Chayanit JumpeeChanakarn OnnomdeePutthiporn CharoenphunPhiphat PhruksarojanakunKrisanat ChuamsaamarkkeeFaculty of Medicine Ramathibodi Hospital, Mahidol UniversityMinistry of Higher Education, Science, Research and InnovationChiang Mai University2022-08-042022-08-042021-09-01Nuclear Technology and Radiation Protection. Vol.36, No.3 (2021), 255-260145139942-s2.0-85125468241https://repository.li.mahidol.ac.th/handle/20.500.14594/76896Selective internal radiation therapy using an 90 Y labelled microsphere is increasingly used to treat hepatocellular carcinoma. Based on its properties,90Y can produce bremsstrahlung radiation which is essential for post-treatment localisation and dosimetry. However, bremsstrah-lung radiation could lead to an increase of radiation exposure of radiation workers. The aim of this work was to determine the90Y bremsstrahlung radiation produced from the polymethyl methacrylate radiation shielding apparatus using the Monte Carlo simulation. A scintillation detector with a 137 Cs standard source was used to validate the Monte Carlo simu-lation. After validation, the 90 Y bremsstrahlung photons spectrum produced from the radiation shielding apparatus was simulated. The radiation equivalent dose rates to the head, neck, body, lower extremities at a distance of 30 centimeters, and finger (contact with the knob) were estimated to be 4.9 ± 0.6, 6.2 ± 0.1, 18.9 ± 0.4, 13.1 ± 0.6, and 3900 ± 50 µSvh–1, respec-tively. The corresponding annual doses exceeded the limit when radiation workers performed 2631, 1563, 769, and 515 cases per year with contact the knob 3, 5, 10, and 15 minutes per case, respectively. The simulation result showed that radiation exposure of radiation workers and the number of selective internal radiation therapy procedures performed should be considered.Mahidol UniversityEnergyEngineeringArticleSCOPUS10.2298/NTRP2103255J