肺癌立体定向放射治疗旋转容积调强计划控制点优化设计

Optimal design of control points of SBRT rotational volumetric intensity-modulated plan for lung cancer

目的:研究Monaco治疗计划系统的放射治疗计划控制点(CP)个数在早期非小细胞肺癌(NSCLC)的体部立体定向放射治疗(SBRT)计划中的影响,为优化肺癌SBRT旋转容积调强计划的CP参数设置提供依据。方法:选取医院收治的9例早期周围型NSCLC患者,其中1例患者左、右肺各有肿瘤,分别行左、右侧两个计划处理(共10幅靶区图像),治疗计划CP使用Monaco治疗计划系统,为每例患者设置SBRT旋转容积调强计划的7个CP参数,其个数分别为10、30、50、80、100、150和200个(记为CP_(10)、CP_(30)、CP_(50)、CP_(80)、CP_(100)、CP_(150)和CP_(200)),以CP_(100)的肺癌SBRT计划进行优化得到计划1(plan1),其他计划在优化参数不变的情况下只改CP。通过方差分析和最小显著性差异(LSD),对比分析靶区剂量分布、危及器官(OAR)受量、计划效率中靶区均匀性指数(HI)、适形性指数(CI)、跌落指数(GI)、机器跳数、计算时间和子野个数,以及执行效率中的Gamma通过率。结果:CP_(30)处的D_(2%)、D_(50%)和HI呈减小趋势,与CP_(100)处相比分别减少1.56%、1.28%和10%。CP_(30)处的CI和GI呈增加趋势,与CP_(100)处相比分别增加1.28%和1.17%;CP_(30)处的靶区内最大剂量D_(2%)、平均剂量D_(50%)和HI呈减少趋势,与CP_(10)处比较分别减少3.53%、1.91%和15%,差异有统计学意义(F=31.137,F=17.556,F=35.617;P<0.05);而CP_(30)处的CI和GI分别比CP_(10)处增加2.63%和2.16%,差异有统计学意义(F=6.026,F=9.437;P<0.05)。在OAR中食管D_(0.03cm^(3))和胸壁D_(2cm^(3))在CP_(30)处与CP_(100)处相比分别增加7.56%和减少3.69%;在OAR中食管D_(0.03cm^(3))和胸壁D_(2cm^(3))分别从CP_(30)处增加8.88%和减少2.95%,差异有统计学意义(F=2.315,F=6.622;P<0.05)。CP_(30)处与CP_(50)~CP_(200)处的计划相比,机器跳数少、计算时间短且子野个数少,差异有统计学意义(F=3.554,F=130.838,F=3.737;P<0.05);所有计划Gamma通过率均>90%。结论:在肺癌SBRT旋转调强计划中,当治疗计划为CP_(30)时,可保证靶区剂量最佳,优化计划和执行效率高,且对OAR影响小。

Objective:To study the influence of the number of control points(CP) of radiation therapy plan of the Monaco treatment planning system on the plan of stereotactic body radiotherapy(SBRT) for early-stage non-small cell lung cancer(NSCLC),so as to provide the basis for optimizing the CP parameters setting of the rotational volume intensity-modulated plan of SBRT for lung cancer.Methods:Nine patients with early peripheral NSCLC admitted to hospital were selected,and one of them,who had cancer in left and right lung,underwent two planned treatments on the left and right sides respectively(there were 10 target images in total).The treatment plan CP used the Monaco treatment planning system to set 7 CP parameters of SBRT rotational volumetric intensity-modulated plan for each patient,and the number of them were 10,30,50,80,100,150 and 200 respectively(which were marked as CP_(10),CP_(30),CP_(50),CP_(80),CP_(100),CP_(150) and CP_(200)).The lung cancer SBRT plan of CP_(100) was optimized to obtain plan 1(plan 1),and other plans only changed the CP under the optimal parameters without change.The dose distribution of target region,the received dose of organ at risk(OAR),homogeneity index(HI) of target region in plan effectiveness,conformity index(CI),gradient index(GI),the number of monitor unit,the calculation time and the number of subfields,and the Gamma pass rate in the execution efficiency were compared and analyzed through variance analysis and the least significant difference(LSD).Results:The D_(2%),D_(50%) and HI appeared diminution trend at CP_(30),which were respectively reduced by 1.56%,1.28% and 10% than those at CP_(100).The CI and GI of CP_(30) appeared increasing trend,and they respectively increased by 1.28% and 1.17% than those of CP_(100).The maximum dose D_(2%),average dose D_(50%) and HI within target region of CP_(30) appeared decreasing trend,and they respectively decreased 3.53%,1.91% and 15% than those of CP_(10),and the differences of them between CP_(30) and CP_(10) were significant(F=31.137,F=17.556,F=35.617,P<0.05).While the CI and GI of CP_(30) were respectively increased by 2.63% and 2.16% than those of CP_(10),and the differences of them between CP_(30) and CP_(10) were significant(F=6.026,F=9.437,P<0.05).In OAR,D_(0.03cm^(3)) of esophagus and D_(2cm^(3)) of chest wall of CP_(30) were increased and decreased respectively by 7.56% and 3.69% than those of CP_(100),and D_(0.03cm^(3)) of esophagus and D_(2cm^(3)) of chest wall were respectively increased by 8.88% and decreased by 2.95% from CP_(30),and the differences of them were significant(F=2.315,F=6.622,P<0.05).And the number of monitor unit,the calculation time and the number of subfields of CP_(30) were significantly less than those of CP_(50)-CP_(200),and the differences of them were significant(F=3.554,F=130.838,F=3.737,P<0.05).Gamma pass rates of all plans were >90%.Conclusion:In the SBRT rotational intensity-modulated plan for lung cancer,the dose of target region can be ensured to be optimal,and the optimal plan and execution efficiency are the highest,and the influences of them are little on OAR when treatment plan is CP_(30).