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@#<b>Objective</b> To monitor the indoor radon concentration of urban residents in Shiyan, China, and to analyze the related influencing factors. <b>Methods</b> From April to July, 2019, RSKS standard detectors were used to measure the indoor radon concentration of 125 households in Shiyan, and the results were analyzed. <b>Results</b> The indoor radon concentration of residents in Shiyan showed a skewed distribution, ranging from 13.8 to 145 Bq/m<sup>3</sup>, and <i>M</i> (<i>P</i><sub>25</sub>,<i>P</i><sub>75</sub>) was 38.3 (29.0,62.0) Bq/m<sup>3</sup>. The estimated annual effective dose of radon and radon daughters from inhalation was 0.52-5.50 mSv, and <i>M</i> (<i>P</i><sub>25</sub>,<i>P</i><sub>75</sub>) was 1.45 (1.10, 2.36) mSv, which was consistent with literature. Building structure (<i>H</i> = 14.10, <i>P</i> < 0.001), floor (<i>H</i> = 24.41, <i>P</i> < 0.001), and geographical region (<i>H</i> = 8.963, <i>P</i> < 0.05) were influencing factors of indoor radon concentration, and the differences were significant. <b>Conclusion</b> The indoor radon concentration of urban residents in Shiyan is lower than the national standard limit. However, in daily life, it is still necessary to take appropriate measures to reduce the concentration of indoor radon as much as possible.
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Objective To determine the current status of occupational internal exposure to 131I in the thyroid of nuclear medicine workers, to explore the influencing factors for internal exposure, and to provide a basis for the radiation safety management of nuclear medicine. Methods The cluster sampling method was used to select 162 workers practicing 131I treatment in 24 hospitals in Hubei Province, China. Thyroid 131I activity levels were measured in vitro using a portable γ-spectrometer, and the committed effective dose was estimated. Results The thyroid 131I activity detected in 13 (54.17%) hospitals was above the lower limit of detection of the instrument. Two hospitals had the highest detection rates, 62.50% and 61.90%; the difference was significant compared with the remaining 11 hospitals (P < 0.0001). Thyroid 131I was detected in 34 workers in total, with a detection rate of 20.99% and a mean activity of 179.09 ± 138.71 (6.02-589.74) Bq. The highest detection rates were found in cleaners and nurses, which were 35.71% and 33.33%, respectively, with no significant difference in detection rate between positions (least P > 0.08). The mean value of the committed effective dose was 0.68 ± 0.52 (0.02-2.22) mSv/a in the 34 workers. Conclusion The 131I consumption and workplace ventilation may be important factors affecting the level of internal exposure. It is important to strengthen the training of nuclear medicine workers on radioprotection and workflow management, as well as the regular monitoring of occupational internal exposure for 131I treatment-related workers.
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Objective To propose a computer recognition algorithm for solid nuclear track images based on the machine learning method, and to realize the automatic, fast and accurate recognition of nuclear tracks and improve the efficiency of solid track image analysis. Methods Firstly, 143 images containing tracks were scanned by morphological method to determine the location of suspected tracks, and 1250 material images were captured. 50% of the material were selected as the training set and 30% as the validation set for training the machine learning model. Another 20% of the material were selected as the test set for testing the model recognition result. The algorithm code was written and trained based on the MATLAB software. Results The established solid track recognition algorithm had a strong recognition capability, and the recognition accuracy of the test set could reach 84.8%. The machine learning model program constructed by the algorithm could evolve continuously with the input of training data, further improving the accuracy. Conclusion Based on image morphology and machine learning, the track recognition algorithm was investigated, by which the automatic recognition of solid tracks was better realized. In the future, we will increase the data input of the model, optimize the algorithm, and improve the recognition accuracy, in order to provide a more accurate and efficient method for automatic image track recognition.
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Objective:To provide a retrospective analysis of the levels of occupational external exposure of radiation workers in Hubei province from 2009 to 2018 in a way to prevent and control its risks.Methods:The external individual doses were surveyed for 50 070 radiation workers between 2009 and 2018 by the effort of the Hubei Provincial Center for Disease Control and Prevention. Under the relevant national standards, the external radiation doses to radiation workers were conducted by using TLDs.Results:The average annual collective effective dose to radiation workers in a 10 years period was 1.93 man·Sv, the median of average annual effective dose of 0.14 mSv ( P25- P75: 0.06-0.30 mSv), and the average annual effective dose of 0.40 mSv. The annual effective doses received by 46 562 workers were less than 1 mSv, accounting for 92.99% of the total monitored workers. The annual effective dose varied dependent on occupational categories, showing a year-by-year decline trend and staying at a low level after 2012. The relative high radiation doses were seen in nuclear medicine and interventional radiology in medical applications, non-destructive testing and well logging in industrial applications, and other types of radiation applications. Conclusions:The average annual effective dose decreased year in a by year manner and kept at a low level. This indicated that the radiological protection measures taken during the 10 years ensure the health of workers. The continuous monitoring result suggest that much more attention should be paid to such categories workers as nuclear medicine, interventional radiology, non-destructive testing, well logging and others through improving radiation protection measures.
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Objective To assess the medical radiation exposure frequency and find out the main factors related to the collective dose derived from X-ray diagnosis procedures. Methods A survey of 3 178 hospitals was conducted to collect the basic information such as types of medical radiation, allocation of radiological diagnosis and treatment devices, the frequency of radiologic examinations, etc. By using a stratified sampling method，36 hospital were selected and more specific details, including 26 types of diagnostic radiologic examinations, were collected to estimate the collective dose to the population in Hubei, combining with the previous literature. Results A total number of 6 843 radiological diagnosis and treatment devices were covered and 33 771 855 medical radiologic procedures were counted in this survey. The result showed a annual frequency of 569.79 examinations per 1 000 population for all types of procedures. A large variation was revealed among different areas and the highest area was with a 4-fold frequency of the lowest area. Although tertiary hospitals accounted for 4.40% of the total hospitals, 48.42% procedures were carried out in them. The collective effective dose from X-ray diagnosis in Hubei was 65 399.55man·Sv, and the average annual effective dose was 1.10mSv, while contribution from CT scans accounted for 86.90% of the dose. Conclusion The frequency of medical radiologic procedures presented a consistent increase in Hubei province, with a uneven development among hospitals from urban and rural areas, or from different regions, or from different levels. Among all types of X-ray examinations, CT scan frequency had the fastest growth rate and accounted for the major annual collective effective dose. In order to reduce the health risk from medical radiologic exposure, CT scan need to be applied more properly and the radiation dose per single CT scan need to be limited to a reasonable level.
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Objective To investigate the residential radon concentration in typical areas of Hubei Province and assess the dose hazards of radon to human body. Methods According to geographical location, five cities including Wuhan, Enshi, Shiyan, Xianning and Daye were selected, and the stratified cluster sampling and monitoring were conducted in accordance with the residential building structure. From April to July, 2019, RSKS standard detectors were placed in the bedroom or living room of the tested families. After continuously sampling for three months, those detectors were returned back to the laboratory for test readings using Radosys system. Results A total of 651 detectors were deployed in 577 households of 70 communities, and 634 detectors were recovered. The recovery rate of detectors was 97.4%. The indoor residential radon concentration in Hubei Province showed a logarithmic normal distribution, with a median (25% quantile and 75% quantile) of 40.52 (29.13,64.74) Bq/m3 and an annual effective dose of 2.02 mSv. The indoor radon concentrations in Wuhan and Enshi were significantly higher than those in Shiyan, Xianning and Daye (P<0.05). The indoor radon concentrations in brick wood or civil structures were significantly higher than those in reinforced concrete structures (P<0.05), and indoor radon concentration in the first floor was significantly higher than those in other floors (P<0.05). The indoor radon concentrations after 2010 were significantly lower than those between 2001 and 2010 (P<0.05). Conclusion The number of households with indoor radon concentrations exceeding the national limit in newly-built buildings accounted for 10.1%; The indoor residential radon concentration levels of in Hubei Province were influenced by building structure, age and floor.
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Objective:To survey and supervise the risk of infection control and radiation safety in the radiological diagnostic workplace for COVID-19, and provide data support for the safety protection of radiographers and related staff.Methods:4 emergency hospitals for COVID-19 including 2 makeshift hospitals, module hospital and brick pattern hospital in Hubei province were performed for testing and evaluation of imaging performance and radiological protection for the 8 new installed CT scanners and places according to the national standards of WS 519-2019 and GBZ 130-2013. The infection control safety factors such as the layout of the equipment room were monitored and investigated. Two COVID-19 designated hospitals including general hospital and infectious disease specialized hospital were selected to carry out field investigation and sampling of environmental biological samples for 4 CT rooms. Then the samples were detected for the nucleic acid of novel coronavirus. The results of radiodiagnostic workplace overall arrangement, infection prevention and the nucleic acid testing were analyzed, and the biological safety reliability and risk point were evaluated.Results:The indicators of imaging performance and radiation protection for 8 CT scanners in emergency hospitals could meet the requirements of national standards.Each of 2 makeshift hospitals had 3 CT rooms with the area of 38.8 m 2 and 4 mm Pb equivalent thickness of protective shielding. The CT rooms in module hospital and brick pattern hospital were 20.0 m 2, and 35.8 m 2 in areas, with 4 mm Pb equivalent and 3 mm Pb equivalent thickness of protection shielding, respectively. The 8 radiological diagnostic workplaces of the emergency hospitals were designed and constructed based on " three zones with two passage ways" . The result of the nucleic acid test indicated that the positive samples were found at the multiple sites such as scanning bed, internal of gantry and ground touched by patients in CT scanning room. The areas such as console panel and ground were risked of pollution by the virus infected hands and feet of radiographers. In addition, the similar positive samples were found in the areas in scanning room with no touch of patients, such as observation window and air outlet. Conclusions:8 CT scanners and rooms in 4 emergency hospitals basically meet the requirements of imaging performance and radiation protection. The disinfection of COVID-19 radiodiagnostic workplace should be standardized.
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Objective To study a method to measure the doses to planned target volume (PTV) and organ at risk (OAR) and 2D dose distribution in IMRT by using TLD and radiochromic film for a verification purpose.Methods Totally 7 different types of medical linear accelerators were selected from seven hospitals in Hubei province.A polystyrene phantom provided by IAEA was CT scanned and then the scanned images were returned to the Treatment Planning System (TPS) for determining the prescribed doses to PTS and OAR and the corresponding MU.After the phantom was irradiated with 6 MV X-ray,the TLDs and films were transmitted to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.Results The IAEA required the relative deviations between TLD-measured and TPS-planned doses to OAR and PTV be within ±7.0％.For PTV,the measured-to-planned deviation values for 7 accelerator were within-5.4％ to 6.5％,all consistent with the IAEA requirements.For OAR,the values for 5 accelerators were within-2.2％ to 6.7％,not consistent the requirements,whereas the values for the other 2 were-8.6％ and 8.2％ respectively,beyond the required values.The IAEA required that the 2D dose distribution 3 mm/3％ pass rate be higher than 90％.The measured values for 7 accelerators were in the range of 90.3％-98.9％,all consistent with the requirements.Conclusions It is feasible scientifically and easy to operate in practice for using TLD and film to carry out dose verification in IMRT.It would be advisable to apply this method to quality verification in IMRT in medical institutions to the extent possible.
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Objective@#To study a method to measure the doses to planned target volume (PTV) and organ at risk (OAR) and 2D dose distribution in IMRT by using TLD and radiochromic film for a verification purpose.@*Methods@#Totally 7 different types of medical linear accelerators were selected from seven hospitals in Hubei province. A polystyrene phantom provided by IAEA was CT scanned and then the scanned images were returned to the Treatment Planning System (TPS) for determining the prescribed doses to PTS and OAR and the corresponding MU. After the phantom was irradiated with 6 MV X-ray, the TLDs and films were transmitted to the secondary standard dosimetry laboratory of China CDC for measurement and estimation.@*Results@#The IAEA required the relative deviations between TLD-measured and TPS-planned doses to OAR and PTV be within ±7.0%. For PTV, the measured-to-planned deviation values for 7 accelerator were within -5.4% to 6.5%, all consistent with the IAEA requirements. For OAR, the values for 5 accelerators were within -2.2% to 6.7%, not consistent the requirements, whereas the values for the other 2 were -8.6% and 8.2% respectively, beyond the required values. The IAEA required that the 2D dose distribution 3 mm/3% pass rate be higher than 90%. The measured values for 7 accelerators were in the range of 90.3%-98.9%, all consistent with the requirements.@*Conclusions@#It is feasible scientifically and easy to operate in practice for using TLD and film to carry out dose verification in IMRT. It would be advisable to apply this method to quality verification in IMRT in medical institutions to the extent possible.
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Objective To verify the leaf positioning accuracy of multi-leaf collimator (MLC) in intensity modulated radiation therapy (IMRT) by using radiochromic films to provide references for IMRT quality control.Methods Medical linear accelerators of different designs,owned by 7 first-class hospitals at grade-3 in Hubei,were selected for this verification study.Five strip picket fence pattern was created by treatment planning system (TPS).Each strip was 0.6 cm wide with a 3 cm strip separation.MLC leaf positions,positioning bias and opening widths were then measured with EBT2 radiochromic films.Results According to IAEA standards,the film-measured and TPS planned MLC leaf position difference was ±0.5 mm.The difference of MCL strip position of No.5 and No.7 accelerator was 0.7 and-1.0 mm,respectively,not in line with the IAEA standards.The difference of film-measured MLC leaf position between each pairs and all pairs of leaves of 7 accelerators were all within ± 0.5 mm,in line with the IAEA requirements.As required by IAEA,the difference of opening width of MLC leave of each pair relative to the averaged widths of all pairs should be within ±0.75 mm.The filem-measured values from 7 accelerators ranged from-0.6 to 0.5 mm,all in line with the IAEA standards.Standard deviation of opening width of all leaves were required to be within 0.3 mm.The measured values from 7 accelerators ranged from 0.1 to 0.2 mm,in line with the IAEA standard.Conclusions The use of EBT2 radiochromic films to verify MLC leaf positioning accuracy is an important means of quality control owing to its simplicity and high measurement accuracy.It is recommended for verification use at a large scale.
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Objective To verify the absorbed dose and two-dimensional dosimetry delivered by MLC-shaped IMRT photon beams using thermoluminescent dosimeters (TLDs) and radiochromic films.Methods Different types of medical linear accelerators at 7 third-grade first-class hospitals in Hubei were selected for this audit study.Besides TLDs and films,a small polystyrene phantom measuring 15 cm × 15 cm × 15 cm,supplied by the International Atomic Energy Agency (IAEA),was also used.The TPS dose calculation were performed with 6 MV X-ray beam and by delivering 6 Gy dose to the TLDs or films at 10 cm depth for 5 cm × 5 cm field size at 90 cm SSD.After irradiation,comparations were conducted of dose derivations between TPS-calculated values and TLD-or film-measured values.The two-dimensional dosimetry audit was carried out by using 30 cm × 30 cm homogeneous solid phantoms in which a 25 cm × 25 cm film was located at 5 cm depth.A single-filed profile generated by TPS was delivered to the film,and the film was measured.And then,two-dimensional dose distribution was analyzed using the film analysis system.Results The results suggested that the relative deviations of TLD and film to TPS dose was-8.5％ and-1.9％ for accelerator 1,5.4％ and 0.5％ for accelerator 7,respectively,whereas those for other accelerators were within ± 5％.The passing rates for two-dimensional dose distribution at all accelerators were all higher than 90％.Conclusions TLD and film quality audit for IMRT can be applied for a wide range of application in view of its simplicity,reliability and postal convenience.
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Objective To verify the reliability of TLD-based quality audit for radiotherapy dosimetry of medical electron accelerator in non-reference condition by monitoring the dose variations from electron beams with different field sizes and 45° wedge and the dose variations from photon beams with different field sizes and source-skin distance.Methods Both TLDs and finger ionization chambers were placed at a depth of 10 cm in water to measure the absorbed dose from photon beams,and also placed at the depth of maximum dose from electron beams under non-reference condition.TLDs were then mailed to National Institute for Radiological Protection,China CDC for further measurement.Results Among the 70 measuring points for photon beams,58 points showed the results with a relative error less than ± 7.0％ (IAEA's acceptable deviation:± 7.0％) between TLDs and finger ionization chambers measurements,and the percentage of qualified point numbers was 82.8％.After corrected by P,value,62 points were qualified and the percentage was up to 88.6％.All of the measuring points for electron beams,with the total number of 24,presented a relative error within ± 5.0％ (IAEA's acceptable deviation:± 5.0％) between TLDs and finger ioization cylindrical chambers measurements.Conclusions TLD-based quality audit is convenient for determining radiotherapy dosimetric parameters of electron beams in non-reference condition and can improve the accuracy of the measuring parameters in connection with finger chambers.For electron beams of 5 MeV ＜ E0 ＜ 10 MeV,the absorbed dose parameters measured by finger ionization chambers,combined with TLD audit,can help obtain the precise and reliable results.