Measurement And Analysis Of Leakage Radiation Of Medical Electron Accelerators On Patients' Radiotherapy Plane

Objective:To find out the existing problems and grope for the rule and provide suggestions and opinions for GBZ126-2011 and to provide the reference data for evaluatving the protective performance of medical electron accelerator and estimating the patients,extra dose through measuring and analyzing the X-ray or neutron leakage radiation levels inside the M area and outside the M area of 18 medical electron accelerators.Methods:18 medical electron accelerators are measured in this experiment according to the measure method of GBZ 126-2011. The X-ray leakage radiation level inside the M area of 17 medical electron accelerators are tested by using thermoluminescent dosemeter(LiF(Mg.Cu.P) plastic tube),The X-ray leakage radiation level inside the M area of 3 medical electron accelerators was tested by using thermoluminescent dosemeter(6Li F?7LiF glass tube); The X-ray leakage radiation level outside the M area of 9 medical electron accelerators are tested by using thermoluminescent dosemeter(LiF(Mg.Cu.P) plastic tube),The X-ray and neutron leakage radiation level outside the M area of 8 medical electron accelerators was tested by using thermoluminescent dosemeter(6LiF?7Li F glass tube).Results:About the ratios of X-ray leakage radiation in M 24 points area of 18 medical electron accelerators,the range of maximums is from 0.007% to 0.073%(the requirement of GBZ126-2011 is ? 2%)and the range of average is from 0.005% to 0.059%(the requirement of GBZ126-2011 is ? 0.75%),except to the seventh accelerator for which the beam limiter is damaged. The maximum and the average ratio of X-ray leakage radiation of 17 medical accelerators inside the M area meet the requirement of GBZ126-2011.The difference between the results of the measurement is very small and the requirement of GBZ126-2011 would be at least an order of magnitude higher than the results.The range of leakage radiation ratios of X-ray are from 0.004% to 0.063% and the average are 0.006% to 0.029% by thermoluminescent dosemeter(Li F(Mg.Cu.P) plastic tube) outside the M area;The range of leakage radiation ratios of X-ray are from 0.005% to 0.091% and the average are 0.014% to 0.046% by thermoluminescent dosemeter(6LiF?7LiF glass tube) outside the M area; the range of leakage radiation ratios of neutron are from 0 to 0.049% and the average are 0.006% to 0.036%.The maximum and the average ratio of X-ray leakage radiation of 17 medical accelerators outside the M area meet the requirement of GBZ126-2011,but the results of the measurement is very close to the requirement of GBZ126-2011. The maximum ratio of neutron leakage radiation of 7 medical accelerators outside the M area meet the requirement of GBZ126-2011;The average ratio of neutron leakage radiation of 2 accelerators does not meet the requirement of GBZ126-2011, while the data of the others meet the requirement of GBZ126-2011,the results of the measurement is also close to the requirement of GBZ126-2011,especially the date of 15 MV accelerator.Conclusion:The thermoluminescent dosemeter as detector to test leakage radiation of X-ray is simple inside the M area,but no matter which method you adopt,the method to test the leakage radiation of X-ray and neutron is complex outside the M area.To provide plain suggestions and opinions for leakage radiation part and the method of the Leakage Radiation of Radiological Protection Standard of Electron Accelerator in Radiotherapy(GBZ126-2011).