Monte Carlo simulation analysis of the design of a medical electron linear accelerator maze / 中国辐射卫生

Objective To analyze the impact of different maze structures of medical electron linear accelerator on the radiation level at the entrance of the treatment room. Methods The Monte Carlo simulation method was used to compare the radiation field distribution in two accelerator rooms with different maze widths and to conduct a detailed analysis of the radiation levels. Results The radiation level at the entrance of the accelerator room with a wide maze was significantly higher than that at the entrance of a compact maze. The neutron radiation level at the entrance of the narrow maze model decreased by 38.6% compared to the wide maze model, and the level of X-ray radiation also showed a declining trend. Conclusion When designing medical electron linear accelerators, a compact maze structure should be adopted to reduce the setting of unnecessary space, thereby lowering the radiation level at the entrance of the treatment room and enhancing the effectiveness of radiation protection.

Analysis of the current situation of occupational stress of radiation workers in typical nuclear power plants / 中国辐射卫生

Objective To investigate the current situation of occupational stress among radiation workers in nuclear power plants in China, to explore the factors influencing occupational stress, and to provide a reference for improving occupational stress. Methods A convenient sampling method was adopted to investigate the occupational stress of 100 radiation workers in two nuclear power plants in Fujian and Liaoning, using the general situation questionnaire, effort-reward imbalance questionnaire, and the radiation protection knowledge questionnaire. Independent samples t-test, one-way analysis of variance, chi-square test, and binary logistic regression analysis were used to examine the current situation of occupational stress and the influencing factors. Results The average value of effort-reward imbalance was 0.99 ± 0.15 and 47 (47%) radiation workers had occupational stress. There were significant differences in the detection rate of occupational stress among radiation workers with different ages, years of radiation work, monthly incomes, sleep durations (day), and exercise habits (P < 0.05). Logistic regression analysis showed that monthly income, sleep duration (day), and exercise habits were the influencing factors for occupational stress. Conclusion The occupational stress of radiation workers in nuclear power plants is a serious issue influenced by many factors. Attention should be given to this issue, and targeted interventions should be implemented to improve the social and working environment of this occupational group and reduce the level of occupational stress.

Indoor radon concentration and its changing trend in northeastern China / 中国辐射卫生

@#<b>Objective</b> To investigate the indoor radon concentration and its changing trend in northeastern China. <b>Methods</b> We measured indoor radon levels cumulatively for over three months by solid state nuclear track detection in a total of 261 houses in multi-story or high-rise buildings in Shenyang, Changchun, Harbin, Heihe, and Yichun in northeastern China. The measurement lasted one year in Changchun for seasonal changes. <b>Results</b> The average indoor radon concentration in the five cities was 88 Bq/m³, ranging from 12 to 558 Bq/m³. The indoor radon concentrations were ≤ 100 Bq/m³ in 75.1% of the houses, and ≤ 300 Bq/m³ in 97.7% of the houses. The indoor radon concentration increased with the age of buildings. The indoor radon concentration was highest in winter, and it was higher in summer than in autumn and spring. <b>Conclusion</b> The indoor radon concentration in northeastern China increased compared with the data of 1980s and 1990s. It is highest in the winter heating season, and higher in summer than in spring and autumn. Indoor radon exposure deserves attention.

Research status of occupational stress among radiation workers in China / 中国辐射卫生

In recent years, occupational stress has become a focus of public attention in public health in China and abroad. Radiation workers are exposed to ionizing radiation in their daily work, which further exacerbates their levels of occupational stress. This not only affects their physical and mental health, but also increases the potential for radiation incidents or accidents. Based on the literature on occupational stress among radiation workers in China throughout the years, this article provides a summary, conclusion, and systematical analysis of the research status of occupational stress among radiation workers, with a detailed sorting of the data. It explores key research issues and directions and provides reference for future work.

Implementation and revision of the Measures for the Management of Radiation Workers’ Occupational Health / 中国辐射卫生

Since the implementation of the Measures for the Management of Radiation Workers’ Occupational Health in November 2007, it has played an extremely important role in protecting the occupational health of radiation workers. There are more than 700 000 radiation workers in about 100 000 workplaces with potential radiation exposure, as well as a large number of miners exposed to high levels of radon. As the radiation health monitoring project suggests, measures of occupational health management such as personal dose monitoring and occupational health examination of radiation workers have been widely implemented and achieved good results in the protection of radiation workers. However, the risks of chromosomal aberration and specific turbidity of the eye lens of radiation workers have increased in high-risk positions such as interventional radiology, nuclear medicine, and industrial flaw detection. The control of high radon exposure in miners needs to be strengthened. It is necessary to adapt to the new situation in view of new challenges and actively promote the revision of the Measures for the Management of Radiation Workers’ Occupational Health, so as to further improve the occupational health management of radiation workers in China.

Radiological protection detection and dose assessment of selective internal radiotherapy with 90Y resin microspheres / 中华放射医学与防护杂志

Objective:To conduct radiation detection and dose assessment in selective internal radiotherapy with 90Y resin microspheres for the purpose of providing a reference for radiological protection. Methods:The dose rates from radiotherapy with 90Y resin microspheres were detected in the process of each operation at different distances from the body surface of patients the levels of dose to the persons concerned were compared with the relevant national regulations and standards. Results:The estimated dose rates were 1.12-454 μSv/h during 90Y resin microspheres dispensing and 2.06-58.2 μSv/h during surgical procedure. The dose rates at 0.5 h after surgery were 22.7-64.1 μSv/h at 5 cm and 0.82-2.55 μSv/h at 1 m from three patient′s body surface. Assuming treating 200 patients a year, the annual individual effective dose to the radiation workers was 0.12-1.03 mSv/year. The annual individual effective dose to the public, comforters and carers of patients was 0.02-0.24 mSv/year after release of a patient. Conclusions:During the treatment, nursing and release of patients, the radiation doses to workers, carers and the public are lower than the individual dose limit given in the GB18871-2002 basic standards for protection against ionizing radiation and for the safety of radiation sources and the management target value set by of the relevant medical institutions.

Measurement and analysis of 90Y radioactivity in urine of patients treated with 90Y resin microspheres / 中华放射医学与防护杂志

Objective:To evaluate 90Y activity concentration in renal excretions during the first 48 hours after being treated with 90Y resin microspheres seleceive internal radiation therapy(SIRI) and to provide advice on the management of patient excreta after surgery. Methods:After surgery, urine excreted from 3 patients during 0-24 h and 24-48 h was collected respectively, and the 90Y activity concentration in urine was tested and analyzed. Results:90Y radioctivity in the urine excreted from 3 patients after surgery was (1 266±258)kBq/GBq during 0-24 h and (140±106) kBq/GBq during 24-48 h, respectively, and 90Y activity concentration were (640±113) kBq/L during 0-24 h and (53±12) kBq/L during 24-48 h. Conclusions:90Y radioactivity in patient′s urine excreted at 1 d was about 10 times higher than that at 2 d. After surgery, patients can accelerate the reduction of free 90Y activity by increasing excretion. Urine excreted by the patients during hospitalization should be handled in accordance with the requirements of the national standard HJ 1188-2021 Radiation protection and safety requirements for nuclear medicine.

Analysis of the current status of radiation protection in non-medical sectors in China / 中华放射医学与防护杂志

Objective:To analyzes the current status of radiation protection in non-medical sectors, together with the vulnerable spots in the prevention and control of occupational radiation sickness in China in order to provides both technical basis for occupational health management in non-medical radiation sectors and the better protection of occupational health benefits for radiation workers.Methods:The monitoring plan for this survey was worked out on the part of the National Institute for Radiological Protection, China CDC. Survey and monitoring of the current status of radiation protection and occupational health management were, under the monitoring the plan, completed by the relevant agencies of all provincial-level regions for the key industries of non-medical sectors countrywide, involving occupational health monitoring, personal dose monitoring, radiation protection monitoring instruments equipped, and radiation protection monitoring in workplace. Based on the survey result , the deficiencies in radiation protection and occupational health monitoring in non-medical sectors were analyzed.Results:The survey of non-medical sectors was divided into general investigation and detailed monitoring, with the general investigations covering 9 075 non-medical institutions in 31 provincial-level regions across the country. Of them, a total of 4 911 institutions within 329 district-level regions received detailed investigation and radiation protection monitoring. As survey result , the X, γ ambient dose equivalent rates for the institutions using ray-generator are greater than 2.5 μSv/h, about 2.35% of the total, with a maximum of 817 μSv/h. The values for those using radioactive sources were greater than 2.5 μSv/h, about 9.57%, with a maximum of 1 700 μSv/h. The frequencies of personal dose monitoring and occupational health examination were 72.9% and 82.1%, respectively.Conclusions:There is still a gap in radiation protection between the current status and the national regulations and standards in non-medical sectors, so both regulation and management of radiation protection should be further strengthened.

Analysis of external exposure dose during 131I treatment for thyroid cancer patient / 中华放射医学与防护杂志

Objective:To explore the existing issues in radiation protection during the treatment of 131I by means of measuring the ambient dose equivalent rate to patients with thyroid cancer and the dose equivalent to the surface of chest of patients during hospitalization. Methods:The ambient dose equivalent rate (peer) was measured by using gamma ray detector for selected 78 patients who received 131I treatment in a hospital 10 min, 1 d, 2 d, 3 d and 5 d after administration with 131I. The measurements were made at distances of 5 cm, 0.5 m and 1 m from the body surface in front, rear, left and right directions. The photoluminescence dosimeter on the chest of the patients was used to measure the effective dose during hospitalization period (6 d). Results:The ambient dose equivalent rate on the surface of chest of patients was up to 4.81 mSv/h 10 min after administration of medicine. The dose equivalent on the surface of chest of patients before discharge ranged 2.6-64.1 μSv/h. The cumulative dose on chest surface during hospitalization was 15.9-58.8 mGy. There was a significant difference in the dose rate at 5 cm from the body surface between 3.7 GBq group and 5.55 GBq group 10 min after medication ( t=-6.11, P<0.05). There was a significant difference in the dose rate at 5 cm from the body surface between male and female groups 10 min after medication ( t=4.52, P < 0.05). There was no significant difference in other groups ( P > 0.05). Conclusions:During the 131I treatment, patients had high level of radiation around them, so it is necessary to strengthen the protection and management of patients and reduce unnecessary exposure to the public.

Shielding calculation and discussion on high energy light source storage ring and synchrotron / 中华放射医学与防护杂志

Objective:To verify and discuss the consistency and applicability of the semi empirical formula and Monte Carlo simulation method in the radiation shielding calculation for high energy synchrotron radiation source.Methods:The semi empirical formula and Monte Carlo simulation were used to calculate the ambient dose equivalent outside of the shielding.Results:The ratio of Jenkins semi empirical formula result to Monte Carlo simulation result was 111%-153%. The ratio of Sakano semi empirical formula result to Monte Carlo simulation result was 201%.Conclusions:For a single shielding material, the semi empirical formula can be simple and conservative to complete the shielding calculation for high-energy electron accelerator. For a variety of shielding materials, Monte Carlo simulation method should be used.

Standard interpretation of radiological protection requirements for the production places of rare earths / 中国辐射卫生

Chinese national standard GBZ139—2019 Radiological Protection Requirements for the Production Places of Rare Earths was published to replace GBZ 139—2002 Radiological Protection standards for the production places of rare-earth elements and implemented from April 1, 2020. Herein, background on which the new standard was based, the main modifications and the foundations were explained. More specific requirements for the production places of rare earths were stipulated in the new standard, which will play an important role in occupational health protection of the workers engaged in the mining, mineral processing and smelting of rare earths.

Activity variation and dose level in patient′s body with differentiated thyroid cancer after 131I therapy / 中华放射医学与防护杂志

Objective:To study the variation in activity in patient′s body with differentiated thyroid cancer (DTC) treated with 131I and external dose level, analyze the relationship between the both, and estimate the correction factor for the dose equivalent rate for the patients with residual activity of 400 MBq. Methods:A total of 43 DTC patients who received 131I therapy for the first time after total thyroidectomy were studied. The dose was 1 850-3 700 MBq and average dose was (2 405±777) MBq. The measurements of residual activity in patient′s body and of dose equivalent rate at 0.3, 1 and 3 m in front of the patients were performed at 2, 6, 20, 22, 24, 27, 30, 44, 46, 48, 54, 68 and 72 h after administration of 131I. Results:The residual activity in patient′s body after 131I therapy varied with time as a function of A= A0 (1.033 16e -0.062 4t+ 0.017 17). It can be estimated that the effective half-life of DTC patients treated with thyroid remnant 131I ablation therapy is 12.19 h. It needs only 26.4-38.9 h to reduce the internal activity to the 400 MBq. The functions of variation with time of normalized dose equivalent rate at 0.3, 1, and 3 m away from patients were: H· 0.3=127.220 7e -0.054 8t+ 3.765 71; H· 1=30.225 8e -0.064 4t+ 0.824 67; and H· 3=4.161 9e -0.061 5t+ 0.167 97, respectively. There was a positive correlation between residual activity and dose equivalent rate at 1 m ( r=0.982, P<0.05), and the function is H· 1=0.025 A+ 1.245. When residual activities in DTC patient′s body were 1 000, 700 and 400 MBq, the corresponding dose equivalent rates at 1 m from patients were 26.2, 18.7 and 11.2 μSv/h, respectively. The correction factors for dose equivalent rate at 0.3, 1 and 3 m from patients with 400 MBq were 0.25, 0.49 and 0.70, respectively. Conclusions:DTC patients with administration of 131I activity below 3 700 MBq need only to be hospitalized for two days to reach the discharge standards. When the residual activity in DTC patient′s body drops to 400 MBq, the dose equivalent rate at 1 m is far less than 25 μSv/h. Simply using the point source formula to estimate the dose equivalent rate around the patient will result in overestimation. Therefore, the correction factor used in the estimation of radiation doses to patients by using the formula needs to be further studied so as to make the model-based estimated result more consistent with the actual situation.

Study on informatization pattern of medical exposure frequency and dose monitoring / 中华放射医学与防护杂志

Objective To realize the efficient monitoring of frequency of medical exposure and dose monitoring in Ningbo by means of informatization. Methods Data transmission process and the key elements of frequency of medical exposure and individual dose were investigated. According to standardization principles of data elements, the standardized data elements for frequency of medical exposure and individual dose were determined. On this basis, modules and functions of data receiving platform on the frequency of medical exposure and individual dose in Ningbo were designed. Results Totally 59 data elements on frequency of medical exposure and individual dose were formed. According to their functions, the data receiving platform was divided into the distribution of radiodiagnosis and radiotherapy resources, the frequency monitoring of medical exposure and dose monitoring for permanent residents, and the dose monitoring. Conclusions The establishment of frequency and dose information monitoring platform on medical exposure in Ningbo and the determination of standardized data elements will be conducive to further progress in medical exposure information monitoring in Ningbo.

Study on informatization pattern of medical exposure frequency and dose monitoring / 中华放射医学与防护杂志

Objective@#To realize the efficient monitoring of frequency of medical exposure and dose monitoring in Ningbo by means of informatization.@*Methods@#Data transmission process and the key elements of frequency of medical exposure and individual dose were investigated. According to standardization principles of data elements, the standardized data elements for frequency of medical exposure and individual dose were determined. On this basis, modules and functions of data receiving platform on the frequency of medical exposure and individual dose in Ningbo were designed.@*Results@#Totally 59 data elements on frequency of medical exposure and individual dose were formed. According to their functions, the data receiving platform was divided into the distribution of radiodiagnosis and radiotherapy resources, the frequency monitoring of medical exposure and dose monitoring for permanent residents, and the dose monitoring.@*Conclusions@#The establishment of frequency and dose information monitoring platform on medical exposure in Ningbo and the determination of standardized data elements will be conducive to further progress in medical exposure information monitoring in Ningbo.

Study on the optimization of radiation protection for therapeutic proton synchrotron / 中华放射医学与防护杂志

Objective@#To investigate the effect of iron shield at different depths within main protection wall on the dose rate outside the protection wall.@*Methods@#By adopting the FLUKA code, a therapeutic room model was constructed with its primary protective barrier consisting of concrete and iron. In order to obtain its ambient dose equivalent rate distribution, the 250 MeV protons and 220 MeV protons impinging on water phantom were simulated separately.@*Results@#With varying depth of iron plate embedded in barrier, the ambient dose equivalent rates in the two simulated conditions differed sinificantly at 30 cm outside the protection wall. The maximum ambient dose equivalent rate(220 MeV: 3.42 μSv/h, 250 MeV: 6.39 μSv/h) was more than 2 times higher than the minimum ambient dose equivalent rate(220 MeV: 1.75 μSv/h, 250 MeV: 3.32 μSv/h).@*Conclusions@#In the design of therapeutic proton accelerator, it is essential to evaluate carefully the location where the iron shield is in main protection wall.

Implementation of survey on diagnostic medical X-ray frequency in 2016 in China / 中华放射医学与防护杂志

To ascertain the background and frequency of diagnostic medical X-ray procedures in China and provide the basis for regulatory oversight of such applications,a total of 557 medical institutions in 25 provinces or municipalities were surveyed by means of the optimally designed questionnaires and through stratified quota sampling.The numbers of procedures were calculated in terms of the type of procedures and the sex and age of examined patients.As a result,the frequencies of diagnostic X-ray procedures for 2016 in the country were derived using multiple linear regression analysis.The frequency of X-ray diagnosis in 10 provinces of China in 2016 was estimated to be 379-1 228 examinations per 1 000 population.Diagnostic X-ray applications have shown a rapid expansion in 2016 as compared with the period of "9th Five-Year Plan".It is very important to strengthen the regulation of medical diagnostic X-ray applications.

Study on estimation of medical exposure frequency in China / 中华放射医学与防护杂志

Objective To study the estimation method of medical exposure frequency in China through the survey of diagnostic radiology and radiotherapy institutions in selected provinces.Methods A survey of medical exposure frequency was carried out involving 557 diagnostic radiology and radiotherapy institutions in 25 provinces.The correlation analysis and multiple linear regression analysis were conducted,with the fitting effects of the models with different variables being compared.Results The total medical exposure frequencies highly correlated with number of outpatient,number of equipment and number of radiation workers (| r| ＞0.5).Representative samples of the daily medical exposure workload were obtained by stratified random sampling from the survey data.Mathematical models were built using the multiple linear regression between total medical exposure frequency and hospital levels,number of outpatients,number of inpatients,number of equipment,and number of radiation workers.The total medical exposure frequency in 2016 was estimated to be 589 million examinations based on the models.In addition,the frequencies of medical procedures were derived using the robust regression and the median regression.Conclusions There are several methods for estimating the total medical exposure frequency.It is desirable to use the stratified random sampling combined with the published statistical and monitoring data.The representativeness of sample is critical.The specification and optimization of models also require further study.

Study on the optimization of radiation protection for therapeutic proton synchrotron / 中华放射医学与防护杂志

Objective To investigate the effect of iron shield at different depths within main protection wall on the dose rate outside the protection wall. Methods By adopting the FLUKA code, a therapeutic room model was constructed with its primary protective barrier consisting of concrete and iron. In order to obtain its ambient dose equivalent rate distribution, the 250 MeV protons and 220 MeV protons impinging on water phantom were simulated separately. Results With varying depth of iron plate embedded in barrier, the ambient dose equivalent rates in the two simulated conditions differed sinificantly at 30 cm outside the protection wall. The maximum ambient dose equivalent rate(220 MeV:3.42 μSv/h, 250 MeV:6. 39 μSv/h) was more than 2 times higher than the minimum ambient dose equivalent rate ( 220 MeV:1. 75 μSv/h, 250 MeV: 3. 32 μSv/h ) . Conclusions In the design of therapeutic proton accelerator, it is essential to evaluate carefully the location where the iron shield is in main protection wall.

Validation and discussion of the time response correction formula for radiation detectors / 中华放射医学与防护杂志

Objective To validate and discuss the time response correction formula for four types of dosimeters (6150AD6 + 6150AD-b,FH40G + FHZ672E-10,451P ionization chamber and AT1123).Methods The ambient dose equivalent rates shown by survey meters were recorded separately when X-ray emission time was 500,200,100 and 50 ms.The corrected values were obtained by the formula of circuit having a capacitance C and asistance R in series.Results Therewas no correlation between the value measured by AT1123 dosimeter and the time of irradiation.The values by other three kinds of dosimeters obviously varied with the time of irradiation.Conclusions It is not required to make the time response correction for the measured value of ATl123 dosemeter,whereas the values measured by the other three dosimeters could be corrected by the time response correction formula.

The feasibility study of gold nanoparticle composites (ssDNA-AuNPs) for the colorimetric detection of gamma radiation dose / 中华放射医学与防护杂志

Objective To establish a simple and convenient method and study the feasibility of using gold nanoparticle composites (ssDNA-AuNPs) for colorimetric detection of gamma radiation.Methods The composites ssDNA-AuNPs were prepared by applying the ssDNA to the surface of AuNPs,and then were irradiated with gamma ray with absorbed doses of 0,5,10,20,and 30 Gy,respectively.Subsequently the color change in the solutions were observed simultaneously with absorption spectra being measured.The linear relationship between the ratio of A625/A521 in the absorption spectrum and the absorbed dose was established.Results With the increase of radiation dose,the color of the solutions changed from wine-red to blue-violet gradually,the ratio of A625/A521 in absorption spectra had excellent liner response for absorbed dose ranging from 0 to 30 Gy,and the linear equation was A625/A521 =0.020 6 + 0.303 6 E(R2 =0.991 5).Conclusions The ssDNA-AuNPs synthesized in this experiment can be successfully used for colorimetric detection of gamma absorbed dose,and a simple and convenient method for detection of gamma radiation has been newly established.