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The effects of backscattered radiation into beam monitor chamber: Study of 6 and 18 MV conventional and removed flattening filter clinical accelerator

Zabihzadeh, M. and Mahdavi, S.R. and Ay, M.R. and Shakarami, Z. (2015) The effects of backscattered radiation into beam monitor chamber: Study of 6 and 18 MV conventional and removed flattening filter clinical accelerator. Biosciences Biotechnology Research Asia, 12. pp. 25-36.

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Abstract

In some linear accelerators (Linac), the collected charges in beam monitor chamber (BMC) is partly caused by the backscattered particles from the accelerator components downstream the BMC that influence the Linac output factors. In the intensity modulated radiation therapy technique, the desired dose distribution can be achieved through an unflattened beam. Although removing the flattening filter provides some advantages, the amount of backscatter radiation into BMC can be changed. In this study, contribution of backscattered particles into the BMC response of a Varian 2300 C/D Linac with and without a flattening filter was determined for 6, 18 MV photon beams. The experimental procedure included telescopic method and calculation procedure consisted of Monte Carlo simulation (MCNPX, version 2.4.0), were used to investigate the contribution of backscattered particles into the BMC performance. Our results showed a 2.3 and 3 increase in backscatter for a 0.5 x 0.5 cm2 field compared to a 40 x 40 cm2 field for 6 MV and 18 MV, respectively. The energy deposition from backscattered radiation is mainly caused by backscattered electrons. Removing the flattening filter did not change the BMC performance for a conventional Linac with a flattening filter. However, this result was not valid for small fields (e.g. 0.5 x 0.5 cm2, 18 MV). The corrected backscatter factors is necessary to taking into account the contribution of backscattered radiation in the monitor chamber response for small fields in the case of the free flattening filter Linacs (18 MV). © 2015, Oriental Scientific Publishing Company. All rights reserved.

Item Type: Article
Additional Information: cited By 0
Uncontrolled Keywords: Article; backscattered radiation; beam monitor chamber; calculation; dosimetry; electron transport; flattening filter; ionization chamber; linear accelerator; measurement; Monte Carlo method; particle size; photon; radiation dose fractionation; radiation equipment; radiological parameters; telescopic method
Subjects: مقالات نمایه شده محققین دانشگاه در سایت ,Web of Science ,Scopus
Divisions: معاونت تحقیقات و فناوری
Depositing User: GOUMS
Date Deposited: 10 Sep 2016 09:13
Last Modified: 10 Sep 2016 09:13
URI: http://eprints.goums.ac.ir/id/eprint/4823

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