Abstract Objective To investigate the optimization of therapeutic regimen through the adjustment of the minimum sub-field area in intensity-modulated radiotherapy (IMRT) for cervical cancer,under the premise of no influence on the dose to target volume or organs at risk. Methods A total of 12 patients with pathologically confirmed cervical cancer were enrolled,and the prescribed dose to the planning target volume (PTV) was 50 Gy in 25 fractions. The Pinnacle 8.0m treatment planning system was used for all patients,and 16 IMRT plans were developed for each patient,with the application of 9 evenly distributed fixed incidence directions (0°,40°,80°,120°,160°,200°,240°,280°,and 320°),a minimum sub-field number of 80,and a minimum sub-field hop count (MU) of 5 MU.The range of sub-field area was 2-81 cm2.Direct machine parameter optimization was used for inverse-planned optimization calculation,and all the plans met the requirements of the clinical prescribed dose. The dose-volume histogram was used to evaluate the dose distribution in target volume and organs at risk. Results With the sub-field area increasing from 2 cm2 to 81 cm2,the total hop count of IMRT plan was reduced from (1 405±170) MU to (490±47) MU (P=0.000),and when the sub-field area increased above 6 cm×6 cm,the total hop count was reduced significantly (P=0.000).In the IMRT plan with a minimum sub-field area of 2-49 cm2,there was no significant difference in dose between the target volume and the organs at risk (P>0.05).The dose to the rectum,the bladder,and both femoral heads showed no significant differences across the IMRT plans with different minimum sub-field areas (P>0.05). Conclusions When the Pinnacle 8.0m treatment planning system is used to develop IMRT plans for cervical cancer,the requirements for clinical dose can still be met with a minimum sub-field area reaching 7 cm×7 cm,and there are significant reductions in sub-field hop count and total hop count.
Qiu Rong,Shang Kai,Li Runxiao et al. Influence of sub-field area on dose distribution in intensity-modulated radiotherapy for cervical cancer[J]. Chinese Journal of Radiation Oncology, 2016, 25(7): 740-744.
Qiu Rong,Shang Kai,Li Runxiao et al. Influence of sub-field area on dose distribution in intensity-modulated radiotherapy for cervical cancer[J]. Chinese Journal of Radiation Oncology, 2016, 25(7): 740-744.
[1]Galvin JM,Ezzell G,Eisbrauch A,et al. Implementing IMRT in clinical practice:a joint document of the American Society for Therapeutic Radiology and Oncology and the American Association of Physicists in Medicine[J].Int J Radiat Oncol Biol Phys,2004,58(5):1616-1634.DOI:10.1016/j.ijrobp.2003.12.008 [2]Jiang Z,Earl MA,Zhang GW,et al. An examination of the number of required apertures for step-and-shoot IMRT[J].Phys Med Biol,2005,50(23):5653-5663.DOI:10.1088/0031-9155/50/23/017 [3]查元梓,张松方,屠永清,等.子野权重优化对CMS XiO宫颈癌调强计划的影响[J].中国医学物理学杂志,2013,30(1):3866-3869.DOI:10.3969/j.issn.1005-202X.2013.01.007. Zha YZ,Zhang SF,Tu YQ,et al. A study of segment weight optimization with the CMS XiO step-and-shoot IMRT technique for cervical cancer[J].Chin J Med Phys,2013,30(1):3866-3869.DOI:10.3969/j.issn.1005-202X.2013.01.007 [4]曹彦坤,迟子锋,焦广青,等.食管癌IMRT计划设计降低子野数及MU数方法研究[J].中国医学物理学杂志,2011,28(2):2460-2463,2470.DOI:10.3969/j.issn.1005-202X.2011.02.002. Cao YK,Chi ZF,Jiao GQ,et al. Study of reducing the number of segments and MUs of esophageal carcinoma IMRT plans[J].Chin J Med Phys,2011,28(2):2460-2463,2470.DOI:10.3969/j.issn.1005-202X.2011.02.002 [5]迟子锋,韩春,刘丹,等.基于蒙特卡罗方法评估四种治疗计划系统对前列腺癌调强放疗的计划质量[J].中华放射肿瘤学杂志,2011,20(3):222-225.DOI:10.3760/cma.j.issn.1004-4221.2011.03.015. Chi ZF,Han C,Liu D,et al. Evaluation of IMRT plans of prostate carcinoma from four treatment planning systems based on Monte Carlo[J].Chin J Radiat Oncol,2011,20(3):222-225.DOI:10.3760/cma.j.issn.1004-4221.2011.03.015 [6]Qi P,Xia P.Relationship of segment area and monitor unit efficiency in aperture- based IMRT optimization[J].J Appl Clin Med Phys,2013,14(3):232-243.DOI:10.1120/jacmp.v14i3.4056 [7]Worthy D,Wu QW.Parameter optimization in HN-IMRT for Elekta linacs[J].J Appl Clin Med Phys,2009,10(2):43-61 [8]李毅,陈鑫,李文荣,等.子野权重优化在宫颈癌术后IMRT计划中的应用研究[J].中华放射医学与防护杂志,2013,33(6):619-622.DOI:10.3760/cma.j.issn.0254-5098.2013.06.013. Li Y,Chen X,Li WR,et al. Application of SWO technique in IMRT plan of post-operative cervical cancer[J].Chin J Radiol Med Prot,2013,33(6):619-622.DOI:10.3760/cma.j.issn.0254-5098.2013.06.013.
2016, Vol. 25 
