219 research outputs found
Matched-filtering and parameter estimation of ringdown waveforms
Using recent results from numerical relativity simulations of non-spinning
binary black hole mergers we revisit the problem of detecting ringdown
waveforms and of estimating the source parameters, considering both LISA and
Earth-based interferometers. We find that Advanced LIGO and EGO could detect
intermediate-mass black holes of mass up to about 1000 solar masses out to a
luminosity distance of a few Gpc. For typical multipolar energy distributions,
we show that the single-mode ringdown templates presently used for ringdown
searches in the LIGO data stream can produce a significant event loss (> 10%
for all detectors in a large interval of black hole masses) and very large
parameter estimation errors on the black hole's mass and spin. We estimate that
more than 10^6 templates would be needed for a single-stage multi-mode search.
Therefore, we recommend a "two stage" search to save on computational costs:
single-mode templates can be used for detection, but multi-mode templates or
Prony methods should be used to estimate parameters once a detection has been
made. We update estimates of the critical signal-to-noise ratio required to
test the hypothesis that two or more modes are present in the signal and to
resolve their frequencies, showing that second-generation Earth-based detectors
and LISA have the potential to perform no-hair tests.Comment: 19 pages, 9 figures, matches version in press in PR
A Avaliação da usabilidade de um sistema médico inteligente: BCCT.core
A avaliação estética da mama é um requisito em diversas aplicações médicas, nomeadamente no tratamento conservador do cancro da mama.
Para ultrapassar as limitações de reprodutibilidade e praticabilidade dos métodos subjectivos correntes, foi
recentemente desenvolvido um sistema inovador, assistido por computador para uso médico, denominado BCCT.core (Breast Cancer Conservative Treatment.cosmetic results), que prevê, automaticamente,
o resultado estético do tratamento conservador do cancro da mama após intervenção [1].
Um dos grandes desafios no desenvolvimento de
qualquer sistema computacional é desenhar interfaces de utilizador eficazes — fáceis de aprender, efectivas e que conduzam a uma experiência agradável.
Neste trabalho, analisamos alguns dos aspectos mais importantes do desenho da interface do BCCT.core, relacionados com o estudo da interacção com o utilizador,
em relação à funcionalidade e usabilidade, através de um questionário dirigido a utilizadores reais dentro do domínio da aplicação.
O desempenho do sistema pôde assim ser avaliado por critérios claros, apoiado numa base sólida que permitiu
avaliar a percepção humana relativamente à interface, conduzindo ao desenvolvimento de um sistema que apoia
efectivamente os utilizadores na realização de tarefas.
De uma forma geral pode concluir-se que a utilização de técnicas de interacção homem-computador na avaliação da funcionalidade e usabilidade do BCCT.core foram
essenciais no sentido de o tornar mais usável, eficiente e com elevado grau de satisfação, neste caso particular, para o utilizador médico
INbreast: Toward a Full-field Digital Mammographic Database
Rationale and Objectives
Computer-aided detection and diagnosis (CAD) systems have been developed in the past two decades to assist radiologists in the detection and diagnosis of lesions seen on breast imaging exams, thus providing a second opinion. Mammographic databases play an important role in the development of algorithms aiming at the detection and diagnosis of mammary lesions. However, available databases often do not take into consideration all the requirements needed for research and study purposes. This article aims to present and detail a new mammographic database.
Materials and Methods
Images were acquired at a breast center located in a university hospital (Centro Hospitalar de S. João [CHSJ], Breast Centre, Porto) with the permission of the Portuguese National Committee of Data Protection and Hospital's Ethics Committee. MammoNovation Siemens full-field digital mammography, with a solid-state detector of amorphous selenium was used.
Results
The new database—INbreast—has a total of 115 cases (410 images) from which 90 cases are from women with both breasts affected (four images per case) and 25 cases are from mastectomy patients (two images per case). Several types of lesions (masses, calcifications, asymmetries, and distortions) were included. Accurate contours made by specialists are also provided in XML format.
Conclusion
The strengths of the actually presented database—INbreast—relies on the fact that it was built with full-field digital mammograms (in opposition to digitized mammograms), it presents a wide variability of cases, and is made publicly available together with precise annotations. We believe that this database can be a reference for future works centered or related to breast cancer imaging
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