Tehran University of Medical Sciences Frontiers in Biomedical Technologies 2345-5837 10 4 2023 04 22 394 399 EN Shiva Rahbar Yazdi Department of Medical Physics, Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran Saman Dalvand Department of Medical Physics, School of Medical Sciences, Tarbiat Modares University Mohammad Ali Broomand Clinical Oncology Department, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Hamed Zamani Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran Mohammad Hosein Zare Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Hamidreza Masjedi Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran 2022 06 10 2022 08 23 Purpose: The purpose of this study was to evaluate the risk of gonad cancer induction attributable to pelvic radiation therapy in adult patients.  Methods: By characterizing the peripheral dose the TLDs were placed on the testis and ovary in two fractions of radiotherapy. All patients delivered a 45 Gy total dose in 4 fields in the prone position with 3D planning. The doses from a linear accelerator at 18 MV photon beam, were investigated. Results: The mean excess relative risk (ERR) based on the BEIR IIV models of men and women after 5 and 10 year of radiotherapy treatment for pelvic radiotherapy was 0.825±0.168, 0.948±0.504, 0.700±0.135, and 0.803±0.407 respectively. Conclusion: Estimating the second cancer risk of untargeted organs is crucial in radiotherapy. Using the single-energy mode linear accelerator and proper shields can be minimized the out-of-field doses.   https://fbt.tums.ac.ir/index.php/fbt/article/view/504 https://fbt.tums.ac.ir/index.php/fbt/article/download/504/320