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Comparison of neutron contamination in small photon fields of secondary collimator jaws and circular cones

Published online by Cambridge University Press:  29 September 2023

Nooshin Banaee Open the ORCID record for Nooshin Banaee [Opens in a new window] ,
Kiarash Goodarzi  and
Elham Hosseinzadeh
Nooshin Banaee*
Affiliation:
Medical Radiation Research Center, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Kiarash Goodarzi
Affiliation:
Medical Radiation Research Center, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Elham Hosseinzadeh
Affiliation:
Department of Medical Physics, Faculty of Medicine, Jundishapur University of Medical Sciences, Ahvaz, Iran
*
Corresponding author: Dr Nooshin Banaee; Email: nooshin_banaee@yahoo.com
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Abstract

Introduction:

Advanced treatment modalities involve applying small fields which might be shaped by collimators or circular cones. In these techniques, high-energy photons produce unwanted neutrons. Therefore, it is necessary to know neutron parameters in these techniques.

Materials and methods:

Different parts of Varian linac were simulated by MCNPX, and different neutron parameters were calculated. The results were then compared to photoneutron production in the same nominal fields created by circular cones.

Results:

Maximum neutron fluence for 1 × 1, 2 × 2, 3 × 3 cm2 field sizes was 165, 40.4, 19.78 (cm–2.Gy-1 × 106), respectively. The maximum values of neutron equivalent doses were 17.1, 4.65, 2.44 (mSv/Gy of photon dose) for 1 × 1, 2 × 2, 3 × 3 cm2 field size, respectively, and maximum neutron absorbed doses reached 903, 253, 131 (µGy/Gy photon dose) for 1 × 1, 2 × 2, 3 × 3 cm2 field sizes, respectively.

Conclusion:

Comparing the results with those in the presence of circular cones showed that circular cones reduce photoneutron production for the same nominal field sizes.

Keywords

Monte Carloneutron contaminationphotoneutronradiotherapysmall fields
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 22 , 2023 , e107
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Copyright
© The Author(s), 2023. Published by Cambridge University Press

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