Commissioning of a medical accelerator photon beam Monte Carlo simulation using wide-field profiles

Peña, J.; Franco, L.; Gómez, F.; Iglesias, A.; Lobato, R Fernández; Mosquera, J.; Pazos, A.; Pardo, José Manuel; Pombar, M.; Rodrı́guez, A. O.; Sendón, J

doi:10.1088/0031-9155/49/21/006

Cited by 22 publications

(23 citation statements)

References 10 publications

(12 reference statements)

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“…Pena et al used a Monte Carlo technique to model the 15 MV Siemens Primus photon spectrum. 29 They reported a nominal incident electron energy of 11.5 MeV with a Gaussian distribution ͑full width at half maximum of 14%͒. 29 In a subsequent publication, Pena et al reported photoneutron spectra for the 15 MV Siemens Primus.…”

Section: Discussionmentioning

confidence: 99%

“…29 They reported a nominal incident electron energy of 11.5 MeV with a Gaussian distribution ͑full width at half maximum of 14%͒. 29 In a subsequent publication, Pena et al reported photoneutron spectra for the 15 MV Siemens Primus. 8 Qualitatively, our spectra are in reasonable agreement with theirs, where our peak energy is slightly lower, and our fluence at the peak is about 20% lower.…”

Section: Discussionmentioning

confidence: 99%

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Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators

et al. 2009

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Neutrons are a by-product of high-energy x-ray radiation therapy ͑threshold for ͓␥ , n͔ reactions in high-Z material ϳ7 MeV͒. Neutron production varies depending on photon beam energy as well as on the manufacturer of the accelerator. Neutron production from modern linear accelerators ͑linacs͒ has not been extensively compared, particularly in terms of the differences in the strategies that various manufacturers have used to implement multileaf collimators ͑MLCs͒ into their linac designs. However, such information is necessary to determine neutron dose equivalents for different linacs and to calculate vault shielding requirements. The purpose of the current study, therefore, was to measure the neutron spectra from the most up-to-date linacs from three manufacturers: Varian 21EX operating at 15, 18, and 20 MV, Siemens ONCOR operating at 15 and 18 MV, and Elekta Precise operating at 15 and 18 MV. Neutron production was measured by means of gold foil activation in Bonner spheres. Based on the measurements, the authors determined neutron spectra and calculated the average energy, total neutron fluence, ambient dose equivalent, and neutron source strength. The shapes of the neutron spectra did not change significantly between accelerators or even as a function of treatment energy. However, the neutron fluence, and therefore the ambient dose equivalent, did vary, increasing with increasing treatment energy. For a given nominal treatment energy, these values were always highest for the Varian linac. The current study thus offers medical physicists extensive information about the neutron production of MLC-equipped linacs currently in operation and provides them information vital for accurate comparison and prediction of neutron dose equivalents and calculation of vault shielding requirements.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators

et al. 2009

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“…13 As the electrons coming from the accelerating tube are highly directional, the divergence of the incident electrons can be neglected 13 thus parallel incident electrons are assumed. Pena et al 14 have studied the influence of electron beam width on the PDD curve and found the effect is small ͑Յ1% for electron beam width ranging from 0.5 to 2 mm in 6 MV mode͒. So it is a good approximation to assume the PDD curve is not sensitive to the incident electron beam size.…”

Section: B Calculation Of Dose Profiles and Penumbraementioning

confidence: 99%

Estimation of the focal spot size and shape for a medical linear accelerator by Monte Carlo simulation

Wang

Leszczyński

2007

Medical Physics

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The focal spot size and shape of a medical linac are important parameters that determine the dose profiles, especially in the penumbral region. A relationship between the focal spot size and the dose profile penumbra has been studied and established from simulation results of the EGSnrc Monte Carlo code. A simple method is proposed to estimate the size and the shape of a linac's focal spot from the measured dose profile data.

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“…Better agreement could potentially be obtained by tuning initial electron beam energy and radial intensity [5,20,31]. Several studies reported that radial intensity of electron beam did not affect PDD curves while dose profiles were affected by the radial and energy distribution of initial electron beam.…”

Section: Discussionmentioning

confidence: 99%

The effect of energy spectrum change on DNA damage in and out of field in 10-MV clinical photon beams

Ezzati

Xiao

Sohrabpour

et al. 2014

Med Biol Eng Comput

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The aim of this study was to quantify the DNA damage induced in a clinical megavoltage photon beam at various depths in and out of the field. MCNPX was used to simulate 10 × 10 and 20 × 20 cm(2) 10-MV photon beams from a clinical linear accelerator. Photon and electron spectra were collected in a water phantom at depths of 2.5, 12.5 and 22.5 cm on the central axis and at off-axis points out to 10 cm. These spectra were used as an input to a validated microdosimetric Monte Carlo code, MCDS, to calculate the RBE of induced DSB in DNA at points in and out of the primary radiation field at three depths. There was an observable difference in the energy spectra for photons and electrons for points in the primary radiation field and those points out of field. In the out-of-field region, the mean energy for the photon and electron spectra decreased by a factor of about six and three from the in-field mean energy, respectively. Despite the differences in spectra and mean energy, the change in RBE was <1 % from the in-field region to the out-of-field region at any depth. There was no significant change in RBE regardless of the location in the phantom. Although there are differences in both the photon and electron spectra, these changes do not correlate with a change in RBE in a clinical MV photon beam as the electron spectra are dominated by electrons with energies >20 keV.

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Commissioning of a medical accelerator photon beam Monte Carlo simulation using wide-field profiles

Cited by 22 publications

References 10 publications

Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators

Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators

Estimation of the focal spot size and shape for a medical linear accelerator by Monte Carlo simulation

The effect of energy spectrum change on DNA damage in and out of field in 10-MV clinical photon beams

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