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《Chinese Journal of Medical Physics》 2007-02
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The Relationship between Field Symmetry and Injecting Current Fluctuation of Linear Accelerator

ZHANG Chun-guang,SHEN Mei-lian,ZENG Da-fu,PAN Guo-xiong(Cancer Center,Sun Yat-sen University,State Key Laboratory of Oncology in South China,Guangzhou Guangdong 510060,China)  
Objective: To Study on the relationship between the change of injection current,field symmetry of linear accelerator,frequency and efficiency of calibration on gun filament,and to establish the necessary quality control(QC) procedure to ensure a better field symmetry for clinical use.Methods: In the service mode of a clinically used linear accelerator,the gun filament current was changed manually with a step of 0.1 A in both positive and minus way from the symmetric point.The corresponding field symmetry and flatness were measured with films.Results: When the injection value was changed 0.2 A away from the best field symmetry point,the symmetry and flatness became worse 3%.Approximately,the actual injection current became(0.1~0.2) A smaller every month for our normal workload.Conclusions: It is possible to evaluate the change on symmetry and flatness caused from the fluctuation of injection current,by monitoring the actual value of the injection current.Periodical checking and calibrating on injection current or gun filament current should be taken to have a good field symmetry and flatness.
【CateGory Index】: R197.39
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1 YANG Shao-zhou,WANG Sheng-jun(Medical Equipment Department of Nanfang Hospital,Guangzhou Guangdong 510515,China);Methods for Verifying and Adjusting the Mechanical Isocenter of Varian Accelerators[J];China Medical Devices;2008-09
【Secondary References】
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1 LIU Wen,MEI Shi-bing,XU Tao Medical Engineering Department,The Military General Hospital of Beijing PLA,Beijng 100700,China;The Design and Application of the Coherence Metrical Ruler of X-Ray Confine[J];China Medical Devices;2011-10
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