Iranian Journal of Medical Physics

Iranian Journal of Medical Physics

Investigation of Neutron Contamination of Flattening Filter and Flattening Filter-Free 10-MV Photon Beams in Elekta InfinityTM Accelerator

Document Type : Original Paper

Authors
Sitti Yani 1
Indra Budiansah 1
Fauzia Puspa Lestari 1
Mohamad Rhani 2
Rasito Tursinah 3
Freddy Haryanto 1
1 Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung
2 Department of Radiation Oncology, Concord International Hospital, Singapore/ Singapore
3 National Nuclear Energy Agency
10.22038/ijmp.2019.37195.1471
Abstract
Introduction: This study aimed to measure the neutron contamination of flattening filter (FF) and flattening filter-free (FFF) 10-MV photon beams delivered by the Elekta InfinityTM accelerator.
Material and Methods: The photoneutron spectrum produced by the Linac head was evaluated using a Monte Carlo (MC) simulation. The geometry and composition of the head Linac material were modelled based on information obtained from the manufacturer. In this simulation, MC N-Particle Transport Code software (MCNP6) was utilized to model the Linac head and simulate the particle transport. Evaluation of neutron contamination was carried out for the Linac with FF and without it (i.e., FFF). In this regard, the FFF beam was built by removing the FF from the Linac components. The scoring plane, as the neutron spectra calculation area for FF and FFF beams, was placed 99 cm from the target.
Results: The neutron type produced by the head Linac Elekta InfinityTM 10-MV photon mode was mostly thermal and fast. Although there were differences in the neutron intensity of FF and FFF beams, the type of neutrons produced by these two modes had the same energy. Based on the photoneutron reaction energy threshold, it can be concluded that the neutrons produced from the head Linac were the result of photoneutron interactions of high-energy photons with molybdenum-96 and tungsten-184 isotopes.
Conclusion: The photoneutron quantity did not change for FF and FFF beams; however, a larger quantity of neutrons was produced in the FF beam.
Keywords
Neutron
Monte Carlo Method Photon Beam
Linear Accelerator
Subjects

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Iranian Journal of Medical Physics
Volume 17, Issue 2 - Serial Number 2
March and April 2020
Pages 126-132

  • Receive Date 25 January 2019
  • Revise Date 11 June 2019
  • Accept Date 05 July 2019