Beam quality conversion factors for parallel-plate ionization chambers in MV photon beams

Muir, B; McEwen, M; Rogers, D. W. O.

doi:10.1118/1.3687864

Cited by 47 publications

(79 citation statements)

References 33 publications

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“…This observation is consistent with recent publications 10,11 that have shown issues with the long-term stability of plane-parallel chamber calibration coefficients obtained in photon and electron beams.…”

Section: Manufacturersupporting

confidence: 82%

Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability

Muir

2015

Medical Physics

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Purpose: To analyze absorbed dose calibration coefficients, N D, w , measured at accredited dosimetry calibration laboratories (ADCLs) for client ionization chambers to study (i) variability among N D, w coefficients for chambers of the same type calibrated at each ADCL to investigate ion chamber volume fluctuations and chamber manufacturing tolerances; (ii) equivalency of ion chamber calibration coefficients measured at different ADCLs by intercomparing N D, w coefficients for chambers of the same type; and (iii) the long-term stability of N D, w coefficients for different chamber types by investigating repeated chamber calibrations. Methods: Large samples of N D, w coefficients for several chamber types measured over the time period between 1998 and 2014 were obtained from the three ADCLs operating in the United States. These are analyzed using various graphical and numerical statistical tests for the four chamber types with the largest samples of calibration coefficients to investigate (i) and (ii) above. Ratios of calibration coefficients for the same chamber, typically obtained two years apart, are calculated to investigate (iii) above and chambers with standard deviations of old/new ratios less than 0.3% meet stability requirements for accurate reference dosimetry recommended in dosimetry protocols. Results: It is found that N D, w coefficients for a given chamber type compared among different ADCLs may arise from differing probability distributions potentially due to slight differences in calibration procedures and/or the transfer of the primary standard. However, average N D, w coefficients from different ADCLs for given chamber types are very close with percent differences generally less than 0.2% for Farmer-type chambers and are well within reported uncertainties. Conclusions: The close agreement among calibrations performed at different ADCLs reaffirms the Calibration Laboratory Accreditation Subcommittee process of ensuring ADCL conformance with National Institute of Standards and Technology standards. This study shows that N D, w coefficients measured at different ADCLs are statistically equivalent, especially considering reasonable uncertainties. This analysis of N D, w coefficients also allows identification of chamber types that can be considered stable enough for accurate reference dosimetry. [http://dx

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Section: Manufacturersupporting

confidence: 82%

Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability

Muir

2015

Medical Physics

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“…However, Stucki and Vörös report chamber‐to‐chamber variations of 1.2% and 1.9% for PTW Roos and NACP‐02 chambers, respectively, which could explain the source of the discrepency. We have not observed this type of variation in electron beams (see Table ) or photon beams . In addition, the electron beam data reported by the National Physical Laboratory (NPL) is not subject to such variability…”

Section: Discussionmentioning

confidence: 65%

Electron beam water calorimetry measurements to obtain beam quality conversion factors

et al. 2017

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READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.http://nparc.nrc-cnrc.gc.ca/eng/copyright Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur.

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“…For the IBA PPC-05 our f Q 0 factor agrees within 0.3% with the value of Panettieri et al (2008), but it differs by 0.8% from the value of Muir et al (2012). As in the case of the Exradin A10 chamber, this discrepancy could arise from the difference between detailed and mixed simulation-which, as mentioned above, is more notorious for small 360 volume ionization chambers like the IBA PPC-05.…”

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confidence: 69%

“…Erazo et al (2014) and Muir et al (2012), respectively. Such large differences are only observed with this ionization chamber model.…”

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confidence: 99%

Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers

2016

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This work calculates beam quality correction factors (k Q ) in monoenergetic proton beams using detailed Monte Carlo simulation of ionization chambers. It uses the Monte Carlo code penh and the electronic stopping powers resulting from the adoption of two different sets of mean excitation energy values for water and graphite: (i) the currently ICRU 37 and ICRU 49 recommended I 75 eV w = and I 78 eV g = and (ii) the recently proposed I 78 eV w = and I 81.1 eV g =. Twelve different ionization chambers were studied. The k Q factors calculated using the two different sets of I-values were found to agree with each other within 1.6% or better. k Q factors calculated using current ICRU I-values were found to agree within 2.3% or better with the k Q factors tabulated in IAEA TRS-398, and within 1% or better with experimental values published in the literature. k Q factors calculated using the new I-values were also found to agree within 1.1% or better with the experimental values. This work concludes that perturbation correction factors in proton beamscurrently assumed to be equal to unity-are in fact significantly different from unity for some of the ionization chambers studied.

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Beam quality conversion factors for parallel-plate ionization chambers in MV photon beams

Cited by 47 publications

References 33 publications

Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability

Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability

Electron beam water calorimetry measurements to obtain beam quality conversion factors

Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers

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Beam quality conversion factors for parallel-plate ionization chambers in MV photon beams

Cited by 47 publications

References 33 publications

Ion chamber absorbed dose calibration coefficients, ND,w, measured at ADCLs: Distribution analysis and stability

Ion chamber absorbed dose calibration coefficients, ND,w, measured at ADCLs: Distribution analysis and stability

Electron beam water calorimetry measurements to obtain beam quality conversion factors

Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers

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Product

Resources

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Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability

Ion chamber absorbed dose calibration coefficients, N_D,w, measured at ADCLs: Distribution analysis and stability