容积旋转调强放疗和常规调强放疗技术在乳腺癌保乳术后同步推量中的剂量学比较

Dosimetric comparison between VMAT ang IMRT for breast-conserving therapy for breast cancer

目的比较容积旋转调强放疗(VMAT)和常规调强放疗(IMRT)两种技术在乳腺癌保乳术后同步推量放疗中剂量学差异。方法随机选择10例左侧乳腺癌保乳术后患者,使用MONACO 5.1计划系统,分别设计VMAT和IMRT计划,处方剂量均为PTV_(50Gy)/25 f、PGTVtb60 Gy/25 f,评估两种计划靶区剂量适形指数(CI)、均匀性指数(HI),以及正常器官受照剂量(Gy)、机器跳数(MU)及治疗时间。结果 VMAT计划中靶区剂量的适形度明显优于IMRT(P<0.05),而患侧肺V_5、V_(10)、V_(20)及健侧肺V_5稍高于IMRT组(P<0.05)。结论对于乳腺癌保乳术后同步推量放疗,VMAT和IMRT计划都可以满足临床剂量学的要求,VMAT在适形度方面对于IMRT计划有优势,并缩短了治疗时间。

Objective To analyze the difference in dosimetric characteristics and protection of organs at risk （OAR） between volumetric modulated arc therapy（VMAT） and intensity modulated radiation therapy（IMRT） for breast cancer patients after breast-con- serving therapy. Methods Ten patients with breast cancer （ in the left breast） were planned in different ways. The prescribed dose for PTV was 50Gy/25f,while the dose for PGTVtb was boosted to 60 Gy/25 f. The dosimetric parameters of the two different plans, inclu- ding the dose conformity index（CI） and homogeneity index（HI） of PTV, dose volume histogram （DVH）of normal tissue coverage, MU and delivery time were also analyzed. Results The dose distribution CI of the VMAT plan were better than that of IMRT（P 〈 0.05）. Compared with IMRT, VMAT increased the volume of the ipsilateral lung at 5,10,20Gy and the volume of the contrlateral lung at 5 Gy （ P 〈 0.05）. Conclusion The two treatment modalities can satisfy clinical requirements. The dose distribution CI of the VMAT plan is better than that of IMRT. Also, the VMAT technology can shorten the duration of treatment.