[an error occurred while processing this directive] | [an error occurred while processing this directive]
Deviation analysis of plan verification results of 260 volumetric modulated arc therapy plans
Wang Bin, Chen Lixin, Zhang Dandan, Hu Jiang, Liu Boji, Chen Along
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 investigate the γ pass rate and contributing factors by summarizing the plan verification results of 260 volumetric modulated arc therapy (VMAT) plans. Methods From 2010 to 2012,two different detector arrays (MapCheck2,Sun,Nuclear,USA;Delta4ScandiDos,Swenden) were used for plan verification in 260 patients. The measured dose distributions were compared with the calculation results of treatment planning system using γ pass rate (Pγ≤1 for 2%/2 mm, 3%/3 mm and 5%/3 mm, threshold 10%).And the results were put under independent-samples t test. The impact of multi-leaf collimator (MLC) on the γ pass rate (3%/3 mm) was analyzed. Results The average γ pass rates of 2%/2 mm, 3%/3 mm and 5%/3 mm of 260 VMAT plans were 91.7%, 98.5% and 99.7%, respectively. Among 260 VMAT plans, 3 VMAT plans (1.2% of the total) failed to meet the clinical acceptable pass rate and needed to be redesigned or re-optimized. The γ pass rate of 2%/2 mm was slightly different between two measurement devices (90.0% vs 93.5%,P=0.000), while the γ pass rate of 3%/3 mm showed no significant difference between two measurement devices and two accelerators (98.5% vs 98.5%,P=0.926 and 98.5% vs 98.6%,P=0.670). The γ pass rate (3%/3 mm) of the treatment plan before MLC calibration was 61.1%, compared to 94.1% after calibration. Conclusions Most dose verification results of treatment plans can meet the clinical requirement.Gantry rotation may influence the γ pass rate of VMAT dose verification under stricter pass rate standard (2%/2 mm). MLC calibration is essential for VMAT.
Wang Bin,Chen Lixin,Zhang Dandan et al. Deviation analysis of plan verification results of 260 volumetric modulated arc therapy plans[J]. Chinese Journal of Radiation Oncology, 2014, 23(3): 252-255.
Wang Bin,Chen Lixin,Zhang Dandan et al. Deviation analysis of plan verification results of 260 volumetric modulated arc therapy plans[J]. Chinese Journal of Radiation Oncology, 2014, 23(3): 252-255.
[1] Li QL, Deng XW, Chen LX, et al. The angular dependence of a 2 dimensional diode array and the feasibility of its application in verifying the composite dose distribution of intensity modulated radiation therapy[J]. Chin J Cancer,2010,29:617-620. [2] Jursinic PA, Sharma R, Reuter J. MapCHECK used for rotational IMRT measurements:step-and-shoot, TomoTherapy, RapidArc[J].Med Phys,2010,37:2837-2846. [3] 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. [4] Low DA, Dempsey JF. Evaluation of the gamma dose distribution comparison method[J]. Med Phys,2003,30:2455-2464. [5] Ezzell GA, Burmeister JW, Gogan N, et al. IMRT commissioning:multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119[J]. Med Phys,2009,36:5359-5373. [6] Basran PS, Woo MK. An analysis of tolerance levels in IMRT quality assurance procedures[J]. Med Phys,2008,35:2300-2307. [7] Tatsumi D, Hosono MN, Nakada R, et al. Direct impact analysis of multi-leaf collimator leaf position errors on dose distributions in volumetric modulated arc therapy:a pass rate calculation between measured planar doses with and without the position errors[J]. Phys Med Biol,2011,56:237-246. [8] Oliver M, Gagne I, Bush K, et al. Clinical significance of multi-leaf collimator positional errors for volumetric modulated arc therapy[J]. Radiother Oncol,2010,97:554-560.
2014, Vol. 23 
