1,720,961 research outputs found
Quantitive Modelling of Tissue Activity Curves of 64Cu-ATSM and Delineation of Tumour Sub-Volumes in Treatment Planning.
Full text linkThe majority of solid tumours develop hypoxia because oxygen demand exceeds oxygen supply. In association with this is the poor prognosis and response to therapy. In oncology, it is well appreciated that merging anatomical and functional information has a significant impact on the extent of disease and target volume delineation. Commercial image-fusion software packages are becoming available but require comprehensive evaluation to ensure reliability of image-fusion and the underpinning registration algorithms, particularly for radiotherapy. The present work seeks to assess such accuracy for a number of available registration methods provided by the commercial package ProSoma™. The molecular imaging modality of Positron Emission Tomography (PET), in conjunction with radio-labelled molecules that undergo chemical changes inside tumours as a result of the presence or absence of oxygen, has became a promising technique for the non-invasive quantification of tumour hypoxia. Herein the relationship between tumour hypoxia and vasculature geometry is considered using a novel mathematical approach, likewise the spatiotemporal distribution of a hypoxia PET sensitive tracer is determined. Representation of the oxygen distribution in 2-D vascular architecture using a reaction diffusion model enables quantitative relationships to be obtained, specifically between tissue diffusivity, tissue metabolism, anatomical structure of blood vessels and oxygen gradients. Similarly, tissue activity curves (TAC) are a potential key in providing information on cellular perfusion and limited-diffusion. In this thesis a development to the work of Kelly and Brady (2006) is described and verified, with a particular interest in simulating TACs of the most promising hypoxia PET sensitive tracer, 64Cu-ATSM
Quantitive Modelling of Tissue Activity Curves of 64Cu-ATSM and Delineation of Tumour Sub-Volumes in Treatment Planning.
No full textThe majority of solid tumours develop hypoxia because oxygen demand exceeds oxygen supply. In association with this is the poor prognosis and response to therapy. In oncology, it is well appreciated that merging anatomical and functional information has a significant impact on the extent of disease and target volume delineation. Commercial image-fusion software packages are becoming available but require comprehensive evaluation to ensure reliability of image-fusion and the underpinning registration algorithms, particularly for radiotherapy. The present work seeks to assess such accuracy for a number of available registration methods provided by the commercial package ProSoma™. The molecular imaging modality of Positron Emission Tomography (PET), in conjunction with radio-labelled molecules that undergo chemical changes inside tumours as a result of the presence or absence of oxygen, has became a promising technique for the non-invasive quantification of tumour hypoxia. Herein the relationship between tumour hypoxia and vasculature geometry is considered using a novel mathematical approach, likewise the spatiotemporal distribution of a hypoxia PET sensitive tracer is determined. Representation of the oxygen distribution in 2-D vascular architecture using a reaction diffusion model enables quantitative relationships to be obtained, specifically between tissue diffusivity, tissue metabolism, anatomical structure of blood vessels and oxygen gradients. Similarly, tissue activity curves (TAC) are a potential key in providing information on cellular perfusion and limited-diffusion. In this thesis a development to the work of Kelly and Brady (2006) is described and verified, with a particular interest in simulating TACs of the most promising hypoxia PET sensitive tracer, 64Cu-ATSM
Quantitative Modeling of Tissue Activity Curves of 64Cu-ATSM and Delineation of Tumour Sub-volumes in Treatment Planning
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Quantitive Modelling of Tissue Activity Curves of 64Cu-ATSM and Delineation of Tumour Sub-Volumes in Treatment Planning.
No full textThe majority of solid tumours develop hypoxia because oxygen demand exceeds oxygen supply. In association with this is the poor prognosis and response to therapy. In oncology, it is well appreciated that merging anatomical and functional information has a significant impact on the extent of disease and target volume delineation. Commercial image-fusion software packages are becoming available but require comprehensive evaluation to ensure reliability of image-fusion and the underpinning registration algorithms, particularly for radiotherapy. The present work seeks to assess such accuracy for a number of available registration methods provided by the commercial package ProSoma™. The molecular imaging modality of Positron Emission Tomography (PET), in conjunction with radio-labelled molecules that undergo chemical changes inside tumours as a result of the presence or absence of oxygen, has became a promising technique for the non-invasive quantification of tumour hypoxia. Herein the relationship between tumour hypoxia and vasculature geometry is considered using a novel mathematical approach, likewise the spatiotemporal distribution of a hypoxia PET sensitive tracer is determined. Representation of the oxygen distribution in 2-D vascular architecture using a reaction diffusion model enables quantitative relationships to be obtained, specifically between tissue diffusivity, tissue metabolism, anatomical structure of blood vessels and oxygen gradients. Similarly, tissue activity curves (TAC) are a potential key in providing information on cellular perfusion and limited-diffusion. In this thesis a development to the work of Kelly and Brady (2006) is described and verified, with a particular interest in simulating TACs of the most promising hypoxia PET sensitive tracer, 64Cu-ATSM
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
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