Analysis of induced radiation and shielding materials in proton therapy room / 中国辐射卫生

Objective To analyze the dose distribution of induced radiation in fixed proton beam therapy room and the influence of shielding materials, and to provide a basis for radiation protection and shielding material selection in proton therapy. Methods FLUKA was used to simulate the dose distribution of induced radiation in fixed proton beam therapy room, the dose over time, and the influence of different concrete materials. Results The dose of induced radiation was mainly concentrated around the target, and the dose rapidly decreased to 1/5-1/10 of the value at the time of stopping irradiation after cooling for 3-5 min. The induced radiation in concrete formed a slightly higher dose area at the end of the main beam near the inner side of the shield. The content of Fe, O, and H in concrete had significant effects on induced radiation (P < 0.01), and the dose was negatively correlated with the content of Fe. Conclusion The patients after proton therapy as well as the induced radiation in air and shielding materials are the main sources of external radiation dose for workers, and waiting for a period of time is the most effective way to protect the staff. Without considering the difficulty in construction and based on the analysis of shielding materials in protection against external irradiation and their influence on induced radiation, heavy concrete with a relatively high level of Fe is the best choice of the shielding material for proton therapy room.

Analysis of radiation dose at the entrance of the medical linear accelerator treatment room / 中国辐射卫生

@#<b>Objective</b> To investigate the radiation dose at the entrance of the accelerator treatment room, and to guide the radiation protection detection at the entrance of the treatment room. <b>Methods</b> The FLUKA program was used to build the model of accelerator head and treatment room. Under the simulation conditions of 10 MV and 600 cGy/min for the accelerator, the radiation dose rate inside the entrance of the treatment room was measured at different gantry angles, irradiation conditions, and labyrinths. <b>Results</b> The entrance dose rate with a water tank was significantly higher than that without a water tank under different inner labyrinth wall thicknesses and gantry angles. The entrance dose rate reached the maximum at the inner labyrinth wall thickness of 1800 mm and the gantry angle of 90°. When the inner labyrinth wall thickness was 1000 mm and the gantry angles were 0° and 180°, the entrance dose rate was significantly higher than that at other conditions. The dose rate at the entrance of the treatment room reached (82.26 ± 48.95) μSv/h to (314.09 ± 96.34) μSv/h under the following conditions: the inner labyrinth wall thickness of 1800 mm, the gantry angle of 90°, with a water tank, and the width of the inner labyrinth entrance of 1400-2200 mm. <b>Conclusion</b> The dose at the entrance of the accelerator treatment room mainly comes from the scattering and leakage radiation of the useful wire harness on the patient’s body surface, and the entrance dose rate increases with the increase in the width of the inner labyrinth entrance. In the entrance protection test, the gantry angle should be determined considering the inner labyrinth wall thickness, and the test should be performed at four angles in the uncertain case to ensure the comprehensiveness and accuracy of test results.

Shielding performance of six different types of concrete in proton therapy room / 中国辐射卫生

@#<b>Objective</b> To study the dose level of proton beams outside the main shield of the 230 MeV proton therapy room with six different types of concrete as the main wall, and to obtain the shielding performance of six different types of concrete. <b>Methods</b> The FLUKA program was used to build a calculation model, and different concrete compositions were introduced into the FLUKA program to simulate the change in ambient dose equivalent rate of the focus with concrete thickness under 230 MeV proton beam irradiation. The transmission curves of six different types of concrete were fitted to obtain shielding performance parameters. <b>Results</b> On the condition that the 230 MeV proton beam irradiated to the water target in 90° direction and the concrete thickness exceeded 40 cm, the proton beam was exponentially decayed for six different types of concrete, and the fitted decay curves had a <i>R</i>² of > 0.99. The linear attenuation coefficients for normal concrete, barite concrete, magnetite concrete, limonite concrete, phosphorite concrete, and ferrosilicate concrete were 0.0148 cm⁻¹, 0.0172 cm⁻¹, 0.0196 cm⁻¹, 0.0219 cm⁻¹, 0.0256 cm⁻¹, and 0.0290 cm⁻¹, respectively. <b>Conclusion</b> The composition and proportion of elements in concrete materials directly affect the shielding ability of concrete against proton beams to a large extent, and the shielding performance of six different types of concrete against proton beams varies greatly. Therefore, shielding materials for the proton therapy room should be selected by a comprehensive consideration of the material compositions and shielding performance of concrete, the difficulty of construction, and construction cost.

Current situation and discussion on common problems of radiation protection for dental X-ray diagnostic project in 44 dental clinics in Guangdong Province, China / 中国辐射卫生

@#<b>Objective</b> To analyze the relevant measures of radiation protection for dental X-ray diagnostic projects in 44 dental clinics in Guangdong Province, China, and discuss common problems. <b>Methods</b> Based on the three principles of radiation protection, relevant laws, regulations and standards of the state, combined with field investigations and test results of radiation protection, the situation of radiation protection and management was analyzed. <b>Results</b> The layout of 56 dental diagnostic rooms in 44 clinics was (basically) reasonable. The protective performances and quality control tests of 56 dental X-ray diagnostic machines met the standard requirements, and the dose equivalent rate around 56 dental diagnostic rooms was from the background to 1.47 μSv/h, which met the national standard. The coincidence rates of ionizing radiation warning signs, working status indicator lights and door light interlocks, automatic door closing devices, power ventilation devices, and personal protective equipment were from 85.70% to 98.20%. The compliance rates of dental radiologists and full-time (part-time) administrative staffs, occupational health monitoring, management system related to radiation protection, and radiation health files were from 79.5% to 100.0%. <b>Conclusion</b> The current situation of radiation protection and management in the dental X-ray diagnostic room is good, and relevant national regulations and standards should be promulgated or improved to standardize the cone-beam CT quality control testing, dental clinic location requirements, and radiation staff configuration.

Influencing factors of occupational stress in female workers of labor-intensive enterprises / 中国职业医学

OBJECTIVE: To investigate the current status and influencing factors of occupational stress in female workers of labor-intensive enterprises. METHODS: Totally 910 female workers from 5 labor-intensive enterprises in Guangdong Province was selected as the research subjects by random cluster sampling method. A questionnaire survey on occupational stress was conducted using the Occupational Stress Inventory-Revised Edition. RESULTS: Among the 910 female workers,14. 9%( 136/910) showed medium or higher scale on occupational role level,20. 1%( 183/910) showed medium or higher scale on occupational stress level,and 21. 4%( 195/910) showed medium or higher scale on personal resources lack. Multivariate logistic regression analysis indicated that the risk of occupational stress was high in single female workers and/or those exposed to occupational hazards( P < 0. 01). The higher the occupational role level,the higher risk of occupational stress( P < 0. 01). The less personal resources,the higher risk of occupational stress( P < 0. 01).CONCLUSION: Some female workers in labor-intensive enterprises showed medium or higher occupational stress level. The main influencing factors of occupational stress are marital status,exposure to occupational hazards,occupational role and personal resources.