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A Monte Carlo Study for Photoneutron Dose Estimations around the High-Energy Linacs.

Mohammadi N, Miri-Hakimabad SH, Rafat-Motavalli L - J Biomed Phys Eng (2014)

Bottom Line: The results of dose calculations at the isocenter and maze showed that photoneutron dose decreases as the function of distance from the isocenter and increases with increasing the distance from the entrance maze.It is concluded that the simplified model of linac head is a useful and reliable method in dosimetry calculations.Calculations illustrated that the photoneutron dose is not negligible and duo to its harmful biological effects on body, it should be considered in the treatment plans.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Faculty of Sciences, Ferdowsi University of Mashhad, Iran.

ABSTRACT

Background: High-energy linear accelerator (linac) is a valuable tool and the most commonly used device for external beam radiation treatments in cancer patients. In the linac head, high-energy photons with energies above the threshold of (γ,n) interaction produce photoneutrons. These photoneutrons deliver the extra dose to the patients undergoing radiation treatment and increase the risk of secondary cancer.

Objective: In this study, a simplified model of the linac head was simulated and photoneutron dose equivalent was calculated at the isocenter and maze in the sphere detector. In addition, the absorbed and equivalent dose of photoneutron were estimated in the some organs of the phantom.

Methods: The simulations were made using the Monte Carlo code. The ICRP reference adult male voxel phantom was used as the human body model for dosimetry calculations.

Results: The results of dose calculations at the isocenter and maze showed that photoneutron dose decreases as the function of distance from the isocenter and increases with increasing the distance from the entrance maze.

Conclusion: It is concluded that the simplified model of linac head is a useful and reliable method in dosimetry calculations. Calculations illustrated that the photoneutron dose is not negligible and duo to its harmful biological effects on body, it should be considered in the treatment plans.

No MeSH data available.


Related in: MedlinePlus

Photoneutron spectra at the isocenter (soft tissue) for 15 MV accelerator
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Figure 5: Photoneutron spectra at the isocenter (soft tissue) for 15 MV accelerator

Mentions: The fluences of photoneutrons in the spheres containing air and soft tissue at the isocenter (for 15 MV) were displayed in figures 4 and 5, respectively. There are two peaks in the spectrum: first one at energy of 0.5 MeV is due to direct neutrons which move directly from the head to the detectors and the second one at energy of 10−7 MeV is related to thermal neutrons produced by scattering from head’s components and walls of treatment room. The results of our calculations for determining photoneutron spectra in air were in good agreements with spectra reported by the other researchers [16-18].


A Monte Carlo Study for Photoneutron Dose Estimations around the High-Energy Linacs.

Mohammadi N, Miri-Hakimabad SH, Rafat-Motavalli L - J Biomed Phys Eng (2014)

Photoneutron spectra at the isocenter (soft tissue) for 15 MV accelerator
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4289520&req=5

Figure 5: Photoneutron spectra at the isocenter (soft tissue) for 15 MV accelerator
Mentions: The fluences of photoneutrons in the spheres containing air and soft tissue at the isocenter (for 15 MV) were displayed in figures 4 and 5, respectively. There are two peaks in the spectrum: first one at energy of 0.5 MeV is due to direct neutrons which move directly from the head to the detectors and the second one at energy of 10−7 MeV is related to thermal neutrons produced by scattering from head’s components and walls of treatment room. The results of our calculations for determining photoneutron spectra in air were in good agreements with spectra reported by the other researchers [16-18].

Bottom Line: The results of dose calculations at the isocenter and maze showed that photoneutron dose decreases as the function of distance from the isocenter and increases with increasing the distance from the entrance maze.It is concluded that the simplified model of linac head is a useful and reliable method in dosimetry calculations.Calculations illustrated that the photoneutron dose is not negligible and duo to its harmful biological effects on body, it should be considered in the treatment plans.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Faculty of Sciences, Ferdowsi University of Mashhad, Iran.

ABSTRACT

Background: High-energy linear accelerator (linac) is a valuable tool and the most commonly used device for external beam radiation treatments in cancer patients. In the linac head, high-energy photons with energies above the threshold of (γ,n) interaction produce photoneutrons. These photoneutrons deliver the extra dose to the patients undergoing radiation treatment and increase the risk of secondary cancer.

Objective: In this study, a simplified model of the linac head was simulated and photoneutron dose equivalent was calculated at the isocenter and maze in the sphere detector. In addition, the absorbed and equivalent dose of photoneutron were estimated in the some organs of the phantom.

Methods: The simulations were made using the Monte Carlo code. The ICRP reference adult male voxel phantom was used as the human body model for dosimetry calculations.

Results: The results of dose calculations at the isocenter and maze showed that photoneutron dose decreases as the function of distance from the isocenter and increases with increasing the distance from the entrance maze.

Conclusion: It is concluded that the simplified model of linac head is a useful and reliable method in dosimetry calculations. Calculations illustrated that the photoneutron dose is not negligible and duo to its harmful biological effects on body, it should be considered in the treatment plans.

No MeSH data available.


Related in: MedlinePlus