Results 121 to 130 of about 321,405 (167)

A simple method for evaluation of half-value layer variation in CT equipment

Physics in Medicine and Biology, 2006
Tandem 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 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 Adequacy of Half-value Layer as a Criterion of X-ray Quality in the Calibration of Dosemeters

The British Journal of Radiology, 1960
Five thimble ionization chambers were compared with a free-air chamber using X rays produced at 20 to 55 kV with half-value layers between 0·05 and 0·20 mm Al. One chamber showed a difference of nearly 4 per cent in its correction factor for beams of the same H.V.L. produced at 20 and 55 kV. With this single exception H.V.L.
N M, PROCTER, J R, GREENING
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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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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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An evaluation of the influence of the half-value layer on the diagnostic quality of intraoral roentgenograms

Oral Surgery, Oral Medicine, Oral Pathology, 1966
Abstract It appears that further attempts to achieve reduction in radiation dose through the use of higher HVL, increased filtration, and higher voltage will not be productive. It is suggested that optimum levels for present equipment and films lie within the ranges now in use.
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Half-value layer determination using thermoluminescent dosimeters for digital mammography

Radiation Measurements, 2010
Abstract 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, M.T. Lin, F.Y. Hsu, J.H. Lee, C.H. Chu, H.Y. Tsai   +5 more
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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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Predicting and matching half-value layers

2022
Gavin Poludniowski, Artur Omar, Pedro Andreo   +2 more
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Problem of Determination of the First Half-Value Layer of X-Ray Radiation

Biomedical Engineering, 2009
The methods for determination of the first half value layer of X-ray radiation are analyzed. The organized comparison revealed significant scatter from different sources of the first half value layer for identical conditions. The analytical expression was derived for calculation of the first half value layer based on the measured value and total ...
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