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Abstract
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Dose escalation with high-energy X rays of medical linear accelerators (linacs) in radiotherapy offers several distinct advantages
over the lower energy photons. However, owing to photoneutron reactions, interaction of high-energy photons (>8 MV)
with various high-Z nuclei of the materials in the linac head components produces unavoidable neutrons. The aim of this
study was to evaluate the photoneutron dose equivalent per unit therapeutic X-ray dose of 18 MV, GE Saturne 20 linac in the
treatment room using Monte Carlo (MC) MCNP linac head full simulation as well as thermoluminescence dosemeter measurements.
This machine is one of the old linac models manufactured by General Electric Company; however, it is widely
used in the developing countries because of low cost and simple maintenance for radiotherapy applications. The results
showed a significant photoneutron dose from Saturne 20 linac head components especially at distances near the linac head
(<150 cm). Results of this work could be used in several applications, especially designing bunker and entrance door shielding
against neutrons produced by photoneutron reactions in GE Saturne 20. However, a detailed cost optimisation for a specific
room would require a dedicated calculation.
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