Determination of room entry times for radiation therapists after routine 15 MV photon treatments

Background: Radiaon therapy uses high-energy radiaon to kill cancer cells. Photoneutron contaminaon and induced radioacvity of high energy therapeuc photon beams are considered as the main source of occupaonal exposure to radiaon therapists who works with linear accelerators operang above 10 MV. Materials and Methods: The gamma dose rates were measured a#er terminaon of different treatment approaches using 15 MV photons and room entry mes for each approach was determined. Based on the results of this study, the annual dose of radiaon therapists was esmated. Results: The highest dose rate that measured in the treatment room was belonged to 3-field pelvic approach which was equal to 5 ± 1.1 μSv/h. The radiaon therapist's room entry mes were determined between 3 to 10 minutes and the annual dose was esmated up to 5.9 mSv/y. Conclusion: Although the esmated annual dose is less than the internaonally permi2ed value, the undesirable dose to radiaon workers could be reduced through considering recommended room entry mes.