, 16, and 21 patients. For 1 and 6 patients in the training data set, the CNN performed better according to sensitivity. However, the sensitivity score of the GAN was higher for 16 patients. As sensitivity and precision are associated with over- and underrepresentation, this could indicate a correcting influence of the discriminator; however, there is no discernible trend amongst all patient data set sizes. For 100 patients, no significant difference was observed between the different architectures resulting in near-identical mean DSCs of bladder, rectum, and femoral heads of 0.89 ± 0.08, 0.84 ± 0.08, and 0.93 ± 0.06, respectively.Conclusion: In this thesis, no significant difference in performance between GAN and CNN could be observed. When compared to other factors, such as network architecture and data preprocessing, it might not be worth training GANs for image segmentation
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
Optical Coherence Tomography Angiography (OCTA) Captures Early Micro-Vascular Remodeling in Non-Melanoma Skin Cancer During Superficial Radiotherapy: A Proof-of-Concept Study
Full text linkBackground/Objectives: This proof-of-concept study evaluated whether optical coherence tomography angiography (OCTA) can non-invasively capture micro-vascular alterations in non-melanoma skin cancer (NMSC) lesions during and after superficial orthovoltage radiotherapy (RT) using radiomics and vascular features analysis. Methods: Eight patients (13 NMSC lesions) received 36–50 Gy in 6–20 fractions. High-resolution swept-source OCTA volumes (1.1 × 10 × 10 mm3) were acquired from each lesion at three time points: pre-RT, immediately post-RT, and three months post-RT. Additionally, healthy skin baseline was scanned. After artifact suppression and region-of-interest cropping, (i) first-order and texture radiomics and (ii) skeleton-based vascular features were extracted. Selected features after LASSO (least absolute shrinkage and selection operator) were explored with principal-component analysis. An XGBoost model was trained to classify time points with 100 bootstrap out-of-bag validations. Kruskal–Wallis tests with Benjamini–Hochberg correction assessed longitudinal changes in the 20 most influential features. Results: Sixty-one OCTA volumes were analyzable. LASSO retained 47 of 103 features. The first two principal components explained 63% of the variance, revealing a visible drift of lesions from pre- to three-month post-RT clusters. XGBoost achieved a macro-averaged AUC of 0.68 ± 0.07. Six features (3 texture, 2 first order, 1 vascular) changed significantly across time points (adjusted p < 0.05), indicating dose-dependent reductions in signal heterogeneity and micro-vascular complexity as early as treatment completion, which deepened by three months. Conclusions: OCTA-derived radiomic and vascular signatures tracked RT-induced micro-vascular remodeling in NMSC. The approach is entirely non-invasive, label-free, and feasible at the point of care. As an exploratory proof-of-concept, this study helps to refine scanning and analysis protocols and generates knowledge to support future integration of OCTA into adaptive skin-cancer radiotherapy workflows
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
106Ru eye plaque brachytherapy : benchmarking and evaluation of a novel 3D treatment planning system for uveal melanoma
No full textAderhautmelanome zählen zu den häufigsten Augentumoren mit einer Inzidenzrate von 1/100.000 pro Jahr. Die meisten Aderhautmelanompatienten profitieren von den verbesserten Strahlentherapietechniken, sodass eine Enukleation nur noch für sehr weit fortgeschrittene Tumorstadien notwendig wird. Hinsichtlich Tumorkontrolle und Nebenwirkungen erzielt die Brachytherapie mit 106Ru Augenapplikatoren exzellente Resultate in gleicher Weise wie Teletherapie mittels Photonen oder Protonen. Vergleicht man den Entwicklungsstand der Augenapplikator-basierten Brachytherapie mit der bildgesteuerten 3-dimensionalen Teletherapie liegt erstere allerdings hinsichtlich Bestrahlungsplanung und Qualitätssicherung hinter Teletherapie.
Derzeit basiert die Bestrahlungsplanung vorwiegend auf simplen 1-dimensionalen Dosisvorschreibungstabellen oder auf überholter Software, die den steigenden Anforderungen bezüglich verbesserter Planungsgenauigkeit, Planungsoptimierung, einer genauen 3D Abbildung von Tumor- und Risikostrukturgeometrie und Postimplantations-Qualitätssicherung nicht mehr genügt. Für die Verbesserung klinischer Ergebnisse sind derartige Weiterentwicklungen hinsichtlich einer Verbesserung der Nebenwirkungen essentiell.
Volumetrische Beschreibungen des Tumors und der Risikostrukturen, sowie die applizierte Dosis sind wesentliche Parameter, um die Abhängigkeit zwischen Dosis und Dosiswirkung zu verstehen. Ein erweitertes Verständnis dieser Beziehung wird somit eine individuellere Behandlung mit 106Ru Augenapplikatoren ermöglichen.
Im Zuge dieser Doktorarbeit wurde eine Forschungsversion eines Behandlungsplanungssystems für die 106Ru basierte Brachytherapie von Aderhautmelanomen entwickelt.
Um Dosis-Volumen Parameter basierend auf tatsächlich applizierten Dosen und einem volumetrischen Augenmodell für jeden Patienten ableiten zu können, wurden 3D Dosisverteilungen für die verschiedenen 106Ru Augenapplikatormodelle berechnet. Die im Monte Carlo Code MCNP6 generierten Nachschlagetabellen wurden mit Daten aus Messungen verglichen. Die Resultate zeigten eine gute Übereinstimmung zwischen errechneten und experimentellen Daten, sowie zu den Referenzwerten. Die resultierende statistische Unsicherheit lag deutlich unter den Angaben des Herstellers. Zusätzlich erlaubten die Filmmessungen eine genauere Beschreibung der 2D Dosisverteilungen über den gesamten Applikator. Die Informationen hieraus wurden genutzt, um Konzepte für Sicherheitssäume zu entwickeln, die auf realistischen dosimetrischen Messunsicherheiten beruhen.
Nach der Validierung der Dosisberechnung des neuen Behandlungsplanungssystems, wurden unterschiedliche Szenarien für Tumorgröße und -position untersucht. Applikatorfehlplatzierungen wurden ebenfalls berücksichtigt, um somit Unsicherheiten durch die chirurgische Platzierung der Plaques zu simulieren. Basierend auf den volumetrischen Dosisverteilungen in diesen unterschiedlichen Szenarien, wurde die Robustheit der Behandlungspläne untersucht. Zudem wurde die Empfindlichkeit von Risikostrukturen in Bezug auf eine ungenaue Positionierung des Applikators und der dosimetrischen Unsicherheit analysiert. Infolgedessen konnten Optimierungsstrategien der Behandlungsplanung entwickelt werden, um das Normalgewebe besser zu schonen.
Im letzten Schritt wurden Patientendaten der Behandlung der vergangenen 20 Jahre mit Brachytherapie gesammelt und hinsichtlich der Dosis-Wirkungs-Beziehung ausgewertet. Die wissenschaftliche Arbeit, die im Rahmen dieser Doktorarbeit durchgeführt wurde, hat einen neuartigen Software-basierten Ansatz für die brachytherapeutische Behandlung von Aderhautmelanomen geschaffen, der sowohl für die klinische Routine, als auch für pro- und retrospektive Studien genutzt werden kann.Uveal melanoma is the most prominent intraocular malignant tumor with an occurrence of 1 per 100,000 people per year. Nowadays, most patients with uveal melanoma benefit from advancements in conservative radiotherapy techniques and the necessity of enucleation is given only for very late stage patients. Among the different modalities utilized in the treatment, such as external beam photon and particle therapy, a long tradition of brachytherapy using 106Ru eye plaques achieves excellent tumor control and low toxicity rates. However, especially when compared to the recent advancements in image-guided three-dimensional external photon beam therapy on linear accelerators, the level of sophistication in aspects of treatment planning and quality assurance is very basic in eye plaque brachytherapy.
So far, treatment planning relies either on simplistic one-dimensional dose prescription tools or on software that appears outdated and does not live up to the requirements for improving the planning accuracy, treatment plan optimization, tumor and critical structure geometry, and post-implantation quality assurance. Such improvements, however, are necessary if the clinical outcome should be amended, especially with respect to side effects. The low radiation sensitivity of uveal melanomas requires the application of very high doses which in turn pose a threat to the functionality of the radiosensitive structures. This frail balance between tumor control and normal tissue complication probabilities (NTCP) demands an accurate dose delivery and provides room for optimization.
Volumetric descriptions of the tumor and critical structures and the dose deposited within these volumes are crucial parameters in order to understand the relationship between dose and response. By expanding the knowledge on this relationship, a more individual application of 106Ru eye plaques will become possible.
The work carried out for this thesis was aimed to tackle these deficiencies in the current treatment methodology. A research version of a treatment planning system for brachytherapy of uveal melanomas was developed, within the scope of this thesis.
In order to derive dose volume metrics based on actual delivered doses and a volumetric eye model for each patient, full three-dimensional dose distributions were calculated for different 106Ru plaque models. In a first step, these lookup tables, generated by the Monte Carlo code MCNP6, were compared to experimental data obtained from measurements using radiochromic films, diodes and Diamond detectors. The resulting data showed good agreement among the calculational, experimental and reference absolute and relative doses well within the uncertainties specified by the manufacturer. Additionally, the film measurements gave a better understanding of 2D dose distributions across the plaque. The information gained was used to establish margin concepts based on realistic dosimetric uncertainties.
Once the dose calculation of the novel TPS was validated, different scenarios of tumor location and size including plaque misplacements to simulate uncertainties after surgery were generated. Based on the calculated volumetric dose distributions in these scenarios, treatment plan robustness and sensitivities of critical structures to an inaccurate plaque positioning and dosimetric uncertainties were analyzed. This step helped to develop treatment plan optimization strategies to improve the sparing of normal tissue.
In a last step, patient data from the last 20 years of brachytherapy treatments at the Medical University of Vienna was collected and evaluated with respect to dose response relationships. The work carried out for the thesis allowed to establish a novel software based approach for treatment planning of ophthalmic plaque brachytherapy of uveal melanoma which can be used for clinical practice as well as a tool for pro- and retrospective studies, respectively.submitted by Gerd Heilemann, MScZusammenfassung in deutscher SpracheAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersMedizinische Universität Wien, Dissertation, 2017OeB
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