1.Comparison of Chinese and international radiation shielding standards in application for after loading bunker shielding design
Lang YU ; Bo YANG ; Xiansong SUN ; Zechen FENG ; Jie QIU
Chinese Journal of Radiological Medicine and Protection 2021;41(7):529-533
Objective:To compare the calculation result and analyzes the reasons for their differences so as to provide reference for the revision and improvement of the current national standards on radiation shielding design for the room of brachytherapy.Methods:For the initial activity 10 Ci (1 Ci=3.7×10 10 Bq) of radioactive sources, the shielding schemes of brachytherapy room were designed in accordance with UK Institnte of Physics and Engineering in Medicine(IPEM) Report 75, USA NCRP Report 151 and the national standard GBZ/T 201.3-2014, respectively. The differences in shielding limits, occupancy factors and other relevant factors are compared in detail. Results:The annual exposure time in a typical brachytherpy room was about 330 h. The point-specific concrete thickness were 70, 65, 61, 70, 50 cm as required by NCRP Report 151, 41, 43, 30, 40, 39 cm by IREM regulations and 84, 79, 46, 88, 39 cm by GBZ/T 201.3, respectively. The concerned concrete shielding thickness calculated under the GBZ/T 201.3-2014 was generally thicker, with lesser difference from NCRP Report 151 result, whereas that from the IPEM75 report was thinnest. The equivalent lead shielding thicknesses of the protective doors calculated using the three method are 1.170, 0.854 and 1.040 cm, respectively.Conclusions:The shielding thickness calculated using the calculation method and evaluation index recommended by the current Chinese shielding standards for brachytherapy bunker is similar to that reported in NCRP151, but is conservative. In particular, the evaluation index of instantaneous dose equivalent rate required by the current national standards and the relative conservative value of occupancy factor will significantly increase the shielding thickness required by the main shielding area.
2.Analysis of performance test results of 141 CT scaners in Beijing
Weijie ZHU ; Xinming WANG ; Jun HAN ; Liwei SUN ; Yongzhong MA ; Zechen FENG ; Jun YU ; Yun LOU
Chinese Journal of Radiological Medicine and Protection 2018;38(6):439-442,460
Objective To analyze the performance differences of CT scanners with different detector rows between different manufacturers,and to provide the basis for the rational allocation and use of these CT scanners.Methods According to the result from the sentinel surveillance in 2014,a total of 148 medical institutions were equipped with CT scanners in 16 districts of Beijing,including general hospital(53),cancer hospital(5),TCM hospitals(25),children′s hospitals(2),community hospitals(30)and other specialized medical institutions(33).According to the principle of simple random sampling,40 medical institutions are selected,including 14 general hospitals,1 cancer hospital,7 Chinese medicine hospitals,1 children′s hospital,8 community hospitals and 9 other specialized medical institutions.A total of 141 CT scanners are selected from all CT sets of the selected medical institutions from 2012 to 2014.According to GB 17589-2011 X-ray computed tomography device quality assurance testing status test,four parameters related closely to image quality were tested,including CT value(water),noise,high contrast resolution,and low contrast detectability.Results No significant differences were found in CT value(water),noise and low contrast detectability among CT scanners produced by different manufacturers(P>0.05),whereas high contrast resolution was found to have a remarkable difference(χ2=34.706,P<0.05).Significant differences were found in noise,high contrast resolution and low resolution detectability between the CT scanners with <64 detector rows and ≥64 detector rows(χ2=6.978,10.040,15.973,P<0.05).However,there is no difference in CT value(water)(P>0.05).For less-than-64 detector row CT scanners,no significant difference was found in CT value(water),noise and low contrast detectability among different manufacturers(P>0.05).only high contrast resolution differed remarkably(χ2=9.941,P<0.05).For more-than-or equal-to-64 detector row CT scanners,CT value(water)and noise have no differences among different manufacturers(P >0.05),whereas,there were significant difference in high contrast resolution and low contrast detectability(χ2=31.376,32.967,P<0.05).Conclusions There were a few differences in the performance testing of CT scanners from different manufacturers,and the less-than-64 detector row CT scanners have advantages in noise and low contrast detectability compared with the more-than-64 detector row CT scanners,whereas the latter have advantages in high contrast resolution and scanning time,allowing its wider application in medical institutions with more special diseases.
3.Output dose investigation and analysis of external beam radiotherapy in Beijing
Zechen FENG ; Yongzhong MA ; Hongfang WANG ; Yaru SUN ; Zhibin ZHANG ; Yun LOU
Chinese Journal of Radiological Health 2021;30(2):123-128
Objective:
To study the output dose of external beam radiotherapy in Beijing and analyze the cause of output
dose deviation. Guidance is given on the selection of measurement methods, calculation formulas and parameters.
Methods:
During 2020, the output doses of medical electron accelerators, tomotherapy, cyberknife, and γ-knife were meas-
ured based on the water absorbed dose calibration factor combined with the requirements in the IAEA TRS398 and TRS483
reports, and low-energy X-rays were measured based on the air kerma calibration factor combined with the requirements in
the AAPM protocal. The output dose was measured and compared with the preset irradiation value.
Results :
A total of
59 external beam radiation therapy equipments’s output dose were investigated.2 of the 49 accelerators’s absolute value of
relative deviation between the system indication value and the measurement exceeded 3%; the deviation of other external beam radiotherapy equipments was less than 3%.
Conclusion
A unified method and multi-party quality control can ensure
the accuracy of the output dose. In the routine operation of the equipment, the hospital should strictly implement periodic inspections to ensure accurate and reliable radiotherapy.
4.Preparation, characterization and biocompatibility of calcium peroxide-loaded polycaprolactone microparticles.
Leidong LIAN ; Zechen SUN ; Jinhao ZHANG ; Shirong GU ; Chenjie XIA ; Kaifeng GAN
Journal of Zhejiang University. Medical sciences 2023;52(3):296-305
OBJECTIVES:
To explore the physicochemical characteristics and biocompatibility of calcium peroxide (CPO)-loaded polycaprolactone (PCL) microparticle.
METHODS:
The CPO/PCL particles were prepared. The morphology and elemental distribution of CPO, PCL and CPO/PCL particles were observed with scanning electron microscopy and energy dispersive spectroscopy, respectively. Rat adipose mesenchymal stem cells were isolated and treated with different concentrations (0.10%, 0.25%, 0.50%, 1.00%) of CPO or CPO/PCL particles. The mesenchymal stem cells were cultured in normal media or osteogenic differentiation media under the hypoxia/normoxia conditions, and the amount of released O2 and H2O2 after CPO/PCL treatment were detected. The gene expressions of alkaline phosphatase (ALP), Runt-associated transcription factor 2 (RUNX2), osteopontin (OPN) and osteocalcin (OCN) were detected by realtime RT-PCR. SD rats were subcutaneously injected with 1.00% CPO/PCL particles and the pathological changes and infiltration of immune cells were observed with HE staining and immunohistochemistry at day 7 and day 14 after injection.
RESULTS:
Scanning electron microscope showed that CPO particles had a polygonal structure, PCL particles were in a small spherical plastic particle state, and CPO/PCL particles had a block-like crystal structure. Energy dispersive spectroscopy revealed that PCL particles showed no calcium mapping, while CPO/PCL particles showed obvious and uniform calcium mapping. The concentrations of O2 and H2O2 released by CPO/PCL particles were lower than those of CPO group, and the oxygen release time was longer. The expressions of Alp, Runx2, Ocn and Opn increased with the higher content of CPO/PCL particles under hypoxia in osteogenic differentiation culture and normal culture, and the induction was more obvious under osteogenic differentiation conditions (all P<0.05). HE staining results showed that the muscle tissue fibers around the injection site were scattered and disorderly distributed, with varying sizes and thicknesses at day 7 after particle injection. Significant vascular congestion, widened gaps, mild interstitial congestion, local edema, inflammatory cell infiltration, and large area vacuolization were observed in some tissues of rats. At day 14 after microparticle injection, the muscle tissue around the injection site and the tissue fibers at the microparticle implantation site were arranged neatly, and the gap size was not thickened, the vascular congestion, local inflammatory cell infiltration, and vacuolization were significantly improved compared with those at day 7. The immunohistochemical staining results showed that the expressions of CD3 and CD68 positive cells significantly increased in the surrounding muscle tissue, and were densely distributed in a large area at day 7 after particle injection. At day 14 of microparticle injection, the numbers of CD3 and CD68 positive cells in peripheral muscle tissue and tissue at the site of particle implantation were lower than those at day 7 (all P<0.01).
CONCLUSIONS
CPO/PCL particles have good oxygen release activity, low damage to tissue, and excellent biocompatibility.
Rats
;
Animals
;
Osteogenesis
;
Core Binding Factor Alpha 1 Subunit
;
Rats, Sprague-Dawley
;
Hydrogen Peroxide/pharmacology*
;
Cell Differentiation
;
Oxygen
;
Hypoxia
;
Cells, Cultured
5.Variation of 137Cs activity concentration in aerosol in Beijing
Huan WANG ; Qinghua MENG ; Yun LOU ; Bin BAI ; Weijie ZHU ; Hongfang WANG ; Yuxia KONG ; Zechen FENG ; Shuguang ZHAI ; Jun YU ; Yaru SUN ; Yongzhong MA
Journal of Environmental and Occupational Medicine 2024;41(9):1038-1042
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.