Determination of Setup Margin for Nasopharyngeal Carcinoma by Using Electroinc Portal Imaging Device
Abstract
Introduction: This study aimed to assess three-dimensional (3D) setup mistakes and provide optimal margins for planned target volume (PTV) coverage in head and neck radiation. Methods: Ten patients participated in the trial, receiving IMRT in conjunction with weekly electronic portal imaging (EPI). A total of 170 portal pictures were analyzed. The systematic (S) and random (s) errors in the population of patients with head and neck cancer were assessed using portal images in the caudocranial longitudinal (CC) and left-right lateral (LR) orientations, measured within the anterior-posterior (AP) field. The clinical-to-planning target volume (CTV-PTV) margins were determined in accordance with ICRU Report 62 guidelines and van Herk’s formulae. Results: The group systematic errors and random errors were 0.19 and 0.26 cm , respectively in the anteroposterior direction; the group systematic errors and random errors were 0.15 cm and 0.24 cm in SI direction, respectively; the group systematic errors and random errors were 0.13 cm and 0.25 cm in LR direction, respectively; According to the classical van-Herk formula MPTV =2.5Σ +0.7σ, we figured out the ideal PTV margins (MPTV) based on the setup errors and 0.65 cm, 0.55 cm, and 0.5 cm were required in the AP, SI, and RL directions. Discussion and conclusions: we can conclude that a 6-mm extension of CTV to PTV margin, as the optimal margin and can be reduced with increasing frequency of online verification (daily imaging) or for patients where the prescribed does not exceed tolerance doses for organs at risk.
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References
R. Wang, and M. Kang, “Guidelines for radiotherapy of nasopharyngeal carcinoma,” Precis. Radiat. Oncol. 5(3), 122–159 (2021). https://doi.org/10.1002/pro6.1123
W.T. Ng, J.C.H. Chow, J.J. Beitler, J. Corry, W. Mendenhall, A.W.M. Lee, K.T. Robbins, S. Nuyts, N.F. Saba, R. Smee, W.A. Stokes, P. Strojan, and A. Ferlito, “Current Radiotherapy Considerations for Nasopharyngeal Carcinoma †,” Cancers (Basel). 14(23), 5773 (2022). https://doi.org/10.3390/cancers14235773
P. Blanchard, J. Biau, F. Huguet, S. Racadot, C. Berthold, S. Wong-Hee-Kam, M.-C. Biston, and P. Maingon, “Radiotherapy for nasopharyngeal cancer,” Cancer/Radiothérapie 26(1–2), 168–173 (2022). https://doi.org/10.1016/j.canrad.2021.08.009
P.L. Yip, R. You, M.-Y. Chen, and M.L.K. Chua, “Embracing Personalized Strategies in Radiotherapy for Nasopharyngeal Carcinoma: Beyond the Conventional Bounds of Fields and Borders,” Cancers (Basel). 16(2), 383 (2024). https://doi.org/10.3390/cancers16020383
A. Sharma, and A. Bahl, “Intensity-modulated radiation therapy in head-and-neck carcinomas: potential beyond sparing the parotid glands,” J. Cancer Res. Ther. 16(3), 425–433 (2020). https://doi.org/10.4103/jcrt.JCRT_880_18
E. Anderson, K. Pilling, S. Iqbal, and R.L. Pearson, “A retrospective analysis comparing set up errors from standard versus customised headrests for head and neck radiotherapy,” Radiography 28(3), 746–750 (2022). https://doi.org/10.1016/j.radi.2022.03.008
I. Kaur, S. Rawat, P. Ahlawat, A. Kakria, G. Gupta, U. Saxena, and M.B. Mishra, “Dosimetric impact of setup errors in head and neck cancer patients treated by image-guided radiotherapy,” J. Med. Phys. 41(2), 144–148 (2016). https://doi.org/10.4103/0971-6203.181640
Y. Chang, F. Xiao, H. Quan, and Z. Yang, “Evaluation of OAR dose sparing and plan robustness of beam-specific PTV in lung cancer IMRT treatment,” Radiat. Oncol. 15, 1–12 (2020). https://doi.org/10.1186/s13014-020-01686-1
K. Bell, N. Licht, C. Rübe, and Y. Dzierma, “Image guidance and positioning accuracy in clinical practice: influence of positioning errors and imaging dose on the real dose distribution for head and neck cancer treatment,” Radiat. Oncol. 13, 1–13 (2018). https://doi.org/10.1186/s13014-018-1141-8
J. Willner, U. Hädinger, M. Neumann, F.J. Schwab, K. Bratengeier, and M. Flentje, “Three dimensional variability in patient positioning using bite block immobilization in 3D-conformal radiation treatment for ENT-tumors,” Radiother. Oncol. 43(3), 315–321 (1997). https://doi.org/10.1016/S0167-8140(97)00055-8
L. Gilbeau, M. Octave-Prignot, T. Loncol, L. Renard, P. Scalliet, and V. Grégoire, “Comparison of setup accuracy of three different thermoplastic masks for the treatment of brain and head and neck tumors,” Radiother. Oncol. 58(2), 155–162 (2001). https://doi.org/10.1016/S0167-8140(00)00280-2
I. Rabinowitz, J. Broomberg, M. Goitein, K. McCarthy, and J. Leong, “Accuracy of radiation field alignment in clinical practice,” Int. J. Radiat. Oncol. Biol. Phys. 11(10), 1857–1867 (1985). https://doi.org/10.1016/0360-3016(85)90046-X
R.-D. Kortmann, C.F. Hess, R. Jany, C. Meisner, and M. Bamberg, “Reproducibility of field alignment in difficult patient positioning,” Int. J. Radiat. Oncol. Biol. Phys. 29(4), 869–872 (1994). https://doi.org/10.1016/0360-3016(94)90578-9
S. Kumar, K. Burke, C. Nalder, P. Jarrett, C. Mubata, R. A’hern, M. Humphreys, M. Bidmead, and M. Brada, “Treatment accuracy of fractionated stereotactic radiotherapy,” Radiother. Oncol. 74(1), 53–59 (2005). https://doi.org/10.1016/j.radonc.2004.06.008
C.F. Hess, R.-D. Kortmann, R. Jany, A. Hamberger, and M. Bamberg, “Accuracy of field alignment in radiotherapy of head and neck cancer utilizing individualized face mask immobilization: a retrospective analysis of clinical practice,” Radiother. Oncol. 34(1), 69–72 (1995). https://doi.org/10.1016/0167-8140(94)01497-Q
A. Bel, R. Keus, R.E. Vijlbrief, and J. V Lebesque, “Setup deviations in wedged pair irradiation of parotid gland and tonsillar tumors, measured with an electronic portal imaging device,” Radiother. Oncol. 37(2), 153–159 (1995). https://doi.org/10.1016/0167-8140(95)01627-S
A. Bel, M. Van Herk, H. Bartelink, and J. V Lebesque, “A verification procedure to improve patient set-up accuracy using portal images,” Radiother. Oncol. 29(2), 253–260 (1993). https://doi.org/10.1016/0167-8140(93)90255-7
S. Molana, F. Arbabi, M. Sanei, E. Hashemi, M. Tajvidi, A. Rostami, A. Tavakol, P. Kiani, Z. Fazli, and H. Ghaffari, “Evaluation of patient setup accuracy and determination of optimal setup margin for external beam radiation therapy using electronic portal imaging device,” Cancer Ther. Oncol. Int. J. 11(2), 48–55 (2018). http://dx.doi.org/10.19080/CTOIJ.2018.11.555808
I.-C. Costin, and L.G. Marcu, “Factors impacting on patient setup analysis and error management during breast cancer radiotherapy,” Crit. Rev. Oncol. Hematol. 178, 103798 (2022). https://doi.org/10.1016/j.critrevonc.2022.103798
T. Gupta, S. Chopra, A. Kadam, J.P. Agarwal, P.R. Devi, S. Ghosh-Laskar, and K.A. Dinshaw, “Assessment of three-dimensional set-up errors in conventional head and neck radiotherapy using electronic portal imaging device,” Radiat. Oncol. 2, 1–8 (2007). https://doi.org/10.1186/1748-717X-2-44
A. Farajollahi, N. Mohammadzadeh, M. Momennezhad, S. Naseri, S. Mohebbi, F. Shahedi, and S. Mohebbi, “Evaluation of Patient Set Up Errors in Head and Neck Three-Dimensional (3D) Conformal and Intensity-Modulated Radiotherapy Using Electronic Portal Imaging Device,” Iran. J. Med. Phys. 19(5), 270–274 (2022). https://doi.org/10.22038/ijmp.2022.58298.1977
J. Bijhold, J.V. Lebesque, A.A.M. Hart, and R.E. Vijlbrief, “Maximizing setup accuracy using portal images as applied to a conformal boost technique for prostatic cancer,” Radiother. Oncol. 24(4), 261–271 (1992). https://doi.org/10.1016/0167-8140(92)90233-K
C.L. Creutzberg, V.G.M. Althof, H. Huizenga, A.G. Visser, and P.C. Levendag, “Quality assurance using portal imaging: the accuracy of patient positioning in irradiation of breast cancer,” Int. J. Radiat. Oncol. Biol. Phys. 25(3), 529–539 (1993). https://doi.org/10.1016/0360-3016(93)90077-9
L. Dong, and A.L. Boyer, “An image correlation procedure for digitally reconstructed radiographs and electronic portal images.,” Int. J. Radiat. Oncol. Biol. Phys. 33(5), 1053–1060 (1995). https://doi.org/10.1016/0360-3016(95)02082-9
T.S. Hong, W.A. Tomé, R.J. Chappell, P. Chinnaiyan, M.P. Mehta, and P.M. Harari, “The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy,” Int. J. Radiat. Oncol. Biol. Phys. 61(3), 779–788 (2005). https://doi.org/10.1016/j.ijrobp.2004.07.696
B. van Asselen, H. Dehnad, C.P.J. Raaijmakers, J.J.W. Lagendijk, and C.H.J. Terhaard, “Implanted gold markers for position verification during irradiation of head-and-neck cancers: a feasibility study,” Int. J. Radiat. Oncol. Biol. Phys. 59(4), 1011–1017 (2004). https://doi.org/10.1016/j.ijrobp.2004.01.022
J. Gildersleve, D.P. Dearnaley, P.M. Evans, and W. Swindell, “Reproducibility of patient positioning during routine radiotherapy, as assessed by an integrated megavoltage imaging system,” Radiother. Oncol. 35(2), 151–160 (1995). https://doi.org/10.1016/0167-8140(95)01536-P
D. Yan, J. Wong, F. Vicini, J. Michalski, C. Pan, A. Frazier, E. Horwitz, and A. Martinez, “Adaptive modification of treatment planning to minimize the deleterious effects of treatment setup errors,” Int. J. Radiat. Oncol. Biol. Phys. 38(1), 197–206 (1997). https://doi.org/10.1016/s0360-3016(97)00229-0
Q.-S. Chen, Y.-H. Zhao, X. Chen, J.-K. Xu, Q. Gao, and J.-Y. Zhu, “Setup error of electronic portal image device in IMRT for thoracic tumors and its influence,” Eur. Rev. Med. Pharmacol. Sci. 27(24), (2023). https://doi.org/10.26355/eurrev_202312_34799
P.A. Asvestas, K.K. Delibasis, N.A. Mouravliansky, and G.K. Matsopoulos, “ESTERR‐PRO: A Setup Verification Software System Using Electronic Portal Imaging,” Int. J. Biomed. Imaging 2007(1), 61523 (2007). https://doi.org/10.1155/2007/61523
P. Shinde, A. Jadhav, V. Shankar, and S.J. Dhoble, “Assessment of dosimetric impact of interfractional 6D setup error in tongue cancer treated with IMRT and VMAT using daily kV-CBCT,” Reports Pract. Oncol. Radiother. 28(2), 224–240 (2023). https://doi.org/10.5603/RPOR.a2023.0020
K. Tsujii, Y. Ueda, M. Isono, M. Miyazaki, T. Teshima, and M. Koizumi, “Dosimetric impact of rotational setup errors in volumetric modulated arc therapy for postoperative cervical cancer,” J. Radiat. Res. 62(4), 688–698 (2021). https://doi.org/10.1093/jrr/rrab044
C. Beltran, A. Pegram, and T.E. Merchant, “Dosimetric consequences of rotational errors in radiation therapy of pediatric brain tumor patients,” Radiother. Oncol. 102(2), 206–209 (2012). https://doi.org/10.1016/j.radonc.2011.06.013
A. Heikkilä, E. Boman, M. Rossi, A. Vanhanen, M. Mankinen, M. Postema, and T. Koivumäki, “Dosimetric effect of rotational setup errors in volumetric modulated arc therapy and field-in-field treatment of left-sided breast cancer,” Phys. Medica, 117, 103203 (2024). https://doi.org/10.1016/j.ejmp.2023.103203
W. Fu, Y. Yang, N.J. Yue, D.E. Heron, and M.S. Huq, “Dosimetric influences of rotational setup errors on head and neck carcinoma intensity-modulated radiation therapy treatments,” Med. Dosim. 38(2), 125–132 (2013). https://doi.org/10.1016/j.meddos.2012.09.003
I. Ahmed, S. Krishnamurthy, R. Bhise, K. Vinchurkar, and M. Kalloli, “Concurrent Weekly Cisplatin and Simultaneous Integrated Boost-IMRT in Locally Advanced Head and Neck Squamous Cell Carcinoma—An Institutional Experience,” South Asian J. Cancer 11(03), 235–242 (2022). https://doi.org/10.1055/s-0042-1743578
L. Zhang, A.S. Garden, J. Lo, K.K. Ang, A. Ahamad, W.H. Morrison, D.I. Rosenthal, M.S. Chambers, X.R. Zhu, and R. Mohan, “Multiple regions-of-interest analysis of setup uncertainties for head-and-neck cancer radiotherapy,” Int. J. Radiat. Oncol. Biol. Phys. 64(5), 1559–1569 (2006). https://doi.org/10.1016/j.ijrobp.2005.12.023
M. Van Herk, “Errors and margins in radiotherapy,” in Semin. Radiat. Oncol., (Elsevier, 2004), pp. 52–64. https://doi.org/10.1053/j.semradonc.2003.10.003
M. Van Herk, P. Remeijer, C. Rasch, and J. V Lebesque, “The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy,” Int. J. Radiat. Oncol. Biol. Phys. 47(4), 1121–1135 (2000). https://doi.org/10.1016/S0360-3016(00)00518-6
W. Tan, Y. Li, G. Han, J. Xu, X. Wang, Y. Li, and D. Hu, “Target volume and position variations during intensity-modulated radiotherapy for patients with nasopharyngeal carcinoma,” Onco. Targets. Ther. 1719–1728 (2013). http://dx.doi.org/10.2147/OTT.S53639
L. Xing, Z.-X. Lin, S.S. Donaldson, Q.T. Le, D. Tate, D.R. Goffinet, S. Wolden, L. Ma, and A.L. Boyer, “Dosimetric effects of patient displacement and collimator and gantry angle misalignment on intensity modulated radiation therapy,” Radiother. Oncol. 56(1), 97–108 (2000). https://doi.org/10.1016/S0167-8140(00)00192-4
G. Liu, S. Zhang, Y. Ma, Q. Wang, X. Chen, L. Zhang, and F. Ma, “Effects of error on dose of target region and organs at risk in treating nasopharynx cancer with intensity modulated radiation therapy,” Pakistan J. Med. Sci. 32(1), 95 (2016). https://doi.org/10.12669/pjms.321.9218
R. Prabhakar, M.A. Laviraj, K.P. Haresh, P.K. Julka, and G.K. Rath, “Impact of patient setup error in the treatment of head and neck cancer with intensity modulated radiation therapy,” Phys. Medica 26(1), 26–33 (2010). https://doi.org/10.1016/j.ejmp.2009.05.001
E.N.J.T. van Lin, L. van der Vight, H. Huizenga, J.H.A.M. Kaanders, and A.G. Visser, “Set-up improvement in head and neck radiotherapy using a 3D off-line EPID-based correction protocol and a customised head and neck support,” Radiother. Oncol. 68(2), 137–148 (2003). https://doi.org/10.1016/S0167-8140(03)00134-8
J.L. Barker Jr, A.S. Garden, K.K. Ang, J.C. O’Daniel, H. Wang, L.E. Court, W.H. Morrison, D.I. Rosenthal, K.S.C. Chao, and S.L. Tucker, “Quantification of volumetric and geometric changes occurring during fractionated radiotherapy for head-and-neck cancer using an integrated CT/linear accelerator system,” Int. J. Radiat. Oncol. Biol. Phys. 59(4), 960–970 (2004). https://doi.org/10.1016/j.ijrobp.2003.12.024
E.K. Hansen, M.K. Bucci, J.M. Quivey, V. Weinberg, and P. Xia, “Repeat CT imaging and replanning during the course of IMRT for head-and-neck cancer,” Int. J. Radiat. Oncol. Biol. Phys. 64(2), 355–362 (2006). https://doi.org/10.1016/j.ijrobp.2005.07.957
L.N. McDermott, M. Wendling, J.-J. Sonke, M. van Herk, and B.J. Mijnheer, “Anatomy changes in radiotherapy detected using portal imaging,” Radiother. Oncol. 79(2), 211–217 (2006). https://doi.org/10.1016/j.radonc.2006.04.003
H. Alabedi, “Assessing setup errors and shifting margins for planning target volume in head, neck, and breast cancer,” J. Med. Life, 16(3), 394 (2023). https://doi.org/10.25122/jml-2022-0241
S.H. Kim, S.A. Oh, J.W. Yea, and J.W. Park, “Prospective assessment of inter-or intra-fractional variation according to body weight or volume change in patients with head and neck cancer undergoing radiotherapy,” PLoS One, 14(5), e0216655 (2019). https://doi.org/10.1371/journal.pone.0216655
M. Coffey, T. Greener, C. Hall, M. Van Herk, B. Mijnheer, and A. Harrison, “Geometric uncertainties in radiotherapy: technical overview of geometric uncertainties in radiotherapy,” BIR Work. Party, (2003).
A. Navran, W. Heemsbergen, T. Janssen, O. Hamming-Vrieze, M. Jonker, C. Zuur, M. Verheij, et al., “The impact of margin reduction on outcome and toxicity in head and neck cancer patients treated with image-guided volumetric modulated arc therapy (VMAT),” Radiother. Oncol. 130, 25–31 (2019). https://doi.org/10.1016/j.radonc.2018.06.032
J. Unkelbach, M. Alber, M. Bangert, R. Bokrantz, T.C.Y. Chan, J.O. Deasy, A. Fredriksson, et al,, “Robust radiotherapy planning,” Phys. Med. Biol. 63(22), 22TR02 (2018). https://doi.org/10.1088/1361-6560/aae659
W. Fangzheng, S. Quanquan, J. Chuner, Y. Zhimin, Y. Shuangyan, Y. Huanhuan, S. Jianfang, M. Sakamoto, Q. Weifeng, and F. Zhenfu, “Optimization of the margin expanded from the clinical to the planned target volume during intensity-modulated radiotherapy for nasopharyngeal carcinoma,” Oncotarget, 8(66), 110201 (2017). https://doi.org/10.18632/oncotarget.22518
G.C. Bentel, L.B. Marks, K. Hendren, and D.M. Brizel, “Comparison of two head and neck immobilization systems.,” Int. J. Radiat. Oncol. Biol. Phys. 38(4), 867–873 (1997). https://doi.org/10.1016/s0360-3016(97)00075-8
M. Humphreys, M.T.G. Urbano, C. Mubata, E. Miles, K.J. Harrington, M. Bidmead, and C.M. Nutting, “Assessment of a customised immobilisation system for head and neck IMRT using electronic portal imaging,” Radiother. Oncol. 77(1), 39–44 (2005). https://doi.org/10.1016/j.radonc.2005.06.039
M. Leech, M. Coffey, M. Mast, F. Moura, A. Osztavics, D. Pasini, and A. Vaandering, “ESTRO ACROP guidelines for positioning, immobilisation and position verification of head and neck patients for radiation therapists,” Tech. Innov. Patient Support Radiat. Oncol. 1, 1–7 (2017). https://doi.org/10.1016/j.tipsro.2016.12.001
S. Androjna, V.Z. Marcius, P. Peterlin, and P. Strojan, “Assessment of set-up errors in the radiotherapy of patients with head and neck cancer: standard vs. individual head support,” Radiol. Oncol. 54(3), 364–370 (2020). https://doi.org/10.2478/raon-2020-0036
M. Verma, A.A. Sait, S.K.S. Kumar, K.J.M. Das, P. Lal, and S. Kumar, “An audit of setup reproducibility in radiotherapy of head and neck cancers,” J. Radiat. Cancer Res. 7(3), 85–89 (2016). https://doi.org/10.4103/0973-0168.197975
L. Belshaw, C.E. Agnew, D.M. Irvine, K.P. Rooney, and C.K. McGarry, “Adaptive radiotherapy for head and neck cancer reduces the requirement for rescans during treatment due to spinal cord dose,” Radiat. Oncol. 14, 1–7 (2019). https://doi.org/10.1186/s13014-019-1400-3
Z. Mulla, R.K. Alwassia, E.M. Senan, S. Soaida, A.A. Mohamed, H. Almerdhemah, H.A. Iqbal, and H.M. Muamenah, “A comparative study between open-face and closed-face masks for head and neck cancer (HNC) in radiation therapy,” Reports Pract. Oncol. Radiother. 25(3), 382–388 (2020). https://doi.org/10.1016/j.rpor.2020.03.009
B. Pehlivan, C. Pichenot, M. Castaing, A. Auperin, D. Lefkopoulos, R. Arriagada, and J. Bourhis, “Interfractional set-up errors evaluation by daily electronic portal imaging of IMRT in head and neck cancer patients,” Acta Oncol. (Madr). 48(3), 440–445 (2009). https://doi.org/10.1080/02841860802400610
V. Rudat, M. Hammoud, Y. Pillay, A.A. Alaradi, A. Mohamed, and S. Altuwaijri, “Impact of the frequency of online verifications on the patient set-up accuracy and set-up margins,” Radiat. Oncol. 6, 101 (2011). http://www.ro-journal.com/content/6/1/101
M.L. Johnston, P. Vial, K.L. Wiltshire, L.J. Bell, S. Blome, Z. Kerestes, G.W. Morgan, D. O’Driscoll, T.P. Shakespeare, and T.N. Eade, “Daily online bony correction is required for prostate patients without fiducial markers or soft-tissue imaging,” Clin. Oncol. 23(7), 454–459 (2011). https://doi.org/10.1016/j.clon.2011.02.013
B. Strbac, and V.S. Jokic, “Evaluation of set-up errors in head and neck radiotherapy using electronic portal imaging,” Phys. Medica, 29(5), 531–536 (2013). https://doi.org/10.1016/j.ejmp.2012.12.001
E.A. Marnouche, M. Abdelhak, I. Lalya, N. Zaghba, A. Bazine, K. Andaloussi, M. Elmarjany, et al., “Set-up errors and imaging verification protocols for head and neck cancers radiotherapy in Morocco,” J. Oncol. Res. Treat 4(131), 2 (2019).
M.A. Youssoufi, M. Bougtib, S. Douama, M.A. Erraisse, F.Z. Abboud, K. Hassouni, and F. Bentayeb, “Evaluation of PTV margins in IMRT for head and neck cancer and prostate cancer,” J. Radiother. Pract. 20(1), 114–119 (2021). https://doi.org/10.1017/S1460396919000931
D. Delishaj, S. Ursino, F. Pasqualetti, F. Matteucci, A. Cristaudo, C. Pietro Soatti, A. Barcellini, and F. Paiar, “Set-up errors in head and neck cancer treated with IMRT technique assessed by cone-beam computed tomography: a feasible protocol,” Radiat. Oncol. J. 36(1), 54 (2018). https://doi.org/10.3857/roj.2017.00493
V. Mongioj, E. Orlandi, M. Palazzi, E. Deponti, F. Marzia, C. Stucchi, C. Sangalli, C. Fallai, G. Zonca, and P. Olmi, “Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins,” Acta Oncol. (Madr). 50(1), 61–71 (2011). https://doi.org/10.3109/0284186X.2010.509108
R. Ove, R. Cavalieri, D. Noble, and S.M. Russo, “Variation of neck position with image-guided radiotherapy for head and neck cancer,” Am. J. Clin. Oncol. 35(1), 1–5 (2012). https://doi.org/10.1097/COC.0b013e3181fe46bb
J. Su, W. Chen, H. Yang, J. Hong, Z. Zhang, G. Yang, L. Li, and R. Wei, “Different setup errors assessed by weekly cone-beam computed tomography on different registration in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy,” Onco. Targets. Ther. 2015(8), 2545–2553 (2015). http://dx.doi.org/10.2147/OTT.S87159
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