The influence of field size and off-axis distance on photoneutron spectra of the 18 MV Siemens Oncor linear accelerator beam

Brkić, Hrvoje; Ivković, Ana; Kasabašić, Mladen; Sovilj, Marina Poje; Jurković, Slaven; Stimac, Davor; Rubin, Otmar; Faj, Dario

doi:10.1016/j.radmeas.2016.07.002

Cited by 23 publications

(21 citation statements)

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“…The aim of this study is to de ter mine the in flu ence of head cover pres ence on neu tron flux around Siemens Oncor med i cal lin ear ac cel er a tor head, place of or i gin of neu trons, in two dif fer ent ap proaches and changes in neu tron spec tra in both cases. These data are rel e vant for de ter min ing the ex act dose that the pa tients and med i cal per son nel re ceive from the neu trons, in fa cil ities where high en ergy med i cal lin ear ac cel er a tors are in stalled, es pe cially if these doses are de ter mined us ing highly de pend ent pas sive de tec tors [3].…”

Section: Introductionmentioning

confidence: 86%

“…The MC model of the ac cel er a tor Siemens Oncor, used at Uni ver sity hos pi tal of Osijek ra dio therapy de part ment, was built us ing MCNP611 ® [19] code, as it was de scribed in pre vi ous stud ies [3]. That model was built with out the head cover (empty model in fur ther text) and in the model pre sented in this paper, we in cluded the head cover (full model in fur ther text), for com par i son of the two mod els.…”

Section: Ma Te Ri Als and Meth Odsmentioning

confidence: 99%

“…As it has been re ported pre vi ously, high en ergy elec tron med i cal lin ear ac cel er a tors can pro duce un desired neu tron con tam i na tion of the pho ton ther a peu tic beams [1][2][3]. This oc curs due to the photonuclear ef fect, caused by pho tons with en er gies higher than 10 MeV [4].…”

Section: Introductionmentioning

confidence: 99%

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Influence of head cover on the neutron dose equivalent in Monte Carlo simulations of high energy medical linear accelerator

et al. 2018

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Neu tron con tam i na tion of radiotherapeutic pho ton beam oc curs when en er gies higher than 10 MeV are used in ra dio ther apy. To cor rectly as sess the neu tron doses that med i cal per son nel and pa tients re ceive, it is highly im por tant to know the spec tra of the pro duced photoneutrons. One of the most com mon ways to de ter mine such spec trum is to per form Monte Carlo sim u lations of the ac cel er a tor. Ma jor is sue in the Monte Carlo mod el ling is that the man u fac tur ers of ten does not pro vide full spec i fi ca tions of the ac cel er a tors head, so some parts of the head are omit ted from the sim u la tion. Within this pa per we pres ent a model that in cludes head cover com pared to the one where it is omit ted, as it can of ten be found in the ref er ences. Neu tron fluxes, spec tra, mean en er gies and place of or i gin are com pared in isocenter, at the point 1 m above tar get and the point 1 m aside from the tar get, in both mod els. In all the con sid ered planes the flux change was found to be more than 20 %, with a sig nif i cantly change in neu tron en ergy, what is also im por tant in neu tron do sim e try. Ig nor ing the head cover in the Monte Carlo mod el ling of the high en ergy elec tron lin ear ac cel er a tors in ra dio ther apy, will in tro duce a large un cer tainty of neu tron doses as sess ing a pa tient, or a med i cal pro fes sional.

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Section: Introductionmentioning

confidence: 86%

Section: Ma Te Ri Als and Meth Odsmentioning

confidence: 99%

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Influence of head cover on the neutron dose equivalent in Monte Carlo simulations of high energy medical linear accelerator

et al. 2018

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“…During the detection of thermal neutrons, 3 He acts as the stopping medium for them with reaction (1); meanwhile, with a higher stopping power than that of 3 He, tritium and protons are stopped by the filling gas. 25,26 The dosimetric measurements taken by the Thermo Scientific RadEye NL neutron detector were analyzed by an automatic reader. To eliminate device-based errors, each measurement was repeated three times.…”

Section: Experimental Partmentioning

confidence: 99%

Investigation of photoneutron contamination from the 18-MV photon beam in a medical linear accelerator

Karaman¹,

Tanir²,

Karaman³

2019

Mater. Tehnol.

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In medical applications, high-energy linear accelerators are increasingly used. However, during a cancer treatment, unwanted photoneutrons caused by high-energy photon beams (>10 MV) increase the secondary cancer risk. This study aimed to investigate the effects of the square field size and distance to the isocenter on the neutron contamination emitted by an Elekta Versa HD medical linear accelerator using a Thermo Scientific RadEye neutron detector. The measurements were carried out for 18-MV photons with different square field sizes and different distances from the isocenter. It was clearly seen that the neutron dose equivalent decreases with both the increasing distance from the isocenter and square field size. Also, in order to analyze the neutron dose equivalent variation with field sizes and distances, Monte Carlo code Fluka was used. It was shown that MC-Fluka modeling and experimental results were consistent with each other. It was concluded that it is crucial to take into consideration the unwanted neutron dose in the radiation treatment.

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“…In these beams, fast neutrons are generated, which results in undesired contamination of the therapeutic beam. [1][2][3][4][5][6] Neutr on contamination in high-energy RT implies an increase of secondary radiation-induced cancer risk. 7 It is also well known that an essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized.…”

Section: Introductionmentioning

confidence: 99%

The influence of shielding reinforcement in a vault with limited dimensions on the neutron dose equivalent in vicinity of medical electron linear accelerator

Ivković

Faj

Kasabašić

et al. 2020

Radiology and Oncology

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BackgroundHigh energy electron linear accelerators (LINACs) producing photon beams with energies higher than 10 MeV are widely used in radiation therapy. In these beams, fast neutrons are generated, which results in undesired contamination of the therapeutic beam. In this study, measurements and Monte Carlo (MC) simulations were used to obtain neutron spectra and dose equivalents in vicinity of linear accelerator.Materials and methodsLINAC Siemens Oncor Expression in Osijek University Hospital is placed in vault that was previously used for 60Co machine. Then, the shielding of the vault was enhanced using lead and steel plates. Measurements of neutron dose equivalent around LINAC and the vault were done using CR-39 solid state nuclear track detectors. To compensate energy dependence of detectors, neutron energy spectra was calculated in measuring positions using MC simulations.ResultsThe vault is a source of photoneutrons, but a vast majority of neutrons originates from accelerator head. Neutron spectra obtained from MC simulations show significant changes between the measuring positions. Annual neutron dose equivalent per year was estimated to be less than 324 μSv in the measuring points outside of the vault.ConclusionsSince detectors used in this paper are very dependent on neutron energy, it is extremely important to know the neutron spectra in measuring points. Though, patient dosimetry should include neutrons, estimated annual neutron doses outside the vault were far below exposure limit of ionizing radiation for workers.

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The influence of field size and off-axis distance on photoneutron spectra of the 18 MV Siemens Oncor linear accelerator beam

Cited by 23 publications

References 20 publications

Influence of head cover on the neutron dose equivalent in Monte Carlo simulations of high energy medical linear accelerator

Influence of head cover on the neutron dose equivalent in Monte Carlo simulations of high energy medical linear accelerator

Investigation of photoneutron contamination from the 18-MV photon beam in a medical linear accelerator

The influence of shielding reinforcement in a vault with limited dimensions on the neutron dose equivalent in vicinity of medical electron linear accelerator

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