Objective To evaluate the ambient dose equivalent rates of photons and neutrons inside and outside the door of a 10 MV accelerator room, and to report the shielding effect of boron-containing polyethylene as maze wall lining. Methods The ambient dose equivalent rates of photons and neutrons inside and outside the door of an accelerator room were taken as the research subject. The Kersey, Falcão, and modified Kersey methods were used to calculate the ambient dose equivalent rates of neutrons and neutron capture gamma rays inside and outside the door of the room before and after renovation. Measurements were made using an X-ray/γ-ray dose rate instrument and a neutron ambient dose equivalent rate meter. Calculated and measured results were compared. Results Before renovation, the measured neutron dose rate inside the door was 409 μSv/h, while the calculated values were 323 μSv/h (Kersey method), 428 μSv/h (Falcão method), and 219 μSv/h (modified Kersey method). The Falcão method yielded a value closest to the measured value, while the Kersey and the modified Kersey methods underestimated the value by 21% and 46%, respectively. After the installation of boron-containing polyethylene plates, the measured neutron dose rate inside the door was 190 μSv/h, with a 54% reduction. The neutron and photon ambient dose equivalent rates outside the door were 5.8 μSv/h and 6.0 μSv/h, respectively, before renovation, and 0.14 μSv/h and 1.6 μSv/h, respectively, after renovation. Conclusion For a 10 MV accelerator room, neutron shielding and protection measurements are necessary, especially for rooms with short mazes. The Falcão method provides the best estimate of neutron dose rates inside and outside the door. Using boron-containing polyethylene plates as maze wall lining is an economical and effective shielding method.

Objective To analyze the layout and shielding effectiveness of medical accelerator vaults, and to provide a reference for the layout, shielding design, and optimization of protection of medical accelerator vaults. Methods Four medical accelerator radiotherapy vaults were selected. The layouts of these vaults were compared with the layout requirements in the radiation therapy protection standards. For each vault, the dose rates at four points of interest outside the shielding were calculated, including the primary shielding area, secondary shielding area, maze outer wall, and lateral shielding area. These values were then compared with the actual measurements obtained using a dose rate meter. Results All four vaults were located on the ground floor of the building and included a maze, with the auxiliary rooms all placed outside the treatment rooms. However, one vault was not located at one end of the building, and in another vault, the control room was exposed to direct irradiation of the useful beam. The calculated dose rates outside the primary shielding area ranged from 0.04 μSv/h to 0.62 μSv/h, while the measured values ranged from 0.10 μSv/h to 0.66 μSv/h, with the measured values being higher than the calculated ones. The calculated dose rates outside the secondary shielding area ranged from 0.0005 μSv/h to 0.12 μSv/h, those outside the maze outer wall ranged from 0.06 μSv/h to 0.18 μSv/h, and those outside the lateral shielding area ranged from 0.009 μSv/h to 0.15 μSv/h; the measured values were all below the detection limit. Conclusion Inadequate layouts were observed in some of the accelerator vaults. The calculated and measured dose rates at points of interest outside the vaults were both significantly lower than the shielding protection requirements in standards, indicating that the shielding designs were overly conservative. Construction units should follow the principle of optimization of radiation protection to design the layout and shielding reasonably and pay attention to the underestimation of dose rates outside the primary shielding caused by the tenth value layer.

Objective To establish typical values for interventional diagnosis and treatment at our institution, use these values as a tool to evaluate patient medical exposure doses, and optimize radiation protection measures. Methods From June to December 2023, we collected information on 593 adult cardiovascular interventional diagnosis and treatment surgeries, including surgery type, equipment model, air kerma-area product (KAP), incident reference point air kerma (K_a,r), perspective time (FT), and exposure mode. Results The typical value of cardiovascular interventional diagnosis at our institution in 2023 was 27.5 Gy·cm². The typical value of cardiovascular interventional treatment was 70.0 Gy·cm². The FT, KAP, and K_a,r of interventional surgeries were significantly higher than those of interventional diagnosis (P < 0.01). There were significant correlations between FT, KAP, and K_a,r (P < 0.01). Conclusion The results of this study were slightly different from those of other studies. They provide typical data and reference values for cardiovascular interventional diagnosis and treatment dose levels in Beijing and are helpful for dose optimization between different medical institutions.

Objective To track and evaluate the implementation and application of the occupational health standard Radiation shielding requirements for radiotherapy room—Part 4: Radiotherapy room of ²⁵²Cf neutron afterloading (GBZ/T 201.4-2015) by radiation health technical service agencies, medical institutions, health supervision agencies, and radiotherapy facility design units, and to provide a scientific basis for the further revision and implementation of this standard. Methods Following the Guideline for health standards tracking evaluation (WS/T 536-2017) and the project implementation plan, relevant practitioners were randomly selected for a questionnaire survey. The survey primarily focused on their awareness, standard training, application, and revision suggestions of GBZ/T 201.4-2015. The results were summarized and analyzed. Results A total of 168 evaluation questionnaires were collected from relevant practitioners in 28 provinces. Only 31.6% of the respondents reported being “well familiar” or “ familiar” with the standard, 27.4% of the respondents believed that the standard was widely used, and 45.2% of the respondents believed that the standard could meet the needs of their work. Only 14.9% of the respondents had received relevant training on the standard, more than half of the respondents had not applied the standard within the past 10 years, and 45.2% of the respondents believed that the standard "needs to be revised". Conclusion Due to the small number of californium-252 neutron afterloading radiotherapy devices in operation on the market, the overall awareness of the standard is low, suggesting that relevant authorities need to strengthen training and publicity of the standard, and that certain sections of the standard need to be revised or merged.

Objective To understand the types, proportions, and radiation dose levels of pediatric cardiac interventional procedures. Methods A retrospective analysis was conducted using the basic information and radiation dose data from all cases of pediatric cardiac interventional procedures performed at two tertiary medical institutions in Beijing from July 2023 to August 2024. The data included air kerma-area product, reference point air kerma, and fluoroscopy time. Descriptive statistical analysis was conducted to evaluate the basic information and dosimetric indicators of the procedures. Non-parametric tests were employed to examine the differences between variables, and Spearman’s correlation coefficient was utilized to investigate the relationships among various factors. All cases were categorized into the diagnostic group and the therapeutic group. In the diagnostic group, the majority of procedures involved catheter examinations and angiography for identifying the type of disease. In the therapeutic group, the primary procedures included patent ductus arteriosus, atrial septal defect, ventricular septal defect, patent foramen ovale, pulmonary stenosis, radiofrequency catheter ablation, major aortopulmonary collateral arteries, complex congenital heart diseases, and other interventional procedures. Results The survey comprised 1008 cardiac interventional procedures involving 476 males and 532 females. The ages of the participants ranged from 0 to 15 years and the body weights from 4.5 to 105 kg. Among these participants, 92 and 916 were classified in the diagnostic and therapeutic groups, respectively. The proportions of interventional procedures were in the order of atrial septal defect (36.9%), radiofrequency catheter ablation (22.3%), patent ductus arteriosus (15.1%), complex congenital heart disease (4.8%), patent foramen ovale (3.1%), pulmonary stenosis (3.1%), ventricular septal defect (2.2%), other procedures (2.0%), and major aortopulmonary collateral arteries (1.5%). The radiation doses of different interventional procedures were statistically different (P < 0.05), with air kerma-area product ranging from 0.02 to 658.4 Gy·cm², reference point air kerma from 0.1 to 2524 mGy, and fluoroscopy time from 0.2 to 62 min. Conclusion In pediatric cardiac interventional procedures, there is considerable variability in radiation doses for the same type of procedure. Additionally, radiation doses for identical procedures vary between different medical institutions, and a few cases carry a risk of deterministic effects.

Objective To track and evaluate the scientificity, applicability, and operability of the current implementation of the Radiation Shielding Specifications for Radiotherapy Treatment Rooms—Part 2: Radiotherapy Room of Electron Linear Accelerators (GBZ/T 201.2—2011) among personnel in medical radiation technology service institutions, and to provide scientific evidence for further improvement of the standard. Methods Following the Guidelines for Health Standards Tracking Evaluation Work (WS/T 536—2017) and the project implementation plan, a survey was conducted among 140 personnel engaged in shielding testing and evaluation of electron linear accelerator rooms in medical radiation technology service institutions from 24 provinces in China. The methods of pre-investigation, on-site research, mailing, and email were used to collect data for analysis. Results Questionnaires were completed by 140 respondents from 98 medical radiation service institutions, including 63 public institutions and 77 private institutions. Of the surveyed individuals, 86.68% claimed to have a good or very good understanding of the standard, while only 64.3% had participated in training related to the standard. The survey indicated a low level of mastery of the standard content among the personnel and insufficient efforts in training and dissemination. Although only 3.57% of the respondents considered the existing standard to be inapplicable in the context of new radiotherapy equipment and technological advancements, 95.71%, 93.57%, and 96.43% believed that shielding calculation examples should be added for tomotherapy devices, CyberKnife systems, and ring accelerators with self-shielding bodies. Furthermore, 65% of the respondents felt that neutron shielding should be considered for 10 MV X-ray accelerator rooms. Conclusion The GBZ/T 201.2—2011 has been widely used for radiation protection in radiotherapy. However, it is imperative to update this standard. Additionally, due to the technical complexity of the standard, it can be challenging for professionals to fully understand and implement it. Therefore, publicity goals should be tailored to different groups and the training of key personnel should be strengthened. A nationwide communication and cooperation mechanism should be established to ensure uniform implementation of the standard.

kV X-ray radiotherapy was the primary mode of radiotherapy widely used to treat many types of cancer, including deep tumors, before the invention of the Co-60 therapy machine and the electron linear accelerator, which gradually replaced kV X-ray radiotherapy. kV X-ray radiotherapy equipment requires less space and shielding, and still has application value in the treatment of skin lesions and superficial tumors. Especially in recent years, kV X-ray has been used in the treatment of keloid, and electronic brachytherapy equipment has been used in intracavitary, intraoperative, and superficial radiotherapy. Therefore, kV X-ray radiotherapy has seen renewed application. The quality control of kV X-ray radiotherapy equipment is the key to ensure the treatment effect and safety of patients. This paper reviews the current status of quality control of kV X-ray radiotherapy equipment and provides a reference for the formulation of quality control assessment standards for kV X-ray radiotherapy equipment.

Objective To compare the response capability of active personal dosimeters (APDs) in the pulse radiation field of interventional radiology, and to find APDs that can be used for dose optimization monitoring for interventional radiology staff. Methods Seven models of APDs and dose monitoring systems were tested in the following four types of radiation fields: continuous radiation field (Cs-137), single-pulse radiation field (80 kV, 10 mA, 10～1000 ms), multi-pulse standard radiation field (70 kV, 20～500 mA, 1～20 ms/pulse, frames per second 1～20), and multi-pulse scattering field (angiography machine, irradiation field: 15 cm × 15 cm, 22 cm × 22 cm, 27 cm × 27 cm, angiography: 65～74 kV, 6.2～8.2 mA; photography: 65 kV, 343～479 mA). Results All APDs showed good dose responses in the continuous radiation field. The ratio of the results obtained with and without phantom was 1～1.1. In the single-pulse radiation field, DMC3000 and TruDose showed good dose response, linearity, and repeatability. Under the main ray of the multi-pulse radiation field, DMC3000 and TruDose showed good dose response, linearity, and repeatability as the dose rate increased, and there were 5%～13% differences in the response ability between the two models. In angiography machine scattering field, the ratios of the results obtained from DMC3000, TruDose, and RaySafei3 to those from thermoluminescence dosimeter were 1.08 ± 0.09, 0.95 ± 0.11, and 1.13 ± 0.11, respectively. Conclusion DMC3000, TruDose, and RaySafei3 can be used in clinics as auxiliary dosimeters to optimize radiation dose monitoring and radiation protection measures for people at high risk of occupational diseases. Interventional radiology workers can implement actions to reduce the cumulative dose based on real-time dose information, thereby reducing the radiation dose.

Background ¹³⁷Cs in atmospheric aerosol is the product of past nuclear weapon tests and nuclear accidents. When ¹³⁷Cs is released into the atmosphere, it will deposit in dry land and marine environment, causing pollution of soil surface, water, agricultural products, and animal byproducts, and affecting public health. Objective To identify the variation pattern of ¹³⁷Cs activity concentration in aerosol and its correlation with dust concentration in Beijing area from 2017 to 2020. Methods A total of 958 aerosol samples were collected from November 1, 2017 to June 30, 2020 in Beijing with a high volume air sampler at a sampling flow rate about 600 m³·h⁻¹ and a collection time for each sample about 24 h. The activity concentration of ¹³⁷Cs in the aerosol samples was determined with a low-background high-purity germanium γ spectrometer. The dust concentration was calculated using the difference in the mass of the aerosol filter before and after sampling. The detection rate of ¹³⁷Cs and dust concentration in different seasons were compared. Spearman rank correlation test was used to analyze the correlation between ¹³⁷Cs activity concentration and dust concentration. Results From 2017 to 2020, the ¹³⁷Cs activity concentrations of 33 from 958 aerosol samples in Beijing were above the minimum detectable activityconcentration, the overall detection rate of ¹³⁷Cs was 3.4%, and the activity concentration ranged from 1.86 to 45.53 μBq·m⁻³, with a median value of 4.85 μBq·m⁻³. The detection rate of ¹³⁷Cs was highest in spring, followed by autumn, and lowest in winter and summer (8.4%, 3.0%, 1.1%, and 0.5%, respectively). The dust concentration ranged from 0.03 to 1.55 mg·m⁻³, with an average value of 0.18 mg·m⁻³. There was a statistically significant difference in the dust concentrations in spring, summer, autumn, and winter (F=45.51, P<0.05), and the highest value was 0.24 mg·m⁻³ in spring (P<0.05). The ¹³⁷Cs activity concentration was positively correlated with the dust concentration (P<0.05). Conclusion The ¹³⁷Cs activity concentration in aerosol in Beijing from 2017 to 2020 fluctuates within the range of background level, and its activity concentration is highest in spring, followed autumn, and lowest in summer and winter.

Objective To evaluate the radiation protection of “four-in-one” dental X-ray equipment and to investigate the safety interlock of the equipment by measuring the scattered radiation at the position of the patient during operation. Methods A cone-beam CT dental phantom was used to simulate the patient’s head. The intra-oral and extra-oral components of the “four-in-one” X-ray equipment were installed in a 5 m² room. The scattered radiation at patient position was measured using a γ/X-ray survey meter, and the effects of intra-oral and extra-oral components were compared. Results For a 5 m² room, when CBCT was exposed under typical conditions, the dose at the patient's position was 10.70 uSv/h when there was an intra-oral component and 10.60 uSv/h when there was no intraoral component. The intra-oral part did not affect the radiation dose at the patient's position. When the intra-oral component was exposed, the dose rate at the patient's position was 4.05-6.85 uSv/h, and the extra-oral part did not affect the scattered dose of the patient examined with intra-oral components. Conclusion The evaluation of radiation protection of new equipment must comprehensively consider radiation safety and equipment operation safety. The results of this study provide suggestions for clinical radiation protection supervision and evaluation of “four-in-one” dental X-ray equipment.