Background: The characteristics of secondary
neutrons in a high energy radiation therapy room
were studied using the MCNPX Monte Carlo (MC)
code. Materials and Methods: Two MC models including
a model with full description of head components
and a simplified model used in previous studies were
implemented for MC simulations. Results: Results
showed 4-53% difference between full and with the
simplified model in the neutron fluence calculation.
Additionally, in full MC model, increase in the field
size decreased the neutron fluence but for simplified
model, increase in the field size led to increase in
neutron fluence. In calculating the neutron and
capture gamma ray dose equivalent, simplified model
overestimated (9-47%) and (20-61%) respectively in
comparison to the full simulated model. However, a
close agreement was seen between two models, for
field size of 10×10 cm2. Conclusion: for MC modeling
of photoneutrons and capture gamma in radiotherapy
rooms, the detailed modeling of linac head instead of
simplified model is recommended. Iran. J. Radiat. Res.,
2010 8 (3): 187-193
Ghiasi H, Mesbahi A. Monte Carlo characterization of photoneutrons in the radiation therapy with high energy photons: a Comparison between simplified and full Monte Carlo models. Int J Radiat Res 2010; 8 (3) :187-193 URL: http://ijrr.com/article-1-650-en.html