Objective To realize independent 3D dose calculation for intensity-modulated radiotherapy (IMRT) by building a two-source beam model of medical linear accelerator combined with a collapsed-cone convolution/superposition (CCCS) algorithm.Methods Two-source beam models of medical linear accelerators (Varian and Elekta) were built to calculate the 3D dose distributions using the CCCS algorithm.Scp,percent depth dose,and off-axis dose distribution were compared with the scanning data of ion chamber to confirm the calculation model.Twelve intensity-modulated treatment plans from each accelerator (a total of 24 plans) were selected for comparison.The calculation results of treatment planning system (TPS) were independently validated,and further compared with the measurement results of detector matrix.Results The dose deviations at the center of rectangle fields were lower than 1%,the deviation between doses at the same position in the field was not higher than 1%,and the positional deviation in the penumbra region was not higher than 1 mm.Gamma analysis based on 3%/3 mm standard was used to compare the results calculated by detectors and TPS.The pass rates were higher than 90%.Conclusions The independent 3D dose calculation for IMRT based on two-source beam model combined with CCCS algorithm has been successfully set up.The comparison between regular field and IMRT plan indicates that this method and calculation model can be used for independent 3D dose calculation of clinical plan.

Objective To establish a quantitative evaluation of quality control image for the onboard imaging system of medical linear accelerator.Methods An MV planar image of electronic portal imaging device (EPID) is acquired by both Elekta iViewGT and Varian aS1000,and a kV planar image and cone-beam computed tomography (CBCT) images of CBCT are acquired by both Elekta X-ray volume imaging (XVI) and Varian On-board Imager (OBI).Phantoms used here included Las Vegas,TOR18FG,and Catphan504.A series of image quality indicators were evaluated by analyzing the images mentioned above using a quantitative method.Results A quantitative value was calculated to represent the contrast resolution of EPID.A modulation transfer function (MTF) to describe spatial resolution and a quantitative value representing contrast resolution were calculated for the kV planar image.As for the CBCT system,a series of quantitative results of noise,uniformity,CT value accuracy,and contrast resolution and a MTF were calculated to represent the performance of CBCT system.Conclusions Based on common phantoms,a complete set of quantitative methods to evaluate the image quality of EPID and CBCT has been developed,which could provide a very good reference for the establishment of quality control system for image-guided radiotherapy.

Objective To study the mathematical predicting model of parotid DVH for the NPC IMRT planning, and its accuracy with the analysis of medical data. Methods 50 NPC radiotherapy treatment plans with same beam setup were chosen as sample data set, then their parotid DVHs and distance of voxels in the parotid to the target volumes were calculated with self-developed program to form the distance to target histogram ( DTHs);principal component analysis was applied to DVHs and DTHs to acquire their principal components ( PCs) ,and then nonlinear multiple variable regression was used to model correlation between the DTHs' PCs, parotids volume, PTVs and the DVHs. Another 10 plans were chosen as test data set to evaluate the efficacy and accuracy of the final model by comparing the DVHs calculated from our model with those calculated from the TPS. Results Up to 97% information of DTHs and DVHs can be represented with 2 to 3 components, the average fitting error of sample data set was (0±3. 5)%;in the 10 test cases, the shapes of DVH curves calculated from predicting model was highly the same with those from the TPS, the average modeling error was (-0.7± 4. 4)%,the accuracy of prediction was up 95%. Conclusions Our developed model can be used as a quality evaluating tool to predict and assure the dose distribution in parotid of NPC radiotherapy treatment planning effectively and accurately.

Objective To develop an accurate 2D dose reconstruction model using electronic portal imaging device (EPID).2D dosimetric verifications of volumetric intensity-modulated arc therapy (VIMAT)were done using the model.And the results were compared to other dosimeters.Methods The EPID-based dose reconstruction model was using convolve,deconvolve and correction function.The dose profiles which were obtained by the ion chamber were used to determine the model parameters.A total of 12 VIMAT plans for the treatment of anatomical sites of various complexities were chosen.The results obtained from EPID were compared to other dosimeters and treatment planning system (TPS).The ion chamber was used to measure the central point absolute doses.Other dosimeters were used to measure the plane dose distributions.All dosimeters measured the dose at 10 cm depth.The results were analyzed using γevaluation method.Results Regarding absolute central point doses,the ion chamber results were within 1.5％ of the EPID results.For the comparison to Seven29 and Matrixx,the average γ pass rates with 2％and 2 mm criteria were 98.9％ and 99.8％ respectively.For the dose distributions measured by EPID and calculated by TPS,the γ pass rates with 3％ and 3 mm criteria were 99.9％.Conclusions The presented results which were obtained from the comparison of measured and calculated doses show the reliability of our EPID-based dose reconstruction model.With the model,EPID can be a reliable and fast tool for IMRT plan dosimetric verification.The model expanded to the 3D dosimetric verification in the uniform phantom will be considered as the next work.

Objective To establish a fast and accurate method for measurement of leaf position accuracy of dynamic multi-leaf collimator (MLC) using electronic portal imaging device (EPID) and EBT3 film dosimeter.Methods A Varian 6 MV accelerator was used with the gantry angle and the collimator angle fixed at zero degree.A total of 11 sliding window MLC fields were designed.Each field contained a group of strip fields with the same width.The width of a strip field ranged from 1 mm to 10 mm and the distance between two adjacent strip fields was 20 mm.The relationship between the width of the strip field (band width) and the full width at half maximum (FWHM) was calibrated using EPID and EBT3 as measurement tools.A field with a band width of 5 mm was designed in the same way and several MLC leaf deviations were made in different positions.EPID and EBT3 film dosimeter were used to analyze the leaf position accuracy.Results A good linear relationship between band width and FWHM was achieved when the band width was larger than 4 mm.The accuracy of band width,distance between peaks,and MLC leaf position were determined as ±0.2 mm,±0.1 mm,and ±0.1 mm by EPID and ±0.3 mm,±0.2 mm,and ± 0.2 mm by EBT3 film dosimeter,respectively.Conclusions This study provides a fast and accurate method for the measurement of MLC leaf position accuracy using EPID or EBT3 film dosimeter,which is helpful for quality assurance of MLC.

Objective:To analyze the risk factors of Intensive Care Unit-Acquired Weakness, and to develop and verify the model.Methods:A total of 247 patients admitted to ICU patients from November 2018 to October 2019 were selected, and risk factors between ICU acquired weakness group ( n=106) and non-ICU acquired weakness group( n=141)were compared using logistic regression for model construction.The Hosmer-Lemeshow test was used to verify the goodness of fit of the model. The area under the ROC curve was used to test the model to predict the effects. From November 2019 to May 2020, 106 patients were recruited for application of the model. Results:The incidence of ICU acquired weakness in this study was 42.91%(106/247), and 44.34%(47/106),the study finally included age ( OR=1.043) ,mechanical ventilation time ( OR=1.140) , APACHE II score ( OR=1.081) , blood sugar ( OR=1.117) , lactic acid( OR=1.459) ,and neuromuscular blockers ( OR=3.499) to construct the risk prediction. The model formula was P=1/1+exp (- Z) =1/1+exp (8.808-0.042×age -1.252×neuromuscular blockers-0.078×APACHE II score -0.110×blood sugar -0.378×lactic acid -0.131×mechanical ventilation time. The area under the ROC curve of this model was 0.896 (95% CI: 0.824-0.914) , the maximum value of the Youden index was 0.577, and the corresponding sensitivity was 0.754,the specificity was 0.823,the cutoff value was 0.503. The model verification results the sensibility of 70.2%, the specificity of 88.1%, and the accuracy of 80.2%. Conclusion:The predictic model of ICU acquired weakness couducted in this study has satisfactory prediction effect, which can provide a reference for clinical screening of high-risk patients.

BACKGROUNDTo elucidate the pattern and mechanism of cisplatin-induced apoptosis and its role in tumor chemotherapy.

METHODSApoptosis induced by cisplatin in human lung adenocarcinoma cell line A549 was detected by cell morphology, agarose gel electrophoresis, DNA-end-labeling and flow cytometry analysis techniques.

RESULTSCisplatin-induced apoptosis of A549 cells persisted and augmented gradually from 12 to 72 hours after treated with 3 mg/L cisplatin. All of A549 cells treated respectively with 1, 3, 5 and 7 mg/L cisplatin showed apoptosis. Apoptotic effects increased in a time-dependent pattern and a concentration-dependent pattern. A549 cells were blocked in G1 phase after treated with cisplatin.

CONCLUSIONSInduction of cell apoptosis may be an important mechanism of anti-tumor efficacy of cisplatin.

Objective To evaluate the efficacy of liraglutide in the treatment of Nonalcoholic Fatty Liver Disease(NAFLD).Methods Randomized controlled trials(RCTs)that evaluated the efficacy of liraglutide for NAFLD treatment were searched in multiple databases,including Pubmed,EMBASE,the Cochrane library,CNKI,Wanfang database and VIP.Literature identification and data extraction were based on the inclusion and exclusion criteria.RevMan 5.3 software was used for Meta-analysis.Results A total of 7 RCTs with 500 patients of NAFLD were included.Improved liver histology,or improved the level of alanine aminotransferase[WMD=-25.32,95％CI(-37.22,-13.41),P<0.01] and aspartate aminotransferase[WMD=-24.56,95％CI(-35.10,-14.03),P<0.01] were seen in 12-48 weeks liraglutide treatment.However,liraglutide could not decreased the level of serum cholesterol[WMD=-14.38,95％CI(-48.95,-20.20),P=0.42] and triglyceride[WMD=-15.55,95％CI(-36.20,-5.10),P=0.14].Conclusion liraglutide has the therapeutic effect of NAFLD.

Objective To investigate the clinical features and related risk factors of osteoporosis and osteoporotic fracture (OPF) in patients with rheumatic diseases (RD),and the fracture predictive values of fracture risk assessment tool fracture risk assessment (FRAX(R))for Han patients.Methods A total of 313 untreated RD patients were included.Each individual BMD was measured at lumbar spine and femoral neck with Dual-energy X-ray absorptionary.Ten-year probability of fracture (％) was calculated by fracture risk assessment tool FRAX(R) of Chinese model.Each individual previous fracture was confirmed by X-ray or CT examination.The associations between BMD,FRAX),previous fracture and age,bone mass index,nationality,erythrocyte sedimentation rate (ESR) and RD types were analyzed.T test or Wilcoxon test was used to compare the difference between groups for statistical analysis.Pearson/Spearman rank order and binary regression were used to analyze the correlations between variables of normal/non-normal and two classification distribution.Results ① The BMD of patients with untreated RD was significantly lower than that of control group (P=0.000).Individuals diagnosed with "osteopenia" in the RD group and control group were accounted for 39.3％ (123/313) and 15.8％ (47/296) respectively.Individuals diagnosed with "osteoporosis" in RD group and control group were accounted for 11.5％ (36/313) and 5.4％ (16/296) respectively.② The next 10-year probability of the hip (Z=-2.28,P=0.02) and major osteoporotic fracture (Z=-1.98,P=0.03) were higher than those of the control group,as well as the actual incidence of OPF (x2=25.11,P=0.00),the difference was statistically significant.③ 27.3％(18/66) and 55.0％(11/20) of the previous OPF patients in RD group and control group achieved the diagnostic criteria of "high risk" of hip fracture.And 12.1％ (8/66) and 35.0％ (7/20) achieved the "high risk" of major osteoporotic fracture.④ Patients with RA,SLE and pSS had significantly increased risk of fracture.Ten-year fracture risks were negatively related to advanced age,female gender and ESR.Conclusion Bone loss and increased fracture risk are prevalent in the early stage of untreated rheumatism patients.RA,SLE plays an important role in low bone mass.The FRAX China model may underestimate 10-year fracture probability of RD patients and controls.Further explore should be done to predict the FRAX China model on different areas and different RDs.

Objective: To study on the genomic stability of male workers engaged in e-waste dismantling area in Tianjin. Methods: In 2016, an e-waste dismantling area in Tianjin and an area 50 km away from the e-waste dismantling area (no e-waste or other chemical, industrial and agricultural pollution nearby) were selected as the study area and the reference area. Male residents of the study area and male farmers who planted vegetables, fruits, and crops in the reference area were selected as the exposed and reference group by using the convenient sampling method. The exposed group included 146 workers who engaged in e-waste recycling work more than 1 year. The reference group included 121 farmers who never engaged in e-waste recycling work. Questionnaires were used to collect information of all subjects. The semen and peripheral blood were also collected. Trace elements and polychlorinated biphenyl concentration in blood were detected. DNA damage in peripheral blood and sperm was detected, and gene expression was analyzed. DNA damage was assessed using tail DNA% (TDNA%), tail moment (TM) and olive tail moment (OTM) of comet assay. Results: The ages of the exposed group and the reference group were (33.6±12.1) and (33.9±11.9) years old, respectively. The proportions of subjects with exposure time of ≤3, 4-6, ≥7 years were 43% (63 cases), 26% (53 cases) and 21% (30 cases), respectively. The Pb and polychlorinated biphenyl(PCB) concentrations in the exposed group [(90.4±15.3) μg/ml and (101±30) ng/ml, respectively] were higher than those in the reference group [Pb and PCB concentrations were (60.2±8.9) μg/ml, and (2.5±1.4) ng/ml, respectively (both P values <0.05)]. The TDNA%, TM and OTM of peripheral blood and sperm in the exposed group were 5.9%±0.3% and 2.6%±0.90%, 0.93±0.16 and 0.51±0.20, 0.82±0.09 and 0.56±0.07, respectively, which were all higher than those in the reference group [TDNA%, TM and OTM of peripheral blood and sperm were 1.8%±0.2% and 1.9%±0.2%, 0.21±0.04 and 0.32±0.10, 0.19±0.03 and 0.20±0.08, respectively (all P values <0.001)]. The results of gene expression showed that 20 differentially expressed genes, including 13 up-regulated genes and 7 down-regulated genes, were detected in the exposed group compared with the reference group. Conclusion There are obvious DNA damage and DNA repair gene disorder in male workers of an e-waste dismantling area in Tianjin. The current operation mode brings potential health risks to workers.