Results 251 to 260 of about 1,514,488 (302)
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Measurement of half‐value layer in x‐ray CT: A comparison of two noninvasive techniques
Medical Physics, 2000The purpose of this paper is to determine the accuracy and reproducibility of two noninvasive methods of measuring half‐value layer (HVL), ring and localization, compared with an invasive technique (suspending tube rotation). The ring method uses concentric aluminum rings about a CTDI ionization chamber at isocenter.
R L, Kruger, C H, McCollough, F E, Zink
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Determination of Half-Value Layer
Radiology, 1959In the determination of half-value layer, the geometry involved is usually described as “good” geometry or “poor” geometry. In general, these terms have reference to measurements made under narrow-beam and broad-beam conditions. Such conditions have not been too well explored.
E D, TROUT, J P, KELLEY, A C, LUCAS
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Uncertainties in half value layer determination in mammography
AIP Conference Proceedings, 2016A critical analysis of the methodologies for evaluating the x-ray half value layer was conducted. Experimental data were fitted by using MATLAB curve fitting toolbox, to an exponential function. Half value layer and its uncertainties were determined directly from the parameter of the fitted function.
S. Mijović +3 more
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On the measurement of half‐value layer in film–screen mammography
Medical Physics, 1990Sources of variations in the measurement of half‐value layer (HVL) in film–screen mammography are evaluated. Two principal sources are the energy responses of ionization chambers and the elemental compositions of the 1100 aluminum‐alloy attenuation materials.
L K, Wagner, B R, Archer, F, Cerra
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Half-value layer determination using thermoluminescent dosimeters for digital mammography
Radiation Measurements, 2010Abstract The quality assurance of digital mammogram has been included in the Standards of Medical Exposure Quality Assurance in Taiwan since July, 2008. According to the Standards, determination of the half-value layer (HVL) is an integral part of mammographic dosimetry which requires the evaluation of patient's glandular dose.
C.J. Tung +5 more
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Rapid Determination of the Half-Value Layer of Radiographic X-Ray Machines
Radiology, 1973Many governmental agencies require verification of the collimator alignment and the half-value layer (HVL). The authors propose a method by which the widely used film technique may be extended to measurement of the HVL. The method is validated and its accuracy verified by measurements of 25 radiographic units.
L, Stanton +3 more
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A Note on the Determination of Half-value Layers of Soft X rays
The British Journal of Radiology, 1952A method is described of deriving a reliable half-value layer of X radiation from measurements made with a dose-meter whose readings require to be corrected for quality. The magnitude of the corrections to the observed half-value layer is considered and the effect this has on the dosemeter quality factor is discussed.
M T, MORRISON, G W, REED
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A simple method for evaluation of half-value layer variation in CT equipment
Physics in Medicine and Biology, 2006Tandem systems, each formed by a pencil ionization chamber with and without a specific covering, were developed and tested in standard radiation beams. These systems were designed to be used in computed tomography radiation beams, where the half-value layer (HVL) determination is not an easy task.
Ana F, Maia, Linda V E, Caldas
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A Technic for Cross-Calibration of X-Ray Units Utilizing Half-Value-Layer Determinations
Radiology, 1961In radiographic installations of more than one x-ray unit the need to reproduce a film technic with different units makes it necessary that they be cross-calibrated. In standard practice the establishment of a film technic requires that visual examination be made of representative films for various anatomical structures.
L, PAPE, S, BAKER, H L, GILDENHORN
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A new portable electronic device for single exposure half-value layer measurement
Proceedings of the 22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. No.00CH37143), 2002A new device to be used for half-value layer (HVL) measurements in quality assurance procedures is presented. This device uses a silicon X-ray sensor coupled to an electronic circuit that is connected to a portable computer (notebook) for data storage and analysis.
H. Schiabel, M.A.C. Vieira, N.S.M. Curi
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