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### The influence of scattered photons on the accurate determination of microcalcification thickness in digital mammography

Grabski, Varlen
arXiv.org, Mar 31, 2004
© ProQuest LLC All rights reserved, Engineering Database, Publicly Available Content Database, ProQuest Engineering Collection, ProQuest Technology Collection, ProQuest SciTech Collection, Materials Science & Engineering Database, ProQuest Central (new), ProQuest Central Korea, SciTech Premium Collection, Technology Collection, ProQuest Central Essentials, ProQuest One Academic, Engineering Collection (ProQuest)
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Title: The influence of scattered photons on the accurate determination of microcalcification thickness in digital mammography
Author: Grabski, Varlen
Contributor: Grabski, Varlen (pacrepositoryorg)
Subject: Signal to Noise Ratio ; Photons ; Shape Recognition ; Mathematical Analysis ; Monte Carlo Method ; Functions (Mathematics) ; Calcification ; Polynomials ; Image Quality ; Reconstruction ; Thickness ; Computer Simulation ; Signal to Noise Ratio ; Scanning
Description: Our interest has been to study the effect that scattered radiation has on contrast, signal-to-noise ratio and thickness reconstruction in digital mammographies. Using the GEANT code we have performed Monte-Carlo simulations of 25 kVp Mo/Mo photons, through a breast phantom which contains a 0.2-1.0 mm thick microcalcifications incident on a 20x106 $$mm^{2}$$ pixelized detector. The data have been analyzed assuming 6 different shapes of the incident beam: a 0.2x0.2 $$mm^{2}$$ narrow'' beam, 4 different 20 mm long scanning beams of various widths, and a 20x100 $$mm^{2}$$ beam with no scatter reduction mechanisms (NSR) . Since the image of a point depends on scattered photons which passed up to 2 cm away from the object (for 4 cm thick phantom), we identify the background definition as a main source of systematic uncertainty in the image quality analysis. We propose the use of two dimensional functions (a polynomial for the background and Gaussians for the signal) for total photon transmission...
Is part of: arXiv.org, Mar 31, 2004
Identifier: 2331-8422 (E-ISSN)
• Several versions

### Deuteron and Antideuteron Production Simulation in Cosmic-ray Interactions

Gomez-Coral, Diego-Mauricio, Grabski, Varlen, Datta, Amaresh, Shukla, Anirvan
arXiv.org, Jun 25, 2018 [Peer Reviewed Journal]

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### New fiber read-out design for the large area scintillator detectors: providing good amplitude and time resolutions

Grabski, Varlen
Cornell University
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Title: New fiber read-out design for the large area scintillator detectors: providing good amplitude and time resolutions
Author: Grabski, Varlen
Subject: Physics - Instrumentation And Detectors
Description: Most of the time-of-flight systems as well as the fast interaction trigger detectors have large surfaces and the principal requirements for the above mentioned detectors is a good time resolution of the order 100-200ps. The easiest solution here is to split the large surface into the small tiles with a read-out directly attached to the photo-sensor. This solution is expensive because the number of the channels grows proportional to the surface. Although if the coverage of the whole surface by the sensors is not sufficient, one can obtain non uniform response, which is not acceptable if uniformity is required. Our suggestion is based on the usage of clear fibres mounted perpendicular on the surface of the scintillator as a matrix providing uniform surface reduction and keeping most of the benefices of the small tiles with the photo-sensors. In this work the design and some analytic estimations of the light collection efficiency for direct and reflected photons will be presented. Also some simple estimations are presented for the time-spread and for the light pulse wave form dependent on the lateral sizes and the thickness of the scintillator.
Identifier: 1909.01184 (ARXIV ID)
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### New fiber read-out design for the large area scintillator detectors: providing good amplitude and time resolutions

Grabski, Varlen
arXiv.org, Sep 3, 2019
© ProQuest LLC All rights reserved, Engineering Database, Publicly Available Content Database, ProQuest Engineering Collection, ProQuest Technology Collection, ProQuest SciTech Collection, Materials Science & Engineering Database, ProQuest Central (new), ProQuest Central Korea, SciTech Premium Collection, Technology Collection, ProQuest Central Essentials, ProQuest One Academic, Engineering Collection (ProQuest)
Available
Title: New fiber read-out design for the large area scintillator detectors: providing good amplitude and time resolutions
Author: Grabski, Varlen
Contributor: Grabski, Varlen (pacrepositoryorg)
Subject: Detectors ; Scintillation Counters ; Sensors ; Tiles ; Sensors ; Instrumentation and Detectors
Description: Most of the time-of-flight systems as well as the fast interaction trigger detectors have large surfaces and the principal requirements for the above mentioned detectors is a good time resolution of the order 100-200ps. The easiest solution here is to split the large surface into the small tiles with a read-out directly attached to the photo-sensor. This solution is expensive because the number of the channels grows proportional to the surface. Although if the coverage of the whole surface by the sensors is not sufficient, one can obtain non uniform response, which is not acceptable if uniformity is required. Our suggestion is based on the usage of clear fibres mounted perpendicular on the surface of the scintillator as a matrix providing uniform surface reduction and keeping most of the benefices of the small tiles with the photo-sensors. In this work the design and some analytic estimations of the light collection efficiency for direct and reflected photons will be presented. Also some...
Is part of: arXiv.org, Sep 3, 2019
Identifier: 2331-8422 (E-ISSN)
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### The influence of scattered photons on the accurate determination of microcalcification thickness in digital mammography

Grabski, Varlen, Brandan, Maria-Ester
Cornell University
Available
Title: The influence of scattered photons on the accurate determination of microcalcification thickness in digital mammography
Author: Grabski, Varlen; Brandan, Maria-Ester
Subject: Physics - Medical Physics
Description: Our interest has been to study the effect that scattered radiation has on contrast, signal-to-noise ratio and thickness reconstruction in digital mammographies. Using the GEANT code we have performed Monte-Carlo simulations of 25 kVp Mo/Mo photons, through a breast phantom which contains a 0.2-1.0 mm thick microcalcifications incident on a 20x106 $mm^{2}$ pixelized detector. The data have been analyzed assuming 6 different shapes of the incident beam: a 0.2x0.2 $mm^{2}$ narrow'' beam, 4 different 20 mm long scanning beams of various widths, and a 20x100 $mm^{2}$ beam with no scatter reduction mechanisms (NSR) . Since the image of a point depends on scattered photons which passed up to 2 cm away from the object (for 4 cm thick phantom), we identify the background definition as a main source of systematic uncertainty in the image quality analysis. We propose the use of two dimensional functions (a polynomial for the background and Gaussians for the signal) for total photon transmission description. Our main results indicate the possible calcification thickness reconstruction with an accuracy of the order of 6% using 3 mm wide scanning beam. Signal-to-noise ratio with the 3 mm wide beam gets improved by 20% with respect to NSR, a figure similar to that obtained with the narrow beam. Thickness reconstruction is shown to be an alternative to signal-to-noise ratio for microcalcification detection. Comment: 13 pages, 14 figures Eq. 6 and 14 have been corrected
Identifier: physics/0403041 (ARXIV ID)
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### Performance of the first prototype of the HAWC Gamma Ray Observatory

Sandoval, Andres, Alfaro, Ruben, Belmont, Ernesto, Grabski, Varlen, Renteria, Alejandro, Vasques, Alejandro, Vazquez, Omar, Gonzalez, M, Carramiñana, Alberto, Alvarez, Cesar
arXiv.org, Dec 17, 2009
© ProQuest LLC All rights reserved, Engineering Database, Publicly Available Content Database, ProQuest Engineering Collection, ProQuest Technology Collection, ProQuest SciTech Collection, Materials Science & Engineering Database, ProQuest Central (new), ProQuest Central Korea, SciTech Premium Collection, Technology Collection, ProQuest Central Essentials, ProQuest One Academic, Engineering Collection (ProQuest)
Available
Title: Performance of the first prototype of the HAWC Gamma Ray Observatory
Author: Sandoval, Andres; Alfaro, Ruben; Belmont, Ernesto; Grabski, Varlen; Renteria, Alejandro; Vasques, Alejandro; Vazquez, Omar; Gonzalez, M; Carramiñana, Alberto; Alvarez, Cesar
Contributor: Alvarez, Cesar (pacrepositoryorg)
Subject: Mexico ; Cerenkov Counters ; Water Tanks ; Arrays ; Gamma Ray Observatory ; Primary Cosmic Rays ; Cosmic Ray Showers ; Photomultiplier Tubes ; Elevation ; Observatories ; Cosmic Rays ; Gamma Rays ; Instrumentation and Methods for Astrophysics ; High Energy Astrophysical Phenomena
Description: The HAWC gamma ray observatory, to be constructed at Sierra Negra, Puebla in Mexico, is a large array of water Cherenkov detectors sited at an elevation of 4100 m, which has been optimized for gamma/hadron discrimination of the primary cosmic rays in the TeV energy range. It is based on the Milagro experience, but the design has been changed from a water pond to individual water tanks. In order to validate the design with large water tanks a prototype array has been constructed near the HAWC site with 3 of the largest commercial rotomolded plastic tanks available in Mexico. They have been instrumented with 20 cm hemispherical photomultiplier tubes and read out with 2 Gsample/s flash ADCs. The performance of a single tank has been measured as well as the response of the array to cosmic ray showers. In this paper we present the first measurements of the performance of the HAWC prototype array.
Is part of: arXiv.org, Dec 17, 2009
Identifier: 2331-8422 (E-ISSN)
• Article
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### Performance of the first prototype of the HAWC Gamma Ray Observatory

Sandoval, Andres, Alfaro, Ruben, Belmont, Ernesto, Grabski, Varlen, Renteria, Alejandro, Vasques, Alejandro R., Vazquez, Omar, Gonzalez, M. Magdalena, Carramiñana, Alberto, Alvarez, Cesar
Cornell University
Available
Title: Performance of the first prototype of the HAWC Gamma Ray Observatory
Author: Sandoval, Andres; Alfaro, Ruben; Belmont, Ernesto; Grabski, Varlen; Renteria, Alejandro; Vasques, Alejandro R.; Vazquez, Omar; Gonzalez, M. Magdalena; Carramiñana, Alberto; Alvarez, Cesar
Subject: Astrophysics - Instrumentation And Methods For Astrophysics ; Astrophysics - High Energy Astrophysical Phenomena
Description: The HAWC gamma ray observatory, to be constructed at Sierra Negra, Puebla in Mexico, is a large array of water Cherenkov detectors sited at an elevation of 4100 m, which has been optimized for gamma/hadron discrimination of the primary cosmic rays in the TeV energy range. It is based on the Milagro experience, but the design has been changed from a water pond to individual water tanks. In order to validate the design with large water tanks a prototype array has been constructed near the HAWC site with 3 of the largest commercial rotomolded plastic tanks available in Mexico. They have been instrumented with 20 cm hemispherical photomultiplier tubes and read out with 2 Gsample/s flash ADCs. The performance of a single tank has been measured as well as the response of the array to cosmic ray showers. In this paper we present the first measurements of the performance of the HAWC prototype array. Comment: 4 pages, 7 figures, 2009 Fermi Symposium, eConf Proceedings C091122
Identifier: 0912.3329 (ARXIV ID)
• Several versions