Hamid Shafaei Douk1, Mahmoud Reza Aghamiri1, Mahdi Ghorbani2, Bagher Farhood3, Mohsen Bakhshandeh4, Hamid Reza Hemmati1. 1. Radiation Medicine Department, Faculty of Shahid Beheshti University, Tehran, Iran. 2. Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 3. Medical Physics and Medical Engineering Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 4. Department of Radiology Technology, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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 MeV electron energies and 10 cm × 10 cm, 15 cm × 15 cm, 20 cm × 20 cm and 25 cm × 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 MeV).
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 MeV electron energies and 10 cm × 10 cm, 15 cm × 15 cm, 20 cm × 20 cm and 25 cm × 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 MeV).
Entities:
Keywords:
Electron energy; Field size; Inverse square law; Monte Carlo simulation; Virtual electron source