Objective To analyze setup errors in cone beam computed tomography (CBCT)-guided radiotherapy for nasopharyngeal cancer (NPC) and evaluate the use frequency of CBCT. Methods Twenty-six patients newly diagnosed with NPC who received CBCT scan no less than 3 times per week during the whole course (7 weeks) of intensity-modulated radiotherapy (IMRT) were enrolled as subjects. Two setup errors were recorded each week:the setup error in the first CBCT analysis (Ef) and the setup error in the subsequent CBCT analysis (Ec). Comparisons of Ef between two different weeks, Ec between two different weeks, and between Ef and Ec in the same week were made by analysis of variance. Resutls During the 7 weeks, there were no significant differences in Ef in the medial-lateral (ML), superior-inferior (SI), or anterior-posterior (AP) direction between any two weeks (all P>0.05);there were also no significant differences in Ec in the ML or SI direction between any two weeks (all P>0.05);there was a significant difference in Ec in the AP direction between two different weeks (P<0.05);there were no significant differences between Ef and Ec in the ML or SI direction in any week (P>0.05);there were also no significant differences between Ef and Ec in the AP direction in any week (P>0.05) except for the first week (P<0.05). Conclutions In IMRT for NPC, the setup errors in the ML and SI directions are stable in the whole course of radiotherapy, while the setup errors in the AP direction are different between the first week and subsequent weeks. Daily CBCT scan in the first week and weekly CBCT scan in the subsequent weeks are highly recommended for most patients to reduce the use frequency of CBCT.
Li Xiaoyu,Zhong Renming,Zhou Jidan et al. Frequency of cone beam computed tomography guidance in radiotherapy for nasopharyngeal carcinoma[J]. Chinese Journal of Radiation Oncology, 2017, 26(11): 1259-1262.
[1] Wu WCV,Leung WS,Kay SS,et al. A comparison between electronic portal imaging device and cone beam CT in radiotherapy verification of nasopharyngeal carcinoma[J].Med Dosim,2011,36(1):109-112.DOI:10.1016/j.meddos.2010.01.005.
[2] Zhou ZX,Chen W,Shen M,et al. Cone beam computed tomographic analyses of alveolar bone anatomy at the maxillary anterior region in Chinese adults[J].J Biomed Res,2014,28(6):498-505.DOI:10.7555/JBR.27.20130002.
[3] Nabavizadeh N,Elliott DA,Chen YY,et al. Image Guided Radiation Therapy (IGRT) practice patterns and IGRT’s impact on workflow and treatment planning:results from a national survey of American society for radiation oncology members[J].Int J Radiat Oncol Biol Phys,2016,94(4):850-857.DOI:10.1016/j.ijrobp.2015.09.035.
[4] Cheo T,Loh Y,Chen D,et al. Measuring radiotherapy setup errors at multiple neck levels in nasopharyngeal cancer (NPC):a case for differential PTV expansion[J].Radiother Oncol,2015,117(3):419-424.DOI:10.1016/j.radonc.2015.09.032.
[5] Ding GX,Coffey CW.Radiation dose from kilovoltage cone beam computed tomography in an image-guided radiotherapy procedure[J].Int J Radiat Oncol Biol Phys,2009,73(2):610-617.DOI:10.1016/j.ijrobp.2008.10.006.
[6] Alaei P,Ding G,Guan HQ.Inclusion of the dose from kilovoltage cone beam CT in the radiation therapy treatment plans[J].Med Phys,2010,37(1):244-248.DOI:10.1118/1.3271582.
[7] Hyer DE,Hintenlang DE.Estimation of organ doses from kilovoltage cone-beam CT imaging used during radiotherapy patient position verification[J].Med Phys,2010,37(9):4620-4626.DOI:10.1118/1.3476459.
[8] Perks JR,Lehmann J,Chen AM,et al. Comparison of peripheral dose from image-guided radiation therapy (IGRT) using kV cone beam CT to intensity-modulated radiation therapy (IMRT)[J].Radiother Oncol,2009,89(3):304-310.DOI:10.1016/j.radonc.2008.07.026.
[9] Sykes JR,Amer A,Czajka J,et al. A feasibility study for image guided radiotherapy using low dose,high speed,cone beam X-ray volumetric imaging[J].Radiother Oncol,2005,77(1):45-52.DOI:10.1016/j.radonc.2005.05.005.
[10] 刘裕杰,周莉钧,管西寅,等.图像引导的放射治疗在头颈部肿瘤治疗中的应用[J].中国癌症杂志,2010,20(9):707-711.DOI:10.3969/j.issn.1007-3639.2010.09.014.
Liu YJ,Zhou LJ,Guan XY,et al. Application of image-guided radiotherapy in head-and-neck cancer[J].China Oncol,2010,20(9):707-711.DOI:10.3969/j.issn.1007-3639.2010.09.014.
[11] 岳丹,杨永净,赵玲,等.kV-CBCT图像引导鼻咽癌IMRT的精确性研究[J].中华放射医学与防护杂志,2016,36(3):211-215.DOI:10.3760/cma.j.issn.0254-5098.2016.03.010.
Yue D,Yang YJ,Zhao L,et al. Clinical feasibility and accuracy of image guidance with kilovoltage cone-beam computed tomography in nasopharyngeal carcinoma intensity-modulated radiotherapy[J].Chin J Radiol Med Prot,2016,36(3):211-215.DOI:10.3760/cma.j.issn.0254-5098.2016.03.010.
[12] 林承光,李国文,刘晓臻,等.鼻咽癌调强放射治疗摆位不确定度对危及器官计划体积(PRV)影响的研究[J].癌症,2008,27(3):327-330.DOI:10.3321/j.issn:1000-467X.2008.03.021.
Lin CG,Li GW,Liu XZ,et al. Influence of patient setup error on planning risk volumes for nasopharyngeal carcinoma patients receiving intensity-modulated radiation therapy[J].Chin J Cancer,2008,27(3):327-330.DOI:10.3321/j.issn:1000-467X.2008.03.021.
[13] Mongioj V,Orlandi E,Palazzi M,et al. Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends,PTV and PRV margins[J].Acta Oncol,2011,50(1):61-71.DOI:10.3109/0284186X.2010.509108.
2017, Vol. 26 
