Comparison and evaluation of VMAT and IMRT for the treatment of initial treated nasopharyngeal carcinoma
ZHANG Dan-dan*, HUANG Shao-min, DENG Xiao-wu, ZHANG Guang-shun, HUANG Xiao-yan, SUN Wen-zhao, LING Hai-lei
*Department of Radiation Oncology, Cancer Center, Sun Yat-sen University, State Key Laboratory of Oncology in Southern China, Guangzhou 510060, China Corresponding author:HUANG Shao-min, Email:huangshm@sysucc.org.cn
Abstract：Objective To compare planning quality, treatment efficiency and delivery accuracy for initial treated nasopharyngeal carcinoma (NPC) with step & shoot intensity modulated radiation therapy (ss-IMRT) and volumetric modulated arc therapy (VMAT). These results will help make a clinic choice of the therapeutical technique. Methods Twenty-six NPC cases were planned with the same dose prescription and objective constrains by means of 9-field ss-IMRT and VMAT respectively.Compare:(1) plan dosimetric distribution, conformity index and homogeneity index of the targets, the average dose, maximum dose and interested dose-volume histograms of organs at risk (OAR) et al;(2) delivery times of the therapy plans ;(3) the accuracy of treatment plans dose verification. Results Both therapeutical plans can achieve the clinic dosimetric demands. Compared to ss-IMRT, VMAT had less inferior target coverage. The CI and HI of the PGTV was 0.57 and 0.08(ss-IMRT), 0.48 and 0.12(VMAT) respectively (t=－4.52,－8.33,P=0.000, 0.000). Except of brain stem, VMAT had higher mean dose and maximum dose of OARs than ss-IMRT (t=－9.57－－3.71,P=0.000－0.001). The spinal cord D1cc and parotids D50% were increased by 11.9% and 6.5% averagely. The treatment times of ss-IMRT and VMAT were 803.7 s and 389.3 s respectively (t=24.12,P=0.000), while VMAT decreasing by 51.6%. The pass ratios of γ(3 mm,3%) from the dose verification were 99.4%(ss-IMRT) and 98.0%(VMAT) respectively (t=5.19,P=0.000). Conclusions The dose distribution of VMAT for initial treated nasopharyngeal carcinoma can achieve the clinic demands, but slightly worse than 9-field ss-IMRT. VMAT has the advantage of high efficiency and dosimetric accuracy.
ZHANG Dan-dan*,HUANG Shao-min,DENG Xiao-wu et al. Comparison and evaluation of VMAT and IMRT for the treatment of initial treated nasopharyngeal carcinoma[J]. Chinese Journal of Radiation Oncology, 2012, 21(4): 364-368.
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2012, Vol. 21 
