Investigation of the effect of Cerrobend Compensator on the neutron dose equivalent at different distances from 18 MV photon beam in Elekta SL 75/25 linear accelerator by Monte Carlo method

Background: High energy photon beams (higher than 7-8 MV), used for external radiotherapy, produce photoneutrons when interact with Linac head components. Cerrobend compensators use as beam shaping during the treatment. The purpose of this study was to Investigation the effect of Cerrobend compensator on neutron dose equivalent at different distances from 18 MV photon beam.Methods: Elekta SL 75/25 were simulated with FLUKA Monte Carlo code. Neutron dose equivalent in the center of the field and at 10, 20 and 50 cm from the center were calculated. In order to investigate the effect of the compensator on neutron contamination, the compensator of cerrobend alloy with a combination of 32% lead, 15.5% tin, and 52.5% bismuth with a density of 9.77 g/cm2 of 67.2 cm from the source was simulated.Results: The results showed that the neutron dose equivalent in the open field at 0, 10, 20 and 50 cm distance was 3.2, 2.1, 2.2 and 1.8 mSv / Gy, respectively, and with Cerrobend compensator was obtained, respectively, 4.1, 2.7, 3.4 and 2.9 mSv / Gy.Conclusion: It was noted that by inserting the Cerrobend compensator in the path of the X-ray beam, the photoneutron dose equivalent was increased compared to open field. Can be concluded that Cerrobend compensator, made from heavy materials may act like the other components of Linac head, producing undesired photoneutrons and thus increasing patient and personnel dose.

Investigation of the effect of Cerrobend Compensator on the neutron dose equivalent at different distances from 18 MV photon beam in Elekta SL 75/25 linear accelerator by Monte Carlo method Keywords:

Photoneutrons , Cerrobend Compensator , Radiotherapy , Monte Carlo