Computation of the electron beam quality<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mrow><mml:msub><mml:mrow><mml:mi>k</mml:mi></mml:mrow><mml:mrow><mml:mtext>Q,</mml:mtext><mml:msub><mml:mrow><mml:mtext>Q</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:msub></mml:mrow></mml:math>factors for the NE2571, NE2571A and NE2581A thimble ionization chambers using PENELOPE

Erazo, Fabián; Brualla, L.; Lallena, A. M.

doi:10.1016/j.ejmp.2017.05.053

Cited by 6 publications

(2 citation statements)

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“…11,12 The beam quality conversion factor, k Q , can also be calculated directly for specific chambers using Monte Carlo simulations. Sempau et al, 21 Araki, 22 Zink et al, 23 Muir and Rogers, [24][25][26] and Erazo et al 27,28 calculated k Q directly for specific chambers. These direct calculations give results which are comparable to TG-51 and TRS-398 values.…”

Section: Introductionmentioning

confidence: 99%

Stopping‐power ratios for electron beams used in total skin electron therapy

Ding

2021

Medical Physics

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Purpose The electron beams for total skin electron therapy (TSET) are often degraded by a scatter plate in addition to extended distances. For electron dosimetry, both the AAPM TG‐51 and IAEA TRS‐398 recommend the use of two formulas developed by Burns et al [Med. Phys. 23, 489–501 (1996)] to estimate the water‐to‐air stopping‐power ratios (SPRs). Both formulas are based on a fit to SPRs calculated for standard electron beams. This study aims to find: (1) if the formulas are applicable to beams used in TSET and (2) the impact of the ICRU report 90 recommendations on the SPRs for these beams. Methods The EGSnrc Monte Carlo code system is used to generate 6 MeV high dose rate total skin electron (HDTSe) beams used in TSET. The simulated beams are used to calculate dose distributions and SPRs as a function of depth in a water phantom. The fitted SPRs using the empirical formulas are compared with MC‐calculated SPRs. Results The electron beam quality specifier, the depth in water at which the absorbed dose falls to 50% of its maximum value, R50, decreases approximately 1 mm for each additional 100‐cm extended distance ranging from 2.24 cm at SSD = 100 to 1.72 cm at SSD = 700 cm. For beams passing through a scatter plate, R50 is 1.76 cm (1.14) at SSD = 300 and 1.48 cm (0.85 cm) at SSD = 600 cm with an Acrylic plate thickness of 3 mm (9 mm), respectively. The discrepancy between fitted and MC‐calculated SPRs at dref as a function of R50 is <0.8%, and in many cases <0.4%. The difference between fitted and MC‐calculated SPRs as a function of depth and R50 is within 1% at depths <0.8R50 for beams with R50 ≥ 1.14 cm. The ICRU‐90 recommendations decrease SPRs by 0.3%–0.4% compared to the use of data recommended in ICRU‐37. Conclusion The formulas used by the major protocols are accurate enough for clinical beams used in TSET and the error caused using the formulas is <1% to estimate SPRs as a function of depth and R50 for depths <0.8R50 for beams used in TSET with R50 ≥ 1.14 cm. The impact of the ICRU‐90 recommendations shows a decrease of SPRs by a fraction of a percent for beams used in TSET.

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Section: Introductionmentioning

confidence: 99%

Stopping‐power ratios for electron beams used in total skin electron therapy

Ding

2021

Medical Physics

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“…Monte Carlo simulations have been performed using the PENELOPE/ penEasy system [15,16] versions 2014 (PENELOPE) and 2018-04-30beta (penEasy), which has been extensively tested for dosimetry problems relevant for the present work [7,17,21,18]. The penEasy tally named 'energy deposition' was used to obtain the energy absorbed in the relevant spatial regions.…”

Section: Monte Carlo Simulationsmentioning

confidence: 99%

Monte Carlo verification of the holder correction factors for the radiophotoluminescent glass dosimeter used by the IAEA in international dosimetry audits

et al. 2021

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The International Atomic Energy Agency (IAEA), jointly with the World Health Organization (WHO), has operated a postal dosimetry audit program for radiotherapy centers worldwide since 1969. In 2017 the IAEA introduced a new methodology based on radiophotoluminescent dosimetry (RPLD) for these audits. The detection system consists of a phosphate glass dosimeter inserted in a plastic capsule that is kept in measuring position with a PMMA holder during irradiation. Correction factors for this holder were obtained using experimental methods. In this work these methods are described and the resulting factors are verified by means of Monte Carlo simulation with the general-purpose code PENELOPE for a range of photon beam qualities relevant in radiotherapy. The study relies on a detailed geometrical representation of the experimental setup. Various photon beams were obtained from faithful modeling of the corresponding linacs. Monte Carlo simulation transport parameters are selected to ensure subpercent accuracy. The simulated correction factors fall in the interval 1.005-1.008 (±0.2%), with deviations with respect to experimental values not larger than 0.2(2)%. This study corroborates the validity of the holder correction factors currently used for the IAEA audits.

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A multicenter study of modified electron beam output calibration

Mahfirotin,

Ferliano,

Handika

et al. 2023

J Applied Clin Med Phys

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PurposeThis study aims to assess the accuracy of a modified electron beam calibration based on the IAEA TRS‐398 and AAPM‐TG‐51 in multicenter radiotherapy.MethodsThis study was performed using the Elekta and Varian Linear Accelerator electron beams with energies of 4–22 MeV under reference conditions using cylindrical (PTW 30013, IBA FC65‐G, and IBA FC65‐P) and parallel‐plate (PTW 34045, PTW 34001, and IBA PPC‐40) chambers. The modified calibration used a cylindrical chamber and an updated based on Monte Carlo calculations, whereas TRS‐398 and TG‐51 used cylindrical and parallel‐plate chambers for reference dosimetry. The dose ratio of the modified calibration procedure, TRS‐398 and TG‐51 were obtained by comparing the dose at the maximum depth of the modified calibration to TRS‐398 and TG‐51.ResultsThe study found that all cylindrical chambers’ beam quality conversion factors determined with the modified calibration to the TRS‐398 and TG‐51 vary from 0.994 to 1.003 and 1.000 to 1.010, respectively. The dose ratio of modified/TRS‐398cyl and modified/TRS‐398parallel‐plate, the variation ranges were 0.980–1.014 and 0.981–1.019, while for the counterpart modified/TG‐51cyl was found varying between 0.991 and 1.017 and the ratio of modified/TG‐51parallel‐plate varied in the range of 0.981–1.019.ConclusionThis multi‐institutional study analyzed a modified calibration procedure utilizing new data for electron beam calibrations at multiple institutions and evaluated existing calibration protocols. Based on observed variations, the current calibration protocols should be updated with detailed metrics on the stability of linac components.

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Computation of the electron beam qualitykQ,Q0factors for the NE2571, NE2571A and NE2581A thimble ionization chambers using PENELOPE

Cited by 6 publications

References 30 publications

Stopping‐power ratios for electron beams used in total skin electron therapy

Stopping‐power ratios for electron beams used in total skin electron therapy

Monte Carlo verification of the holder correction factors for the radiophotoluminescent glass dosimeter used by the IAEA in international dosimetry audits

A multicenter study of modified electron beam output calibration

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