Monte Carlo estimation of photoneutrons spectra and dose equivalent around an 18MV medical linear accelerator

Alem-Bezoubiri, A.; Bezoubiri, F.; Badreddine, A.; Mazrou, H.; Lounis-Mokrani, Z.

doi:10.1016/j.radphyschem.2013.07.013

Cited by 29 publications

(13 citation statements)

References 33 publications

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“…5 showed that the largest equivalent neutron dose was at isocenter 0.15 mSv/Gy reached to 0.02 mSv/Gy at 100cm. this data correlated with the previous published works [17,18,19]. In reference [17] the equivalent neutron dose is greater at the isocenter 1.35 mSv/Gy and decreases gradually with the distance away from the isocenter 0.0469 mSv/Gy at 75 cm, and decreased from 1.288mSv/Gy at the isocenter to 0.062mSv/Gy at 100cm as found in reference [19].…”

Section: Resultssupporting

confidence: 92%

Assessment the Photo-neutron Contamination of IMRT and 3D-Conformal Techniques Using Thermo-luminescent Dosimeter (TLD)

Mohamedy

Fathy

Khalil

et al. 2019

JPRI

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The aim of the study is to evaluate the dependence of photo-neutron production on field size, depth in phantom and distance from isocenter and also to calculate the equivalent neutron doses for PTV and OARs of IMRT and 3DCRT techniques using TLD (600/700).The Linac Siemens Oncor installed at Nasser Institute, Cairo, Egypt. TLDs, Neutron Monitor, Ionization chamber were provided by NIS, the duration of the study was from November 2017 to July 2018. 5 prostate cancer cases were selected treated with high energy beam (15MV) Linear accelerator using 3DCRT and IMRT treatment plans. The OARs were bladder, rectum and femur. Once the plans were completed, there were copied from the planning system onto the RW3 slab phantom in which pairs of TLD chips (600/700) were placed at the exact site of PTV and OARs. The results showed that: The measured photo-neutron decreases from 0.2 mSv/Gy to 0.09 mSv/Gy as increases field sizes from 2x2 cm2 to 20x20 cm2. The measured photo-neutron was maximum at dmax =0.15 mSv/Gy and decreases gradually as increases the depth in phantom reaches to 0.07 mSv/Gy at 10cm depth in phantom. The measured photo-neutron decreases from 1.5 mSv/Gy to 0.02 mSv/Gy when measured at isocenter and at 100cm along the patient couch. Using 3DCRT for PTV and OARs were ranging from 0.027 to 0.39 mSv per photon Gy and for IMRT were 0.135 to 2.34 mSv per photon Gy. In conclusion the photo-neutron production is decreases as increases field size and distance from isocenter along patient couch while increases with depth in phantom up to dmax and decreases gradually as increases depth in phantom. IMRT requires longer beam-on time than 3DCRT leading to worse OARs sparing and increase the production of photo-neutrons than 3DCRT.

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Section: Resultssupporting

confidence: 92%

Assessment the Photo-neutron Contamination of IMRT and 3D-Conformal Techniques Using Thermo-luminescent Dosimeter (TLD)

Mohamedy

Fathy

Khalil

et al. 2019

JPRI

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“…From Table 1 , one can note a good agreement achieved between the obtained results and the related values in the literature. [ 19 34 35 36 37 ] It can also see, the average relative difference of our results with literature is 5.4% and 20.1% for the flux and the ambient dose equivalent of neutrons, respectively. These differences are reasonable, because the type of study (measurement/simulation), cross-section libraries for photoneutrons production, as well as the treatment room geometries differed.…”

Section: Discussionsupporting

confidence: 51%

Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

et al. 2018

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Background:In the past, GRID therapy was used as a treatment modality for the treatment of bulky and deeply seated tumors with orthovoltage beams. Now and with the introduction of megavoltage beams to radiotherapy, some of the radiotherapy institutes use GRID therapy with megavoltage photons for the palliative treatment of bulky tumors. Since GRID can be a barrier for weakening the photoneutrons produced in the head of medical linear accelerators (LINAC), as well as a secondary source for producing photoneutrons, therefore, in terms of radiation protection, it is important to evaluate the GRID effect on photoneutron dose to the patients.Methods:In this study, using the Monte Carlo code MCNPX, a full model of a LINAC was simulated and verified. The neutron source strength of the LINAC (Q), the distributions of flux (φ), and ambient dose equivalent (H*[10]) of neutrons were calculated on the treatment table in both cases of with/without the GRID. Finally, absorbed dose and dose equivalent of neutrons in some of the tissues/organs of MIRD phantom were computed with/without the GRID.Results:Our results indicate that the GRID increases the production of the photoneutrons in the LINAC head only by 0.3%. The calculations in the MIRD phantom show that neutron dose in the organs/tissues covered by the GRID is on average by 48% lower than conventional radiotherapy. In addition, in the uncovered organs (by the GRID), this amount is reduced to 25%.Conclusion:Based on the findings of this study, in GRID therapy technique compared to conventional radiotherapy, the neutron dose in the tissues/organs of the body is dramatically reduced. Therefore, there will be no concern about the GRID effect on the increase of unwanted neutron dose, and consequently the risk of secondary cancer.

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“…The difference in copy number of the FDXR and RAD51 genes under 6 and 18 MV beam energies is related to two components, namely the effect of higher energy (18 MV versus 6 MV) and neutron contamination (photo neutron) at 18 MV. Rapid neutron contamination is caused by X-ray beams over 10 MV ( 25 , 26 ). Figures 3 and 4 show that the DNA damage in cells was increased with increasing dose in low and intermediate doses (0.2, 0.5, and 2 Gy).…”

Section: Discussionmentioning

confidence: 99%

Dose–Response Curves of the FDXR and RAD51 Genes with 6 and 18 MV Beam Energies in Human Peripheral Blood Lymphocytes

Saberi

Khodamoradi

Birgani

et al. 2016

Iran Red Crescent Med J

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BackgroundRapid dose assessment using biological dosimetry methods is essential to increase the chance of survival of exposed individuals in radiation accidents.ObjectivesWe compared the expression levels of the FDXR and RAD51 genes at 6 and 18 MV beam energies in human peripheral blood lymphocytes. The results of our study can be used to analyze radiation energy in biological dosimetry.MethodsFor this in vitro experimental study, from 36 students in the medical physics and virology departments, seven voluntary, healthy, non-smoking male blood donors of Khuzestan ethnicity with no history of exposure to ionization radiation were selected using simple randomized sampling. Sixty-three peripheral blood samples were collected from the seven healthy donors. Human peripheral blood was then exposed to doses of 0, 0.2, 0.5, 2, and 4 Gy with 6 and 18 MV beam energies in a Linac Varian 2100C/D (Varian, USA) at Golestan hospital in Ahvaz, Iran. After RNA extraction and cDNA synthesis, the expression levels of FDXR and RAD51 were determined 24 hours post-irradiation using the gel-purified reverse transcription polymerase chain reaction (RT-PCR) technique and TaqMan strategy (by real-time PCR).ResultsThe expression level of FDXR gene was significantly increased at doses of 2 Gy and 4 Gy in the 6 - 18 MV energy range (P < 0.001 and P < 0.008, respectively). The medians with interquartile ranges (IQRs) of the copy numbers of the FDXR gene at 2 Gy and 4 Gy doses under 6 and 18 MV beam energies were 2393.59 (1798.21, 2575.37) and 2983.00 (2199.48, 3643.82) and 3779.12 (3051.40, 5120.74) and 5051.26 (4704.83, 5859.17), respectively. However, RAD51 gene expression levels only showed a significant difference between samples at a dose of 2 Gy with 6 and 18 MV beam energies, respectively (P < 0.040). The medians with IQRs of the copy numbers of the RAD51 gene were 2092.77 (1535.78, 2705.61) and 3412.57 (2979.72, 4530.61) at beam energies of 6 and 18 MV, respectively.ConclusionsThe data suggest that the expression analysis of the FDXR gene, contrary to that of the RAD51 gene, may be suitable for assessment of high-energy X-ray. In addition, RAD51 is not a suitable gene for dose assessment in biological dosimetry.

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Monte Carlo estimation of photoneutrons spectra and dose equivalent around an 18MV medical linear accelerator

Cited by 29 publications

References 33 publications

Assessment the Photo-neutron Contamination of IMRT and 3D-Conformal Techniques Using Thermo-luminescent Dosimeter (TLD)

Assessment the Photo-neutron Contamination of IMRT and 3D-Conformal Techniques Using Thermo-luminescent Dosimeter (TLD)

Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

Dose–Response Curves of the FDXR and RAD51 Genes with 6 and 18 MV Beam Energies in Human Peripheral Blood Lymphocytes

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