水平射野对肺癌调强计划结果的影响研究

Effects of horizontal beam on IMRT plan for lung cancer

目的 探讨水平方向射野对肺癌调强计划结果的影响.方法 收集肺癌患者18例,其中左肺癌患者10例,右肺癌患者8例,设计普通调强（IMRT计划）和在普通调强基础上添加一个水平方向射野（H-IMRT计划）的计划,比较机器跳数、子野数及靶区和危及器官（OARs）的剂量分布.结果 两种计划PTV的Dmax、Dmin及Dmean,患侧肺的V30和Dmean,健侧肺的V200和V30,全肺的V30差异均无统计学意义.与IMRT计划相比,添加水平射野后,PTV的均匀性（HI）及适形度（CI）都有显著提高（t=-9.33、10.88,P＜0.05）;肺的其他剂量指标均变差（t=-1.55～-7.58,P＜0.05）;心脏的保护更优（t=1.84 ～3.99,P＜0.05）;MUs及子野数量降低（t=12.57、3.19,P＜0.05）.结论 在肺癌的IMRT治疗中,添加水平射野可以改善靶区的剂量分布,但会使肺的低剂量照射体积增加,无益于肺的保护.

Objective To explore the effect of horizontal beam on IMRT plan for lung cancer.Methods Totally 18 patients were enrolled,including 10 cases of left lung cancer and 8 cases of right lung cancer.Two intensity modulated radiation therapy （IMRT） plans were generated：one was the normal IMRT plan and another was the IMRT plan including a horizontal beam （H-IMRT）.MUs,sub-field and the dose distribution of target and organs at risk （OARs） were compared.Results There were no statistically significant differences between two plans in D Dminand D of PTV,the V30 and D of the ipsilateral lung,V20 and V30 of the contralateral lung,and V30 of the total lung.When the horizontal beam was added,the PTV heterogeneity index （HI） and conformity index （CI） were significantly increased （t=-9.33,10.88,P〈0.05）,the other dose index in lung was inferior （t =-1.55--7.58,P〈 0.05）,whleheart sparing were clearly better （t =1.84-3.99,P〈0.05）,the number of MUs and segments were less（t =12.57,3.19,P 〈 0.05）.Conclusions IMRT in the treatment of lung cancer can further improve the PTV coverage when the horizontal beam is added.However,the increasing lung volume of low dose irradiation is not conducive to lung protection.