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.

Objective To investigate the effect of the clinical teaching model based on the miniclinical evaluation exercise (Mini-CEX) scale in Department of General Surgery,and to provide a reference for improving the quality of clinical teaching in Department of General Surgery.Methods A total of 82 nursing interns in Department of General Surgery from June 2016 to June 2018 were enrolled,among whom 41 undergraduates in 2016 were enrolled as control group and 41 undergraduates in 2017 were enrolled as intervention group.The undergraduates in the control group were taught with the traditional clinical teaching method,and those in the intervention group were taught with the clinical teaching model based on the Mini-CEX scale.The two groups were compared in terms of department examination results,score of the Mini-CEX scale,and quality assessment score of clinical nursing teaching,in order to evaluate the teaching quality in Department of General Surgery.Results Compared with the control group,the intervention group had significantly higher department examination score [(96.56 ± 4.23) vs.(90.42 ± 5.12)] and total score of Mini-CEX scale [(5.22 ± 0.45) vs.(4.01 ± 1.03)].The intervention group had a significantly higher excellent rate than the control group (P＜0.05).The intervention group also had a significantly higher quality assessment score of clinical nursing teaching than the control group [(98.34 ± 6.12) vs.(92.45 ± 5.16)].Conclusion The clinical teaching model based on the Mini-CEX scale can improve the quality of teaching and clinical teaching skills in department of general surgery and thus improve the clinical skills and comprehensive quality of nursing interns.

Objective: To explore the application effect of Mini-Clinical Evaluation Exercise(Mini-CEX) in clinical teaching rounds of nursing students, and to provide reference for improving the quality of clinical teaching. Methods: A total of 120 nursing students from June 2017 to June 2018 were divided into control group and intervention group by the time of practice with 60 cases each. The control group adopted traditional nursing teaching rounds, while the intervention group adopted Mini-CEX-based nursing teaching rounds. The comprehensive results of nursing students′practice, Mini-CEX and autonomous learning ability of the two groups were compared and analyzed. Results: The overall evaluation of Mini-CEX of nursing students was (7.23 ± 0.51) in the intervention group and (5.27 ± 1.12) in the control group, and the difference was statistically significant (t=12.337, P <0.01). The excellent rate of nursing students was 58.3%(35/60) in the intervention group and 30.0%(18/60) in the control group, and the difference was statistically significant (χ²=10.914, P <0.01). The total score of autonomous learning ability was (114.85 ± 6.27) in the intervention group and (90.78 ± 8.22) in the control group, and the difference was statistically significant (t=18.034, P < 0.01). The comprehensive results of nursing students′ practice was (87.04 ± 6.46) in the intervention group and (74.35 ± 6.04) in the control group, and the difference was statistically significant (t=11.115, P< 0.01). Conclusions Clinical teaching rounds based on mini-clinical exercise assessment scale can improve the clinical comprehensive service ability, self-learning ability and humanistic care ability of intern nurses.