射野角度优化在颅脑多发转移瘤中的应用研究

Application of beam angle optimization for multiple intracranial metastases

目的 探讨在颅脑多发转移瘤中,不同射野角度对逆向调强放疗计划剂量的影响及射野角度优化的可行性.方法 单纯随机取样法选取11例多发脑转移瘤患者,采用射野角度优化逆向调强计划（BAO组）,并与射野角度均分逆向调强计划（BAF组）进行比较,统计分析危及器官和正常组织的受照剂量、靶区剂量分布及机器跳数,分析不同射野角度引起的剂量学差异.结果 与BAF组相比,BAO组中左、右眼晶状体最大受照剂量降低了45％、37％（t=-5.707、-4.438,P＜0.05）;左、右眼球平均受照剂量分别降低了42.6％、44.5％（t=-4.380、-5.638,P＜0.05）;右侧眼球的最大剂量平均降低32.5％（t=-2.518,P＜0.05）;右侧视神经的最大剂量降低了23％（t=-3.105,P＜0.05）;正常脑组织平均受量降低了3％（t=-3.437,P＜0.05）.两组逆向调强计划的靶区剂量、适形度和均匀性指数差异无统计学意义（P＞0.05）.角度优化逆向调强计划降低了脑干、视交叉的最大受照剂量和机器跳数,但两组结果差异无统计学意义（P＞0.05）.结论 射野角度优化后的逆向调强计划,可保持与射野角度均分的逆向调强计划相当的靶区剂量,同时降低了部分危及器官的受照剂量.对于多发脑转移瘤,射野角度优化的逆向调强计划是可行且有益的.

Objective To study the dosimetric impact of different angle fields in intensitymodulated radiotherapy （IMRT） and the feasibility of beam angle optimization （BAO） for multiple intracranial metastases.Methods In total,11 patients with multiple intracranial metastases were included in these analyses.Two treatment techniques were designed for each patient：the 7 equal spaced fields （BAF group） IMRT,and 7 fields by beam angle optimization （BAO group） IMRT.The dose distribution in the target,the dose to the organs at risk and normal brain tissues,and total MU in two groups were compared to explore the dosimetric differences.Results In comparison to the BAF group,the BAO group reduced the maximum dose to left and right lenses by an average of 45%,37% （t =-5.707,-4.438,P 〈 0.05）;the mean dose to the left and right eyes were reduced by an average of 42.6%,44.5% （t =-4.380,-5.638,P 〈0.05）;the maximum dose to the right eyes were reduced by an average of 32.5% （t =-2.518,P 〈 0.05）.The maximum dose of the right optic nerve and the mean dose of normal brain tissue were reduced by an average of 23% and 3% （t =-3.105,-3.437,P 〈0.05）,respectively.For the target dose,conformity and homogeneity in PTV,no statistical differences were observed between the two groups （P 〉 0.05）.The BAO group reduced the maximum dose of the brainstem and the optic chiasm,as well as the number of MU,however,the differences were not statistically significant （P 〉 0.05）.Conclusions In comparison to the BAF group,the BAO group shows a similar target dose and reduces the dose for the organs at risk.For multiple intracranial metastases,IMRT protocols with BAO are feasible and beneficial.