Objective: To analyze and compare the influence of different collimator for planning dosimetry of treating trigeminal neuralgia(TN)by using CyberKnife(CK)so as to provide reference for choosing best collimator.Methods:The clinical documents of 21 patients with TN who underwent treatment of CK were enrolled into the study.In these patients,position of TN of 14 cases were at right side and that of 7 cases were at left side.The three planning groups(5mm collimator,7.5mm collimator and 5mm combined with 7.5mm collimator)were designed and they were defined as C5 group,C7.5 group and C5 combined with C7.5 group,respectively.The prescribed dose of planning target volume(PTV)was 64 Gy/1F,and the limited dose of normal tissue accorded to the requirement of TG101 report of American association physicists medicine(AAPM).The series of parameters included cover degree,conformal degree and therapy efficiency of prescribed dose on target region were assessed.Results: For coverage rate of target region,the rate of C7.5 group was worse,and the difference of that between C5 group and C5 combined with C7.5 group was no significant(F=17.811,P＞0.05).While,the advantage of C5 combined with C7.5 group became obviously little by little with the increasing of target region volume,and some advantages appeared in factor analysis of the shortest distance between target region and brainstem.For conformal degree of target region,the difference between C5 group and C5 combined with C7.5 group was no significant(F=4.604,P＞0.05),and the results both of two groups were better than that of C7.5 group.For treatment efficiency,the time of C7.5 group was shortest,and that of C5 group was longest.Conclusion: As the definition of target region for TN,the double collimator plan of 5mm combined with 7.5mm not only can obtain more perfect dose distribution of target region under ensuring the dose limitation for normal tissue,but also guarantee the relative high efficiency in implementing plan,and it can be the optimal choice of collimator for treating TN by using CK.%目的:分析比较不同准直器选择对射波刀(CK)治疗三叉神经痛(TN)计划剂量学的影响,以期为最优准直器的选择提供参考.方法:选取21例接受CK治疗的TN患者的临床资料,其中患病部位右侧14例,左侧7例.分别设计5 mm准直器、7.5 mm准直器以及5 mm和7.5 mm双准直器3组计划,并分别定义为C5组、C7.5组以及C5联合C7.5组.给予计划靶区(PTV)处方剂量64 Gy/1 F,正常组织限量参照美国物理师学会(AAPM)TG101报告.评估靶区处方剂量覆盖度、适形度及治疗效率等参数.结果:①靶区覆盖率C7.5组较差,C5组和C5联合C7.5组间比较差异无统计学意义(F=17.811,P＞0.05),但随着靶区体积的增大,C5组和7.5组的优势逐渐突出,且在靶区距离脑干最短距离的因素分析中体现出一定的优势;②靶区适形度C5组与C5联合C7.5组间比较差异无统计学意义(F=4.604,P＞0.05),且两组结果均优于C7.5组;③治疗效率C7.5组治疗时间最短,C5组治疗时间最长.结论:依照TN靶区的定义,在实施CK治疗时,5 mm联合7.5 mm双准直器计划既可以在保证正常组织剂量限制的前提下得到更为理想的靶区剂量分布,又可以保证计划实施的相对高效,可为CK治疗TN最佳准直器选择.
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