多叶准直器叶片宽度对容积旋转调强放疗剂量分布的影响  

Effect of different leaf widths of multileaf collimator on the dosimetric distribution of volumetric modulated arc therapy

作　　者：张国峰[1] 全红[1] 张俊[2] 胡军[3] 唐焱[3] 

机构地区：[1]武汉大学物理科学与技术学院,湖北武汉430072 [2]武汉大学中南医院放疗科,湖北武汉430071 [3]克拉玛依市中心医院血液肿瘤科,新疆克拉玛依834000

出　　处：《中国医学物理学杂志》2016年第11期1081-1085,共5页Chinese Journal of Medical Physics

基　　金：国家自然科学基金(10875092);湖北省自然科学基金(2012FKB04449)

摘　　要：目的:研究多叶准直器(MLC)叶片宽度在容积旋转调强放疗(VMAT)中对剂量分布的影响。方法:选取头部肿瘤患者12例,划分成大靶区体积(脑胶质瘤)组和小靶区体积(垂体瘤)组。在Eclipse治疗计划系统中,对每例患者使用相同的剂量学限制条件,并将肿瘤靶区置于窄MLC叶片(5mm)区和宽MLC叶片(10mm)区,分别制定两个VMAT治疗计划。通过计算对比剂量分布图和剂量学指标,分析MLC叶片宽度对不同靶区体积肿瘤剂量分布的影响。结果:无论是大体积靶区肿瘤还是小体积靶区肿瘤,使用较窄的MLC叶片都可以改善剂量学指标,但是这种改进不具有统计学差异(P>0.05)。而对于给定宽度(5mm或10mm)的MLC叶片,大体积靶区肿瘤组的VMAT治疗计划剂量学指标优于小体积靶区肿瘤组,并且具有统计学差异(P<0.05);另一方面,随着肿瘤体积的减小,剂量学指标的改进率明显提高。结论:VMAT放疗技术可以改善剂量学指标,并且能够有效减小MLC叶片宽度对剂量分布的影响;靶区体积的大小是影响VMAT治疗计划剂量学指标改进率的重要因素。在VMAT临床应用中,应根据肿瘤靶区体积大小及其与危及器官的位置关系,合理选择MLC叶片厚度以达到最佳疗效。Objective To investigate the dosimetric effect of different leaf widths of multileaf collimator （MLC） in the volumetric modulated arc therapy （VMAT） for small- and big-volume targets. Methods Twelve selected patients with tumor in the head were divided into big-volume target group （glioma） and small-volume target group （pituitary tumor）. With the same dose constraints in the Eclipse treatment planning system, planning target volume （PTV） was located in the narrow- and wide- leaf area （5 and 10 ram, respectively） of MLC, respectively, and two VMAT plans were designed for each patient. The dosimetric distribution and dosimetric index were calculated and compared to analyze the effect of different leaf widths of MLC on the dosimetric distribution of the VMAT for small- and big-volume targets. Results Although the narrow-leaf MLC resulted in better dosimetric index in both small- and big-volume targets, the improvement was not statistically significant （P〉0.05）. Using the MLC with certain leaf width （5 or t 0 mm）, the big-volume target group showed better dosimetric index than the other group, with statistical differences （P〈0.05）. With the reduction of target volume, the improvement ratio of dosimetric index increased significantly. Conclusion VMAT improves dosimetric index and reduces the effect of leaf width of MLC on dosimetric distribuction. Target volume is the important factor affecting the improvement ratio of dosimetric index in VMRT plan. Tumor target volume and the position in relation to organs at risk should be taken into consideration in clinical practice to decide the optimal leaf width of MLC.

关 键 词：多叶准直器 容积旋转调强放疗 靶区体积 剂量学指标 

分 类 号：R815.6[医药卫生—放射医学]