open access

Vol 19, No 1 (2014)
Original research articles
Published online: 2014-01-01
Submitted: 2013-02-06
Get Citation

Monte Carlo characterizations mapping of the (,) and (,) photonuclear reactions in the high energy X-ray radiation therapy

Hosein Ghiasi
DOI: 10.1016/j.rpor.2013.07.003
·
Rep Pract Oncol Radiother 2014;19(1):30-36.

open access

Vol 19, No 1 (2014)
Original research articles
Published online: 2014-01-01
Submitted: 2013-02-06

Abstract

Aim

The aim of this work was to map the characteristics of (n,γ) and (γ,n) reactions in a high energy photon radiation therapy.

Background

Photoneutrons produced in the high energy X-Ray radiation therapy may damage patients and staff. It is due to high RBE of the produced neutrons according to their energy and isotropic emission. Characterization of the photoneutrons can help us in appropriate shielding.

Materials and methods

This study focused on the photoneutron and capture gamma ray phenomena. Characteristics such as dose value, fluence and spectra of both the neutrons and the by produced prompt gamma ray were described.

Results and discussion

Neutron and prompt gamma spectra in different points showed the neutrons to be thermalized when increasing the distance from the linac. Energy of the neutrons changed from about 0.6[[ce:hsp sp="0.25"/]]MeV at the isocentre to around 10−08[[ce:hsp sp="0.25"/]]MeV at the outer door position. Although the neutrons were found as fast neutrons, their spectra showed they were thermal neutrons at the outer door position. Additionally, it was seen that the energy of the gamma rays is higher than the scattered X-ray energy. The energy of gamma rays was seen to be up to 10[[ce:hsp sp="0.25"/]]MeV while the linac photons had energy lower than 1[[ce:hsp sp="0.25"/]]MeV. Neutron source strength obtained in this work was in good agreement with the published data, which may be a confirmation of our simulation accuracy.

Conclusion

The study showed that the Monte Carlo simulation can be applied in the radiotherapy and industrial radiation works as a useful and precise estimator. We also concluded that the dose from the prompt gamma ray at the outer door location is higher than the scattered radiation from the linac and should be considered in the shielding.

Abstract

Aim

The aim of this work was to map the characteristics of (n,γ) and (γ,n) reactions in a high energy photon radiation therapy.

Background

Photoneutrons produced in the high energy X-Ray radiation therapy may damage patients and staff. It is due to high RBE of the produced neutrons according to their energy and isotropic emission. Characterization of the photoneutrons can help us in appropriate shielding.

Materials and methods

This study focused on the photoneutron and capture gamma ray phenomena. Characteristics such as dose value, fluence and spectra of both the neutrons and the by produced prompt gamma ray were described.

Results and discussion

Neutron and prompt gamma spectra in different points showed the neutrons to be thermalized when increasing the distance from the linac. Energy of the neutrons changed from about 0.6[[ce:hsp sp="0.25"/]]MeV at the isocentre to around 10−08[[ce:hsp sp="0.25"/]]MeV at the outer door position. Although the neutrons were found as fast neutrons, their spectra showed they were thermal neutrons at the outer door position. Additionally, it was seen that the energy of the gamma rays is higher than the scattered X-ray energy. The energy of gamma rays was seen to be up to 10[[ce:hsp sp="0.25"/]]MeV while the linac photons had energy lower than 1[[ce:hsp sp="0.25"/]]MeV. Neutron source strength obtained in this work was in good agreement with the published data, which may be a confirmation of our simulation accuracy.

Conclusion

The study showed that the Monte Carlo simulation can be applied in the radiotherapy and industrial radiation works as a useful and precise estimator. We also concluded that the dose from the prompt gamma ray at the outer door location is higher than the scattered radiation from the linac and should be considered in the shielding.

Get Citation

Keywords

Photoneutron; Monte Carlo; Shielding; Capture gamma ray

About this article
Title

Monte Carlo characterizations mapping of the (,) and (,) photonuclear reactions in the high energy X-ray radiation therapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 19, No 1 (2014)

Pages

30-36

Published online

2014-01-01

DOI

10.1016/j.rpor.2013.07.003

Bibliographic record

Rep Pract Oncol Radiother 2014;19(1):30-36.

Keywords

Photoneutron
Monte Carlo
Shielding
Capture gamma ray

Authors

Hosein Ghiasi

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