Electron beam qualityk_Q,Q0factors for various ionization chambers: a Monte Carlo investigation with penelope

Abstract

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

“…Monoenergetic k Q,Q 0 values overestimate by ∼ 0.4% those found for the Clinac beams at low R 50 while the contrary occurs for R 50 above 6-7 cm where the differences are slightly larger than 0.5%. A similar behavior was pointed for the Exradin A10, A11, A11TW, P11, P11TW, T11 and T11TW, manufactured by Standard Imaging (Middleton, USA), as well as for the NACP-02, all of them plane-parallel ionization chambers [14]. In this previous work it was demonstrated that an important contribution to this discrepancy may be ascribed to the secondary photons produced in the linac head and the air separating it from the phantom.…”

“…The simulations performed in the present work were carried out in a way similar to those of previous works [13][14][15], following the prescription of Sempau and Andreo [26] for the optimal values of the PENELOPE tracking parameters to simulate ionization chambers. Specifically, we used C 1 = C 2 = 0.02 for all materials of the ionization chamber and a water volume extending 2 cm around it.…”

“…The absorbed dose scored within the chamber active volume provided us with the doses D c,Q . The scoring voxel considered to estimate the dose absorbed in water, D w,Q , was similar to that used by other authors in previous calculations [4,9,12,14,28]. It consisted of a cylinder with a radius of 1 cm and a height of 0.025 cm centered in the beam axis and situated at the reference depth.…”

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

“…This explains the larger effect on the 350 A10 chamber, which has a small sensitive volume. The f Q 0 factor of the NACP-02 chamber agrees within 0.2%, 0.2% and 0.4% with the values of Muir et al (2012), Erazo et al (2014) and Panettieri et al (2008), respectively, but it differs by 0.7% from the value of Zink and Wulff (2012). This discrepancy could be explained in terms of the different material composition of the collecting electrode 355 used by Zink and Wulff (2012), which may affect f Q 0 by up to 0.5% (Muir et al 2012).…”

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

“…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.…”