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@#<b>Objective</b> To monitor the cumulative terrestrial γ radiation dose around Shidaowan nuclear power plant, Shandong, China before operation, to analyze the dose levels and influencing factors, and to estimate the annual effective dose to local residents. <b>Methods</b> Fifty-six monitoring sites were selected within 30 km around the nuclear power plant. The environmental γ radiation dose was measured by the thermoluminescence dosimeter monitoring method. The γ radiation dose levels were investigated for 369 days in four monitoring periods (January 16 to April 14, April 15 to July 20, July 21 to October 21, 2021, and October 22, 2021 to January 20, 2022 for periods I to IV, respectively). Relations between γ radiation and monitoring time, altitude, distance from the nuclear power plant were analyzed, and the annual effective dose of terrestrial γ radiation to residents was estimated to reflect the background terrestrial γ radiation level in the area. <b>Results</b> The average values of terrestrial γ radiation dose rate in the four monitoring periods in the area were (76.196 ± 3.366), (81.773 ± 6.144), (93.554 ± 7.449), and (97.604 ± 9.396) nGy/h, respectively, and the terrestrial γ radiation dose rate in the whole year was (87.282 ± 6.589) nGy/h. The effective dose to residents was 0.428 mSv. The terrestrial γ radiation level was high from July 2021 to January 2022. There was no significant difference in the γ radiation dose rate at the monitoring sites with different distance from the nuclear power plant. No impact upon the terrestrial γ radiation dose by the altitude was observed in this study. <b>Conclusion</b> The terrestrial γ radiation level around Shidaowan nuclear power plant in 2021 was at the background level.
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@#<b>Objective</b> To investigate and analyze the levels of γ dose rate and radon concentration at all sites in a large open-pit coal mine with radioactivity that had been mined for many years in Xinjiang, China, and to estimate the effective dose exposed to the personnel. <b>Methods</b> A portable γ dose-rate instrument FH40G was used for fixed-point monitoring of the mining area, and a continuous radon detector was used for 24 h continuous monitoring of radon concentration level in the site. The personnel exposure dose was estimated according to the measured γ dose rate and radon concentration. <b>Results</b> In this open-pit coal mine, the range of γ dose rate was 51.4-435.8 nGy/h; the mean 24 h radon concentration was 15-25 Bq/m<sup>3</sup>; the range of annual effective dose to the personnel was 0.29-1.29 mSv/a. <b>Conclusion</b> According to the results of the survey, radon concentration levels at all sites are low, and no remedial action is required. The personnel exposure dose at most of the sites is far below the standard requirements, and some protective measures need to be taken in some areas of the dump.
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Objective:To conduct a meta-analysis to analyze the efficacy and adverse reactions of fractionated high dose rate brachytherapy (HDR-BT) as monotherapy for localized prostate cancer.Methods:Relevant databases were searched to collect the clinical trials on HDR-BT as monotherapy in patients with localized prostate cancer. Included studies were limited to full-text publications of fractionated HDR-BT as monotherapy with a median follow-up of at least 5 years, and adequate reporting of treatment outcomes and adverse reactions data. Stata 12.0 was used for data analysis.Results:According to the inclusion and exclusion criteria, a total of 11 clinical trials involving 2 683 patients with prostate cancer were included in this meta-analysis. The results of the meta-analysis showed that 5-year biochemical recurrence-free survival (bRFS) rate and overall survival (OS) rate were 94% (95% CI: 93% - 96%) and 96% (95% CI: 94% - 98%), respectively. Long-term (≥5 years) cancer-specific survival (CSS) rate and distant metastasis-free survival (DMFS) rate were 99% (95% CI: 98% - 100%) and 98% (95% CI: 98% - 99%), respectively. Long-term (≥5 years) late grade ≥3 grade gastrointestinal and genitourinary adverse reactions rates were 2% (95% CI: 1% - 3%) and 9% (95% CI: 6% - 13%), respectively. Conclusions:Fractionated HDR-BT as monotherapy is an effective treatment for patients with localized prostate cancer. Its long-term efficacy is encouraging, and the treatment is well tolerated and safe.
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In recent years, ultra-high dose rate (FLASH) radiotherapy has become one of the most advanced research topics in the field of radiotherapy. Experimental data indicate that FLASH radiotherapy can significantly reduce the irradiation damage in normal tissues while being as effective as clinical conventional dose rate radiotherapy in tumor control. The oxygen depletion hypothesis is considered as one of the key mechanisms underlying the FLASH effect. In this article, research progress on the discovery, experimental evidence and reaction principle of oxygen depletion was reviewed, the measurement methods and biological effect modeling methods of the oxygen depletion hypothesis were summarized, and the oxygen depletion difference between normal tissue and tumor was also discussed.
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Objective:To evaluate the usability of Gafchromic HD-V2 film for dose dosimetry in the ultra-high dose-rate (UD) electron beam from a modified medical linac, and to investigate the response between the energy and dose-rate dependence to the film.Methods:The HD-V2 film was utilized to measure the average dose-rate of the UD electron beam. The measured result was compared with those by advanced Markus chamber and alanine pellets. And characteristics of the UD electron beam were also measured by HD-V2 film. Energy dependence of HD-V2 film at three beam energies (6 MV X-ray, 9 MeV and 16 MeV electron beam) was investigated by obtaining and comparing the calibration curves based on the clinical linear accelerator in the dose range of 10-300 Gy. The dose-rate dependence of HD-V2 film was also studied by varying the dose rate among 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s, and range of 100-200 Gy/s.Results:The measured average maximum dose-rate of 9 MeV UD electron beam at source skin distance (SSD) 100 cm was approximately 121 Gy/s using HD-V2 film, consistent with the results by advanced Markus chamber and alanine pellets. The measured percentage depth dose (PDD) curve parameters of the UD electron beam were similar to the conventional 9 MeV beam. The off-axis dose distribution of the UD electron beam showed the highest central axis, and the dose was gradually decreased with the increase of off-axis distance. The energy dependence of HD-V2 film had no dependency of 6 MV and 9, 16 MeV while measuring the dose in the range from 20 to 300 Gy. The HD-V2 film had no significant dose-rate dependency at the dose rate of 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s for the clinical linear accelerator. Likewise, there was also no dose-rate dependence in the range 100-200 Gy/s in the modified machine.Conclusion:HD-V2 film is suitable for measuring ultra-high dose rate electron beam, independent of energy and dose rate.
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Compared with conventional radiotherapy, FLASH radiotherapy has advantages in protecting normal tissues, while the dose rate is increased by more than 100 times. If the shielding design of the treatment room is carried out according to the existing standard, the thickness and cost of the shielding wall will be significantly increased, or even hardly to meet the requirement of the standards, resultsing in the failure of the application of FLASH radiotherapy. By investigating the domestic and foreign standards and literature, this paper analyzes the challenges brought by FLASH radiotherapy technology to the shielding design of radiotherapy treatment room in China. Dose rate control standards adopted by different countries in the shielding design are emphatically compared as well. In several countries, the average dose rate under the actual treatment conditions was considered in the shielding design. In China, the method of instantaneous dose rate taking acount of occupancy factor is adopted. However, if FLASH radiotherapy technology is applied, the requirement of instantaneous dose rate will be difficult to meet. In order to improve the high dose rate radiotherapy technology such as FLASH radiotherapy, the revision of the existing standards is advised if the authorized limits are not changed. To use the average dose rate limit within a certain period of time for control, or to raise the control standard in the case of flash radiotherapy, are also avaliable.
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Objective:To study the effects of FLASH irradiation (FLASH-RT) and conventional irradiation (CONV-RT) on gene expression profile in mouse liver, in order to provide theoretical basis of the potential mechanism of FLASH-RT.Methods:A total of 11 C57BL/6J male mice were divided into healthy control group (Ctrl group), CONV-RT group and FLASH-RT group according to random number table method. Mouse abdomen was treated with 12 Gy CONV-RT or FLASH-RT. Then the mice were killed by neck removal, and the liver tissues were collected to extract total RNA for transcriptome sequencing (RNA-Seq) that was then analyzed by bio-informatics analysis to investigate the changes of gene expression profiles. The mRNA expression levels of Stat1, Irf9 and Rela were verified by quantitative real-time PCR assay.Results:1 762 differentially expressed genes (DEGs) were identified in group FLASH-RT vs. CONV-RT. Among them, 660 genes were up-regulated and 1 102 genes were down-regulated. 1 918 DEGs were identified in groups FLASH-RT vs. Ctrl. Among them, 728 genes were up-regulated and 1 190 genes were down-regulated. 1 569 DEGs were identified in group CONV-RT vs. Ctrl. Among them, 1 046 genes were up-regulated and 523 genes were down-regulated. According to Gene Ontology (GO) analysis, these DEGs from groups FLASH-RT vs. CONV-RT were involved in various functions including defense response to virus, other organisms in cell components, adenylyltransferase activity in molecular function activity. These DEGs from group FLASH-RT vs. Ctrl were involved in various functions including defense response to other oranisms, endoplasmic reticulum chaperone complex, double-stranded RNA binding and so on. These DEGs from group FLASH-RT vs. CONV-RT were involved in several Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways including influenza A, Herpes simplex infection and so on. These DEGs from group FLASH-RT vs. Ctrl were involved in several KEGG pathways including influenza A, NOD-like receptor signaling pathway. Stat1 was likely to be activated by FLASH radiation. The quantitative real-time PCR assay showed that FLASH-RT obviously increased the mRNA expressions of Stat1, Irf9 and Rela ( t=6.62, 2.11, 1.67, P<0.05). Conclusions:FLASH-RT and CONV-RT could alter gene expression profiles in mouse liver tissues, and these DEGs are involved in multiple radiobiological functional pathways. In comparison with CONV-RT, FLASH-RT induces a low level of liver injury, which may due to hypoxia radiation resistance.
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Objective:To compare the effects on DNA strand break induced by ultra-high dose rate (FLASH) electron beam and conventional irradiation, and investigate whether FLASH effect was correlated with a reduction of radiation response.Methods:Aqueous pBR322 plasmid was treated with FLASH (125 Gy/s) and conventional irradiation (0.05 Gy/s) under physioxia (4% O 2) and normoxia (21% O 2). Open circle DNA and linear DNA were detected by agarose gel electrophoresis, and the plasmid DNA damage was quantified with an established mathematical model to calculate the relative biological effect (RBE) of DNA damage. In some experiments, Samwirin A (SW) was applied to scavenge free radicals generated by ionizing radiation. Results:Under physioxia, the yields of DNA strand breakage induced by both FLASH and conventional irradiation had a dose-dependent manner. FLASH irradiation could significantly decrease radiation-induced linear DNA compared with conventional irradiation ( t=5.28, 5.79, 7.01, 7.66, P<0.05). However, when the aqueous plasmid was pretreated with SW, there was no difference of DNA strand breakage between FLASH and conventional irradiation ( P>0.05). Both of the yields of open circle DNA and linear DNA had no difference caused by FLASH and conventional radiotherapy at normoxia, but were significantly higher than those under physioxia. In addition, the yields of linear DNA and open circle DNA induced by FLASH irradiation per Gy were (2.78±0.03) and (1.85±0.17) times higher than those of conventional irradiation, respectively. Conclusions:FLASH irradiation attenuated radiation-induced DNA damage since a low production yield of free radical in comparison with conventional irradiation, and hence the FLASH effect was correlated with oxygen content.
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Objective:To investigate the feasibility of transforming conventional medical accelerator to achieve ultra-high dose rate required to achieve Flash radiotherapy (Flash-RT), and to understand the physical properties of the Flash-RT beam.Methods:By transforming the Varian 23CX medical accelerator, the radiation average dose rate at the isocenter was not less than 40 Gy/s. The relevant physical measurement scheme was designed to accurately measure the actual radiation dose rate of different source skin distance (SSD) conditions, the percent depth dose (PDD) curve and the off-axis dose distribution of the beam.Results:The average dose rate of 9 MeV electron beam after the transformation was measured using the HD-V2 type film, the average dose rate of 3 s was 97.9 Gy/s, and the average dose rate of 6 s was 99.27 Gy/s. When the SSD was 100 cm, 80 cm and 60 cm, the average dose rate of 9 MeV electron beam after the transformation was 99.3 Gy/s, 168 Gy/s and 297.5 Gy/s, respectively. After the transformation, the R100 of the 9 MeV beam was 2.2 cm underwater, R50 was 3.87 cm underwater, the electron range Rp was 4.58 cm, and the maximum possible energy Ep,0 on the phantom surface was 9.28 MeV. These parameters were slightly higher than those of the conventional 9 MeV beam, manifested with slight increase in the surface dose and widening high dose flat area. The overall deposit dose distribution exhibited the highest central axis and the increase in dose declines from the axis distance. Under the condition that the field size was 20 cm×20 cm and the SSD was 100 cm, the FWHM of the vertical and horizontal off-axis dose distribution curves were 16.6 cm and 16.4 cm, respectively. Conclusion:By transforming conventional medical accelerator, the average dose rate of the beam at the isocycle meets the requirement of Flash-RT, and the average dose rate under the condition of 60 cm SSD is much higher than the requirement of at least 40 Gy/s for Flash-RT.
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Objective:To analyze the data of ultra-high dose rate (FLASH) radiotherapy in GEO (Gene Expression Omnibus) database by bioinformatics method, in order to find the hub genes involved in flash radiotherapy induced acute T-lymphoblastic leukemia.Methods:The gene expression profiles of malignant tumors receiving FLASH radiotherapy were downloaded from GEO database. The R software was used to screen the differential expressed genes (DEGs) and analyze their biological functions and signal pathways. The protein-protein interaction (PPI) network of DEGs was analyzed by online tool of STRING, and Hub genes were screened by Cytoscape plug-in. The expressions of screened Hub genes in acute T lymphoblastic leukemia were identified with TCGA (The Cancer Genome Atlas) and GTEx (Genotype-Tissue Expression) database.Results:Based on the analysis of GSE100718 microarray dataset of GEO database, a total of 12 800 genes were found to be associated with radiosensitivity of acute T lymphoblastic leukemia, of which 61 significantly altered DEGs were selected for further analysis. It was found that these genes were involved in the biological processes of metabolism, stress response, and immune response through the pathways of oxidative phosphorylation, unfolded protein response, fatty acid metabolism, and so on. PPI analysis indicated that HSPA5 and SCD belonged to the Hub genes involved in the regulation of FLASH radiosensitivity, and they were significantly highly expressed in acute T lymphoblastic leukemia combined with TRD/LMO2-fusion gene.Conclusions:Through bioinformatics analysis, the Hub genes involved in regulating the sensitivity of FLASH radiotherapy and conventional radiotherapy can be effectively screened, and thus the gene expression profiles can be used to guide the stratification of cancer patients to achieve a precise radiotherapy.
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@#<b>Objective</b> To investigate the radiation dose at the entrance of the accelerator treatment room, and to guide the radiation protection detection at the entrance of the treatment room. <b>Methods</b> The FLUKA program was used to build the model of accelerator head and treatment room. Under the simulation conditions of 10 MV and 600 cGy/min for the accelerator, the radiation dose rate inside the entrance of the treatment room was measured at different gantry angles, irradiation conditions, and labyrinths. <b>Results</b> The entrance dose rate with a water tank was significantly higher than that without a water tank under different inner labyrinth wall thicknesses and gantry angles. The entrance dose rate reached the maximum at the inner labyrinth wall thickness of 1800 mm and the gantry angle of 90°. When the inner labyrinth wall thickness was 1000 mm and the gantry angles were 0° and 180°, the entrance dose rate was significantly higher than that at other conditions. The dose rate at the entrance of the treatment room reached (82.26 ± 48.95) μSv/h to (314.09 ± 96.34) μSv/h under the following conditions: the inner labyrinth wall thickness of 1800 mm, the gantry angle of 90°, with a water tank, and the width of the inner labyrinth entrance of 1400-2200 mm. <b>Conclusion</b> The dose at the entrance of the accelerator treatment room mainly comes from the scattering and leakage radiation of the useful wire harness on the patient’s body surface, and the entrance dose rate increases with the increase in the width of the inner labyrinth entrance. In the entrance protection test, the gantry angle should be determined considering the inner labyrinth wall thickness, and the test should be performed at four angles in the uncertain case to ensure the comprehensiveness and accuracy of test results.
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Brachytherapy has played an important role in localized prostate cancer. High-dose-rate brachytherapy has evolved over the decades, as either monotherapy or in combination with external beam, it offers many advantages over other treatment alternatives. Precise control over dose delivery allows for focal dose escalation while sculpting dose around organs at risk to maintain excellent tolerance. The high dose per fraction exploits the low α/β ratio of prostate cancer and triggers transcriptional changes in the tumor genome, thereby enhancing radiation sensitivity. In this article, the development, patient selection, application of techniques, clinical efficacy and adverse events for high-dose-rate brachytherapy were summarized.
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Objective:To evaluate the 3-year survival outcomes and late injury between the self-designed patent single-channel applicator, which was modified from the traditional tandem applicator and wrapped with a oval-shield alloy around the source channel and standard Fletcher-type applicator in the high-dose-rate brachytherapy for cervical cancer.Methods:Patients initially diagnosed with cervical cancer in the Affiliated Hospital of Southwest Medical University from December 2011 to April 2017 were enrolled and randomly assigned into the external beam radiotherapy (EBRT)+ single-channel intracavitary applicator group (the patent single-channel group) and EBRT+ the Fletcher applicator group. The whole pelvis irradiation was delivered with 6-MV photons via a four-field box variant or anterior and posterior parallel fields. Five to six fractions of intracavitary brachytherapy were performed at a dose of 7 Gy at point A once a week after 30 Gy (Equivalent Dose in 2 Gy at point A: 80-90 Gy). Chemotherapy was given with intravenous injection of cisplatin at a dose of 40 mg/m 2 once weekly during EBRT. Clinical efficacy and safety were evaluated after corresponding treatment. Results:In total, 150 eligible cases were assigned into the Fletcher applicator group and 149 cases into the patent single-channel group. Up to December 2020, all patients had been followed up for 3 years, and the median duration of follow-up was 61 months. In the Fletcher group, the 3-year overall survival, progression-free survival and locoregional failure-free survival was 76.3%, 78.1% and 75.4%, and 83.8%, 80.3% and 85.5% in the single-channel group, respectively. In the Fletcher group, the cumulative rate of grade 3-4 late rectal complications was 3.3% and 6.7% in the single-channel group ( P=0.122). The cumulative rate of grade 3-4 bladder complications was 1.3% in the Fletcher group and 0.7% in the single-channel group ( P=1.000). Conclusion:The self-designed patent single-channel intracavitary applicator yields equivalent long-term clinical efficacy and safety to the standard Fletcher-type three-channel applicator in the HDR brachytherapy for uterine cervical cancer.
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FLASH radiotherapy (FLASH-RT) is a treatment modality that delivers ultra-high dose rate and ultra-fast radiation for cancer treatment. Compared to conventional dose rate radiotherapy, FLASH-RT can yield similar efficacy for tumors and achieve normal tissue protection, translating to an increased therapeutic window. Due to this unique feature, FLASH-RT is attracting increasing attention from the radiotherapy community, both academia and industry. Due to its unique Bragg peak as well as intrinsic high dose rate, application of FLASH has more value and profound significance in proton therapy while achieving highly conformal dose deposition simultaneously. This article reviews research progress on FLASH-RT, relevant cell and animal studies, experimental conditions and results. Moreover, this article also investigates the potential biological mechanisms, technical challenges for implementation and potential clinical applications of FLASH-RT.
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Objective:To study the radiation dose rate and effective dose in ambient environment due to 125I seed implantation in the treatment of the patients suffering abdominal and pelvic tumors, so as to provide reference for occupational protection of different groups. Methods:Within 24 hours after operation, the radiation dose rate to 42 patients with abdominal and pelvic tumor with 125I seed implantation was monitored by using pocket dosimeter. The relationships between the total activity in the implanted particles and the measured dose rate, as well as between the implanted depth and the dose rate under the standard activity, were obtained by curve fitting. According to the formula, the relationship between the dose rate and the warning time was calculated. Results:The dose rates at 30 cm, 50 cm and 100 cm of vertical particle implantation site were (6.92±2.87), (4.10±1.62) and (1.30±0.48) μSv/h, respectively ( χ2=73.71, P<0.05). The dose rates on the left and right sides were (0.378±0.156) and (0.384±0.153) μSv/h at 30 cm, (0.170±0.089) and (0.17±0.086) μSv/h at 50 cm, (0.039 ±0.014) and (0.043±0.017) μSv/h at 100 cm, respectively ( χ2=76.19, 76.33, P<0.05). There was a linear relationship between the dose rate at the vertical particle implantation site and the total activity in the implanted particles, and between the dose rate and the implantation depth under the standard activity. The relationship between the warning time and the dose rate to adults in the same bed, co-workers, minors in the same bed and pregnant women were as follows: t ( d)=-106.616+ 83.779ln D( t), t ( d)=26.556+ 85.933ln D ( t), t( d)=3.088+ 85.017ln D( t). Conclusions:After 125I seed implantation, the radiation dose in the ambient environment is low, ensuring the radiation safety; and the measured dose rate decreases with the decrease in the total activity in the implanted particle and the increase in the implantation depth; at the same time, the warning time for different groups is calculated according to the measured dose rate or the total activity in the implanted particle and the depth of the implanted particle, so as to carry out individualized protection.
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Objective:To validate the feasibility of establishing a dosimetric model for insect species by investigating the ecological environment of an inland site in the northwestern China.Methods:For Damalacore, a simplified anatomical model based on anatomy and geometry and a model based on CT scan sequence image were established to produce a voxel model. In combination with the Monte Carlo particle transport process, the deposited energy of the radionuclides in the insect tissues/organs was obtained. The dose rate from 90Sr and 137Cs to Damalacore was calculated on the basis of empirical formula. Results:The dose rate from internal exposure to the simplified anatomical model was 8.58×10 -2for 90Sr and 4.25×10 -3μGy/h for 137Cs, whereas the dose rate from external exposure to the simplified anatomy model was 2.81×10 -2for 90Sr and 2.56×10 -1μGy/h for 137Cs, respectively. The internal exposure to the voxel model from 90Sr and 137Cs was 3.91×10 -2and 2.91×10 -3μGy/h, whereas the external exposure to the voxel model from 90Sr and 137Cs was 2.81×10 -2 and 2.56×10 -1μGy/h, respectively. The internal exposure from 90Sr and 137Cs to ERICA model was 1.46×10 -1 and 1.46×10 -2μGy/h, whereas the external exposure to the ERICA model from 90Sr and 137Cs was 5.79×10 -2 and 2.58×10 -1μGy/h, respectively. Conclusions:The calculated results based on the two models are similar to those based on ERICA model and therefore are proved reliable. With improved model accuracy, the calculated result are more close to the practical situation and feasible.
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As a method for local treatment, radiotherapy plays a key role in the management of tumors. In the past few decades, great progress has been made in radiotherapy technology, with improvements in conformity, homogeneity, and radiotherapy efficiency, and the results are encouraging. Nevertheless, the maximum tolerated dose of normal tissue has limited the further increase in radiotherapy dose in the tumor area. If radiation-induced toxicities can be reduced, a higher radiotherapy dose can be delivered to tumor tissue, so as to achieve a better treatment response. In recent years, the unique FLASH effect of ultra-high-dose-rate radiotherapy (FLASH-RT) is capable of maintaining a consistent tumor response whilst reducing radiation-induced toxicities in normal tissue, and therefore, FLASH-RT has become a research hotspot in the field of radiotherapy across the world. At present, some scholars tend to explain the FLASH effect using the theory of acute oxygen depletion, but the protective effect of FLASH-RT on normal tissue remains to be clarified. In addition, preliminary clinical studies have been conducted for FLASH-RT, and the results are promising. Based on existing evidence, this article elaborates on the research advances in FLASH-RT in the treatment of malignant tumor, so as to provide a reference for the translation and application of this new technique.
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Objective:To investigate the application of therapeutic grade ionization chamber to rapid measurement of short pulsed and high-dose-rate X-ray.Methods:The half-value layer of pulsed X-ray caused by an electron accelerator was measured by interpolation method and its equivalent energy was estimated. The cumulative doses from a certain amount of pulsed radiation at different distances in the same direction around the equipment were compared using the therapeutic grade ionization chamber and thermoluminescence measurement method . The relationship between the measurement result by using ionization chamber dosimeter and the distances away from source was analyzed. The cumulative doses from a certain amount of pulsed radiation at the same location at different frequencies were compared.Results:In working condition, 100 pulses of radiation were received accumulatively at 1 to 12 meters away from the outer wall of the equipment. The range of air Kerma was 0.08-9.65 mGy measured by using thermoluminescence dometers and 0.08 - 9.85 mGy using the ionization chamber dosimeters, respectively. The difference between both is within 10%. At different frequencies (1-10 Hz), there was no significant difference in X-ray air Kerma from 100 pulses measured by ionization chamber dosimeter at 2 m away from the front of the equipment ( P>0.05). Conclusions:The therapeutic grade ionization chamber dosimeter can be used for the rapid measurement of short pulsed X-ray radiation dose in the range of dose rates and pulse frequencies involved in the experimental accelerator device.
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Objective:To explore the influence of dose-rate on radiation-induced gene expression in human peripheral blood.Methods:Human peripheral blood ex vivo was irradiated with 0, 1, 2, 4 and 6 Gy of 60Co γ-rays with different dose-rates of 0.2, 1 and 2 Gy/min. Human blood cells were harvested at 24 h post-irradiation. Following RNA isolation, the mRNA expression levels ofCDKN1A, MDM2, PCNA, FDXR, GADD45A, PHPT1, ASTN2, TNFSF4, POLH, GDF-15 and PPM1D were measured by quantitative real-time PCR. The stepwise regression method was used to establish the gene combination models. Results:The relative mRNA expression levels of 11 genes significantly increased in a dose-dependent manner within the dose range of 0-6 Gy with three dose-rates of irradiation ( R2=0.744-0.998, P< 0.05). Following the exposure to 2 Gy(0.2 Gy/min) 60Co γ-rays, the expression levels of CDKN1A, FDXR, PHPT1 and TNFSF4 genes were significantly higher than that of the 1 and 2 Gy/min groups ( t=3.73, 5.73, 2.44, 2.77, 3.53, 2.68, 2.43, 2.05, P< 0.05). With 6 Gy irradiation, the changes of radiation-induced PPM1D expression level under a dose rate of 2 Gy/min were significantly higher than other two dose-rates( t=3.82, 2.54, P< 0.05). The combined expression model at different dose rates was composed of 2-3 genes, and the R2values of regression equations were 0.976, 0.964 and 0.951, respectively. Conclusions:In a certain range, the dose-rate may affect the changes of radiation-induced gene expression in human peripheral blood.
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Objective The radioactivity level survey was carried out in Weizhou Island area of Beihai, to comprehensively master the radiation environment status in the area, understand the natural radioactivity level and its distribution law, and provide basic data for scientific evaluation of radiation environment quality. Methods According to the relevant standards and technical specifications, the air absorbed dose rate of gamma radiation in Weizhou Island area was monitored from April 2020 to March 2021, the concentrations of radionuclides in water, soil and other environmental samples were sampled and analyzed, and the monitoring results were analyzed and discussed in combination with the regional characteristics. Results The results show that the air absorbed dose rate of gamma radiation in Weizhou Island area ranges from 0.2～122 nGy/h; the activity concentrations of 238U, 226Ra, 232Th, 40K and 137Cs in solid samples range 17.0～37.3 Bq/kg, < 0.501～29.5 Bq/kg, < 0.766～54.3 Bq/kg, 18.7～369 Bq/kg and < 0.212～1.48 Bq/kg, respectively, the concentrations of U and Th in well water and reservoir water range 0.065～0.25 μg/L, 0.046～0.079 μg/L, the activities of 226Ra, 40K, total α and total β range 1.42～3.08 mBq/L, 0.069～0.231 Bq/L, 0.025～0.163 Bq/L, 0.082～0.572 Bq/L, respectively, the concentrations of U and Th in seawater samples range 1.81～2.25 μg/L, 0.634～0.648 μg/L, and the activities of 226Ra, 40K, 90Sr and 137Cs range 9.38～19.7 mBq/L, 11.3～11.8 Bq/L、0.193～0.866 mBq/L、1.13～1.42 mBq/L. Conclusion The environmental ionizing radiation level in Weizhou island of Beihai is in the range of background fluctuation and at a relatively low level, indicating that the radiation environmental quality of Weizhou Island and its surrounding areas is good.