Evaluation of the linac neutron dose profile for various depths and field sizes: A Monte Carlo study

Dewa Ngurah Yudhi Prasada, Nikita Ciamaudi, Muhamad Fadli, Rasito Tursinah, Supriyanto Ardjo Pawiro

Research output: Contribution to journalArticlepeer-review


High-energy medical linear accelerator (Linac) has been widely used for treating cancer patients. However, with its effectiveness, high-energy linac yields an undesirable amount of neutron contamination. An MCNPX code version 2.6.0 was used for calculating photoneutron contamination from Varian Clinac iX 15 MV linac heads in this study. The fast neutrons were dominantly produced inside the linac head. The neutron fluence, absorbed dose, and dose equivalent calculations occurred inside a linac head and a water phantom model. The fast neutrons begin to be moderated after 1 cm inside the water phantom by calculating the energy spectra. Variations in the field sizes from 2 × 2, 5 × 5, 10 × 10, and 15 × 15 cm2 show that the neutron production yield would increase for larger field sizes. The maximum neutron dose equivalents are 3.745; 7.687; 11.794 and 14.197 μSv/MU for 2 × 2, 5 × 5, 10 × 10 and 15 × 15 cm2 field sizes, respectively. These calculations predict the photoneutron characteristics with more detail inside a treated patient during radiation therapy procedures.

Original languageEnglish
Article number067003
JournalBiomedical Physics and Engineering Express
Issue number6
Publication statusPublished - Nov 2021


  • High-energy linac
  • MCNPX monte carlo
  • Neutron contamination
  • Radiotherapy


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