open access

Vol 23, No 2 (2018)
Original research articles
Published online: 2018-03-01
Submitted: 2017-06-20
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Accuracy evaluation of distance inverse square law in determining virtual electron source location in Siemens Primus linac

Hamid Shafaei Douk, Mahmoud Reza Aghamiri, Mahdi Ghorbani, Bagher Farhood, Mohsen Bakhshandeh, Hamid Reza Hemmati
DOI: 10.1016/j.rpor.2018.01.002
·
Rep Pract Oncol Radiother 2018;23(2):105-113.

open access

Vol 23, No 2 (2018)
Original research articles
Published online: 2018-03-01
Submitted: 2017-06-20

Abstract

Aim

The aim of this study is to evaluate the accuracy of the inverse square law (ISL) method for determining location of virtual electron source (SVir) in Siemens Primus linac.

Background

So far, different experimental methods have presented for determining virtual and effective electron source location such as Full Width at Half Maximum (FWHM), Multiple Coulomb Scattering (MCS), and Multi Pinhole Camera (MPC) and Inverse Square Law (ISL) methods. Among these methods, Inverse Square Law is the most common used method.

Materials and methods

Firstly, Siemens Primus linac was simulated using MCNPX Monte Carlo code. Then, by using dose profiles obtained from the Monte Carlo simulations, the location of SVir was calculated for 5, 7, 8, 10, 12 and 14[[ce:hsp sp="0.25"/]]MeV electron energies and 10[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm, 15[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]15[[ce:hsp sp="0.25"/]]cm, 20[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]20[[ce:hsp sp="0.25"/]]cm and 25[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]25[[ce:hsp sp="0.25"/]]cm field sizes. Additionally, the location of SVir was obtained by the ISL method for the mentioned electron energies and field sizes. Finally, the values obtained by the ISL method were compared to the values resulted from Monte Carlo simulation.

Results

The findings indicate that the calculated SVir values depend on beam energy and field size. For a specific energy, with increase of field size, the distance of SVir increases for most cases. Furthermore, for a special applicator, with increase of electron energy, the distance of SVir increases for most cases. The variation of SVir values versus change of field size in a certain energy is more than the variation of SVir values versus change of electron energy in a certain field size.

Conclusion

According to the results, it is concluded that the ISL method can be considered as a good method for calculation of SVir location in higher electron energies (14[[ce:hsp sp="0.25"/]]MeV).

Abstract

Aim

The aim of this study is to evaluate the accuracy of the inverse square law (ISL) method for determining location of virtual electron source (SVir) in Siemens Primus linac.

Background

So far, different experimental methods have presented for determining virtual and effective electron source location such as Full Width at Half Maximum (FWHM), Multiple Coulomb Scattering (MCS), and Multi Pinhole Camera (MPC) and Inverse Square Law (ISL) methods. Among these methods, Inverse Square Law is the most common used method.

Materials and methods

Firstly, Siemens Primus linac was simulated using MCNPX Monte Carlo code. Then, by using dose profiles obtained from the Monte Carlo simulations, the location of SVir was calculated for 5, 7, 8, 10, 12 and 14[[ce:hsp sp="0.25"/]]MeV electron energies and 10[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm, 15[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]15[[ce:hsp sp="0.25"/]]cm, 20[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]20[[ce:hsp sp="0.25"/]]cm and 25[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]25[[ce:hsp sp="0.25"/]]cm field sizes. Additionally, the location of SVir was obtained by the ISL method for the mentioned electron energies and field sizes. Finally, the values obtained by the ISL method were compared to the values resulted from Monte Carlo simulation.

Results

The findings indicate that the calculated SVir values depend on beam energy and field size. For a specific energy, with increase of field size, the distance of SVir increases for most cases. Furthermore, for a special applicator, with increase of electron energy, the distance of SVir increases for most cases. The variation of SVir values versus change of field size in a certain energy is more than the variation of SVir values versus change of electron energy in a certain field size.

Conclusion

According to the results, it is concluded that the ISL method can be considered as a good method for calculation of SVir location in higher electron energies (14[[ce:hsp sp="0.25"/]]MeV).

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Keywords

Virtual electron source; Inverse square law; Electron energy; Field size; Monte Carlo simulation

About this article
Title

Accuracy evaluation of distance inverse square law in determining virtual electron source location in Siemens Primus linac

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 2 (2018)

Pages

105-113

Published online

2018-03-01

DOI

10.1016/j.rpor.2018.01.002

Bibliographic record

Rep Pract Oncol Radiother 2018;23(2):105-113.

Keywords

Virtual electron source
Inverse square law
Electron energy
Field size
Monte Carlo simulation

Authors

Hamid Shafaei Douk
Mahmoud Reza Aghamiri
Mahdi Ghorbani
Bagher Farhood
Mohsen Bakhshandeh
Hamid Reza Hemmati

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