Characterization of photoneutron fluxes emitted by electron accelerators in the 4–20 MeV range using Monte Carlo codes: A critical review

Sari, Adrien

doi:10.1016/j.apradiso.2022.110506

Cited by 15 publications

(4 citation statements)

References 105 publications

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“…It should be noted that differences in neutron yields can however be expected depending on the MC code used, which have different implementations of nuclear data, photonuclear physics modeling and cross‐section data 35 . For example, underestimation of photonuclear activation calculations compared to experimental data have been reported in the 4−20 MeV energy range, in particular in the case of tungsten emissions and with the MCNP code 36 …”

Section: Discussionmentioning

confidence: 99%

“…35 For example, underestimation of photonuclear activation calculations compared to experimental data have been reported in the 4−20 MeV energy range, in particular in the case of tungsten emissions and with the MCNP code. 36 Numerous studies have already been carried out to quantify and compare the proportions of photons generated in the accelerators equipped with electron-beam scattering foils. For example it has been shown that bremsstrahlung generated in the treatment head generally dominates, but the phantom-generated bremsstrahlung can be as much as 20% of total bremsstrahlung dose for clinical electron energies up to 22 MeV.…”

Section: Discussionmentioning

confidence: 99%

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Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

Deut,

Ronga,

Bonfrate

et al. 2023

Medical Physics

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Background Electrons with kinetic energy up to a few hundred MeV, also called very high energy electrons (VHEE), are currently considered a promising technique for the future of radiation therapy (RT) and in particular ultra‐high dose rate (UHDR) therapy. However, the feasibility of a clinical application is still being debated and VHEE therapy remains an active area of research for which the optimal conformal technique is also yet to be determined. Purpose In this work, we will apply two existing formalisms based on analytical Gaussian multiple‐Coulomb scattering theory and Monte Carlo (MC) simulations to study and compare the electron and bremsstrahlung photon dose distributions arising from two beam delivery systems (passive scattering with or without a collimator or active scanning). Methods We therefore tested the application of analytical and MC models to VHEE beams and assessed their performance and parameterization in the energy range of 6–200 MeV. The optimized electron beam fluence, the bremsstrahlung, an estimation of central‐axis and off‐axis x‐ray dose at the practical range and neutron contributions to the total dose, along with an extended parameterization for the photon dose model were developed, together with a comparison between double scattering (DS) and pencil beam scanning (PBS) techniques. MC simulations were performed with the TOPAS/Geant4 toolkit to verify the dose distributions predicted by the analytical calculations. Results The results for the clinical energy range (between 6 and 20 MeV) as well as for higher energies (VHEE range between 20 and 200 MeV) and for two treatment field sizes (5 × 5 and 10 × 10 cm2) are reported, showing a reasonable agreement with MC simulations with mean differences below 2.1%. The relative contributions of photons generated in the medium or by the scattering system along the central‐axis (up to 50% of the total dose) are also illustrated, along with their relative variations with electron energy. Conclusions The fast analytical models parametrized in this study allow an estimation of the amount of photons produced behind the practical range by a DS system with an accuracy lower than 3%, providing important information for the eventual design of a VHEE system. The results of this work could support future research on VHEE radiotherapy.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

Deut,

Ronga,

Bonfrate

et al. 2023

Medical Physics

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“…They showed that different codes produce relatively different results due to the use of various models and photoneutron cross-sections. A critical review was published by Sari in 2023 [19] on photoneutron production through electron LINAC in the energy range of 4-20 MeV. Sari showed that the results of the MCNP6.2 code for deuterium, beryllium, and tungsten targets have some errors both in the energy spectrum of photoneutrons and their threshold energy due to defects in the used model and photoneutron cross-sections.…”

Section: Jinst 18 P05021mentioning

confidence: 99%

A reconsideration of photoneutron production through a 5 MeV electron LINAC using MCNP and FLUKA

2023

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In the present study, photoneutron production using a 5 MeV electron linear accelerator (LINAC) was investigated based on new photoneutron cross-sections (IAEA/PD-2019.2) from the International Atomic Energy Agency (IAEA). A detailed reconsideration of a past study has been done in order to make a photoneutron source based on a heavy water target. In this regard, new cross-sections of deuterium and beryllium were added to the library of the MCNP6.1 Monte Carlo code for the simulation of photoneutron production. In addition, the FLUKA4-3.0 Monte Carlo code was employed for comparison and data validation. Moreover, the obtained results from those two codes (MCNP and FLUKA) were compared and discussed with the theory and the previous study. Finally, it is concluded that the simulation of photoneutron production through an electron LINAC can have relatively different results based on the photoneutron cross-sections and even on the Monte Carlo code used. Therefore, a special attention should be paid to the difference between photoneutron cross-sections as well as the difference in Monte Carlo codes to maintain reliability.

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“…For example, studies have shown the accuracy of MCNP software (considered one of the reference MC codes) for the calculation of photoneutron yields for medical accelerators (Ongaro et al 1999, 2000, Garnica-Garza 2005. MCNP simulations use Evaluated Nuclear Data File (ENDF) libraries to produce and transport photoneutrons (Chadwick et al 2011) with an accuracy of tens of percent with respect to measured data in the clinically relevant (10-20 MeV) electron range (Sari 2023).…”

Section: Introductionmentioning

confidence: 99%

TOPAS simulation of photoneutrons in radiotherapy: accuracy and speed with variance reduction

Ramos-Mendez,

Ortiz,

Schuemann

et al. 2024

Phys. Med. Biol.

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We provide optimal particle split numbers for speeding up TOPAS Monte Carlo simulations of linear accelerator (linac) treatment heads while maintaining accuracy. In addition, we provide a new TOPAS physics module for simulating photoneutron production and transport. TOPAS simulation of a Siemens Oncor linac was used to determine the optimal number of splits for directional bremsstrahlung splitting as a function of the field size for 6MV and 18MV x-ray beams. The linac simulation was validated against published data of lateral dose profiles and percentage depth-dose curves (PDD) for the largest square field (40cm side). In separate simulations, neutron particle split and the custom TOPAS physics module was used to generate and transport photoneutrons, called “TsPhotoNeutron”. Verification of accuracy was performed by comparing simulations with published measurements of: 1) neutron yields as a function of beam energy for thick targets of Al, Cu, Ta, W, Pb and concrete; and 2) photoneutron energy spectrum at 40cm laterally from the isocenter of the linac from an 18MV beam with closed jaws and MLC. The optimal number of splits obtained for directional bremsstrahlung splitting enhanced the computational efficiency by two orders of magnitude. The efficiency decreased with increasing beam energy and field size. Calculated lateral profiles in the central region agreed within 1mm/2% from measured data, PDD curves within 1 mm/1%. For the TOPAS physics module, at a split number of 146, the efficiency of computing photoneutron yields was enhanced by a 27.6 factor, whereas it improved the accuracy over existing Geant4 physics modules. This work provides simulation parameters and a new TOPAS physics module to improve the efficiency and accuracy of TOPAS simulations that involve photonuclear processes occurring in high-Z materials found in linac components, patient devices, and treatment rooms, as well as to explore new therapeutic modalities such as very-high-energy electron therapy.

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Characterization of photoneutron fluxes emitted by electron accelerators in the 4–20 MeV range using Monte Carlo codes: A critical review

Cited by 15 publications

References 105 publications

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

A reconsideration of photoneutron production through a 5 MeV electron LINAC using MCNP and FLUKA

TOPAS simulation of photoneutrons in radiotherapy: accuracy and speed with variance reduction

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