1,721,439 research outputs found
Advantages of quasi-monochromatic X-ray sources in absorption mammography
No full textMammography is a challenging field of medical imaging. Early detection of breast cancer requires identifying small contrast details. The choice of the appropriate monochromatic energy enhances the visibility of such details. Thomson scattering source can provide tunable quasi-monochromatic X-ray beams. In this work, we investigate by Monte Carlo simulations the optimal monochromatic energy to image mammographic phantoms. In order to mimic a Thomson scattering source, we consider the effect on image quality of the presence of an energy spread and of the presence of higher-order harmonics
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
Visibility of tumor-like details in inline phase contrast mammography using quasi monochromatic X-ray sources
No full text
Visibility of tumor-like details in inline phase contrast mammography using quasimonochromatic X-ray sources
No full textA new generation of quasimonochromatic high-flux X-ray sources, based on the X-ray radiation
produced through Compton scattering between an electron beam and a laser beam, is under
development. One of the possible applications of this source is inline phase contrast mammography,
based on the observation of the edge-enhancement effect that can be observed at the border of structures
inside the breast in images produced using a partially or totally coherent X-ray beam. In this work we
present the results of a set of simulations of inline phase contrast mammography using typical inverse
Compton scattering sources parameters. The simulated sample was a tumour-like mass having spherical
shape, diameter between 200 mm and 5 mm, placed inside a breast-like matrix, 4 cm thick, and a
standard composition of 50% glandular tissue and 50% adipose tissue. We discuss the minimum
requirements for mammography using inverse Compton scattering sources and we discuss how the
working parameters of the experimental setup (focal spot size, source–object distance, object–detector
distance, detector point spread function, mean energy, energy bandwidth) affect the image quality, and
specifically the edge-enhancement visibility. In particular, we show that the energy bandwidth does not
significantly affect the visibility up to several keV. On the other hand, the edge-enhancement visibility
depends substantially on other parameters such as source–object distance and detector point spread
function
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