The high energy photon from medical linear accelerator (Linac) have been widely used for cancer treatment with radiotherapy. However, when high energy photon interact with Linac head components the undesirable neutrons contamination can be produced by photo-nuclear reaction. This work aims to evaluate photo-neutron dose generated from Linac 10 MV. The polycarbonate base layer of compact disc (CD) has been applied to neutron dosimetry by combining with polyethylene converter and boron converter for the fast neutrons and the thermal neutrons measurement, respectively. The pieces of CD track detector were irradiated with high energy photon from 10 MV Elekta Precise Linacs in the solid water phantom at depth of 0, 2.5, 5, 10, 15 and 20 cm, then etched with PEW solution (potassium hydroxide, ethanol and water) with ratio of 15: 45: 40 at various solution’s temperature and etching times. The neutron response of CD track detector, CR-39 track detector and MCNP simulation have been compared. The results showed that the shape of the fluence responses of neutron and the neutron dose equivalent of them were agreed. This CD track detector for neutron measurement system allows users to measure all energy ranges of neutrons produced in the radiotherapy room more easily.
Keywords: LINAC, Photo-Neutron, Neutron measurement, Compact disc, CR-39, MCNP