局部提量方法在宫颈癌静态调强放疗中的剂量学分析

Booster dose in specific region in static intensity-modulated radiotherapy for cervical cancer: a dosimetric analysis

目的:通过比较采用局部提量方法前后宫颈癌静态调强放疗计划的剂量学参数,评估局部提量方法用于设计宫颈癌静态调强放疗计划的可行性。方法:选取10例接受宫颈癌调强放疗患者,基于CMS XiO4.80计划系统,以4500 cGy处方剂量分别对同一患者设计采用局部提量方法前后的两种放疗计划,比较两种计划的剂量学参数、机器跳数、治疗时间和二维剂量验证通过率。结果:两种计划均满足计划靶区(PTV)剂量要求,所得PTV的D2%、Dmean、D98%无明显差异(P>0.05);采用局部提量方法所得PTV的靶区覆盖率、适形度指数(CI)、均匀性指数(HI)更优(P<0.05);两种计划都能较好地保护危及器官。采用局部提量方法后,危及器官剂量体积均略有增大,除小肠、直肠、膀胱V45和两侧股骨头V40差异具有统计学意义外(P<0.05),其它参数无明显差异(P>0.05);正常组织受照剂量除V15未见明显差异外(P>0.05),采用局部提量方法后,其它参数均略有增大;两种计划机器跳数和治疗时间差异具有统计学意义(P<0.05),二维剂量验证通过率无明显差异(P>0.05)。结论:局部提量方法有利于优化PTV的靶区覆盖率、CI、HI,对其它参数的改变在可接受范围内,建议在设计宫颈癌静态调强放疗计划时采用该方法。

Objective To compare the dosimetric parameters in static intensity-modulated radiotherapy(IMRT)for cervical cancer before and after booster dose in specific region for evaluating the feasibility of booster dose in specific region in static IMRT for cervical cancer.Methods Ten patients with cervical cancer were enrolled in the study.Two plans with the same prescription dose of 4 500 cGy with or without booster dose in specific region were designed based on CMS XiO 4.80 system.The dosimetric parameter,monitor unit,treatment time and the passing rate in two-dimensional dose verification were analyzed and compared.Results Both of the two plans satisfied target dose requirements and provided a significant sparing of organs-at-risk.There was no significant difference in the D2%,Dmean and D98%of planning target volume(P>0.05).However,the target coverage rate,conformity index and homogeneity index of target areas in plan with booster dose in specific region were superior to those in plan without booster dose in specific region(P<0.05).After booster dose in specific region,the dose volume of organs-at-risk was slightly increased,and statistical significances were only found in the V45 of small intestine,rectum and bladder and the V40 of bilateral femoral heads(P<0.05).After booster dose in specific region,the dosimetric parameters of normal tissues were increased,except for the V15 of normal tissues(P>0.05).Moreover,the comparison between two plans showed that there were statistical significances in monitor units and treatment time(P<0.05),not in the passing rate of two-dimensional dose verification(P>0.05).Conclusion Booster dose in specific region which is conducive to optimizing target coverage rate,and the conformity index and homogeneity index of target areas while the changes to other parameters are acceptable is recommended in the planning of static IMRT for cervical cancer.