Study on Induced Radioactivity of Different Materials in the Proton Therapy Facility

Background: Proton therapy facilities have improved in recent years, not only providing benefits to patients but also bringing potential radiation hazards and risks. Induced radioactivity in patients is a crucial issue that remains unresolved for a long time and deserves further investigation. Therefore, this study aimed to investigate the induced radioactivity in proton therapy rooms under various treatment conditions. Materials and Methods: The Monte Carlo code FLUktuierende KAskade (FLUKA) and advanced interface Flair are employed to simulate residual dose rate distribution and different material activation levels in the proton therapy room. The simulation involved irradiating the phantom with energies of 220, 150, and 70 MeV for 2 minutes, respectively. Results and Discussion: The total specific activity of the patient exceeds that of other materials but rapidly attenuates thereafter after 2 minutes of irradiation. The residual dose rate at shutdown exceeds 2.50 mu Sv/hr at 30 cm from the patient's surface in high energy conditions, and the time required to reduce it to 2.50 mu Sv/hr differs with different energy scenarios (10 minutes, 8 minutes, and none for scenarios A, B, and C, respectively). Conclusion: The patient plays a crucial role in identifying the radiation dose, although their importance significantly diminishes over time due to the presence of radionuclides with short half-lives. Diverse irradiation scenarios cause varying activation levels. Thus, we manage the timing of staff entry for positioning or escorting in the treatment room and introduce customized protective measures based on the specific requirements of the tumor.