Objective To investigate the effect of SKP2 expression on radiation induced bystander effect (RIBE) of esophageal cancer cells.Methods The esophageal cancer cell lines with different SKP2 levels were applied for the study and the SKP2 expression was identified by Western blot.Micronuclei (MN) assay and DNA foci assay were used to evaluate the effect of SKP2 on RIBE.The cells were transfected with SKP2 gene or SKP2 siRNA to further verify the effect of SKP2 on RIBE.Results MN assay showed that the bystander effect induced by the cells with a high level of SKP2 was lower than that induced by the cells with a lower level of SKP2 (t =8.06,P ＜ 0.01).These results were further confirmed by the gene transfection experiments.When the expression of SKP2 was increased,RIBE was decreased (t=11.12,10.16,P ＜ 0.01).Contrarily,when the expression of SKP2 was reduced,RIBE was increased (t =8.39,8.83,P ＜ 0.01).γ-H2AX foci formation assay disclosed that when SKP2 expression in the irradiated cells increased,the repair ability of DNA damage in the bystander cells was higher than the control (t =6.85,7.10,P ＜ 0.01).With the expression of SKP2 decreased,the repair ability of DNA damage was lower than the control (t =7.66,8.47,P ＜ 0.01).Conclusions Over-expression of SKP2 inhibits RIBE of esophageal cancer cells,at least partly through regulating DNA damage repair ability.

Objective To evaluate the radiation protection of occupational hazards in a hospital Clinac 23EX medical electronic accelerator construction project so as to ensure the health and safety of the relevant people involved.Methods According to the relevant laws,regulations and standards of China,combined with the relevant materials provided by the construction unit,the radiation protection tests and comprehensive assessment of this project were carried out.Results The performance test results of the medical electron accelerator met the requinements of GB/T 19046-2013 The ambient dose equivalent rate in the workplace was between the background dose rate (0.10 μ,Sv/h) and 11.5 μSv/h,which suggested the computer room shielding met the requirements of radiation protection.The total body effective dose,the for 7 radiation workers were 0.85,1.19,1.64 mSv,respectively,which were lower than the dose management control values of the construction unit and the national standards.Radiation protection supplies and the management system of the construction unit met the national requirements.Conclusions The construction project can effectively control the radioactive occupational hazard factors in normal operation,and the radiation protection facilities have reached the completion requirements.

Objective:To study the dose response of two-dimensional ionization chamber matrix detectors under IMRT fields irradiation at different gantry angles and different directions.Methods:After the dose calibration of the medical accelerator and the two-dimensional ionization chamber matrix detector respectively, the solid water phantom was used to cover the upper part of the two-dimensional ionization chamber matrix detector. Adjusting the thickness of the solid water, the effective distances between the effective measuring center of the two-dimensional ionization chamber matrix detector and the incident point of the central axis of the radiation on the surface of the phantom was always controlled at 5 cm. Four locations with 0、45、90 and 135 degrees of the long axis of the treatment bed were selected, and each location was irradiated by IMRT fields at different frame angle of 60°, 45°, 30°, 15°, 0°, -15°, -30°, -45° and -60°, respectively.Results:The dose deviation of the medical accelerator was less than 0.18% in the range of different rack angles. The directional response deviation of the two-dimensional ionization chamber matrix detector was less than 0.63%, and the measurement deviation of each probe of the two-dimensional ionization chamber matrix detector to its center probe was less than 0.50%.Conclusions:The two-dimensional ionization chamber matrix detector has good directional response and it is a useful tool for developing intensity-modulated radiotherapy technology. The method proposed in this study can provide a basic basis for the relevant medical accelerator metrology departments to formulate corresponding quality control test specifications.

Objective:To asscentain the 131I activity concentration in 131I treatment workplaces and to explore the method of estimating the internal dose to workers by air sampling and to analyze its influencing factors. Methods:Air sampling method was used to collect aerosols containing radioactivity in 10 randomly selected workplaces in Zhengzhou where 131I therapy was performed. Aactivity concentration of 131I in treatment workplace was measured for gamma emitters by gamma-ray spectrometry. The internal dose due to 131I inhalation was estimated based on measurement result and field investigation result. Results:The activity concentration of 131I in air samples from 19 subpacking rooms ranged from 0.087 to 570 Bq/m 3, with an average of (51.04 ± 128.58) Bq/m 3. Those from 11 wards ranged from 0.162 to 54.6 Bq/m 3, with an average of (7.97 ± 15.89) Bq/m 3. In terms of the work hours recommended by the national standard GBZ 129-2016 Specifications for individual monitoring of occupational internal exposure, the estimated annual effective dose to radiation workers due to the inhalation of 131I ranges from 0.002 to 10 mSv, with an average of (0.61 ± 1.80) mSv, below the dose limit specified in the national standards. Conclusions:The samples with high 131I activity concentration in nuclear medicine workplaces of 10 medical institutions selected in Zhengzhou are mostly distributed in tertiary class hospitals operating large amount of radionuclide with large numbers of thyroid cancer patients adimitted. The result ing internal dose to radiation workers cannot be ignored. Estimating the internal dose based on the measurement result of air samples has a large uncertainty.However, air sampling method can promptly detect radioactive contamination in case of abnormal events or accidents, providing early warning for workers to carry out dose measurement from external exposure and internal exposure assessment.

Objective:To investigate the conversion of low-energy CBCT images into high-energy CBCT images in clinical radiotherapy based on the deep learning method of U-Net network, in order to provide dual-energy CBCT images and reduce radiation dose.Methods:The CBCT image data of CIRS electron density phantom and CIRS head phantom at 80 and 140 kV were collected by the on-board CBCT in radiotherapy equipment. The dataset was divided into training set and test set according to 10∶1. The U-Net network was used to predict CBCT images at high energy (140 kV) from low-energy (80 kV) CBCT images. Four parameters, including mean absolute error (MAE), structural similarity index (SSIM), signal-to-noise ratio (SNR) and peak signal-to-noise ratio (PSNR) were used to quantitatively evaluate predicted high-energy CBCT images.Results:The overall structural difference between the predicted high-energy image and the real high-energy image was smaller (SSIM: 0.993 ±0.003). The noise of predicted high-energy image was lower (SNR: 15.33±4.06), but there was a loss of inter-tissue resolution. Predicted high-energy images had slightly lower average CT values than real high-energy images, with less difference in low-density tissues (<10 HU, P > 0.05) and greater differences in high-density tissues (<21 HU, t = -7.92, P < 0.05). Conclusions:High-energy CBCT images with high structural similarity can be obtained from energy CBCT images by using deep learning method. The predicted high energy CBCT images have the potential to be applied to clinical dual-energy CBCT imaging technology in radiotherapy.

Objective:To discuss the problems existing in the implementation of the Chinese health industry standard WS 523-2019 by testing SPECT device.Methods:Under the WS 523-2019 standards, a total of 10 SPECT devices were tested with regard to their SPECT reconstructed spatial resolution (SRSR), system planar sensitivity (SPS), system spatial resolution (SSR), whole body system spatial resolution (WSSR), intrinsic uniformity (IU), intrinsic count rate performance (ICR), intrinsic spatial resolution (ISR) and intrinsic spatial linearity(ISL).Result:Under the requirements of WS 523-2019 standards for qualified limits, there are 3 devices with ISL unqualified and the rest of the performances qualified. The new standards basically can meet the clinical requirements and reflected the overall performance of SPECT.Conclusions:The distance between the radiation source and the surface of the detector has great influence on the spatial resolution.In the measurement of ISL, there must be a lead grid separately in the x and y directions. The lead grids with the parallel slits shall be positioned on the detector with the center slit centered on the detector. It is suggested to add rotation center in the new standards.

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.

Objective The purpose of this study is to grasp the current situation of radiation protection in some non-medical institutions in Hangzhou, and to provide basis and reference for the relevant authorities departments to make the radioactive hazard factors monitoring plan for non-medical institutions. Methods The configuration of the personnel protective equipment and radiation level of radiation sources and radiation devices in 5 non-medical monitoring institutions in Hangzhou were investigated and analyzed by means of questionnaire survey and on-site detection. Results The radiation workers of 5 monitoring institutions have carried out personal dose monitoring, and their annual individual dose equivalent meets the requirements of relevant national standards. The ambient dose equivalent rates around the radiation source and radiation device room are lower than the minimum detection limit of the instrument. When the source is stored, the maximum ambient dose equivalent rates at 5 cm and 100 cm away from the external surface of the source container were 22.2 μSv/h and 2.0 μSv/h, respectively. When the source is in use, the maximum ambient dose equivalent rates at 5 cm and 100 cm away from the external surface of the source container were 44.3 μSv/h and 5.0 μSv/h, respectively. Conclusion Under normal operation, the radiation dose level of some non-medical monitoring institutions in Hangzhou is at a low level, while the ambient dose equivalent rates around the external surface of the source container is at a high level. Therefore, non-medical institutions should improve their awareness of radiation protection and strengthen radiation management.

Objective To measure the peripheral dose distributions of the mobile head cone beam computed tomography (CBCT) and evaluate the impact of CBCT on the surrounding personnel and environment, and provide data support for clinical radiation protection management. Methods Combined with the structural characteristics of CBCT, AT1123 was used in the direction of 0° (counterclockwise), 45°, 90°, 135°, 180°, 225°, 270° and 315° in front of CBCT to measure the ambient dose equivalent rate of 30 cm, 80 cm and 130 cm away from the ground when the equipment was normally out of the beam, and the boundary of the temporary control area was drawn. At the same time, the dose level behind the lead screen 1 m away from the external surface of the equipment was measured and analyzed. Results The dose field around CBCT was symmetrically distributed with the dividing line of 0° and 180°, and the radiation dose level of 5.5 m in the direction of 0°, 3.5 m in the direction of 45°, 0.5 m in the direction of 90° and within 1.0 m in the direction of 180° (inside the "spoon" type) was higher than 2.5 μSv/h. The radiation dose levels of CT aperture 0° (straight forward), 45° and 315° behind the lead screen 1 m away from the equipment surface were 0.37 μSv/h, 0.22 μSv/h and 0.54 μSv/h, respectively. Conclusion The results show that the radiation dose around the mobile head cone beam CT is in a low dose level, the distribution of the dose field can provide necessary reference for the administrative and medical personnel to strengthen the radiation safety management. At the same time, it is suggested that lead screens should be set up in the clinical use of mobile CT to ensure the health and safety of the surrounding people and the environment.

Objective 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. Methods 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. Results 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. Conclusion 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.