摘要
目的:分析基于几何不确定性的鲁棒优化计划对肝癌立体定向放疗(SBRT)剂量分布的影响。方法:选取12例肝癌SBRT患者,对每例制作3个调强计划:①基于PTV(ITV-PTV 5 mm)的常规优化(PTV-BasedPlan);②基于ITV非均匀几何不确定性(本中心计算的不确定性值:进出方向7 mm,左右和前后方向4 mm)的鲁棒优化(Robust Plan_(actual));③基于ITV均匀5 mm几何不确定性的鲁棒优化(RobustPlan_(5 mm))。所有计划都以95%的PTV满足处方剂量作为目标,以等中心均匀偏移4、5、7 mm计算扰动剂量评估鲁棒性。结果:计划①②③的均匀性指数(HI)分别为0.083±0.027、0.099±0.035、0.096±0.026,不具有统计学意义;计划①②③的适形性指数(CI)分别为0.98±0.02、1.02±0.05、1.00±0.04,计划②③相对于计划①的CI具有统计学意义。计划③的正常肝组织平均受量和V_(2500)相对于计划①②分别下降了4.1%、2.5%和5.4%、3.0%,且具有统计学意义(P=0.034、P=0.021和P=0.004、P=0.004),计划②相对于计划①的正常肝组织平均受量和V_(2500)不具有统计学意义(P=0.308和P=0.182),但下降了1.6%和2.5%。对于其鲁棒性,计划②③的5 mm-D_(99%)、5 mm-D_(98%)、5 mm-D_(95%)的剂量-体积直方图带宽(DVHBW)差值相对于计划①更小,随着摆位不确定度的增大,其DVHBW差值越大。结论:在肝脏SBRT治疗中,采用鲁棒优化能够提高靶区剂量分布质量,即使在摆位不确定度有所增加的情况下,仍可以保证ITV的剂量覆盖同时不增加正常组织的照射剂量。
Objective To analyze the effects of robust optimization plan based on geometric uncertainty on the dose distribution of stereotactic body radiotherapy(SBRT)for liver cancer.Methods Twelve patients treated by SBRT for liver cancer were enrolled in the study.For each case,3 different kinds of plans were designed by different optimization methods,including①conventional optimization(PTV-Based Plan)based on PTV(ITV-PTV _(5 mm)),②robust optimization(Robust Plan_(actual))based on non-uniform geometric uncertainty for ITV(the uncertainties calculated by our center were 7 mm in superior-inferior direction,4 mm in medial-lateral and anterior-posterior directions),③robust optimization(Robust Plan_(5 mm))based on uniform geometric uncertainty of 5 mm for ITV.All plans were based on the target that 95%ITV met the prescribed dose,and the perturbation dose was calculated with uniform uncertainties of 4,5,7 mm from the isocenter to evaluate the robustness.Results The homogeneity index of plans①②③was 0.083±0.027,0.099±0.035 and 0.096±0.026,respectively,without statistical significance;and the conformity index of plans②③was 1.02±0.05,1.00±0.04,significantly different from that of plan①which was 0.98±0.02.Compared with those in plans①②,the average dose to normal liver tissues in plan③was decreased by 4.1%and 2.5%(P=0.034,P=0.021),and V_(2500) was decreased by 5.4%and 3.0%(P=0.004,P=0.004),respectively.The average dose to normal liver tissue and V_(2500)in plan②were not statistically different from those in plan①(P=0.308 and P=0.182),but decreased by 1.6%and 2.5%.For robustness,the differences in dose-volume histogram bandwidth(DVHBW)of 5 mm-D_(99%),5 mm-D_(98%),5 mm-D_(95%)in plans②③were smaller than those in plan①.With the increase of setup uncertainty,the difference in DVHBW became greater.Conclusion In liver SBRT,robust optimization can optimize target dose distribution.Even if the setup uncertainty increases,it can still ensure the dose coverage of ITV,without increasing the irradiation d
作者
刘登洪
王雪桃
钟仁明
LIU Denghong;WANG Xuetao;ZHONG Renming(Department of Radiotherapy(State Key Laboratory of Biotherapy),Cancer Center,West China School of Medicine(West China Hospital),Sichuan University,Chengdu 610041,China)
出处
《中国医学物理学杂志》
CSCD
2022年第2期162-168,共7页
Chinese Journal of Medical Physics
基金
四川大学华西医院临床研究孵化项目(2021HXFH029)
四川省科技厅重点研发项目(2021YFQ0065)。
关键词
肝癌
立体定向放疗
鲁棒优化
几何不确定性
liver cancer
stereotactic body radiotherapy
robust optimization
geometric uncertainty
