Research On The Detection Of Radiation Protection Performance Of Medical Electron Linear Accelerator Based On IEC Standard

Objective:The detection and analysis of the radiation protection performance of the 6MV medical electron linear accelerator after the initial installation is carried out to understand whether it meets the requirements of international and national standards to ensure the quality of the accelerator equipment and to ensure the radiation of the clinical radiotherapy staff,the patient and the surrounding public Safety.Based on the development needs,compare the national standards and IEC standards of convergence,to determine the current accelerator quality control testing practice,and improve the understanding of key performance indicators for the future according to IEC standards for similar equipment to provide a meaningful reference.Methods:Select the typical field standard,compare the structure and content of IEC 60976:2007,IEC/TR 60977:2008 and IEC 60601-2-1-2014 and GB 15213-1994,GB/T 19046-2013,GB9706.5-2008 and related standards,the medical electron linear accelerator with a 6MV as the research object,in accordance with the standard requirements and acceptance of equipment manufacturers reference manual,radiation protection performance test accelerator that will be the scene of the measurement results obtained with the standard limit value analysis.Results:(1)The performance of the medical accelerator: Reproducibility was 0.08%,Proportionality was 0.36%,Dependence on angular positions was 0.42%,Dependence on gantry rotation was-0.46%,Dependence on the shape of the radiation field was 1.20% Stability after high absorbed dose delivered was 0.74 %,Stability throughout the day was 1.08%,Stability throughout the week was 1.29%,Stability in moving beam radiotherapy was 1.62%,Quality index was 0.59,Relative surface dose for 10 cm × 10 cm radiation field was 52.70%,Relative surface dose for maximum radiation field(27 cm × 27 cm)was 58.71%.Flatness of square X-ray field of 5 cm × 5 cm was X103.9%,Y103.1%,Flatness of square X-ray field of 10 cm × 10 cm was X105.9%,Y105.0%,Flatness of square X-ray field of 27 cm × 27 cm was X106.0% 、Y105.5%.Symmetry of square X-ray field of 5 cm × 5 cm was X101.5% 、Y 100.3%,Symmetry of square X-ray field of 10 cm × 10 cm was X101.3% 、Y100.4%,Symmetry of square X-ray field of 27 cm × 27 cm was X101.4%、Y100.7%.Maximum ratio of absorbed dose was 102%,5 cm × 5 cm radiation field penumbra was 7.9 mm,10 cm × 10 cm radiation field penumbra was 9.0 mm,20 cm × 20 cm radiation field penumbra was 10.5 mm,≤ 20 cm × 20 cm Radiation field Numerical field-indication was 1.0 mm,> 20 cm × 20 cm Radiation field Numerical field-indication was-2.0 mm,≤ 20 cm × 20 cm radiation field Light field-indicator was 2.0mm,> 20 cm × 20 cm radiation field l Light field-indicator was 2.0mm,Maximum distance between the centres of the radiation field and the light field was 1.0mm,For rectangular radiation fields,Without BLD,Maximum angular deviation,in degrees,from parallelity of the opposing edges was 0.3 °,For rectangular radiation fields,Without BLD,Maximum angular deviation,in degrees,from orthogonality of the adjacent edges was 0.5 °,Displacement of the radiation beam axis from the isocentre and Indication of the isocentre was 0~0.5mm,Indication of distance along the radiation beam axis was-0.5mm,Congruence of the opposed radiation fields was 0.5mm,Vertical movement of the table was 1.0mm,Isocentric rotation of the table was 0.5mm,Maximum angle of lateral tilt from horizontal of the plane of the table top as the table is laterally displaced was 0 °,Longitudinal rigidity of the table was 1mm,Maximum deviation of the height of the table top as the table is laterally displaced was 0~ 0.5mm.(2)The medical accelerator protective performance results:The medical electron linear accelerator equipment and the operation of the safety interlock system testing content were in line with the standard requirements;Relative surface dose was 58.71%;M area on the patient plane X-ray radiation leak maximum rate was 1.34%,X,Y measurements at different combinations of diaphragm conditions which mean was 0.21%,0.26%,respectively,multi leaf collimator leakage radiation rate maximum was 3.46%;The maximum leakage radiation combination condition of outside the area M for the gantry was 0 °,and the beam limiting system was 0 °,the X-ray radiation leak maximum rate was 0.11%,and average was 0.08%;Outside the patient plane X-ray radiation leak maximum rate was 0.25%,and the maximum value of ambient dose equivalent rate was 0.08μSv/h.Conclusions:(1)The dose monitoring system,depth absorbed dose characteristic,uniformity of radiation fields,indication of radiation fields,isocentre,indication of distance along the radiation beam axis,zero position of rotational scales,congruence of the opposed radiation fields,movements of the patient table and so on can reach the performance requirements of IEC 60976:2007 and IEC 60977:2008 standard.(2)Protection against incorrect absorbed dose in the treatment volume,protection against stray radiation in the radiation field,protection against radiation in the patient plane outside the radiation field and radiation safety for patients and others of the medical electron linear accelerator can reach the IEC 60601-2-1 standard protection requirements.(3)IEC standard update timely and comprehensive content,in terms of product safety performance is extremely strict,and some technical performance parameters detection is difficult,radiation protection performance test items are numerous,this study involves the national IEC standard,chapter name and the order of the basic Consistent,We should reasonably set QC test frequency,design QC plan and management to ensure efficiency,appropriateness,practicality and operability.We should increase the use of international standards.The revision of such standards in the radiological standard system should be further strengthened with a view to the promotion of valuable methods.