矩形孔准直器伽玛刀的剂量学特征

Dosimetric Characteristics of Rectangular Collimator Gamma Knife

目的对一种矩形孔准直器伽玛刀的射野形状、大小、半影等剂量学参数进行测量,并对射野聚焦形成的剂量分布、静态和动态拉弧的剂量分布进行分析,以归纳矩形孔准直器的伽玛刀剂量学特征。方法在Luna-260型伽玛刀上,用EBT3剂量胶片测量不同射野的剂量分布,通过胶片分析软件得到矩形孔准直器的剂量学参数,选取3号和6号准直器在放射治疗计划系统中进行不同角度拉弧聚焦,分析不同截面上形成的剂量线。结果矩形孔准直器形成的矩形野大小、半影测量结果均符合国标WS 582-2017《X、γ射线立体定向放射治疗系统质量控制检测规范》的要求。1~6号准直器尺寸偏差均在1 mm内,静态聚焦野半影最大为4.3 mm。3种截面(横断面、冠状面、矢状面)的剂量分布形状与拉弧角度大小相关。对于50%剂量线大小,在Z方向上,两种准直器50%剂量线大小均为14 mm左右,在X、Y方向上,两种准直器50%剂量线大小变化幅度不同,其中3号准直器变化幅度较大,6号准直器变化幅度较小。结论矩形准直器射野尺寸及半影大小均符合国标要求,矩形孔准直器拉弧角度影响剂量分布,其剂量学特性能够为临床应用提供参考。

Objective To measure the radiation field shape,size,penumbra and other dosimetric parameters of a rectangular collimator Gamma knife,and to analyze the dose distribution formed by the radiation field focus,static and dynamic arc to obtain the dosimetric characteristics of rectangular collimator Gamma knife.Methods EBT3 films were used to measure the dose distribution of different radiation fields on the Luna-260 Gamma knife.The dosimetric parameters of the rectangular collimator were obtained by the film analysis software.The collimators No.3 and No.6 were selected for focusing at different angles in the radiotherapy planning system,and the dose lines formed on different cross sections were analyzed.Results The radiation field size and penumbra measurement results of the rectangular collimator met the requirements of the national standard WS 582-2017 Specifications for Testing of Quality Control in X andγRay Stereotactic Radiotherapy System.The size deviations of No.1 to 6 collimator were all within 1 mm,and the maximum value of the static focusing field penumbra was 4.3 mm.The dose distribution shape of the three cross sections(cross section,coronal plane and sagittal plane)was related to the size of the arc angle.For the 50%dose line size,in the Z direction,the 50%dose line size of the two kinds of collimator was about 14 mm.In the X and Y direction,the 50%dose line size of the two kinds of collimator was different,in which the change amplitude of the No.3 collimator was larger,and the change amplitude of the No.6 collimator was smaller.Conclusion The field size and penumbra size of the rectangular collimator meet the requirements of the national standard.The arc angle of the rectangular collimator affects the dose distribution,and its dosimetric characteristics can provide reference for clinical application.