Results 261 to 270 of about 418,007 (311)

An alternative method for calculation of half-value layers without the knowledge of attenuation coefficient

Applied Radiation and Isotopes, 2023
Radiation protection is crucial for the safe utilization of ionizing radiation and minimizing the harmful effect upon exposure, hence some standards have been defined by some relevant organizations for the safe uses of radiation. One of the parameters relevant to the calculation of gamma ray shielding is the half-value layer (HVL), which is normally ...
Mehdi Hassanpour, Marzieh Hassanpour, Mayeen Uddin Khandaker, Mohammad Rashed Iqbal Faruque, B. Alshahrani, Hamid Osman   +5 more
openaire   +2 more sources

A Note on the Determination of Half-value Layers of Soft X rays

The British Journal of Radiology, 1952
A 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
openaire   +2 more sources

Rapid Determination of the Half-Value Layer of Radiographic X-Ray Machines

Radiology, 1973
Many 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, J L, Day, R E, Stanton, D A, Lightfoot   +3 more
openaire   +2 more sources

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
openaire   +2 more sources

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
openaire   +2 more sources

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
openaire   +2 more sources

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)
openaire   +1 more source

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
openaire   +2 more sources

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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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
openaire   +1 more source