Abstract：Objective To investigate the factors of effecting with γ index analysis of delivery for helical tomotherapy (HT). Methods Measuring γ index with the ArcCheck device for introduced errors in HT. The errors include setup errors in three-dimensional, the gantry angle error, calculating the dose in the phantom, low dose rate. All the results were compared with the 3%/3 mm and 2%/2 mm criteria. The effect of the accuracy in the application of kilovoltage computed tomography (KVCT) and mega-voltage computed tomography (MVCT) images in HT was also analyzed. Paired-t test method was used for difference compared. Results When the errors were introduced to the HT, theγ passing rate of left-right, superior-inferior, anterior-posterior direction dropped 2.7%, 7.2%, 3.6% under the 3%/3 mm criteria (P=0.002,0.022,0.007), with 4.6%,15.7%,7.6% under the 2%/2 mm criteria (P=0.001,0.003,0.002) respectively. There was no statistical significance for theγ passing between scanning the ArcCheck phantom with the KVCT and MVCT under the 3%/3 mm and 2%/2 mm criteria (98.6% vs 98.7%,P=0.859 and 92.7% vs 92.8%,P=0.984). Conclusions The errors of the setup position and machine paraments can lead to the dose delivery errors in HT, the quality accurance of machine and plan should be enhanced to minimize the dose errors. The results also showed that there is no difference of KVCT and MVCT image on the delivery of HT.
Yue Qi,Duan Jimei,Wang Zhiwei et al. The research on the factors of effecting with γ passing rate of delivery quality assurance for helical tomotherapy[J]. Chinese Journal of Radiation Oncology, 2014, 23(3): 269-271.
[1] Mackie TR, Holmes T, Swerdloff S, et al. Tomotherapy:a new concept for the delivery of conformal radiotherapy[J]. Med Phys,1993,20:1709-1719. [2] Yang JN,Mackie TR,Reckwerdt P,et al. An investigation of tomotherapy beam delivery[J]. Med Phys,1997,24:425-436. [3] 徐寿平,邓小武,戴相昆,等.螺旋断层放疗系统调强放射治疗验证[J].中华放射肿瘤学杂志,2008,17:395-397. [4] 徐寿平,解传滨, 戴相昆,等.二维半导体阵列实施旋转调强治疗计划验证的剂量学评估[J].中国医学物理学杂志,2009,26:1477-1494. [5] 解传滨,徐寿平,鞠忠建,等.二维电离室阵列与EDR2胶片在螺旋断层治疗计划剂量验证中的应用研究[J].中华放射肿瘤学杂志,2011,20:330-333. [6] Chong NS, Lee J, Kung WH, et al. Patient delivery quality assurance for linac-based IMRT and helical tomotherapy using solid state detectors[J]. Radiat Measurements,2011,46:1993-1995. [7] Li GJ,Zhang YJ,Jiang XQ, et al. Evaluation of the ArcCHECK QA system for IMRT and VMAT verification[J]. Phys Med,2013,29:295-303. [8] Feygelman V, Zhang G, Stevens C, et al. Evaluation of a new VMAT QA device evaluation of the ArcCHECK QA system for IMRT and VMAT verification. Physica Medical or the"X" and"O" array geometries[J]. Med Phys,2011,12:146-168. [9] Olch AJ. Evaluation of the accuracy of 3DVH software estimates of dose to virtual ion chamber and film in composite IMRT QA[J]. Med Phys,2012,39:81-86. [10] Nelmsb BE, Zhen H, Tomé WA, et al. Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors[J]. Med Phys,2011,38:1037-1044.
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