1,721,002 research outputs found
Spatial linearity improvement for discrete scintillation imagers
No full textIn principle, a scintillation imager made by a crystal array and a position-sensitive photomultiplier shows spatial non linearities at borders due to the undersampling of scintillation light distributions. To improve the response of such detectors a method has been carried out based on the comparison between experimental and simulated images. A computer simulation code has been developed and used to foresee the imager response. The code computes the tapered charge-weighting factors giving the optimized event centroiding in terms of crystal-pixel identification. The comparison between measured centroids and crystal axes produces the effective correction table for image linearization. Experimental results concerning a 8x8 crystal array coupled to a position sensitive photomultiplier tube (1 inch square) are presented and discussed
DISIS - A computer simulation code for discrete scintillation imagers
No full textA computer simulation code has been developed in order to foresee the response of discrete scintillation imaging devices. Discrete Scintillation Imager Simulator (DISIS) has been designed for imagers based on a scintillation array coupled to a position sensitive light sensor (like position sensitive photomultiplier tube or avalanche photodiode array) by a planar light guide. The simulator is a deterministic code that uses: (i) a model describing the single photon light distribution emerging from a crystal pixel for charge integrals evaluation; (ii) the assigned algorithm for centroid calculation and; (iii) the Gaussian spread for localizing, crystal by crystal, the events on the image. In particular DISIS allows us to study the spatial response over the imager field of view changing parameters individually. The imager optimization can be obtained searching an acceptable pixel identification. To this aim a good trade-off between the spread of light distribution, the light sampling capability over the light-sensor area and the centroiding algorithm has to be found. © 2004 IEEE
Mammotone breast cancer biopsy: combined guided with X-ray stereotaxis and imaging probe
No full textMammotome breast cancer biopsy: combined guided with X-ray stereotaxis and imaging probe.
No full textA combined application for breast cancer detection was described. Imaging probe (IP) was put inside a Fisher digital stereotactive device prepared for mammotome biopsy, so biopsy was driven by X-ray stereotaxis and 99mTc-Sestamibi (MIBI) images from IP. High-resolution IP scintigraphy showed substantial matching between MIBI hot spots and X-ray opacities
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
The role of Monte Carlo transport simulations in the new design of a small scintigraphic detector
No full textThe development of a scintigraphic imager is a time-consuming, high-cost interdisciplinary task. Aim of this work is to illustrate the role of Monte Carlo Nuclear Particle (MCNP) transport code in the development of an intra-operative Imaging Probe (IP). A MCNP transport model was used to test some improvement hypotheses regarding collimation and scintillating crystal. On the basis of the simulation outcome, an improved imager prototype was built and preliminary tested. Experimental results were compared with simulation predictions showing a good agreement. These results encourage us to continue the development of a more complex model to be used as "ideal observer" for the imaging probe performance evaluations. © 2005 Elsevier B.V. All rights reserved
Monte Carlo simulations of a human phantom radio-pharmacokinetic response on a small field of view scintigraphic device
No full textThe limiting factors for the scintigraphic clinical application are related to i) biosource characteristics (pharmacokinetic of the drug distribution between organs), Detection chain (photons transport, scintillation, analog to digital signal conversion, etc.) Imaging (Signal to Noise ratio, Spatial and Energy Resolution, Linearity etc) In this work, by using Monte Carlo time resolved transport simulations on a mathematical phantom and on a small field of view scintigraphic device, the trade off between the aforementioned factors was preliminary investigated
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
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