两种直线加速器射野剂量学特性测试分析

Analysis of Beam Dosimetric Characteristics of Two Linear Accelerators

目的比较国产联影uRT-linac 506c直线加速器与Varian IX直线加速器在射野剂量学上的差异。方法采用PTW MP3三维水箱和PTW MEPHYSTO软件,分别测量联影uRT-linac 506c和Varian IX直线加速器6 MV X射线3～30 cm^2射野的百分深度剂量(Percentage Depth Dose,PDD),cross plane和in plane方向射野离轴比(Off Axis Ratio,OAR);比较两加速器PDD20、PDD10及OAR曲线的平坦度、对称性、射野宽度、半影等。采用一维Gamma分析方法,对两组PDD和OAR曲线进行匹配分析。结果联影uRT-linac 506c加速器的PDD_(10)和PDD_(20)相对于Varian IX的偏差分别为1.00%±0.64%和1.89%±0.94%,10 cm×10 cm射野的PDD_(20/10)偏差为1.22%;平坦度和对称性满足国家标准;uRT-linac 506c加速器射野半影较Varian IX增大(0.60±0.24)mm。一维Gamma匹配分析结果显示,各PDD曲线平均Gamma(1 mm/1%)通过率为98.26%;OAR曲线在射野内的平均Gamma(1 mm/1%)通过率是97.60%。结论国产联影uRT-linac 506c直线加速器与Varian IX直线加速器的X射线射野剂量学特性相近,PDD和OAR曲线匹配结果较好。

Objective To compare the beam dosimetry parameters between United Imaging uRT-linac 506 c and Varian IX linear accelerators. Methods The percentage depth dose(PDD) and off-axial ratio(OAR) in cross-plane and in-plane directions of United Imaging uRT-linac 506 c and Varian IX linear accelerators with 6 MV X ray and 3~30 cm2 beam were measured respectively via PTW MP3 water tank and PTW MEPHYSTO software. Meanwhile, PDD20, PDD10, and the flatness, symmetry,field and penumbra of OAR were compared. One dimension Gamma analysis method was adopted to analyze the matching degree of PDD and OAR curves. Results The deviations of PDD10 and PDD20 between United Imaging uRT-linac 506 c and Varian IX linear accelerators were 1.00%±0.64% and 1.89%±0.94%, respectively. The deviation of PDD20/10 was 1.22% in the beam of 10 cm×10 cm. The flatness and symmetry met the national standards. The field penumbrae of United Imaging uRT-linac 506 c accelerator was(0.60±0.24) mm lager than that of Varian IX. The results of one dimension Gamma analysis showed that the average Gamma(1 mm/1%) passing rate of PDD curves was 98.26%, while the average Gamma(1 mm/1%) passing rate of OAR curves within the radiation fields was 97.60%. Conclusion Domestic United Imaging uRT-linac 506 c linear accelerator has similar X-ray beam dosimetry characteristics with Varian IX linear accelerator, with good matching rate of PDD and OAR curves.