Design of Free-Air Ionization Chambers for the Soft X-Ray Region (20–100 kv)

Ritz, Victor H.

doi:10.1148/73.6.911

Cited by 23 publications

(16 citation statements)

References 3 publications

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“…Three parallel-plate chambers were constructed more than 30 years ago, characterized to provide x-ray air-kerma standardization within this energy range, and are used almost exclusively in the W-anode x-ray calibration facilities at NIST. These free-air chambers are identified as the Lamperti chamber [ 1 ] for 10 kVp to 20 kVp, the Ritz chamber [ 2 , 3 ] for 20 kVp to 100 kVp, and the Wycoff-Attix chamber [ 4 ] for 50 kVp to 300 kVp. More recently, NIST added a new cylindrical free-air ionization chamber of an Attix design [ 5 ] to provide air-kerma standardization for mammography x-ray beams from both Mo and Rh anodes operated in the 23 kVp to 40 kVp range [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

New national air-kerma-strength standards for I-125 and Pd-103 brachytherapy seeds

Seltzer

Lamperti

Loevinger

et al. 2003

J. Res. Natl. Inst. Stand. Technol.

104

117

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The new U.S. measurement standard for the air-kerma strength from low-energy photon-emitting brachytherapy seed sources is formally described in detail. This instrument-based standard was implemented on 1 January 1999, with its salient features and the implications of differences with the previous standard given only through a series of informal communications. The Wide-Angle Free-Air Chamber (WAFAC) is specially designed to realize air kerma from a single-seed source emitting photons with energies up to about 40 keV, and is now used to measure the wide variety of seeds used in prostate-cancer therapy that has appeared in the last few years. For the two 125I seed models that have been subject to both the old and new standards, the new standard reduces the air-kerma strength by 10.3 %. This change is mainly due to the removal of the influence on the measurement of the Ti K x rays produced in the source encapsulation, a component with no clinical significance.

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Section: Introductionmentioning

confidence: 99%

New national air-kerma-strength standards for I-125 and Pd-103 brachytherapy seeds

Seltzer

Lamperti

Loevinger

et al. 2003

J. Res. Natl. Inst. Stand. Technol.

104

117

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show abstract

“…The photon scatter correction (k p ) accounts for the ionization resulting from scattered and bremsstrahlung x rays that are not part of the primary beam. 7 The differences shown in Tables III and IV between the two free-air chambers are insignificant. The ion recombination correction (k s ), which is exposure-rate dependent, corrects for ionization lost due to ion recombination prior to collection.…”

Section: B Exposure Measurementmentioning

confidence: 86%

Comparison of exposure standards in the mammography x‐ray region

et al. 1997

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Direct comparisons of the National Institute of Standards and Technology's (NIST) Ritz 20 kV to 100 kV standard free-air ionization chamber and a portable variable-length free-air ionization chamber designed by the University of Wisconsin-Madison Accredited Dosimetry Calibration Laboratory (UW-ADCL) were made on NISTs low-energy tungsten x-ray range. As a result of this direct comparison, NIST has established a UW-ADCL designed chamber, the Attix chamber, as the national standard chamber for the mammography energy x-ray range. The Ritz standard chamber and the Attix standard chamber have been extensively compared using the new molybdenum and rhodium beam qualities. The results indicate that exposure measurements in the mammography energy x-ray region with the two free-air chambers can be made with a discrepancy of less than 0.35%.

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“…Typically, these corrections account for scatter contribution to the signal, signal reduction due to electron-loss from the collecting volume and attenuation of the photon beam along the path from the POM to the center of the sensitive volume. While such correction factors have been determined experimentally in the past, [121][122][123] measuring some of them directly involves taking the FAC apart, thus modifying the primary standard. This is the case for the corrections accounting for photon scatter and electron-loss.…”

Section: Resultsmentioning

confidence: 99%

“…These assigned systematic uncertainties are very conservative and rather arbitrary. One would need to validate the MC values against the original experimental values from Ritz 123 and assess whether the current practice of interpolating and extrapolating these corrections for arbitrary beam qualities is accurate. This approach has been used in many NMIs based on the fact that these corrections vary very slowly with beam quality.…”

Section: Fac Conclusionmentioning

confidence: 99%

Efficient Monte Carlo simulations in kilovoltage x-ray beams

Hing¹

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Design of Free-Air Ionization Chambers for the Soft X-Ray Region (20–100 kv)

Cited by 23 publications

References 3 publications

New national air-kerma-strength standards for I-125 and Pd-103 brachytherapy seeds

New national air-kerma-strength standards for I-125 and Pd-103 brachytherapy seeds

Comparison of exposure standards in the mammography x‐ray region

Efficient Monte Carlo simulations in kilovoltage x-ray beams

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