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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.
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Objective:To determine and optimize the radiation quality of the calibration system for mammography dosimeters in IAEA/WHO Secondary Standard Dosimetry Laboratory and to study the requirements for accuracy of thickness of the aluminum sheets used in the measurement, with a view to ensure the accuracy of the radiation quality.Methods:For the measurements of tube voltage and RQR-M radiation quality, a standard kV meter was used to determine the actual tube voltage value of the system under continuous exposure for 30 s by setting tube voltage of 25, 28, 30 and 35 kV, respectively, and aluminum sheet method was used to determine the first half value layer (HVL 1). The kV values were adjusted to make the reading of the standard kV meter as close as possible to its nominal value, so as to obtain the set kV value, actual tube voltage and HVL 1 per 1 kV within the nominal 25-35 kV range. For effects of different thickness of aluminum sheets on the result of HVL 1 measurement, a comparison was made between HVL 1 measured by aluminum sheet with thickness of 0.318 mm and 0.369 mm and HVL 1 measured under 18 different groups of aluminum sheet using a selected 30 kV tube voltage. Results:After the set kV values were adjusted, the actual tube voltage deviations from the nominal values under 25, 28, 30 and 35 kV were reduced from 0.55, 0.34, 0.33, 0.30 to 0.04, 0.02, -0.04, -0.01, and the HVL 1 deviations were reduced from 0.011, 0.007, 0.010, 0.012 to 0.000, 0.003, 0.003, 0.010, respectively. When the thickness differences between the two types of aluminum sheet and the reference HVL 1 were both within 0.1 mm, the deviations of the measured HVL 1 were all less than 0.01 mm Al, and the result was relatively accurate. However, when the differences exceeded that of 0.1 mm, most of the deviations of the measured HVL 1 were between 0.01 and 0.02 mm Al, and the measured result was not accurate. Conclusions:Although the RQR-M radiation quality of the calibration system was deviated, it is still within the range specified under the IEC 61267-2005. The radiation quality was closer to the standard values after fine-tuning the system tube voltage. In order to measure the HVL 1 more accurately, the thickness differences between the used aluminum sheet and nominal HVL 1 should not be greater than 0.1 mm Al.
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Objective To analyze the changes in distribution of occupational radiation cases reported from 2013 to 2017 in China and learn about the occupational health risks of radiation workers.Methods Descriptive analyses were made of regional distribution,disease category distribution,occupation category distribution and exposure mode distribution of these cases,according to the reports (2013-2017) of occupational radiation sickness from " Occupational Health of Radiation Workers Management System".Results There were 54 diagnostic radiology agencies for occupational radiation sickness in China that covered all provinces,autonomous regions and municipalities except Tibet and Production and Construction Corps of Xinjiang.A total of 106 new cases were reported from 2013 to 2017.Most of the cases were radiogenic neoplasm (43.40％),and chronic radiation sickness were from external exposure (16.98％) and radiation cataract (16.04％).Most of the cases (70.75％) were engaged in medical application and a small part of the cases (13.21％) engaged in industry application.Chronic exposure (80.19％) was the most frequent form of exposure mode,but acute exposure (5.66％) was very few.A part of cases (14.15％) were reported without exposure mode.Conclusions The morbidity of occupational radiation sickness declined generally in China and occupational health management of key workers should be strengthened continuously.
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The Fukushima nuclear accident happened in 2011.This article introduced the recent studies about thyroid dose estimation,incidence of thyroid nodule,thyroid cyst and thyroid cancer in the children in Fukushima prefecture after the accident.The results suggested that the incidence of thyroid nodule and thyroid cyst had no significant increase.Nevertheless,the present research noted that the incidence of thyroid cancer was obviously higher than that in other areas in Japan,but high incidence may be due to the choice of the control group or the screening effect.Meanwhile,the contribution of 132Te to the thyroid dose and the incidence of thyroid cancer might not be ignored.The continuous monitoring before and after the operation of the nuclear power plant and the health evaculation after the accident are of importance.
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OBJECTIVE To study the effect of valproic acid ( VPA) on radiosensitivity to MCF7 breast cancer cells. METHODS MCF7 cells were pretreated with VPA 0.5 and 1 mmol.L-1 for 0, 24, 48 and 72 h respectively, irradiated with 8 Gy lR, and at 6 h post-lR, the γ-H2 AX foci formation in MCF7 cells was tested by immunofluorescence assay. MCF7 cells were pretreated with VPA 0.5 and 1 mmol.L-1 for 72 h, irradiated with 4 Gy lR, and at 48 h post-lR, the cell survival rate was detected by MTT assay. MCF7 cells were pretreated with VPA 0.5 mmol.L-1 for 24 h, and then irradiated according to the amount of cells: 2 Gy (500 and 1000 cells per plate), 4 Gy (2000 and 4000 cells per plate), 6 Gy (8000 and 16000 cells per plate), and the cloning efficiency was calculated. MCF7 cells were pretreated with VPA 0.5 and 1 mmol.L-1 for 0, 24, 48 and 72 h respectively and the cell cycle profile was analyzed via flow cytometry. RESULTS After treatment with VPA alone for 24 h, MCF7 cells showed a significant increase in the amount of γ-H2 AX foci formation ( P < 0. 01). lt was also found that VPA increased lR-induced γ-H2 AX foci formation, which obviously prolonged the pretreatment time of VPA(P<0.01) in a time-dependent manner(r=0.98, P<0.05). VPA 0.5 and 1 mmol.L-1 had the same effect on γ-H2 AX foci formation. Furthermore, VPA was able to cause a significant decrease in lR-induced clonogenic survival but an increase in lR-induced cytotoxicity by MTT assay. Also, VPA alone decreased the plating efficiency of MCF7 cells. However, the cycle profile of MCF7 cells treated with both VPA 0.5 and 1 mmol.L-1 was not changed. CONCLUSION Without affecting the cell cycle profile, both the safe and critical dose of VPA used in clinical epilepsy treatment can significantly increase the accumulation of DNA double strand breaks in the cells and sensitize the cells to lR treatment, suggesting that VPA can induce radio-sensitization of breast cancer cells.
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<p><b>OBJECTIVE</b>The functional characters of MCF7 and HCC1937 cell lines were compared through the activity of BRCA1 and p53 following DNA damage in order to provide more research evidence for the related studies in both breast cancer cell lines.</p><p><b>METHODS</b>The protein level of BRCA1 and p53 in two breast cancer cell lines and the protein level of BRCA1 in MCF7, HCC1937 and HCC1937 wtBRCA1 breast cancer cell lines treated with 10Gy after 1 h, 4 h or 8 h were detected by western blotting analysis. The distribution and foci formation of BRCA1 in the cells were observed through immunostaining assay and the percentage of BRCA1 or Rad51 foci formation after ionizing radiation was calculated. Cell cycle profiling was analyzed using flow cytometry.</p><p><b>RESULTS</b>Most of BRCA1 and p53 localized in nucleus, and both proteins responded to DNA damage in MCF7 cells. In MCF7 cells,BRCA1 and Rad51 foci formation respectively increased to (59.40 ± 3.66)% from (11.80 ± 3.51)% (t = 16.26, P < 0.05) and (73.90 ± 8.66) % from (16.70 ± 3.76) % (t = 10.49, P < 0.05) after 10 Gy 8 h ; p53 and p21 protein level was further separately induced and enhanced to (82.54 ± 1.04) from (23.75 ± 0.51) (t = 87.90, P < 0.05) and (90.95 ± 1.13) from (50.19 ± 0.89) ( t = 49.11, P < 0.05) after 10 Gy 8 h; and the cells were accumulated in G1 phase. In contrast to MCF7, in HCC1937 cell line, both of BRCA1 and p53 were defective in nucleus since both proteins were mutated; in response to DNA damage, BRCA1 foci formation was not found, p53 and p21 was not induced; there was no cell accumulation in both of G1-S and G2-M phases. However, after complementation of wild-type BRCA1 in HCC1937 cells, DNA damage-induced Rad51 foci formation increased to (61.70 ± 4.03) % from (6.22 ± 2.27) % (t = 20.78, P < 0.05) and accumulation of cells in G2-M phase was also restored after 10 Gy 8h , which was similar to that of in MCF7 cells.</p><p><b>CONCLUSIONS</b>We have identified that BRCA1 and p53 have dramatically different functions in MCF7 and HCC1937 cell lines in response to DNA damage.</p>
Subject(s)
Humans , Cell Cycle , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p21 , DNA Damage , MCF-7 Cells , Rad51 Recombinase , Radiation, Ionizing , Tumor Suppressor Protein p53 , Ubiquitin-Protein LigasesABSTRACT
Purpose Changes of hepatic perfusion and volume of normal adults living at different altitudes are investigated with hepatic perfusion imaging using multi-slice spiral CT to explore the perfusion status of normal human liver in hypoxia condition, and to provide the basis for the diagnosis and treatment of liver diseases. Materials and Methods Sixty volunteers were divided into three groups according to altitude:22 cases in group A with altitude from 2260 to 3100 meters, 20 cases in group B with altitude from 3260 to 4100 meters, and 18 cases in group C with altitude from 4260 to 5260 meters, time-density curves within the ROI was drawn with hepatic hilar region as the center, and hepatic artery perfusion (HAP), portal vein perfusion (PVP), total hepatic perfusion (TLP), hepatic arterial perfusion index (HPI) were calculated using deconvolution method;and point circle method was used to measure the volume of liver manually. Results HAP of group A, B, C were (10.50±3.62) ml/(100 ml · min), (15.03±4.27) ml/(100 ml · min) and (18.39±7.20) ml/(100 ml · min) respectively, and there was significant difference between group A and group C (P<0.05);PVP of three groups were (138.78±14.29) ml/(100 ml · min), (80.42±16.80) ml/(100 ml · min), and (63.78±7.79) ml/(100 ml · min) respectively, signiifcant differences (P<0.05) can be detected for the comparison between each two of them; TLP of the three groups were (149.30±15.55) ml/(100 ml · min), (95.57±18.75) ml/(100 ml · min) and (82.19±10.56) ml/(100 ml · min) respectively, statistically signiifcant differences (P<0.05) can also be found for the comparison between each two of them. HPI of the three groups were 7.00±2.17, 16.27±4.22 and 22.05±7.90 respectively, statistically signiifcant differences (P<0.05) were observed for the comparison between each two of them;liver volume of the three groups were (1173.5±155.2) cm3, (1282.9±362.2) cm3 and (1525.4±352.2) cm3, difference between group A and group C was statistically signiifcant (P<0.05). Conclusion Liver perfusion can be affected by altitude, with the altitude increasing, HAP and HPI will also raise gradually, while PVP and TLP will decrease accordingly, indicating that hypoxia environment due to high altitude will do certain damage on the liver. MSCT perfusion imaging is able to relfect the hemodynamic changes of liver, thus is useful in clinical diagnosis and treatment of liver diseases.
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Breast cancer susceptibiIity gene 1( BRCA1)is a tumor suppressor,but mutated get BRCA1 is cIoseIy reIated to the deveIopment of breast cancer. Current study has reveaIed that BRCA1 can get invoIved in the DNA damage repair process as a key mediator. DNA doubIe-stranded break (DSB)is the most serious form in DNA Iesions,and BRCA1 pIays an important roIe in repairing DSB through reguIation of homoIogous recombination( HR). In this articIe,the moIecuIar mechanism of BRCA1 in reguIating HR is reviewed with reference to the activity of functionaI domains in BRCA1 struc-ture,the mutations occurring in main domains of BRCA1,the reIationship of BRCA1 with BRCA2, Rad51 or CtIP,and phosphoryIation of BRCA1. In addition,the association of the defective BRCA1-mediated HR repair mechanism with the sensitivity to different DNA damaging agents and synthetic IethaIity in tumor ceIIs is aIso addressed.
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Objective To study CT and MRI findings of the eclamptic encephalopathy in plateau.Methods CT and MRI findings in 28 patients in plateau with eclamptic encephalopathy were retrospectively analyzed.Results CT and MRI appearances of eclamptism were as follow:normal in brain in 3 cases;cerebral edema in 18 cases,including slight encephaledema in 2 cases,focal encephaledema in 11 cases and diffuse encephaledema in 5 cases;cerebral hemorrhage in 6 cases and sinovenous thrombosis in 1 case.Conclusion CT and MRI scan are of significant value in diagnosis and treatment of eclamptic encephalopathy in plateau.