Sensitivity of passing rates of intensity-modulated radiotherapy plans in dose verification against gantry angle errors
Wang Ning,Wang Bin,Chen Along,Huang Xiaoyan
Department of Medical Imaging,Zhongshan Traditional Chinese Medicine Hospital,Zhongshan 528400,China (Wang N); State Key Laboratory of Oncology in South China,Department of Radiation Oncology,Cancer Center,Sun Yat-sen University,Guangzhou 510060,China (Wang B,Chen AL,Huang XY)
Abstract： Objective To analyze the sensitivity of passing rates of intensity modulated radiation therapy (IMRT) plans in dose verification against gantry angle errors. Methods Gantry angle errors (±2.0°, ±1.0°, and ±0.5°) were introduced into the clinical IMRT plans of 9 patients. There were 7 IMRT plans for each patient, containing 1 original IMRT plan and 6 IMRT plans with gantry angle errors. The dose distribution of the original and modified plans for each patient was measured by ArcCHECK array. Based on the dose distribution of the original plan, the passing rate of each plan was calculated using absolute distance to agreement (DTA) analysis and Gamma analysis with the criteria of 3%/3 mm and 2%/2 mm. The obtained passing rates were analyzed by non-parametric Wilcoxon rank test. Results Under the criteria of 3%/3 mm, the mean passing rate in 9 original IMRT plans was 95.2% using DTA analysis and 96.5% using Gamma analysis. According to Gamma analysis, the plans with gantry angle errors of-2.0°,2.0°,1.0°,-0.5°, and 0.5°had the mean passing rates decreased by 12.2%, 23.5%, 6.3%, 0.9%, and 2.9%, respectively (P=0.008,0.008,0.008,0.036,0.012). According to DTA analysis, the above plans had the mean passing rates decreased by 16.2%, 23.8%, 1.7%, 6.8%, and 3%, respectively (all P=0.008). The passing rates calculated by DTA method were more sensitive to the gantry angle errors than those by Gamma method, while the passing rates under the criterion of 2%/2 mm were more sensitive than those under the criterion of 3%/3 mm. Conclusions The greater the gantry angle errors, the larger the decrease in the mean passing rate. IMRT dose verification is even sensitive enough to detect the gantry angle errors within 0.5°. Enhanced quality control and assurance of gantry angle is needed to guarantee the accuracy of IMRT delivery.
Wang Ning,Wang Bin,Chen Along et al. Sensitivity of passing rates of intensity-modulated radiotherapy plans in dose verification against gantry angle errors[J]. Chinese Journal of Radiation Oncology, 2016, 25(12): 1327-1330.
[1] 戴建荣,胡逸民,张红志,等.,针对患者调强放射治疗计划的剂量学验证[J].中华放射肿瘤学杂志,2004,13(3):229-233.10.3760/j.issn:1004-4221.2004.03.020. Dai JR,Hu JM,Zhang HZ,et al. Plan-specific dosimetric verification for patient treated with intensity-modulated radiation therapy[J].Chin J Radiat Oncol,2004,13(3):229-233.10.3760/j.issn:1004-4221.2004.03.020. [2] 黄晓延,黄劭敏,张黎,等.三维治疗计划系统的剂量学验证[J].中华放射肿瘤学杂志,2006,11(15):496-500.10.3760/j.issn:1004-4221.2006.06.015. Huang XY,Huang SM,Zhang L,et al. Dosimetric verification of a commercial three-dimension treatment planning system[J].Chin J Radiat Oncol,2006,11(15):496-500.10.3760/j.issn:1004-4221.2006.06.015. [3] Li GJ,Zhang YJ,Jiang XQ,et al. Evaluation of the ArcCHECK QA system for IMRT and VMAT verification[J].Phys Med,2013,29(3):295-303.http://dx.doi.org/10.1016/j.ejmp.2012.04.005. [4] 李成强,李光俊,冀传仙,等.ArcCHECK半导体探头特性及在容积调强弧形治疗剂量验证应用研究[J].中华放射肿瘤学杂志,2013,22(3):253-257.10.3760/cma.j.issn.1004-4221.2013.03.024. Li CQ,Li GJ,Ji CC,et al. The characteristics and clinical application of the ArcCHECK diode array for volumetric-modulated arc therapy verification[J].Chin J Radiat Oncol,2013,22(3):253-257.10.3760/cma.j.issn.1004-4221.2013.03.024. [5] Bedford JL,Lee YK,Wai P,et al. Evaluation of the Delta4 phantom for IMRT and VMAT verification[J].Phys Med Biol,2009,54(9):N167-N176.10.1088/0031-9155/54/9/N04. [6] 蒋胜鹏,李智华.加速器机架角度对多叶准直器叶片到位精度的影响[J].中华放射肿瘤学杂志,2009,18(4):317-320.10.3760/cma.j.issn.1004-4221.2009.04.317. Jiang SHP,Li ZHH.The accelerator gantry angle position accuracy of multi leaf collimator[J].Chin J Radiat Oncol,2009,18(4):317-320.10.3760/cma.j.issn.1004-4221.2009.04.317. [7] 阮长利,徐利明,宋启斌,等.不同机架角时多叶准直器叶片对不同调强放疗剂量影响[J].中华放射肿瘤学杂志,2011,20(4):345-347.10.3760/cma.j.issn.1004-4221.2011.04.024. Ruan CL,Xu LM,Song QB,et al. Impact of accelerator′s multi-leaf collimator leaves on the intensity modulated radiation therapy dose at different gantry angles[J].Chin J Radiat Oncol,2011,20(4):345-347.10.3760/cma.j.issn.1004-4221.2011.04.024. [8] Garcia-Vicente F,Fernandez V,Bermúdez R,et al. Sensitivity of a helical diode array device to delivery errors in IMRT treatment and establishment of tolerance level for pretreatment QA[J].J Appl Clin Med Phys,2012,13(1):3660.10.1120/jacmp.v13i1.3660. [9] Jursinic PA,Nelms BE.A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery[J].Med Phys,2003,30(5):870-879.10.1118/1.1567831. [10] Low DA,Harms WB,Mutic S,et al. A technique for the quantitative evaluation of dose distributions[J].Med Phys,1998,25(5):656-661.10.1118/1.598248. [11] Low DA,Dempsey JF.Evaluation of the gamma dose distribution comparison method[J].Med Phys,2003,30(9):2455-2464.10.1118/1.1598711. [12] Low D A,Moran JM,Dempsey JF,et al. Dosimetry tools and techniques for IMRT[J].Med Phys,2011,38(3):1313-1338.10.1118/1.3514120. [13] Kutcher G J,Coia L,Gillin M,et al. Comprehensive QA for radiation oncology:report of AAPM radiation therapy committee task group 40[J].Med Phys,1994,21(4):581-618.10.1118/1.597316.
2016, Vol. 25 
