Results 161 to 170 of about 1,506,118 (205)

A Technic for Cross-Calibration of X-Ray Units Utilizing Half-Value-Layer Determinations

Radiology, 1961
In 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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Half-Value Depth and Fall-Off Ratio as Functions of Portal Area, Target-Skin Distance, and Half-Value Layer

Radiology, 1957
The purpose of this communication is to present, in convenient form, values for the half-value depths and fall-off ratios corresponding to the entire range of radiation qualities, portal areas, and target-skin distances likely to be encountered in clinical roentgen therapy. Compilation of these data is believed to be useful for several reasons.
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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), 2002
A 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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A Nomogram for the Determination of Half-value Layers

The British Journal of Radiology, 1936
Although a statement of the half-value layer alone does not specify the X-ray quality of the radiation in the sense of the accepted definition, it is often sufficient to characterise the radiation. An analysis of the results of several workers shows that a statement of exciting voltage, filtration and type of generator (constant—or pulsating—potential)
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On the choice of material for half‐value‐layer measurements for megavoltage x rays

Medical Physics, 1977
The relative sensitivity of various materials for the measurement of half‐value‐layer thickness has been calculated for bremsstrahlung x‐ray spectra in the energy range 5–40 MeV. It is concluded that low‐atomic‐number materials such as water are more sensitive to changes in spectral quality of megavoltage x rays than high‐atomic‐number materials such ...
R, Nath, R J, Schulz
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Measurement of half‐value layer in x‐ray CT: A comparison of two noninvasive techniques

Medical Physics, 2000
The 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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Characterization of X-ray Beam for Half and Quarter Value Layers

Annals of Computational Physics and Material Science
Introduction: The aim of this work is to assess the penetrating ability of an X-ray beam through a specific material, in conditions of narrow-beam geometry. Materials and Methods: During the experiment, samples were switched with the X-ray tube turned off, and the primary intensity of the unshielded X-ray beam (fixed 2.5mm shielding) was measured ...
Khazratov Diyor, Kodirov Kuvondik, Girma Biniyam Solomon, Dogo Federico   +3 more
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EXPERIMENTAL AND MATHEMATICAL MODELING OF HALF-VALUE LAYER MEASUREMENTS FOR X-RAY EQUIPMENT

Biomedical Engineering: Applications, Basis and Communications, 2016
A linear mathematical modeling of half-value layer measurements for X-ray equipment is discussed. The consistency check shows that a linear model is consistent with the value of an exponential model, provided that the thickness of the aluminum absorber used in the calculations is close to 2.5[Formula: see text]mm.
Modesto Sosa, Jesús Bernal-Alvarado, Juan C. Azorín, Ana C. Cuevas, Teodoro Córdova, Francisco Mesa   +5 more
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A parametric method for determining mammographic X‐ray tube output and half value layer

The British Journal of Radiology, 2001
In the National Health Service Breast Screening Programme, regular assessment of the mean glandular doses received by a group of women is recognized as an important part of a quality assurance programme. The use of different tube voltages, to improve the beam penetration for thick or dense breasts, and of X-ray units with programmable exposure modes ...
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A simple method of obtaining off‐axis half‐value layers for megavoltage photon beams

Medical Physics, 1995
We describe a simplified technique for the acquisition of off‐axis beam‐quality data (i.e., half‐value layers in water) for medical linear accelerators. A measurement protocol is presented in which an ordinary beam‐scanning water phantom is used to accurately position an ionization chamber at appropriate measuring positions.
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