Study Of A Rapid Measurement Method For Radiation Field Of Medical Electronic Linear Accelerators

Radiation therapy has become one of the main methods for the treatment of malignant tumors at present,and the linear accelerators,as the main equipment of radiation therapy,are directly related to the results whether radiation therapy is successful or not.Therefore,the quality assurance and quality control of linear accelerator radiation field is particularly important.With the rapid development of linear accelerators,many new technologies have been applied.There are various kinds of quality control testing tools,each of which has its own advantages and disadvantages.The traditional quality control testing tools include ionization chamber,two-dimensional matrix detector,radiant color film,electronic portal image device,and three-dimensional scanning water tank.One of them may be complicated in operation,not be read instantly,be too expensive,or not be popularized.It is difficult to measure the radiation field of a linear accelerator in a short time.In addition,the number of cancer patients and radiation therapy equipments in China is large and the relative shortage of quality control workers still exists,how to ensure the quality assurance and quality control of radiation therapy equipments in a limited time has become a problem to be solved urgently.In this study,a rapid measurement device for the radiation field of a medical electronic linear accelerator is used to measure the radiation field of a linear accelerator,and the method of measuring the radiation field of a linear accelerator is studied.In this study,the rapid measurement device was applied to two linear accelerator radiation fields in Varian Clinac 600CD and Elekta Synergy.In the measurement of the output dose of the central axis,the results of the rapid measurement device were compared with the results of the dosimeter,and the results of the device were compared with the results of three-dimensional water tank in the test of the flattness and symmetry of the field.The first measurement results were normalized as the reference values,and the relative deviation was calculated.In the 600CD linear accelerator 6MV X-ray testing results,the results of flattness and symmetry measured by the rapid measurement device were close to that measured by the three-dimentional water tank,and the maximum deviations of central axis output dose,flattness along the left and right direction,flattness along the gun and target direction,symmetry along the left and right direction,symmetry along the gun and target direction were 0.87%,0.96%,0.48%,0.40%and 0.59%,respectively.In the Synergy linear accelerator test results,under the condition of 6MV X ray,the maximum deviations of central axis output dose,flattness along the left and right direction,flattness along the gun and target direction,symmetry along the left and right direction,symmetry along the gun and target direction were 0.89%,0.47%,0.19%,0.20%and 0.40%,respectively;in 10MV X-ray results,the maximum deviations of central axis output dose,flattness along the left and right direction,flattness along the gun and target direction,symmetry along the left and right direction,symmetry along the gun and target direction were 0.55%,0.20%,0.39%,0.29%and 0.39%,respectively.The deviations of test results of all parameters were within 1%.And the results were stable and reliable,it was simple in operation,and the testing time was less.So the rapid measurement device of radiation field could realize the rapid test of the radiation field of linear accelerators.As an integrated equipment for measuring the basic dosimetry parameters of linear accelerators,the rapid measurement device designed by ourselves in this study can realize the quality control of the radiation field of a linear accelerator in a short time.The linear accelerator works once,the measurement device can obtain a series of dosimetry parameters such as the central axis output dose,the flattness of the field,the symmetry of the field,the ray quality and so on.It can display the results immediately and results can be preserved for a long time.It is easy to operate,small and convenient to carry,and the price is relatively low,so it can be popularized and widely used.In practical application,it can not only save a lot of time for the test of the radiation field of linear accelerators,achieving a simple and rapid measurement for the radiation field of linear accelerators,but also provide data support for the long-term monitoring of the linear accelerators.