上段食管癌SIB-IMRT治疗计划比较

目的 对上段食管癌实施同时整和加量调强放射治疗(simultaneous integrated boost intensity-modulated radiation therapy，SIB-IMRT)计划，研究肿瘤及预防照射区的剂量分布情况和危及器官受量，并比较不同照射野数目对剂量分布的影响。方法 对2例上段食管癌的原发灶和预防照射区进行SIB-IMRT计划设计。定义2个靶区：PTVl为需要加量照射的原发灶靶区，给予67．2Gy；PTV2为预防照射区，给予50．4Gy的剂量。设计4个计划，采用共面、360度范围等角度分布的照射野，野数分别为3、5、7、9，4个计划使用相同的剂量-体积约束条件进行逆向优化。比较这4个计划的剂量分布、剂量体积直方图(dose volume histogram，DVH)、适合度指数等指标。结果 3个调强照射野即可使2个靶区获得满意的剂量分布。随着照射野数目的增加，靶区剂量均匀性、适合度指数提高，危及器官受量减小。当照射野数由7增加到9时，剂量分布没有改善。结论 5～7个调强照射野即可使上段食管癌的同时整和加量(simultaneous integrated boost，SIB)治疗获得理想的剂量分布。原发肿瘤可以获得比常规分割高的等效剂量。共面、等角度分布的照射野设计简单、效率高。SIB-IMRT治疗的疗效还有待于临床的结果。

Comparison of SIB-IMRT treatment plans for upper esophageal carcinoma

Objective To implement simultaneous integrated boost intensity-modulated radiotherapy(SIB-IMRT)plans for upper esophageal carcinoma and investigate the dose profiles of tumor and electively treated region and the dose to organs at risk (OARs).Methods SIB-IMRT plans were designed for two patients with upper esophageal carcinoma.Two target volumes were predefined:PTV1,the target volume of the primary lesion,which was given to67.2Gy,and PTV2,the target volume of electively treated region,which was given to50.4Gy.With the same dose-volume constraints,but different beams arrangements(3,5,7,or9equispaced coplanar beams),four plans were generated.Indices,including dose distribution,dose volume histogram (DVH)and conformity index,were used for comparison of these plans.Results The plan with three intensity-modulated beams could produce good dose distribution for the two target volumes.The dose conformity to targets and the dose to OARs were improved as the beam number increased.The dose distributions in targets changed little when the beam number increased from7to9.Conclusions Five to seven intensity-modulated beams can produce desirable dose distributions for simultaneous integrated boost(SIB)treatment for upper esophageal carcinoma.The primary tumor can get higher equivalent dose by SIB treatments.It is easier and more efficient to design plans with equispaced coplanar beams.The efficacy of SIB-IMRT remains to be determined by the clinical outcome.