Earticle

Background: This study aimed to investigate the activation characteristics of concrete in synchrotron- type proton therapy facilities for future decommissioning. The larger synchrotrontype proton therapy facilities have a greater potential impact on decontamination than the cyclotron proton therapy facilities investigated in our previous study. Specific activity levels in the concrete after 30 years of operation in synchrotron-type proton therapy facilities were predicted from the measured thermal neutron fluence rates on the concrete during the operation to compare them with the clearance level. Materials and Methods: The investigations were conducted in the synchrotron-type proton therapy facilities at Medipolis Proton Therapy Research Center and Proton Medical Research Center, University of Tsukuba Hospital. The thermal neutron fluence rates on the concrete during the operation were measured by three different methods: using 24Na radioactivity produced in concrete, thermoluminescence dosimeters, and Au foils. Results and Discussion: The specific activity levels in the concrete throughout the synchrotron proton therapy facilities were negligible compared with the clearance level. The specific activity level of concrete in the accelerator room in synchrotron-type proton therapy facilities where an accelerator controls the proton energy was much lower than that in cyclotron-type proton therapy facilities where a degrader controls the proton energy. Conclusion: Concrete does not need to be treated as radioactive waste when decommissioning synchrotron-type proton therapy facilities.

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 μSv/hr at 30 cm from the patient’s surface in high energy conditions, and the time required to reduce it to 2.50 μSv/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.

본 연구는 융복합 첨단 암 치료 방법인 양성자 치료의 특징 및 임상적 유효성에 대해 알아보고자 하였다. 양성자 치료의 임상 자료를 분석하였다. 양성자는 기존 X선과 달리 몸을 통과할 때 적은 에너지를 방출하면서 물체에 에너지를 전달하다 일정 지점에 접근하면서 에너지 축적이 증가하면서 최대 에너지를 전달한다. 이러한 물리적 특징으로 인해 병변 앞쪽과 뒤쪽의 정상 조직에 조사되는 방사선량을 줄이고 이로 인해 발생할 수 있는 방사선 손상을 최소화할 수 있다. 양성자 치료로 임상 결과의 향상과 치료 관련 부작용의 감소를 기대할 수 있다. 현재 양성자 치료는 다양한 암에서 사용되고 있으며 임상 결과를 축적해 가고 있다. 향후 기술 및 관련 학문의 추가 연구가 필요하다.

This study was conducted to evaluate the clinical effectiveness of proton therapy as an advanced convergent cancer therapy. Clinical data of proton therapy were analyzed. As proton enters patient's body, it releases low dose of energy and shows an increasing energy deposition as it reaches certain point unlike x-ray. It may therefore reduce the radiation dose to the normal tissues in front and beyond the lesion and minimize the radiation damage. Proton therapy is expected to improve clinical outcomes and reduce treatment related toxicities. It is used in various cancers. Further studies are necessary.