Enhancement of the EGSnrc code egs_chamber for fast fluence calculations of charged particles

Failing, Thomas; Hartmann, Günther H.; Hensley, Frank W.; Keil, Boris; Zink, Klemens

doi:10.1016/j.zemedi.2022.04.003

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…MC simulation is a technique that provides both accurate and detailed calculation of particle fluence, energy reflected/deposited/ transmitted and dose in a slab or any volume of interest (VOI). There are a number of MC code packages currently available such as MCNP (Jabbari & Seuntjens, 2014;Yani et al, 2019), Geant4 (Arce & Aguilar-Redondo, 2020), Penelope (Alva-Sánchez & Pianoschi, 2020), EGSnrc (Mohammed et al, 2016;Failing et al, 2022), and PHITS (Yani et al, 2022). However, each packages has advantages and disadvantages of each that affect the results obtained despite the fact that all geometry and physical aspects are identical.…”

Section: Introductionmentioning

confidence: 99%

egs++: Optimization of Simulation Transport Parameters

Yani¹

2023

J. Ilmu Fis.

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MC transport parameters used are common to all egs++ applications. The eﬀect of each transport parameter need to understand to optimize the simulation process. Therefore, the purpose of this study was to investigate the efficiency of egs++ simulation for different transport parameters in water phantom. This water phantom has built using slab. Collimated source defined 100 cm above the phantom. The simulation parameters such as the efficiency, statistical uncertainty, and accuracy of selecting transport parameters such as electron and photon cut-oﬀ energies, spin eﬀects, atomic relaxations, and bound Compton scattering was investigated. The selection of ECUT and PCUT greatly affects the simulation time. The simulation time, efficiency and energy fractions have same value for varied ECUT except for 0.521 MeV. The energy fraction have been shifted but the simulation time and efficiency were same. Turning on spin effects in this simulation increases simulation time by 25%. The simulation time increases by about 15% when relaxations are turned on. The more accurate result of deposited energy using EGSnrc algorithm is about 30% slower than the less accurate PRESTA-I algorithm. Therefore, The optimization of transport parameters is needed in the simulation of egs++ to provide the best efficiency.

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Section: Introductionmentioning

confidence: 99%

egs++: Optimization of Simulation Transport Parameters

Yani¹

2023

J. Ilmu Fis.

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Investigations on the beam quality correction factor for ionization chambers in high-energy brachytherapy dosimetry

Failing,

Hensley,

Keil

et al. 2024

Phys. Med. Biol.

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Objective: To enhance the investigations on MC calculated beam quality correction factors of thimble ionization chambers from high-energy brachytherapy sources and to develop reliable reference conditions in source and detector setups in water. Approach: The response of five different ionization chambers from PTW-Freiburg and Standard Imaging was investigated for irradiation by a high dose rate Ir-192 Flexisource in water. For a setup in a Beamscan water phantom, Monte Carlo simulations were performed to calculate correction factors for the chamber readings. After exact positioning of source and detector the absorbed dose rate at the TG-43 reference point at one centimeter nominal distance from the source was measured using these factors and compared to the specification of the calibration certificate. The Monte Carlo calculations were performed using the restricted cema formalism to gain further insight into the chamber response. Calculations were performed for the sensitive volume of the chambers, determined by the methods currently used in investigations of dosimetry in magnetic fields.Main results: Measured dose rates and values from the calibration certificate agreed within the combined uncertainty (k=2) for all chambers except for one case in which the full air cavity was simulated. The chambers showed a distinct directional dependence. With the restricted cema formalism calculations it was possible to examine volume averaging and energy dependence of the perturbation factors contributing to the beam quality correction factor also differential in energy.Significance: This work determined beam quality correction factors to measure the absorbed dose rate from a brachytherapy source in terms of absorbed dose to water for a variety of ionization chambers. For the accurate dosimetry of brachytherapy sources with ionization chambers it is advisable to use correction factors based on the sensitive volume of the chambers and to take account for the directional dependence of chamber response.

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Spectral analysis of Monte Carlo calculated fluence correction and cema conversion factors for high-energy photon beams at different depths

Roers

Czarnecki²,

Alissa³

et al. 2023

Front. Phys.

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Purpose: The aim of this study is to investigate the depth-dependent detector response of detailed thimble air-filled ionization chambers by calculating spectral charged particle fluence correction factors at different depths in water. Those spectral correction factors will help to understand, how the detector response varies at different depths and what kind of influences disparate effects have on the spectral detector response.Methods: The cema-approach can be used to obtain spectral charged particle fluence-based correction factors for various measurement conditions by substituting the commonly well-known dose conversion factor with a conversion factor based on the dosimetric quantity cema (“converted-energy per unit mass”). The resulting spectral fluence correction factors were calculated with the EGSnrc software toolkit and analyzed for two air-filled cylindrical ionization chambers (PTW type 31021 Semiflex 3D, SNC125c™) at different depths in a water phantom irradiated with a 6 MV linear accelerator x-ray spectrum. The ionization chamber models have been stepwise decomposed to investigate the perturbation caused by internal and external effects on the fluence distribution within the detector.Results: Monte Carlo calculated fluence-based perturbation correction factors revealed that for all investigated detectors, considerable fluence disturbances occur, especially in the build-up region of depth-dose curves. Our results have shown that even slight variations in depth can have major consequences on the differential charged particle fluence within the ionization chamber, mainly due to internal cavity-specific effects. Furthermore, the results showed that in the case of relative dose measurements, the depth-depending detector response can significantly differ from unity in a range of 1.4%–2.8% depending on the ionization chamber design.Conclusion: The complexity of different effects on the fluence disturbance could be broken down with regard to their influence on the spectral fluence distribution in the sensitive volume of the investigated detectors. It could be demonstrated, that the displacement of water is a depth-depending effect, which can not be compensated or corrected ideally for each investigated water depth by the shift of the effective point of measurement. Generally, the spectral analysis of those energy-dependent correction factors serves to a deeper understanding of the detector response under various conditions.

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Enhancement of the EGSnrc code egs_chamber for fast fluence calculations of charged particles

Cited by 3 publications

References 23 publications

egs++: Optimization of Simulation Transport Parameters

egs++: Optimization of Simulation Transport Parameters

Investigations on the beam quality correction factor for ionization chambers in high-energy brachytherapy dosimetry

Spectral analysis of Monte Carlo calculated fluence correction and cema conversion factors for high-energy photon beams at different depths

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