Evaluation of machine performance check (MPC) system in accelerator / 中华放射肿瘤学杂志

ABSTRACT

Objective:To verify the reliability, accuracy and stability of the machine performance check (MPC) system of Varian′s TrueBeam series accelerator.Methods:After the installation was completed, the acceptance data were compared with the results of the first MPC operation to verify the reliability of the MPC results; the accuracy of the MPC results in the image-guided radiotherapy (IGRT) application was verified by the method of artificially introducing errors. The mechanical performance results of 60 groups of MPC from March 2019 to March 2020 were collected to calculate the mean value and standard deviation and compare the stability differences of each index.Results:The equipment error parameters obtained by MPC were all lower than those obtained by acceptance. The maximum difference between two sets of data was only 2mm and the threshold ratio was less than 20%. MPC had a high sensing accuracy for radiation and imaging position shift, and the r values were more than 90%. The vertical direction of the couch had a poor sense of displacement accuracy, and the r value was less than 73.7%. For this verification project, the angle of the treatment bed was the most stable, and the standard deviation did not exceed 0.01. The stability of other indexes did not significantly differ.Conclusions:MPC can be used as a verification tool for routine quality assurance of IGRT. The verification accuracy of radiation and imaging centers are better than the mechanical accuracy of gantry, collimator and couch.