Measurement of thyroid 131I activity in 162 iodine treatment workers in Hubei Province, China / 中国辐射卫生

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.

Quality control analysis of test items based on Philips Digital Diagnost DR / 中国辐射卫生

@#<b>Objective</b> To explore the quality control results of Digital Diagnost digital radiography (DR), and also to analyze the differences in signal transfer characteristics (STP) of DR from different manufacturers, in order to provide a reference for quality control of testers and daily supervision of administrative staff. <b>Methods</b> According to WS 76—2020 “Specification for testing of quality control in medical X-ray diagnostic equipment”, the test items such as automatic exposure control (AEC) repeatability, AEC response, detector dose indication (DDI), STP, high-contrast resolution, and low-contrast resolution of Digital Diagnost DR were qualitatively controlled, and several common DRs on the market were selected to analyze their STP functional relationships. <b>Results</b> The baseline values of DDI, high-contrast resolution, and low-contrast resolution of Digital Diagnost DR were 19733, 2.8 Lp/mm, and H5 of image central pixel value, respectively; the quality control results of other test items met the requirements of WS 76—2020. The STP functional relationships of common DRs were mainly linear and logarithmic, but different models of DR from the same manufacturer might also have different STP functional relationships. <b>Conclusion</b> When testing some special test items of DR, attention should be paid to the influence of a variety of factors, while refining the test steps and condition settings for the test items. The simulation should be performed in accordance with the functional relationship provided by the manufacturer when analyzing the STP.

Infection control status of novel coronavirus pneumonia and radiation safety at CT workplace / 中华放射医学与防护杂志

CT is an important imaging tool for the diagnosis of novel coronavirus pneumonia (COVID-19), therefore, it′s necessary to strictly control the disinfection of CT workplace and equipment and biosafety to avoid the place from becoming a potential infection source and to reduce the risk of infection of patients and radiological staff. It is also necessary to reduce the CT scan dose to minimize the radiation hazards on patients under the premise of ensuring the CT image quality and diagnostic efficiency. Based on the survey that novel coronavirus residues after disinfection at some CT workplace in domestic and overseas and the application of low-dose CT scan in diagnosis of COVID-19, as well as the current situation of radiological protection management in emergency hospital, this paper summarizes and proposes suggestions on infection control and radiological protection for CT workplace to strengthen the defense line of COVID-19 prevention and control.

Frequency and collective dose of medical radiation exposure in Hubei Province in 2018-2019 / 公共卫生与预防医学

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.

Levels of occupational external exposure of radiation workers in Hubei province from 2009 to 2018 / 中华放射医学与防护杂志

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.

Verification of doses to PTV and OAR and 2D dose distribution in IMRT for 7 accelerators in Hubei province / 中华放射医学与防护杂志

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.

Verification of doses to PTV and OAR and 2D dose distribution in IMRT for 7 accelerators in Hubei province / 中华放射医学与防护杂志

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.

Verification of positioning accuracy of MLC leaves of 7 medical linear accelerators in IMRT in Hubei province / 中华放射医学与防护杂志

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.

Effects of crystalline silica with different exposure patterns on lung fibrosis in rats / 中华劳动卫生职业病杂志

Objective@#To investigate the effects of crystalline silica with different exposure patterns on lung fibrosis in rats.@*Methods@#A total of 20 adult male Wistar rats were randomly divided into 4 groups consisting of five animals each and received intratracheal instillation of sterile saline or silica suspension in different patterns: saline once at day 0, saline once/week, crystalline silica 50 mg at day 0, crystalline silica 6.25 mg/week. The rats were sacrificed at 8 weeks. The lung tissues were collected for pathological analyses, and determining mRNA and protein levels of related fibrogenic molecules.@*Results@#The collagen deposition induced by crystalline silica in lung tissues were increased. The mRNA levels of IL-1β and Col I in group c were significantly elevated than those in group saline once at day 0 (all P<0.05). Compared with group saline once/week, the mRNA levels of IL-1β, TGF-β, Col I, Col III and CTGF were significantly increased in group crystalline silica 6.25 mg/week (P<0.05) . The mRNA levels of Col I and CTGF were significantly increased in group crystalline silica 6.25 mg/week in comparison with those in group crystalline silica 50 mg at day 0 (P<0.05) .@*Conclusion@#Given the same cumulative dose of crystalline silica, multiple exposures were likely to induce more severe lung fibrosis.

Verification of absorbed dose and single-field dosimetry of MLC-shaped IMRT photon beams in Hubei province / 中华放射医学与防护杂志

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.