Electron dosimetry based on the absorbed dose to water concept: A comparison of the AAPM TG‐51 and DIN 6800‐2 protocols

Dohm, O.; Christ, Günter; Nüsslin, Fridtjof; Schüle, E; Bruggmoser, G.

doi:10.1118/1.1414008

Cited by 10 publications

(10 citation statements)

References 8 publications

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“…The average difference is 0.8% and it ranges from 0.4% up to 1.2%. The overall agreement with reported experimental values 13,14,[37][38][39][40] is better for the present calculations, excluding the value of Wittkamper et al 13 for the NACP01 chamber.…”

Section: P Wall Values In-phantomsupporting

confidence: 85%

Calculations for plane-parallel ion chambers in 60Co beams using the EGSnrc Monte Carlo code

2003

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The EGSnrc Monte Carlo simulation system is used to obtain, for 10 plane-parallel ionization chambers in 60Co beams, the correction factors Kcomp and Pwall that account for the nonequivalence of the chamber wall material to the buildup cap and the phantom material, respectively. A more robust calculation method has been used compared to that used in previous works. A minor conceptual error related to the axial nonuniformity correction factor, Kan, has been identified and shown to have an effect of about 0.2%. The assumption that Pwall in-phantom is numerically equal to Kcomp calculated for a water buildup cap is shown to be accurate to better than 0.06%, thereby justifying the use of Kcomp calculations which are much more efficient. The effect on the calculated dose to the air in the cavity of the particle production threshold and transport energies used in the simulations is studied. Uncertainties in the calculated correction factors due to uncertainties in the photon and electron cross-section data are studied. They are 0.14% and 0.24%, respectively (1 standard deviation), for Kcomp factors. The uncertainties on Kwall factors are 0.03% from photon cross-section uncertainties and negligible from electron cross-section uncertainties. A comparison with previous EGS4/PRESTA calculations shows that present results are systematically higher by an average of 0.8%, ranging from 0.4% up to 1.4%. The present results are in better agreement with reported experimental values.

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Section: P Wall Values In-phantomsupporting

confidence: 85%

Calculations for plane-parallel ion chambers in 60Co beams using the EGSnrc Monte Carlo code

2003

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“…A compilation is given in tables 1 and 2. References include the comparisons between TG-51 and TG-21 protocols by Ding et al (2000), Cho et al (2000), Huq and Andreo (2001), Huq et al (2001b) and Tailor and Hanson (2002); between TRS-398 and TRS-277, 381 by Andreo et al (2001Andreo et al ( , 2002; between TRS-398, TG-51, TRS-277, TRS-381, NCS report-2 and report-5 by Palmans et al (2002Palmans et al ( , 2003; between TRS-398, TG-51, TRS-277 and the Japanese protocol JARP by Araki and Kubo (2002) and between TG-51 and German DIN 6800-2 by Dohm et al (2001) graphical presentation of data published for all combinations of chamber types, beam types and energies and protocols is impractical, only selected combinations of such data will be presented to bring out the salient features of the differences between the N D,w and the N K based protocols.…”

Section: Comparison Between N Dw and N K Based Protocolsmentioning

confidence: 99%

“…Experimental comparison between the TRS-398 and TG-51 protocols in high-energy photon and electron beams has been performed by Huq et al (2001a), Palmans et al (2002Palmans et al ( , 2003 and Araki and Kubo (2002), whereas Dohm et al (2001) have compared TG-51 with DIN. The beam energies and chamber types used in these comparisons, as well as a summary of the dose ratios obtained, are listed in tables 1 and 2.…”

Section: Comparison Between N Dw Based Protocolsmentioning

confidence: 99%

Advances in the determination of absorbed dose to water in clinical high-energy photon and electron beams using ionization chambers

Huq

Andreo

2004

Phys. Med. Biol.

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During the last two decades, absorbed dose to water in clinical photon and electron beams was determined using dosimetry protocols and codes of practice based on radiation metrology standards of air kerma. It is now recommended that clinical reference dosimetry be based on standards of absorbed dose to water. Newer protocols for the dosimetry of radiotherapy beams, based on the use of an ionization chamber calibrated in terms of absorbed dose to water, N(D,w), in a standards laboratory's reference quality beam, have been published by several national or regional scientific societies and international organizations. Since the publication of these protocols multiple theoretical and experimental dosimetry comparisons between the various N(D,w) based recommendations, and between the N(D,w) and the former air kerma (NK) based protocols, have been published. This paper provides a comprehensive review of the dosimetry protocols based on these standards and of the intercomparisons of the different protocols published in the literature, discussing the reasons for the observed discrepancies between them. A summary of the various types of standards of absorbed dose to water, together with an analysis of the uncertainties along the various steps of the dosimetry chain for the two types of formalism, is also included. It is emphasized that the NK-N(D,air) and N(D,w) formalisms have very similar uncertainty when the same criteria are used for both procedures. Arguments are provided in support of the recommendation for a change in reference dosimetry based on standards of absorbed dose to water.

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“…In the years following its publication, TG-51 was extensively tested and compared with other protocols based on both absorbed-dose and air-kerma standards. [4][5][6][7][8][9][10][11] Although its accuracy and applicability to the calibration of clinical linacs has not been challenged, developments have occurred in the fifteen years since the TG-51 protocol was published that necessitate updating and expanding the protocol:…”

Section: Introduction and Rationalementioning

confidence: 99%

Addendum to the AAPMˈs TG‐51 protocol for clinical reference dosimetry of high‐energy photon beams

et al. 2014

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An addendum to the AAPM's TG-51 protocol for the determination of absorbed dose to water in megavoltage photon beams is presented. This addendum continues the procedure laid out in TG-51 but new k Q data for photon beams, based on Monte Carlo simulations, are presented and recommendations are given to improve the accuracy and consistency of the protocol's implementation. The components of the uncertainty budget in determining absorbed dose to water at the reference point are introduced and the magnitude of each component discussed. Finally, the consistency of experimental determination of N D,w coefficients is discussed. It is expected that the implementation of this addendum will be straightforward, assuming that the user is already familiar with TG-51. The changes introduced by this report are generally minor, although new recommendations could result in procedural changes for individual users. It is expected that the effort on the medical physicist's part to implement this addendum will not be significant and could be done as part of the annual linac calibration.

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Electron dosimetry based on the absorbed dose to water concept: A comparison of the AAPM TG‐51 and DIN 6800‐2 protocols

Cited by 10 publications

References 8 publications

Calculations for plane-parallel ion chambers in 60Co beams using the EGSnrc Monte Carlo code

Calculations for plane-parallel ion chambers in 60Co beams using the EGSnrc Monte Carlo code

Advances in the determination of absorbed dose to water in clinical high-energy photon and electron beams using ionization chambers

Addendum to the AAPMˈs TG‐51 protocol for clinical reference dosimetry of high‐energy photon beams

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