应用二维半导体矩阵进行螺旋断层加速器射野离轴剂量分布稳定性的分析

Off-axis dose distribution of tomotherapy accelerator analyzed with two-dimensional diode array

目的:利用二维半导体矩阵TomoDose定期检测螺旋断层直线加速器射野离轴剂量分布,分析其稳定性。方法:在正确摆位条件下,分别用二维半导体矩阵TomoDose和三维扫描水箱BPH测量螺旋断层直线加速器射野的横向截面剂量分布和纵向截面剂量分布,将两种设备测量结果进行比较,确定TomoDose准确性,并且于前5周重复测量5次,检测二维半导体矩阵的重复性。分析后续自2016年3~9月共计25次TomoDose测量结果,分析螺旋断层直线加速器离轴剂量分布稳定性。结果:TomoDose和三维扫描水箱BPH测量的横向及纵向截面剂量分布曲线进行γ分析(2 mm/2%),通过率平均值分别为97.8%和95.6%。25周测量结果与首次水箱测量值相比,横向为(97.9±0.6)%,纵向为(96.2±0.7)%。结论:二维半导体矩阵TomoDose测量的射野离轴剂量分布曲线与三维扫描水箱BPH测量的结果具有较好的一致性,通过该设备测量可知螺旋断层直线加速器具有较好的束流稳定性。

Objective To periodically measure the off-axis dose distribution of tomotherapy linear accelerator using two-dimensional （2D） diode array and to analyze the consistency of the off-axis dose distribution.Methods With the patients in proper setup,the dose distribution in transverse and longitudinal beam fields of tomotherapy linear accelerator were measured using 2D diode array TomoDose and blue phantom helix （BPH）,separately,and the results measured by the two devices were compared in order to verify the accuracy of TomoDose.The repeatability of TomoDose was detected by repeating the experiment 5 times in the first 5 weeks.A total of 25 TomoDose measured data obtained from March to September,2016 was analyzed to evaluate the consistency of the off-axis dose distributions of tomotherapy linear accelerator.Results The Gamma passing rates （2 mm/2%）of dose distributions in transverse and longitudinal beam fields measured by TomoDose and BPH were 97.8% and 95.6%,respectively,and that of the measured results after 25 weeks compared with the first data measured by BPH was （97.9±0.6）% in transverse profile and （96.2±0.7）% in longitudinal profile.Conclusion 2D diode array TomoDose shows a good consistency with BPH in the measurement of off-axis dose distribution of tomotherapy linear accelerator,and the measurement shows that tomotherapy linear accelerator has a good beam consistency.