基于医用直线加速器轨迹日志进行放射治疗剂量投照的质控

A method research of radiotherapy dosimetry quality control based on medical linear accelerator trajectory log file

目的:探讨基于TrueBeam加速器轨迹日志和Matlab自编程序进行放射治疗剂量投照质量控制的可行性。方法:TrueBeam加速器执行计划生成二进制轨迹日志,由Matlab编程读取其中患者ID、计划及射野名称、射线能量及各控制点处机架/小机头角度、铅门/MLC位置、剂量率、投照剂量、治疗床等信息的期望值、实际值,对两者进行比对。而后按照计划中的控制点间隔离散化日志中的信息,并与计划信息比对,验证计划执行的准确性。由Eclipse制定3D-CRT、IMRT、VMAT计划各6例,其中1例IMRT引入人为误差,验证上述方法的可靠性。结果:所编程序能准确读取计划及轨迹日志中的信息。加速器分别执行有无人为引入误差计划所生成的日志,各参数的期望值及实际值差别与引入误差大小均一致。所有测试期望值、实际值与计划值误差均在允许限内。3D-CRT MLC位置、投照剂量误差(±0.0010 mm、0.0030 MU)较IMRT(±0.8135 mm、±0.0220 MU)、VMAT(±0.9231 mm、±0.0250 MU)小。结论:利用Matlab自编程序,基于TrueBeam加速器轨迹日志,可实现对放射治疗剂量投照的质量控制。

Aim:To investigate the feasibility of combining TrueBeam accelerator trajectory log and a customized Matlab based program to control the quality of radiotherapy dosimetry.Methods:The trajectory log file was created when the TrueBeam linac performed a plan.Then,the expected and actual values of each parameter recorded in the file,such as patients identification,name of plan and beams,beam energy,control point information,gantry angle,collimator angle,jaw and MLC position,dose rate,delivery dose,couch position and so,were extracted and compared by a customized Matlab-based program.After that,information above was discretized according to the interval of control point in the plan and compared to the corresponding plan values used in the program.At last,six 3D-CRT,IMRT and VMAT plans were created separately by Eclipse and artificial errors were introduced to one of the IMRT plans to verify the reliability of the method.Results:The in-house program could accurately read and analyse the parameters information from the plan and trajectory log files.The expected values of the parameters between logs with and without artificial errors were consistent with the introduced error.The differences between the expected,actual and planned values were all within the tolerance limit.The MLC positions error and the delivery dose error of 3D-CRT,IMRT and VMAT were(±0.0010 mm,0.0030 MU),(±0.8135 mm,±0.0220 MU)and(±0.9231 mm,±0.0250 MU),respectively,and those of 3D-CRT were smaller.Conclusion:The proposed method which could verify the radiotherapy dosimetry accurately by a customized program is feasible and practical.