Objective To compare the γ passing rate between measurements at actual degree gantry angle and zero degree gantry angle for dose verification of intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma (NPC) and cervical carcinoma. Methods Thirty patients with NPC and thirty patients with cervical carcinoma were randomly chosen from 87 patients with NPC and 54 patients with cervical carcinoma, respectively. Using a gamma criterion of 3 mm/3%, the γ passing rates at actual gantry angle and zero degree gantry angle were measured using ArcCHECK and compared by paired t test. Results The γ passing rate was significantly lower at actual gantry angle than at zero degree gantry angle in patients with NPC or cervical carcinoma ((93.8±3.6)% vs. (97.8±1.1)%, P=0.00;(96.3±2.1)% vs. (98.2±1.0)%, P=0.00). Moreover, the variation range of the γ passing rate at actual gantry angle was larger than that at zero degree gantry angle. Both γ passing rates at actual gantryangle and zero degree gantryangle were lower in the patients with NPC than in the patients with cervical carcinoma. Conclusions
Compared with that at zero degree gantry angle, the γ passing rate at actual gantry angle is closer to reality. Therefore, the actual gantry angle is recommended for dose verification. In order to meet the clinical requirement, a higher standard of γ passing rate should be proposed when zero degree gantry angle is used for dose verification.
Jiang Renwei,Guo Shuanshuan,Chen Shuting et al. A comparative study of ArcCHECK measurements at actual and zero degree gantry angles for dose verification of intensity-modulated radiotherapy[J]. Chinese Journal of Radiation Oncology, 2017, 26(1): 66-68.
[1] Zhen HM,Nelms BE,Tomé WA.Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA[J].Med Phys,2011,38(10):5477-5489.DOI:10.1118/1.3633904.
[2] Ezzell GA,Galvin JM,Low D,et al. Guidance document on de-livery,treatment planning,and clinical implementation of IMRT:report of the IMRT subcommittee of the AAPM radiation therapy committee[J].Med Phys,2003,30(8):2089-2115.DOI:10.1118/1.1591194.
[3] Bedford JL,Warrington AP.Commissioning of volumetric mod-ulated arc therapy (VMAT)[J].Int J Radiat Oncol Biol Phys,2009,73(1):53-60.DOI:10.1016/j.ijrobp.2008.08.055.
[4] Low DA,Moran JM,Dempsey JF,et al. Dosimetry tools and techniques for IMRT[J].Med Phys,2011,38(3):1313-1338.DOI:10.1118/1.3514120.
[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 ZW,et al. The research on the factors of effecting with γ passing rate of delivery quality assurance for helical tomotherapy[J].Chin J Radiat On-col,2014,23(3):269-271.DOI:10.3760/cma.j.issn.1004-4221.2014.03.024.
[6] 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.DOI:10.3760/cma.j.issn.1004-4221.2013.03.024.
Li CQ,Li GJ,Ji CX,et al. The characteristics and clinical application of the ArcCHECK diode array for volume-tric-modulated arc therapy verification[J].Chin J Radiat On-col,2013,22(3):253-257.DOI:10.3760/cma.j.issn.1004-4221.2013.03.024.
[7] Létourneau D,Gulam M,Yan D,et al. Evaluation of a 2D diode array for IMRT quality assurance[J].Radliother On-col,2004,70(2):199-206.DOI:10.1016/j.radonc.2003.10.014.
[8] Yan GH,Lu B,Kozelka J,et al. Calibration of a novel four-dimensional diode array[J].Med Phys,2010,37(1):108-115.DOI:10.1118/1.3266769.
[9] Kozelka J,Robinson J,Nelms B,et al. Optimizing the accuracy of a helical diode array dosimeter:a comprehensive cali-bration methodology coupled with a novel virtual incli-nometer[J].Med Phys,2011,38(9):5021-5032.DOI:10.1118/1.3622823.
[10] 徐庆丰,周莉,李涛,等.重力对二维探测器阵列验证静态调强计划的影响[J].华西医学,2010,25(12):2143-2146.
Xu QF,Zhou L,Li T,et al. Impacts of gravity on the verification of intensity-modulated radiotherapy plans with 2-dimensional detector arrays[J].West China Med J,2010,25(12):2143-2146.
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