https://www.tandfonline.com/doi/pdf/10.1080/16583655.2022.2050097?needAccess=true

A Monte Carlo model of an agility head for a 10-MV photon beam

Investigation of level density and Gama strength function for photoneutron reaction in medical linacs in Beamline.

Abstract The aim of this study is to develop in-house Monte Carlo (MC) algorithm as an alternative tool to simulate all mechanisms of interactions for dose calculation in radiation therapy. Additionally, evaluating the MC-SCAN algorithm with beam modeling of Elekta VersaHD Linac was aimed. Mohan 6 MV photon spectrum was used and the source was modeled as a point source. The absorbed dose is calculated via modeling all interaction mechanisms to gain energy deposition. TPR 20/10 , PDD, photon profile of different field sizes as well as point dose was calculated after that, a comparison of all the achieved results with experimental measurements went through. The difference between calculated mean energy and theoretical one was obtained &lt; 1%. The calculated TPR 20/10 value was (0.685 ± 0.03). The difference between experimental PDD and photon profile, and the calculated ones by new model was &lt; 3% for all field sizes. A new MC algorithm can be used as an alternative tool to simulate virtual source model on an Elekta VersaHD Linac. All calculated values turned out to present the difference between experimental measurements to be &lt; 3% for homogeneous mediums. Nonetheless, further research was needed to be done for the better improvement. 

Developing a New Monte Carlo Algorithm as an Alternative Tool to Simulate Virtual Source Model on an Elekta Versa Hd Linac

Commissioning a simulation model of the linear accelerator (Linac) in radiotherapy needs to be done to validate the dose distribution accuracy. For this purpose, the Monte Carlo simulation method is commonly employed, and it involves using the EGSnrc software. This software consists of BEAMnrc for modeling Linac and DOSXYZnrc for calculating dose distribution in a water phantom. This study used Monte Carlo simulation to commission the Linac Flattening Filter-Free (FFF) Elekta Infinity™ 6 MV photon mode. The commissioning results show that the simulated dose distribution satisfied the acceptance criteria of simulation results using initial electron energy of 6.9 MeV at 5 × 5, 10 × 10, and 20 × 20 cm2 field sizes with average local difference of percent depth dose (PDD) of about 2.99%. The dose and dmax increasedwith higher initial electron energy increased, while percentage depth dose (PDD) decreased at smaller field sizes. At larger field sizes, the dose profile widened and the PDD Linac FFF decreased more significantly than PDD Linac Flattening Filter (FF). Additionally, both exhibited differences in the uniformity of dose values in the umbra area. The surface dose for a 10 × 10 cm2 field size was 25.2% and 34.4% for both 6 MV-FF and 6 MV-FFF, respectively. 

Commissioning of Elekta Infinity™ 6 MV flattening filter-free using Monte Carlo simulation

Relevance. The photofission of shielded nuclear materials is widely used to develop methods for non-destructive analysis of their isotopic composition. To stimulate the photofission reaction, bremsstrahlung beams obtained on electronic accelerators are used. Their parameters significantly depend on the design features of accelerators and sample activation schemes.

Purpose. Theoretical modelling of parameters of an optimal scheme for stimulating the photofission of shielded nuclear materials on an electronic accelerator – Microtron M-30 for the analysis of their isotopic composition, considering its technical characteristics, and experimental verification of its parameters.

Methodology. Theoretical calculations of the parameters of bremsstrahlung beams for the Microtron M-30 were carried out using the GEANT4 toolkit. For experimental studies of the influence of structural elements of the optimal stimulation scheme on the integral characteristics of inhibitory photons, secondary photoneutrons, the method of activation of detectors made of gold was used; for residual electrons – the transmission method based on a passage chamber and a Faraday cylinder.

Results. As a result of the combination of theoretical and experimental studies, optimal parameters of the activation scheme of nuclear materials on the Microtron M-30 have been established. The scheme provides experimental conditions under which the losses of bremsstrahlung photon beams interacting with the test samples (with energies ≥6 MeV) do not exceed 35% of their initial values, with the practical absence of residual electrons (98% of electrons are absorbed) and secondary photoneutrons (no more than 1E-9 n/e).

Conclusions. The parameters of the developed stimulation scheme for the Microtron M-30 can be applied to various types of accelerators, considering their design features, characteristics of the samples, and implemented activation schemes

Optimal scheme for stimulating photofission of shielded nuclear materials on the Microtron M-30: a combination of theoretical and experimental studies

https://journals.viamedica.pl/rpor/article/download/74110/54203

Monte carlo model and output factors of elekta infinity™ 6 and 10 MV photon beam.

Introduction: This study aimed to measure the neutron contamination of flattening filter (FF) and flattening filter-free (FFF) 10-MV photon beams delivered by the Elekta InfinityTM accelerator. Material and Methods: The photoneutron spectrum produced by the Linac head was evaluated using a Monte Carlo (MC) simulation. The geometry and composition of the head Linac material were modelled based on information obtained from the manufacturer. In this simulation, MC N-Particle Transport Code software (MCNP6) was utilized to model the Linac head and simulate the particle transport. Evaluation of neutron contamination was carried out for the Linac with FF and without it (i.e., FFF). In this regard, the FFF beam was built by removing the FF from the Linac components. The scoring plane, as the neutron spectra calculation area for FF and FFF beams, was placed 99 cm from the target. Results: The neutron type produced by the head Linac Elekta InfinityTM 10-MV photon mode was mostly thermal and fast. Although there were differences in the neutron intensity of FF and FFF beams, the type of neutrons produced by these two modes had the same energy. Based on the photoneutron reaction energy threshold, it can be concluded that the neutrons produced from the head Linac were the result of photoneutron interactions of high-energy photons with molybdenum-96 and tungsten-184 isotopes. Conclusion: The photoneutron quantity did not change for FF and FFF beams; however, a larger quantity of neutrons was produced in the FF beam.

https://ijmp.mums.ac.ir/article_13423_85d1bb69744dae139e37e4ea4cf691d8.pdf

Investigation of Neutron Contamination of Flattening Filter and Flattening Filter-Free 10-MV Photon Beams in Elekta InfinityTM Accelerator

https://journals.viamedica.pl/rpor/article/download/74095/54188

Study of efficiency in five-ﬁeld and ﬁeld-by-ﬁeld intensity modulated radiation therapy (IMRT) plan using DOSXYZnrc Monte Carlo code.

Target is one of the important components in a linear accelerator (linac). Target materials depend on the energy of linac so that they have different spectrums produced. This study investigates the spectrum characteristic of target material for some linacs using Monte Carlo codes. The target geometry and material simulated was collected from Varian Medical System. The simulation was carried out on two different Monte Carlo codes, namely PHITS and EGSnrc. In the simulation process, the cut-off energy of electron and photon are set in the same value at 0.521 MeV and 0.01 MeV, respectively. The SLAB geometry is implemented to model the target. The spectrum of photon and electron was collected at the end of the target. The deviation of electron and photon spectrum collected from PHITS and EGSnrc was calculated. The results show that the spectrum of photon and electron from PHITS and EGSnrc have the same trend with a deviation of more than 25%. The maximum differences between the codes were obtained at energy 0.04 MeV<E<0.3 MeV for 15 MeV sources. Differences between PHITS and EGSnrc are more than 17% in electron energy 18 and 20 MeV. The big deviation is caused by the cross-section data applied in PHITS and EGSnrc being different in some photon and electron interaction cross-sections.

Indra Budiansah

Papers

Monte carlo model and output factors of elekta infinity™ 6 and 10 MV photon beam.

Investigation of Neutron Contamination of Flattening Filter and Flattening Filter-Free 10-MV Photon Beams in Elekta InfinityTM Accelerator

Study of efficiency in five-ﬁeld and ﬁeld-by-ﬁeld intensity modulated radiation therapy (IMRT) plan using DOSXYZnrc Monte Carlo code.

Monte Carlo Simulation of particle production in target material linac 15, 18, and 20 MV photon beam