Standard ionization-chamber requirements for 250- to 500-kilovolt x-rays

Wyckoff, Harold O.; Kirn, F.S.

doi:10.6028/jres.058.015

Cited by 10 publications

(16 citation statements)

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“…2), the absorption is less than for those producing electrons like ei. However, it has been shown [5] that even for 500-kv X-rays the I contribution of electrons like e3 is so small that the effective center for electron production is j essentially the center of the collector. Therefore ' the air-absorption correction should be made for the distance between the center of the collector and the aperture.…”

Section: Characteristics Of Free-air Chambersmentioning

confidence: 99%

Design of free-air ionization chambers

Wyckoff¹,

Attix²

1957

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These include the develop¬ ment and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to Government Agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. A major portion of the Bureau's work is performed for other Government Agencies, particularly the Department of Defense and the Atomic Energy Commission. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover. their gratitude to members of these two groups who have read the manuscript and have given them the benefit of their criticisms.

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Section: Characteristics Of Free-air Chambersmentioning

confidence: 99%

Design of free-air ionization chambers

Wyckoff¹,

Attix²

1957

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“…It is generally recommended that the transmitted photons should be less than 0.1% of the initial beam. [ 23 ] Electron loss correction factor varied from 0.02% at 60 kV to 0.5% for 100 kV X-ray potential. For X-ray beams with tube potential higher than 100 kV and also additional filtration >3 mm, electron loss correction factor of 0.5% was applied as the calculations are based on RITZ and NIST publications for tube potential up to 100 kV and additional filtration of 3 mm aluminum.…”

Section: R Esults and Discussionmentioning

confidence: 99%

Establishment and Dissemination of Radiological Standards in the Field of Diagnostic Radiology in India

Panyam

Rakshit

Dhole

et al. 2021

Journal of Medical Physics

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Background: The increased use of ionizing radiation for diagnostic purpose has resulted in an increase in the world population dose. Patient dosimetry in X-ray diagnostic radiology is required to establish diagnostic reference levels (DRLs) and to assess the average dose received by organs and tissues. International bodies have recommended DRLs to be based on dosimetric quantities. Aim: To cater to the increased requirement for dosimetry in diagnostic radiology, international guidelines are provided to establish and disseminate traceable calibration for dosimeters used in X-ray diagnostic radiology. X-ray diagnostic beams established are standardized using a diagnostic range free-air ionization chamber (DFAIC) (20-150 kV). Materials and Methods: Characterization of the DFAIC and determination of the correction factors for the air kerma measurements were evaluated experimentally and by theoretical calculations. Results: The paper details the establishment of 18 diagnostic beam qualities using DFAIC along with the associated uncertainties. The overall uncertainty for the air kerma measurements was within ±0.5% at 1 sigma level. Eight diagnostic range air kerma measurements using DFAIC were compared with the medium energy primary standard FAIC (50–300 kV) maintained in the laboratory. Conclusion: The air kerma rates agreed within ±1% and are within the overall standard uncertainty of both the chambers at the time of the comparison. Dissemination to the users in the field of diagnostic radiology in the country has been carried out by calibrating their ionization chambers and solid-state detector-based instruments against the DFAIC. The methodology followed to standardize the beams using DFAIC and calibration of dosimeters is presented in this work.

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“…A sep arate piece of equipment similar to that previously used [13] provides a m eans of determining t he di stance required for electronic equilibrium [11] . A grid chamber ( fig.…”

Section: Crtllmentioning

confidence: 99%

“…From the m eas ured currents to plates 4, 5, 6, a nd 7, it is possible [1 4] to compute the loss in ionization (electron loss) obtained beyond differ ent radii and also the contribution to the ionization provided by t he scatter ed photons. In order to compare the resul ts obtained at different pr essures for each so urce, the radii at each pressure are corrected for the di am ete r of the gamma-ray b eam [13] . fig .…”

mentioning

confidence: 99%

Measurement of cobalt-60 and cesium-137 gamma rays with a free-air chamber

Wyckoff¹

1960

J. RES. NATL. BUR. STAN. SECT. C. ENG. INSTR.

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D esign data for free-air chambers measuring cobalt-60 a nd cesium-1 37 gamma rays in roentgen s a.re prese nted: It has been shown that t ho Jatfc-Zanstra method of obtain ing t he. saturatIOn current IS adequate for a ll' press ures of about 4 to 12 atmospheres. Also, rad IatIon measurements of t he gamma rays from cobalt-60 and cesium-137 made by a cavity chamber and a free-air chamber agree to within the experimental errors.

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Standard ionization-chamber requirements for 250- to 500-kilovolt x-rays

Cited by 10 publications

References 0 publications

Design of free-air ionization chambers

Design of free-air ionization chambers

Establishment and Dissemination of Radiological Standards in the Field of Diagnostic Radiology in India

Measurement of cobalt-60 and cesium-137 gamma rays with a free-air chamber

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