Applying an ArcCHECK detector to the dose verification for ultra-long target volumes of cervical cancer / 中华放射医学与防护杂志

Objective:To explore the feasibility of applying an ArcCHECK detector to the dose verification for ultra-long target volumes of cervical cancer.Methods:This study retrospectively selected patients suffering from cervical cancer with ultra-long target volumes (lengths: ≥ 26 cm; 50 cases; the ultra-long target volume group) and conventional target volumes (lengths: < 26 cm; 50 cases; the conventional target volume group). Subsequently, this study designed treatment plans using the Volumetric Modulated Arc Therapy (VMAT) technique and then collected and verified doses using an ArcCHECK detector. The dose detection for the conventional target volume group was performed at the central point of the detector (marked by iso and Short-0 cm). Then, the detector was moved for 5 cm along the bed exit direction (marked by iso 1), followed by the dose verification of the ultra-long target volume group (marked by Long-5 cm) and conventional target volume group (marked by Short-5 cm). The geometric parameters (the length and volume of a target volume), mechanical parameters (machine hop count and the duration of irradiation), and gamma pass rates (GPRs) under different detection conditions of each group were analyzed.Results:The target lengths, target volumes, machine hop counts, and irradiation durations of the ultra-long target group were higher than those of the conventional target group ( t = 2.61-18.56, P < 0.05). For the conventional target group, the GPRs at iso 1 were significantly lower than those at iso ( t = 2.14-8.17, P < 0.05). Meanwhile, the GPRs at iso 1 of the ultra-long target volume group were significantly lower than those of the conventional target volume group ( t = -4.70 to -2.73, P < 0.01). The GPRs of each group met clinical requirements for criteria of both 3%/3 mm and 3%/2 mm. Conclusions:The deviation of the positioning center and the length of the target volume serve as primary factors affecting the dose verification result of cervical cancer. For ultra-long target volumes, dose verification can be performed by moving the positioning center, thus ensuring treatment accuracy for cervical cancer patients.

Radiomics-based prediction of gamma pass rates for different intensity-modulated radiation therapy techniques for pelvic tumors / 中华放射医学与防护杂志

Objective:To explore the feasibility of a classification prediction model for gamma pass rates (GPRs) under different intensity-modulated radiation therapy techniques for pelvic tumors using a radiomics-based machine learning approach, and compare the classification performance of four integrated tree models.Methods:With a retrospective collection of 409 plans using different IMRT techniques, the three-dimensional dose validation results were adopted based on modality measurements, with a GPR criterion of 3%/2 mm and 10% dose threshold. Then prediction were built models by extracting radiomics features based on dose documentation. Four machine learning algorithms were used, namely random forest (RF), adaptive boosting (AdaBoost), extreme gradient boosting (XGBoost), and light gradient boosting machine (LightGBM). Their classification performance was evaluated by calculating sensitivity, specificity, F1 score, and AUC value. Results:The RF, AdaBoost, XGBoost, and LightGBM models had sensitivities of 0.96, 0.82, 0.93, and 0.89, specificities of 0.38, 0.54, 0.62, and 0.62, F1 scores of 0.86, 0.81, 0.88, and 0.86, and AUC values of 0.81, 0.77, 0.85, and 0.83, respectively. XGBoost model showed the highest sensitivity, specificity, F1 score, and AUC value, outperforming the other three models. Conclusions:To build a GPR classification prediction model using a radiomics-based machine learning approach is feasible for plans using different intensity-modulated radiotherapy techniques for pelvic tumors, providing a basis for future multi-institutional collaborative research on GPR prediction.

Prediction of radiomics-based machine learning in dose verification of intensity-modulated pelvic radiotherapy / 中华放射医学与防护杂志

Objective:Based on radiomics characteristics, different machine learning classification models are constructed to predict the gamma pass rate of dose verification in intensity-modulated radiotherapy for pelvic tumors, and to explore the best prediction model.Methods:The results of three-dimensional dose verification based on phantom measurement were retrospectively analyzed in 196 patients with pelvic tumor intensity-modulated radiotherapy plans. The gamma pass rate standard was 3%/2 mm and 10% dose threshold. Prediction models were constructed by extracting radiomic features based on dose documentation. Four machine learning algorithms, random forest, support vector machine, adaptive boosting, and gradient boosting decision tree were used to calculate the AUC value, sensitivity, and specificity respectively. The classification performance of the four prediction models was evaluated.Results:The sensitivity and specificity of the random forest, support vector machine, adaptive boosting, and gradient boosting decision tree models were 0.93, 0.85, 0.93, 0.96, 0.38, 0.69, 0.46, and 0.46, respectively. The AUC values were 0.81 and 0.82 for the random forest and adaptive boosting models, respectively, and 0.87 for the support vector machine and gradient boosting decision tree models.Conclusions:Machine learning method based on radiomics can be used to construct a prediction model of gamma pass rate for specific dosimetric verification of pelvic intensity-modulated radiotherapy. The classification performance of the support vector machine model and gradient boosting decision tree model is better than that of the random forest model and adaptive boosting model.

Study on the sensitivity of a volumetric modulated arc therapy plan verification equipment on multi-leaf collimator opening and closing errors and its gamma pass rate limit / 生物医学工程学杂志

To investigate the γ pass rate limit of plan verification equipment for volumetric modulated arc therapy (VMAT) plan verification and its sensitivity on the opening and closing errors of multi-leaf collimator (MLC), 50 cases of nasopharyngeal carcinoma VMAT plan with clockwise and counterclockwise full arcs were randomly selected. Eight kinds of MLC opening and closing errors were introduced in 10 cases of them, and 80 plans with errors were generated. Firstly, the plan verification was conducted in the form of field-by-field measurement and true composite measurement. The γ analysis with the criteria of 3% dose difference, distance to agreement of 2 mm, 10% dose threshold, and absolute dose global normalized conditions were performed for these fields. Then gradient analysis was used to investigate the sensitivity of field-by-field measurement and true composite measurement on MLC opening and closing errors, and the receiver operating characteristic curve (ROC) was used to investigate the optimal threshold of γ pass rate for identifying errors. Tolerance limits and action limits for γ pass rates were calculated using statistical process control (SPC) method for another 40 cases. The error identification ability using the tolerance limit calculated by SPC method and the universal tolerance limit (95%) were compared with using the optimal threshold of ROC. The results show that for the true composite measurement, the clockwise arc and the counterclockwise arc, the descent gradients of the γ passing rate with per millimeter MLC opening error are 10.61%, 7.62% and 6.66%, respectively, and the descent gradients with per millimeter MLC closing error are 9.75%, 7.36% and 6.37%, respectively. The optimal thresholds obtained by the ROC method are 99.35%, 97.95% and 98.25%, respectively, and the tolerance limits obtained by the SPC method are 98.98%, 97.74% and 98.62%, respectively. The tolerance limit calculated by SPC method is close to the optimal threshold of ROC, both of which could identify all errors of ±2 mm, while the universal tolerance limit can only partially identify them, indicating that the universal tolerance limit is not sensitive on some large errors. Therefore, considering the factors such as ease of use and accuracy, it is suggested to use the true composite measurement in clinical practice, and to formulate tolerance limits and action limits suitable for the actual process of the institution based on the SPC method. In conclusion, it is expected that the results of this study can provide some references for institutions to optimize the radiotherapy plan verification process, set appropriate pass rate limit, and promote the standardization of plan verification.

Observation on effect of immersive scenario simulation training on improving the competency of infection prevention for health-care workers / 中华医学教育探索杂志

Objective:To analyze the effect of immersive scenario simulation training on improving the competency of infection prevention for health-care workers (HCWs).Methods:Taking the implementation time of immersive scenario simulation teaching training in Sir Run Run Shaw Hospital, Zhejiang University School of Medicine (August 2020) as the boundary, 352 new HCWs entered the hospital before the training (August 2019) were included as control group taking traditional teaching method, and 298 new HCWs entered the hospital after the training (August 2020) were included as observation group taking immersive scenario simulation combined with theoretical training. The mastery status of nosocomial infection-related knowledge and the implementation status of infection control measures (hand hygiene compliance, hand hygiene accuracy, correct personal protective equipment (PPE) selection, 100% of pass rate of PPE on and off, and qualified disposal of medical waste) were compared between the two groups of HCWs after theoretical teaching and different forms of practical training. The training effect (final assessment results) and training satisfaction (Minnesota satisfaction questionnaire, MSQ) of the two groups of HCWs were compared. SPSS 22.0 was used for t test and chi-square test. Results:The assessment results of the two groups of new HCWs trained by theoretical lecturing and immersive scenario simulation training were significantly improved compared with those just received theoretical lecturing, and the results of observation group were significantly higher than those of control group ( P<0.05). The implementation status of infection control measures after practical training were obviously improved in the two groups of HCWs compared to after theoretical lecturing, and the correct rates of PPE selection and all the procedure of donning and doffing PPE of observation group were significantly higher than those of control group ( P<0.05), but there were no significant differences in the hand hygiene accuracy and qualified disposal of medical waste between the two groups ( P>0.05). At the end of training, the final assessment results and satisfaction MSQ score of HCWs in observation group were significantly higher than those in control group ( P<0.05). Conclusion:Immersive scenario simulation teaching and training intervention is beneficial to improve the mastery of nosocomial infection knowledge of new HCWs, standardize their clinical infection control behaviors such as hand hygiene and aseptic operation, and finally obtain good training effect of infection prevention competency.

Effect of phantoms with different cavity thickness on dose verificationupper esophageal cancer / 中国辐射卫生

Objective To investigate the dose calculation accuracy of two algorithms in Monaco TPS for self-made phantoms with different cavity thickness, and analyze the influence of phantoms with different cavity thickness on dose verification of upper esophageal cancer. Methods The phantoms with different cavity thickness were placed on the simulated CT positioning machine to scan and acquire images. In Monaco TPS, the irradiation fields with energy of 6 MV, 100 MU and different square field sizes were added to the acquired images. The dose of the cavity of the ionization chamber was calculated by two algorithms, and measured on the accelerator by dosimeter under the same conditions. At the same time, 20 patients with upper esophageal cancer who received dynamic intensity modulation in fixed field were randomly selected and included in the study, and two algorithms were used for dose verification on phantoms with different cavity thickness. The results were statistically analyzed by SPSS 22.0 software. Results The maximum deviations between the calculated values and the measured values were 0.66% and −1.8%, in the calculation of phantoms with different cavity thickness by algorithms of Monte Carlo and Pencil Beam. In Monte Carlo algorithm, the result of RD pair t test is P > 0.05. Paired t test of AD (0 mm, 10 mm), (5 mm, 10 mm) and (10 mm, 20 mm) groups showed no significant difference (P < 0.05). The maximum deviation was 1.1%, and the rest groups were not statisticely significant (P > 0.05); In Pencil Beam algorithm the t test results of RD (0 mm, 20 mm) and (5 mm, 20 mm) pairs were (P < 0.05), the maximum deviation was 0.58%, and the rest groups were (P > 0.05). In AD group, (P < 0.05), the maximum deviation was 2.78%; The paired t test between the two algorithms was (P < 0.05), and the maximum deviations in RD and AD groups were 2.49% and 4.14%, respectively. Conclusion Monte Carlo algorithm has accurate calculation and high gamma pass rate of dose verification, and there is no clinical difference in gamma pass rate of dose verification among phantoms with different cavity thickness, pencil Beam algorithm is not recommended in cavity phantom calculation.

Dosimetric feasibility of iterative kV CBCT for radiation therapy planning for pelvis / 中华放射医学与防护杂志

Objective:To study the feasibility of using pelvic iterative cone beam CT images for dose calculation of radiation therapy planning, so as to provide support for adaptive radiotherapy.Methods:The CIRS 062 M phantom was scanned by Varian Halcyon v2.0 o-ring accelerator, and the average CT number under different scattering conditions was calculated, and then the ICBCT-ED conversion curve was established. CT images of CIRS 002PRA pelvic IMRT phantom and ICBCT images at different positions were collected. Treatment plan using VMAT technique based on CT image was designed and transplanted into ICBCT image with dose recalculated. The differences of gamma passing rate among target volume, organs at risk and 3-dimensional dose were compared. Based on the actual treatment plan of patients, the differences of 3-dimensional dose gamma passing rate in 10 pelvic patients were analyzed retrospectively.Results:There was a large CT value deviation at central position between the isolated no-scattering condition and the full-scattering condition, and the maximum deviation was 144 HU. The CT values of other positions in full-scattering condition were similar to those of the central position, and the maximum deviation was less than 50 HU. Based on the calculated result of ICBCT images at different positions of the pelvic phantom, the dose deviation of the target volume or organs at risk was less than 1 Gy. Compared with the plan based on CT images, the average 3-dimensional dose gamma passing rate under the criteria of 1% dose difference (DD)/1 mm distance-to-agreement (DTA) and 2% DD/2 mm DTA in plan based on ICBCT images were (88.86 ±1.18)% and (98.38±0.89)%, respectively. The ranges of average 3-dimensional dose gamma passing rate under the criteria of 2% DD/2 mm DTA and 3% DD/3 mm DTA in 10 patients with pelvic tumors were 90.03%-95.43% and 93.58%-97.78%, respectively, and the worst result was only 85.90% and 92.90%, respectively. The main reason of the worst result was the dose difference caused by large variation of bladder contour due to over-filling.Conclusions:Under comprehensive scattering conditions, the ICBCT-ED conversion curve is reconstructed and the treatment plan can be designed by using the ICBCT image of Halcyon v2.0 linear accelerator. The accuracy meets the standards of clinical application, which provides assurance for adaptive radiotherapy in the future.

The impact of dose grid resolution during VMAT planning on COMPASS pass rate / 中华放射医学与防护杂志

Objective To investigate the impact of adopting different dose grid resolution during volumetric modulated arc therapy (VMAT) planning on COMPASS pass rate.Methods A total of 10 patients with cervical cancer were enrolled.Four types of VMAT plans (plan1,plan2,plan3,plan4) were designed for each patient,with dose grid resolution of 0.2 cm × 0.2 cm × 0.2 cm,0.3 cm × 0.3 cm ×0.3 cm,0.4 cm ×0.4 cm ×0.4 cm and 0.5 cm ×0.5 cm ×0.5 cm,respectively.The plans were exported to Linac and conducted,then measured by COMPASS.The discrepancies were analyzed,which were obtained by comparing reconstructed dose from COMPASS and dose from TPS optimization.Results For tumor volume,the mean value of Dmean and D95 were ＜ 0.5％ and ＜ 1.3％ respectively,and the standard deviation were both ＜ 1.0％.For organs at risk (OAR),the max discrepancies were Dmean of femur with-6.7％,-7.0％,-8.0％,-5.8％,and V35 of rectum with 4.9％,-6.3％,-6.1％,-5.7％ in four types of VMAT plans.The γ (3％,3 am) rate of tumor volume was ＞95％ with standard deviation ＜ 2.5％,with no statistically significant difference among the four types of plans (P ＞0.05).The γ (3％,3 mm) rate of OARs were ＞ 98％ except femur (＞ 95％),and the standard deviations were within 1.9％-6.1％,with no statistical significance (P ＞0.05).The average γ rate of tumor volume and OARs were ＜ 0.4 except femur (＞ 0.4),with no statistically significant difference among four types of VMAT plans (P ＞ 0.05).Conclusions COMPASS pass rate was not influenced by the dose grid resolution between 0.2 ～ 0.5 cm for VMAT plan.

An analysis on the candidate profile and pass rate of the pilot qualification examination for registered dietitians in Shanghai / 中华临床营养杂志

Objective To investigate the candidate profile and pass rate of the 2016 pilot qualification examination for registered dietitians in Shanghai,and attempt to inform the improvement of the examination.Methods An analysis was conducted on the profiles of all the 193 qualified candidates in the signing-up system of the 2016 pilot examination.Questionnaire surveys were carried out to collect feedback from the candidates on the enrollment requirements of the examination.The pass rates were compared between subgroups divided by age,gender,education,major,workplace (as employee or intern),working years and academic rank.Results 81.3％ of the candidates were aged between 20 and 29.Females accounted for 80.3％.The candidates had all received bachelor's degree,75.6％ from full-time undergraduate programs and 96.4％ from programs of nutrition.78.3％ of the candidates rated the enrollment requirements of the examination as "reasonable" or "relatively reasonable".The overall pass rate of the examination was 38.3％.The pass rate of the examinees working or doing internship in hospitals (45％) was significantly higher than that of others (24.5％) (P=0.012).Conclusions The overall pass rate is reasonable.Examinees working or doing internship in hospitals had a higher pass rate than those working in other places.The majority of the candidates had bachelor's degree of nutrition,which is in accordance with the requirement of similar exams in other parts of the world.

Effects of position shift and dose adjustment on pass rate of IMRT dose verification / 医疗卫生装备

Objective To analyze the effects of position shift and dose adjustment on the pass rate of IMRT dose verification to facilitate to obtain rapidly high-pass-rate IMRT dose verification report.Methods At first,the dose unit of measuring dose map image and planning Dose Profile was unified.Secondly,the planning Dose Profile was moved at lateral and cephal-ocaudal directions respectively in contrast mode so as to determine the position error with the maximum pass rate.Thirdly,the highest pass rate point of dose verification was found in the range of dose adjustment.Fourthly,the plan report with the highest pass rate of dose verification was found out by adjusting position error and dose coefficient.Results The highest pass rate was obtained in case the displacement was-3 mm at lateral direction or +3 mm at cephal-ocaudal direction;high pass rate was got when dose adjustment coefficient was 1.02;high pass rate was achieved in case the displacement was-3 mm at lateral direction,+2 mm at cephal-ocaudal direction and the dose adjustment coefficient was 1.02,which was significantly different from those with other combined values (P＜0.05).Conclusion The dose verification technique is convenient and quick when used to obtain a high-pass-rate dose verification report.

Analysis of 2 010 patient-specific intensity-modulated radiation therapy dosimetric verification results / 中华放射医学与防护杂志

Objective To analyze the patient-specific dosimetric verification results of 2010 intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans from different treatment sites,and provide a reference for improving the patient-specific dosimetric verification program.Methods A total of 2 010 (965 IMRT and 1 045 VMAT) patient-specific dosimetric verification results were reviewed for isocenter dose difference and percentage of pixels passing planar dose γ analysis.All plans were designed with Eclipse planning system and delivered with Trilogy linear accelerator from February 2012 to February 2016.The dosimetric verification was performed with MatriXX array together with Muhicube phantom.Point dose difference larger than ± 3％ and/or γ pass rate (3％/ 3 mm) less than 90％ was defined as plan failure.Additional analysis was conducted for trends in difference of pass rates with treatment site and delivery technique (IMRT vs.VMAT).Results The mean isocenter difference between measured and calculated doses was-0.3％ ± 2.4％ for 2 010 plans.The mean percentage of pixels passing the γ criteria was 97.9％ ± 3.4％.88.2％ and 96.7％ of plans passed the point and planar dose verification,respectively.The γ pass rate was different among the treatment sites (F =3.09,P ＜ 0.05).The pass rate of point and planar dose difference was different among the treatment sites(x2 =40.93,39.15,P ＜0.05).There was no difference between IMRT and VMAT plans for both point dose and planar dose evaluation (P ＞ 0.05).Conclusions Most of IMRT and VMAT plans passed the tolerance criteria of ±3％ and 90％ for point and planar dose verification with MatriXX together with Multicube phantom,respectively.Both point and planar dose verification results varied among treatment sites,whereas no significant difference was found between IMRT and VMAT.

A study of the iso-center point coincidence between accelerator and radiotherapy planning system / 中华放射肿瘤学杂志

Objective To study the iso-center point coincidence of two accelerators with treatment planning system (TPS) based on γ passing rates of intensity-modulated radiotherapy (IMRT) plan verification.Methods Twenty-one IMRT plans were verified by Varian accelerator and twenty by Elekta accelerator with a gamma criterion of 3 mm/3％.The passing rates were measured when the iso-center point of TPS had-2,-1,0,1,and 2 mm shift in the x or y direction.A binomial curve of γwas fit to figure out the values of the two accelerators on the x and y axes when γ value reached the maximum.The γ pass rate difference was analysed by x2 test.Results The mean values of γ-2,γ-1,γ0,γ1,and γ2 in the x direction were (92.56±3.27) ％,(96.53± 1.82) ％,(96.13± 1.41) ％,(90.14± 2.87) ％,and (82.28± 4.69) ％ for Varian accelerator,and (94.82± 2.04) ％,(97.05± 2.02) ％,(98.38± 1.33) ％,(97.96± 1.44) ％,and (94.49±2.34)％ for Elekta accelerator.There was no significant difference in the mean value of γ0between the two accelerators (P=0.332).When γvalue reached the maximum,the values on the x and y axes were0.65 and-0.30 mm for Varian accelerator and 0.01 and 0.30 mm for Elekta accelerator,respectively.Conclusions In the same TPS,different accelerators have different degrees of coincidence of the actual field center point with the iso-center point of TPS,to which more attention should be paid in clinical practice.

Impact of calculation resolution on Gamma pass rate for plan verification of intensity-modulated radiotherapy / 国际生物医学工程杂志

Objective To analyze the impact of dose calculation resolution on Gamma pass rate for planar dose distribution verification of intensity-modulated radiotherapy (IMRT),and to find out the appropriate calculation resolution value with specific applied criteria.Methods 25 IMRT plans were selected for the planar dose verification.The Gamma pass rates with 3 mm/3％,2 mm/2％ and 1 mm/1％ criteria were compared and analyzed.The planar dose distributions were calculatedand exported from TPS with different resolutions of 0.5,1,2,3,4 and 5 mm.The pass rates of Gamma analysis between the computed dose distributions with different resolutions and the dose distributions measured by Mapcheck device were compared and analyzed.Results The average Gamma pass rates of all the 225 fields decreased with the increment of calculation resolution.When the pass rates of Gamma analysis were calculated using 3 mm/3％ criteria,the gamma pass rate with 1 mm and 0.5 mm calculation resolution were (98.3±1.3)％ and (98.3±1.2)％,respectively.The results were almost the same and the difference wasn't statistically significant (P＞0.05).The gamma pass rates with greater than or equal to3 mm calculation resolution were significantly less than the pass rate with 0.5 mm calculation resolution (P＜0.05).When the pass rates of Gamma analysis were calculated using 2 mm/2％ criteria,all the pass rates with greater than 0.5 mm calculation resolution were significantly less than the pass rate with 0.5 mm calculation resolution (P＜0.05).Conclusions The Gamma pass rates of planar dose verification reduce significantly with the increment of calculation resolution.In order to reduce the effect of calculation resolution on Gamma pass rate,the lower calculation resolution should be used.When using the 3 mm/3％ criteria for the Gamma analysis,1 mm calculation resolution is recommended.When using the 2 mn/2％ criteria for the Gamma analysis,0.5 mm calculation resolution is recommended.The appropriate calculation resolution will ensure the reliability of planar dose verification.

Deviation analysis of plan verification results of 260 volumetric modulated arc therapy plans / 中华放射肿瘤学杂志

Objective To investigate the γ pass rate and contributing factors by summarizing the plan verification results of 260 volumetric modulated arc therapy (VMAT) plans.Methods From 2010 to 2012,two different detector arrays (MapCheck2,Sun,Nuclear,USA ; Delta4 ScandiDos,Swenden) were used for plan verification in 260 patients.The measured dose distributions were compared with the calculation results of treatment planning system using γ pass rate (Pγ ≤ 1 for 2％/2 mm,3％/3 mm and 5％/3 mm,threshold 10％).And the results were put under independent-samples t test.The impact of multi-leaf collimator (MLC) on the γ pass rate (3％/3 mm) was analyzed.Results The average γ pass rates of 2％/2 mm,3％/3 mm and 5％/3 mm of 260 VMAT plans were 91.7％,98.5％ and 99.7％,respectively.Among 260 VMAT plans,3 VMAT plans (1.2％ of the total) failed to meet the clinical acceptable pass rate and needed to be redesigned or re-optimized.The γ pass rate of 2％/2 mm was slightly different between two measurement devices (90.0％ vs 93.5％,P =0.000),while the γ pass rate of 3％/3 mm showed no significant difference between two measurement devices and two accelerators (98.5％ vs 98.5％,P =0.926 and 98.5％ vs 98.6％,P =0.670).The γ pass rate (3％/3 mm) of the treatment plan before MLC calibration was 61.1％,compared to 94.1％ after calibration.Conclusions Most dose verification results of treatment plans can meet the clinical requirement.Gantry rotation may influence the γ pass rate of VMAT dose verification under stricter pass rate standard (2％/2 mm).MLC calibration is essential for VMAT.

Empirical research on the efficacy of medical colleges assessment reform / 中华医学教育探索杂志

Course assessment is the important part of teaching and education.Double effects of improving the teaching and education quality can be achieved through emphasizing assessment methods,separating teaching and testing,building test bank and network exam,offering course of basic clinical skills as well as verified assessment methods,such as stage-based comprehensive exam,unified exam of the course,national entrance exam.The first pass rate of national medical practitioner qualification exam can be guaranteed through implementing these measures.

The feasibility study of independent check for intensity-modulated radiotherapy / 中华放射肿瘤学杂志

Objective To investigate of the accuracy and feasibility of independent check for intensity-modulated radiotherapy (IMRT).Methods Inputing the linear accelerator Varian 600C/D physical data to IMsure ( a independent checking software) and constructing a calculation model.Use of IMsure to calculate the point dose and fluence of 25 cases IMRT treatment plans which have been calculated by Eclipse treatment planning system (TPS),and do a actual measurement of these plans by Matrixx at the same time.IMsure,TPS calculation results and measurement results of Matrixx were compared.Results Select Matrixx's center probe as a reference point,to TPS calculated results as the standard,then the average difference of the IMsure calculation and Matrixx measurement were ( -0.13 + 1.24)％ (t =0.20,P =0.840 ) and ( - 0.18 ± 1.45 ) ％ ( t =0.86,P =0.400 ),respectively.Compared IMsure with 3 mm/3 ％and 2 mm/2％ standard respectively,the average γ rate of TPS were (98.7 ±2.8)％ and (94.9 ±7.2)％ ;compared matrixx measurement results,the average γ rate of TPS were ( 99.0 + 2.0 ) ％ and ( 93.2 ±6.9) ％.The results show that the difference of the point dose and the γ rate of dose distribution by Matrixx measurement and IMsure calculation was no statistically significant difference ( t =1.54,P =0.126 ).Conclusions Independent checking software can be used in the treatment planning system to acceptance and initial clinical tests.In routine,a independent checking software as IMsure may do a pre-verificaton of IMRT treatment plan,or even partially replace of the actual measurement if the adequate conventional quality assurance do well,thus reducing the daily measurements.

Application of 2-D Ionization Chamber Array For Validation of Electron Arc Therapy Plan / 中国医学物理学杂志

Objective:To inspect the dosimetry characteristic of a 2-D ionization chamber array and its response to oblique incident electron beam.And to discuss feasibility to using it to validate the electron arc therapy plan.Materials and methods:(1)The 2-D ionization chamber array was calibrated referring to a themble chamber,comparing the response to electron beams with incidence angle ranged from-50°to 50°.(2)Phantom test plans of 6 and 10MeV electron beam arc therapy were designed,with the beam rotation arcs of 30°,60°and 90° respectively,symmetric to the Central axis of 0°gantry angle.Dose distribution of each plan was verifled with the 2-D array.Results:(1)Measurement differences between the central detector of the array and the thimble chamber were less than 2%,under the planned oblique inddent 6/10MeV electron beam.(2)For the all test plans,dose error was less than 3%at dmax in the symmetric axis of the electron beam arcs.Off-axis dose error was less than 2%within the central 70%area of the profile in non-rotating direction,and smaller than 1.5%in the rotational direction.The measured dose distribution had good agreement with the TPS calculation in isodose curves between 100%and 20%.The gammapass rates(△D=5%,△d=5cm)were 99.98%、99.89%、99.74%、98.64%、99.16%and 99.44%respectively for 6 and 10 MeV plans with electron beam arcs of 30°,60°and 90°.Conclusion:it is practicable using the tested 2-D ionization chamber array to verify and validate the electron beam arc therapy plan.

Variability Dependent on the Previous Year in the Pass Rate of the National Examination for Physicians' License of Japan / 医学教育

The pattern of variability in the pass rate of the national examination for physicians' license of Japan was analyzed. The variation in the pass rate of a medical school in a given year was moderately dependent on the variation in the pass rate in the previous year. There was a moderate negative correlation (r =-0.454, n=1262) between the variations in the pass rates in consecutive years. We termed this phenomenon “the previous-year effect.” The previous-year effect was greatest (r =-0.494, n=475) when the average pass rate of all medical schools changed from decrease to increase, but was smaller (r =-0.393, n=551) when the average pass rate changed from increase to decrease. These phenomena can be explained by interactions between the factors of examinees and examiners.