Independent check is one of the key measures of quality control (QC) in radiotherapy and is essential for the assurance of radiotherapy accuracy.In recent years,with the application of computer-aided system,the automaticity of independent check,as well as its accuracy and efficiency,increases.Meanwhile,QC has evolved from a device-centered to a process-centered program.Therefore,independent check has been increasingly systematic and specific.This review gives a brief summary of the implementation and development of independent check.

Objective A high-performance liquid chromatography(HPLC)method was modified and used to determine the inhibitory effects of GM6001 and inhibitor A on tumor necrosis factor-α converting enzyme(TACE).Methods TACE and polypeptides substrate were incubated for 15 min at 37°C.Ala-Dpa was added as internal standard of quantitative analysis.Then the solution was analyzed by HPLC.The 55% methanol aqueous solution was used as the mobile phase.The wavelength of detector was 353 nm.The ratio of the peak area of remaining substrate to that of internal standard was determined.And the amounts of inverted substrate could be obtained from calibration curve.The TACE activity could be calculated.Results The relative peak areas of substrate were linearly increased depending on the growth of substrate concentration.The correlation coefficient was 0.996 8 and linear range was from 10 to 400 μmol/L.Precision experiments indicated that the precision was improved obviously by using internal standard method in the determination of TACE activity by HPLC.The values of 50% inhibitory concentration IC50 of GM6001 and inhibitor A determined by the newly proposed method were 317.5 and 175.8 nmol/L,respectively.Conclusion The HPLC method assaying TACE activity with Ala-Dpa as internal standard is more accurate,and more practical for screening of TACE inhibitors.

In vivo dosimetry (IVD) is currently the most direct and effective means of quality assurance.The electronic portal imaging device (EPID) has been widely used for IVD verification owing to its favorable dosimetric properties.In recent years,an increasing number of EPID-based IVD studies have emerged around the world.The purpose of this paper is to give an overview of the present progress in EPID-based IVD studies,and to provide a reference for the subsequent application of EPID in IVD.

Objective To analyze the impact of electronic portal imagingdevice (EPID) position error on three-dimensional dose verification of volumetric modulated arc therapy (VMAT).Metbods Five Suremark SL-20 lead points were fixed on Elekta tray,and EPID images were collected in 0-360° rotation,one image per 5°.The position error relative to the accelerator was analyzed via Matlab.Then the images position error was corrected according to the analysis,and the 3D dose was reconstructed with the corrected images.The dose distributions of double arcs,clockwise arc(arc 1),and counterclockwise arc (arc 2) of 16 nasopharyngeal carcinoma patients' VMAT plan were evaluated by γ analysis,and the results of before and after position error correction were compared.Results Compared to 0° gantry angle,the error of source to the image distance (SID) was maximum (1.20 cm) when the gantry angle was 180°.On account of the SID change,the maximum error along the up-down (y) direction in the iso-center planar was 2.28 mm and the left-right (x) direction error was within ± O.5 mm.The 3D γ analyses of 16 nasopharyngeal carcinoma in VMAT plans were obviously increased after the position error along y was corrected.The double arcs,arc1 and arc 2 were increased by (4.12 ±1.67) ％ (t =-9.86,P＜ 0.05),(3.47±1.64) ％ (t=-8.46,P＜ 0.05) and (5.08±1.30) ％ (t=-15.63,P＜ 0.05) in 5％/3 mm standard,respectively.However,in 3％/3 mm standard,γ value of the double arcs,arc 1 and arc2 were increased by (7.63 ±2.24) ％ (t =-13.63,P＜ 0.05),(6.03 ±2.07) ％ (t =-11.66,P＜ 0.05),(9.17 ±2.23) ％ (t =-16.41,P＜ 0.05),respectively.Since the EPID position error along x was corrected after y,the 3D γ analysis of reconstruction dose indicated that the average of the 5％/3 mm and 3％/3 mm γ value were increased by 0.23％ and 0.24％,respectively.Conclusions EPID motion error along the gantry to table direction of the accelerator can't be ignored.When reconstruct dose based on EPID,a modification should be made for rebuilding more accurate patients' 3D dose distribution.

Abstract Gram-negative ( G-) bacteria, such as denitrifying bacteria and anaerobic ammonia oxidation bacteria, are highly social organisms capable of sophisticated cooperative behavior mediated via quorum sensing. As signal molecules of the chemical communication, N-acyl-homoserine lactones ( AHLs ) can mediate the quorum sensing of the functional microbial population and regulate the population density. To understand the growth of functional microbial population and the mechanism for biological nitrogen removal in upflow microaerobic sludge reactors ( UMSRs ) treating organic wastewater with low ratio of chemical oxygen demand to total nitrogen, a method was established to simultaneously detect AHLs in the microaerobic processes. Water-sludge mixtures sampled from the UMSRs were pretreated in sequence by liquid-liquid extraction using ethyl acetate, rotary evaporation, constant volume with methanol, separation by C18 column. Gradient elution was carried out using 5 mmol/L ammonium acetate ( containing 0 . 1% formic acid ) and methanol as mobile phases. On the base of multiple reaction monitoring analysis, a triple quadrupole mass spectrometer with an electrospray ionization was introduced to detect the target compounds. Nine kinds of AHLs were used to evaluate the established method and the results showed that the detection limits were 0 . 01-0 . 5 μg/L and all of the AHLs presented excellent linearity with the concentration ranging from 0 . 5 to 100 μg/L. The recovery and relative standard deviation ranged from 62. 5% to 118. 1% and 2. 9% to 12. 1%, respectively. The analysis could be finished within 6. 5 min. The rapid, accurate and precise method for detecting AHLs provided a new insight into the growth and metabolic activity of functional microbial population in the activated sludge processes to understand the mechanism of biological nitrogen removal, suggesting a good application in regulation and operation of wastewater biological treatment processes.

Aim To investigate the antinociception, tolerance and withdrawal abstinence of δ/μ/κ opioid receptor triple agonist KUST201 ( DPI-125 ) in rats. Methods Male Sprague-Dawley rats were used to de-termine the time course of analgesic effects and ED50 effects of co-administration of naltrindole were assessed as well. In withdrawal experiments, KUST201 was ad-ministrated twice daily for 3 d with increasing doses each day. On the 4th day, the rats were given a single dose, challenged with naloxone 3 h later, and signs of abstinence were monitored. Results The ED50 values of KUST201 were 0. 34 mg·kg-1 in tail-pinch test and 0. 68 mg · kg-1 in hot-plate test. The antinociception actions of KUST201 started to decrease 1 h after ad-ministration, and disappeared after 2 h. In chronic tol-erance experiments, the antinociception actions started to decrease on d 3 , and completely disappeared on d 7 . Naltrindole could reduce the antinociceptive action of KUST201. In withdrawal experiments, abstinence scores increased significantly in the dose range between 2~8 times of tail-pinch ED50 . Conclusion Compared with previously reported δ/μ/κ triple agonist DPI-3290 , KUST201 exhibits similar antinociceptive effects in rats. The chronic tolerance to KUST201 actions de-velops less quickly, but the abstinence scores of KUST201 are slightly higher. The activation of δ-opi-oid receptor can synergistically enhance the antinoci-ception mediated by μ-receptor.

Objective To investigate the precision and stability of optical surface imaging (OSI)system Catalyst in guiding radiotherapy positioning.Methods A total of 52 patients with five different tumor sites who underwent cone-beam computed tomography (CBCT)-guided radiotherapy were recruited in this investigation.For the first treatment fraction,the setup error was recorded as C after online CBCT correction,and the surface images of patients taken by Catalyst were set as the reference images Cref.For the following treatment fraction,patients were pre-corrected according to the Catalyst Cref image with the acceptable errors within 2 mm/ 2,and the pre-corrected errors were recorded as C1.Then,after online CBCT correction,the setup errors were recorded as C.The errors between post-corrected Catalyst surface image and Cref image were recorded as C2.For each treatment fraction,the difference between Catalyst correction errors C1 and CBCT corrected errors C was recorded as d1,and the difference between the post-corrected Catalyst errors C2 and Cref image was recorded as d2.d3=d1-d2.The values of d1 and d3 in the 6 dimensions were analyzed using single sample t-test.The correlation between C-C1 and d1-d2 was statistically analyzed by Pearson correlation analysis.Results The mean value of d1 and d3 for 52 patients were within 2 mm/2 °.CBCT-C1 and d1-d2 were both significantly correlated (R =3,7,P=0.00,0.01).Conclusions OSI system yield high accuracy and stability in radiotherapy positioning,which is of certain significance in radiotherapy positioning for cancer patients.

Objective: To investigate postoperative recurrent pattern of the thoracic esophageal squamous cell carcinoma (TESCC), aiming to provide a basis for the delineation of postoperative radiotherapy volume for TESCC. Methods: Clinical data of 66 TESCC patients who recurred after the radical esophagectomy in Zhongnan Hospital of Wuhan University from 2011 to 2017 were retrospectively analyzed. According to the AJCC 8^th edition-defined classification of esophageal carcinoma, regional lymph node stations 1 to 8M were defined as the upper-middle mediastinum region (UMMR), and stations 8Lo, 9 and 15 were defined as the inferior mediastinum region (IMR), stations 16 to 20 were regarded as the upper abdominal lymph node region (UAR). Results: Among all 66 patients, 41 cases (62%) experienced loco-regional recurrence alone, 25 cases (38%) presented with distant metastasis alone. A total of 54 patients with 148 lymph node recurred after treatment. The highest risk region of lymph node recurrence was UMMR (118/148, 80%), after that, followed by UAR (24/148, 17%). With regard to 9 cases of UAR, 6 patients had lower TESCC, and 8 patients (89%) were graded as ≥ pathological stage Ⅲ. Conclusions The highest risk region of lymph node recurrence is UMMR in TESCC patients undergoing radical esophagectomy, which should be considered as the target volume in postoperative radiotherapy. For patients with lower TESCC ≥ pathological stage Ⅲ, UAR might be the target volume with cautions. Anastomosis and IMR are probably not the routine treatment volumes.

With the rapid development of radiotherapy technology, traditional quality management will shift from a device-centric strategy to a process involving multiple people. In recent years,failure mode and effect analysis(FMEA)based on predictive risk assessment has gradually been applied in the quality management of radiotherapy process. The FMEA approach mainly includes four steps: process tree management,FMEA, error tree analysis, and the design of scheme for process quality management. The specific methods and results are different due to the specificity of radiotherapy process and the subjectivity of participants. Its reliability and feasibility have also been considered and verified. This article reviews the application of FMEA approach in some radiotherapy centers.

Objective:To analyze the intensity-modulated radiotherapy (IMRT) process based on the TG100 report, aiming to improve the quality control method and guarantee the safety and quality of IMRT.Methods:Based on the TG100 report, a risk analysis team was established. The flow chart of overall and each sub-step of IMRT was constructed. The failure mode and effect analysis method were adopted to determine all potential error modes in the process. The probability of of the error mode, the probability of being checked out and the severity of the effect of the error mode on the clinical bed were evaluated based on the pre-set scoring standard. The priority value of each error mode was calculated and ranked from high to low priority value. The top 20% is defined as the high-risk error mode, which was analyzed by error tree to improve the quality control method.Results:IMRT consisted of 11 main steps and 41 sub-steps, and 180 failure modes were detected. The priority values were ranged from 30 to 178. A total of 36 high-risk failure modes were found. The top 5 high-risk failure modes (RPN) consisted of setup error (178), electronic portal imaging device (EPID) registration (172), contouring error (166), treatment delivery error (160) and prescription dose error (156).Conclusion:TG100 report is practical and convenient to utilize, which can effectively and systematically improve IMRT process and provide safety and quality assurance of IMRT process.