A primary research of intensity-modulated dose verification based on anatomic structure of three-dimensional images
Chen Along*, Chen Lixin, Chen Li, Hu Jiang, He Huilang, Xia Jingtao
*Department of Radiation Therapy, Sun Yat-sen University Cancer Center,Collaborative Innovation Center for Cancer Medicine,State Key Laboratory of Oncology in South China, Guangzhou 510060, China
Abstract：Objective To verify IMRT plans in point, planar and 3D dose, and to concretely analyze the dose differences of 3D anatomic structure based on Gamma passing rate. Methods Thimble ion-chamber, Matrixx and ArcCheck were separately used to measure six nasopharyngeal carcinoma treatment plans and six lung cancer treatment plans. The dose measurement deviation of the center point was compared as well as the Gamma passing rate of dose verification under the criteria of both 3%/3㎜ and 2%/2㎜,the group t-test and one-way ANOVA were also proceeded. 3DVH system was used to analyze the dose measurement deviation of target volume (TV) and organ at risk (OAR) through DVH. Results For IMRT and VMAT treatment plans, the mean deviation of point dose was (0.59±1.31)% and (－1.00±1.03)% respectively, and the maximum deviation was less than 3%. Under the criterion of 3%/3㎜, the Gamma passing rate measured by Matrixx, ArcCheck and 3DVH for IMRT plans was 96.28%,97.55% and 99.02% respectively, and for VMAT plans, the corresponding results of three different detectors were 97.24%,99.67% and 98.48%. The results analyzed and compared by 3DVH showed that even under the condition of high Gamma pass rate (more than 95% for a Gamma criterion of 3%/3 mm), the DVH metrics of both TV and OAR in two cases (account for 16.7% of the total plan) were significantly different on the clinical parameters, including GTV, spinal cord and brain stem etc. Conclusions The analysis of dose difference of the measurement results based on Gamma pass rate and on anatomic structure of 3D images can more effectively evaluate the influence of dose error to the implementing of clinical plan and the impact to the clinical treatment.
Chen Along*,Chen Lixin,Chen Li et al. A primary research of intensity-modulated dose verification based on anatomic structure of three-dimensional images[J]. Chinese Journal of Radiation Oncology, 2014, 23(4): 352-356.
[1] Zhen H, Nelms BE, Tomé WA. Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA[J]. Med Phys,2011,38:5477-5489. [2] Ezzell GA, Galvin JM, Low D, et al. Guidance document on delivery, treatment planning, and clinical implementation of IMRT:report of the IMRT subcommittee of the AAPM radiation therapy committee[J]. Med Phys,2003,30:2089-2115. [3] Bedford JL, Warrington AP. Commissioning of volumetric modulated arc therapy (VMAT)[J]. Int J Radiat Oncol Biol Phys,2009,73:537-545. [4] Yan G, Lu B, Kozelka J,et al. Calibration of a novel four-dimensional diode array[J]. Med Phys,2010,37:108-115. [5] Low DA, Harms WB, Mutic S, et al. A technique for the quantitative evaluation of dose distributions[J]. Med Phys,1998,25:656-661. [6] 林海磊,黄劭敏,邓小武,等.基于解剖在线测量的调强放疗三维剂量验证系统测试与应用[J].中华放射肿瘤杂志,2012,21:271-275. [7] Nelms BE, Zhen HM, Tome WA.Per-beam planar IMRT QA passing rates do not predict clinically relevant patient dose error[J]. Med Phys,2011,38:1037-1043. [8] Carrasco P, Jornet N, Latorre A, et al. 3D DVH-based metric analysis versus per-beam planar analysis in IMRT pretreatment verification[J]. Med Phys,20121,39:5040-5049. [9] Wolfsberger LD, Wagar M, Nitsch P, et al. Angular dose dependence of Matrixx TM and its calibration[J]. J Appl Clin Med Phys,2010,11:3057. [10] Nelms BE, Opp D, Robinson J, et al. VMAT QA:measurement-guided 4D dose reconstruction on a patient[J]. Med Phys,2012,39:4228-4238. [11] Zhu JH, Chen LX, Jin GH, et al. A comparison of VMAT dosimetric verifications between fixed and rotating gantry positions[J].Phys Med Biol,2013,58:1315-1322.
2014, Vol. 23 
