Abstract：Objective To study the iso-center point coincidence of two accelerators with treatment planning system (TPS) based on γ passing rates of intensity-modulated radiotherapy (IMRT) plan verification. Methods Twenty-one IMRT plans were verified by Varian accelerator and twenty by Elekta accelerator with a gamma criterion of 3 mm/3%. The passing rates were measured when the iso-center point of TPS had -2,-1, 0, 1, and 2 mm shift in the x or y direction. A binomial curve of γ was fit to figure out the values of the two accelerators on the x and y axes when γ value reached the maximum. The γ pass rate difference was analysed by χ2 test. Results The mean values of γ-2,γ-1, γ0, γ1, and γ2 in the x direction were (92.56±3.27)%,(96.53±1.82)%,(96.13±1.41)%,(90.14±2.87)%, and (82.28±4.69)% for Varian accelerator, and (94.82±2.04)%,(97.05±2.02)%,(98.38±1.33)%,(97.96±1.44)%, and (94.49±2.34)% for Elekta accelerator. There was no significant difference in the mean value of γ0between the two accelerators (P=0.332). When γ value reached the maximum, the values on the x and y axes were-0.65 and-0.30 mm for Varian accelerator and 0.01 and 0.30 mm for Elekta accelerator, respectively. Conclusions In the same TPS, different accelerators have different degrees of coincidence of the actual field center point with the iso-center point of TPS, to which more attention should be paid in clinical practice.
Sun Xiaoyang,Yang Bo,Pang Haowen et al. A study of the iso-center point coincidence between accelerator and radiotherapy planning system[J]. Chinese Journal of Radiation Oncology, 2016, 25(6): 625-627.
[1] 李兴德,赵瑾,张明云等.胸部肿瘤放疗两种体膜固定方法的摆位精度分析[J].中华放射肿瘤学杂志,2013,22(5):397-399.DOI:10.3760/cma.j.issn.1004-4221.2013.05.017. Li XD,Zhao J,Zhang MY,et al. Analysis of set-up accuracy of two body membrane fixation methods in radiotherapy for thoracic neoplasms[J].Chin J Radiat Oncol, 2013,22(5):397-399.DOI:10.3760/cma.j.issn.1004-4221.2013.05.017. [2] 彭应林,刘松然,黄伯天等.图像配准方法对肺癌放疗图像引导摆位精度的影响[J].中华放射肿瘤学杂志,2015,24(2):184-188. DOI:10.3760/cma.j.issn.1004-4221.2015.02.019. Peng YL, Liu SR,Huang BT,et al. The accuracy of image registration methods for image-guided positioning in lung cancer radiotherapy[J]. Chin J Radiat Oncol, 2015,24(2):184-188.DOI:10.3760/cma.j.issn.1004-4221.2015.02.019. [3] Low DA,Harms WB,Mutic S,et al A technique for the quantitative evaluation of dose distributions[J]. Med Phys,1998,25(5):656-661.DOI:dx.doi.org/10.1118/1.598248. [4] Low DA,Dempsey JF. Evaluation of the gamma dose distribution comparison method[J]. Med Phys,2003,30(9):2455-2464.DOI:dx.doi.org/10.1118/1.1598711. [5] 岳麒,段继梅,王志伟等.螺旋断层治疗剂量验证γ通过率影响因素研究[J].中华放射肿瘤学杂志,2014,23(3):269-271.DOI:10.3760/cma.j.issn.1004-4221.2014.03.024. Yue Q,Duan JM,Wang ZHW,et al. The research on the factors of effecting with γ passing rate of delivery quality assurance for helical tomotherapy[J].Chin J Radiat Oncol,2014,23(3):269-271.DOI:10.3760/cma.j.issn.1004-4221.2014.03.024. [6] 张建英.插值对二维电离室矩阵调强验证Gamma通过率的影响[J].中国医学物理学杂志,2010,27(6):2224-2226.DOI:10.3969/j.issn.1005-202X.2010.06.006. Zhang JY. The Effort to Gamma Pass Rates of Interpolation During the 2D Chamber Array IMRT QA[J]. Chinese Journal of Medical Physics,2010,27(6):2224-2226.DOI:10.3969/j.issn.1005-202X.2010.06.006. [8] 曹午飞,黄晓延,孙文钊等.剂量分布验证中分辨率对Gamma通过率的影响[J].中华放射肿瘤学杂志,2012,21(2):172-175.DOI:10.3760/cma.j.issn.1004-4221.2012.02.023. Cao WF,Huang XY,Sun WZH,et al. The impact of resolution to Gamma pass rate in the verification of dose distribution[J].Chin J Radiat Oncol,2012,21(2):172-175.DOI:10.3760/cma.j.issn.1004-4221.2012.02.023. [9] 张达光,蒋胜鹏,杨成文等.计算分辨率对调强放疗计划验证Gamma通过率的影响[J].国际生物医学杂志,2014,37(2):103-114.DOI:10.3760/cma.j.issn.1673-4181.2014.02.009. Zhang DG,Jiang SHP,Yang CHW,et al. Impact of calculation resolution on Gamma pass rate for plan verification of intensity-modulated radiotherapy[J]. International Journal of Biomedical Engineering,2014,37(2):103-114.DOI:10.3760/cma.j.issn.1673-4181.2014.02.009.
2016, Vol. 25 
