A study of the photoneutron dose equivalent resulting from a Saturne 20 medical linac using Monte Carlo method

High-energy X-rays offer several advantages over lower energy photons including: lower skin dose, higher depth dose, smaller scattered dose to tissues outside the target volume and less rounded isodose curves. These advantages in physical dose distributions have led to significant improvements in clinical radiotherapy, and high energy linear accelerators are now a standard fixture of radiotherapy clinics. However, high-energy X-ray machines present a significant radiation protection problem by producing small amounts of neutrons. Neutrons can be produced by a photonuclear reaction. The total neutrons produced are composed of two parts: photonuclear reactions via bremsstrahlung, and electron production via virtual photons. In general, the cross sections of electron production interaction are expected to be of the order of the fine structure constant (α ≈ 1/137) times of the cross sections of photonuclear reactions [11]. High energy photons generate neutrons through interactions with accelerator structures and treatment rooms [5]. Photonuclear absorption cross section for low atomic number materials such as O, C, and N is about a millibarn, but for high atomic number A study of the photoneutron dose equivalent resulting from a Saturne 20 medical linac using Monte Carlo method Seyed M. Hashemi, Bijan Hashemi-Malayeri, Gholamreza Raisali, Parvaneh Shokrani, Ali A. Sharafi