1,720,997 research outputs found
Special Section Guest Editorial:Clinical near-infrared spectroscopy and imaging of the brain
No full textImplementation of the extended Kalman filter for determining the optical and geometrical properties of turbid layered media by time-resolved single distance measurements
Get PDFIn this article we propose an implementation of the extended Kalman filter (EKF) for the retrieval of optical and geometrical properties in two-layered turbid media assuming a dynamic setting, where absorption of each layer was changed in different steps. Prior works implemented the EKF in frequency-domain with several pairs of light sources and detectors and for static parameters estimation problems. Here we explore the use of the EKF in single distance, time-domain measurements, together with a corresponding forward model. Results show good agreement between retrieved and nominal values, with rather narrow analytical credibility intervals, indicating that the recovery process has low uncertainty, especially for the absorption coefficients.Fil: Baez, Guido Rodrigo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: García, Héctor Alfredo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Grosenick, Dirk. Physikalisch-technische Bundesanstalt; AlemaniaFil: Wabnitz, Heidrun. Physikalisch-technische Bundesanstalt; Alemani
Depth selectivity in time-domain fNIRS by analyzing moments and time windows
Get PDFTime-domain fNIRS facilitates the elimination of the influence of extra-cerebral, systemic effects on measured signals since it contains time-of-flight information that is related to the penetration depth. Employing perturbation and Monte-Carlo simulations, we quantitatively characterized and compared the performance of measurands based on moments and time windows of time-of-flight distributions. We extend our analysis to investigate whether higher moments and Mellin-Laplace(ML)moments promise improvements in performance. The comparison is based on spatial sensitivity profiles as well as metrics forrelative contrast, contrast-to-noise ratio (CNR), depth selectivity, and the product of CNR and depth selectivity for layered absorption changes.The influence of reduced scattering coefficient, thickness of the superficial layer, and source-detector distance was analyzed.The third central moment performs similarly to variance and is worth considering for data analyzes.Higher order ML moments perform similarly to time windows and they likewise provide variable depth selectivity
Assessment of tissue ischemia of nail fold precapillary zones using a fluorescence capillaroscopy
Get PDFAn optical instrument for nailfold fluorescence capillaroscopy and image registration has been developed. With this instrument, an effect of increasing fluorescence intensity in the spectral range of NADH fluorescence during ischemia was detected
Towards real-time functional human brain imaging with diffuse optical tomography
No full textA framework for efficient formulation of the inverse model in diffuse optical tomography, incorporating parallel computing is proposed. Based on 24 subjects, a tenfold speed increase and a hundredfold memory efficiency is reported, whilst maintaining reconstruction quality.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Multispectral diffuse optical tomography of finger joints
No full textRheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovial inflammation. The current treatment paradigm for earlier, more aggressive therapy places importance on development of functional imaging modalities, capable of quantifying joint changes at the earliest stages. Diffuse optical tomography (DOT) has shown great promise in this regard, due to its cheap, non-invasive, non-ionizing and high contrast nature. Underlying pathological activity in afflicted joints leads to altered optical properties of the synovial region, with absorption and scattering increasing. Previous studies have used these optical changes as features for classifying diseased joints from healthy. Non-tomographic, single wavelength, continuous wave (CW) measurements of trans-illuminated joints have previously reported achieving this with specificity and sensitivity in the range 80 - 90% [1]. A single wavelength, frequency domain DOT system, combined with machine learning techniques, has been shown to achieve sensitivity and specificity in the range of 93.8 - 100% [2]. A CW system is presented here which collects data at 5 wavelengths, enabling reconstruction of pathophysiological parameters such as oxygenation and total hemoglobin, with the aim of identifying localized hypoxia and angiogenesis associated with inflammation in RA joints. These initial studies focus on establishing levels of variation in recovered parameters from images of healthy controls.</p
Variations on the Author
Get PDF“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
- …
