多叶准直器角度因素对调强放疗计划实施效率的影响

The influence of multileaf collimator angle on delivery efficiency for IMRT treatment

目的 探讨调强放疗计划优化时多叶准直器（MLC）角度因素对优化结果中子野数（滑窗模式下为控制点数）和机器跳数影响,以及由此对调强放疗实施效率的影响.方法 选择10例拟行调强放疗的靶区形状为长条状的患者CT图像,在MLC运行方向与靶区长轴垂直（横向）和平行（纵向）方向分别以静态子野调强方式和滑窗调强方式设计计划并进行优化,在保证靶区和危及器官受量相同情况下,分别比较静态子野调强模式和滑窗调强模式下两种准直器角度时计划子野数或控制点数和机器跳数差别.结果 MLC纵向方式较横向方式静态子野数平均增加52.8％,滑窗调强控制点数增加58.2％,机器跳数平均增加幅度分别为49.6％和61.9％,子野数或控制点数和机器跳数均不同（P =0.000）.结论 在MLC调强放疗计划优化中选择MLC运行方向垂直于靶区长轴,在不影响靶区和危及器官受量情况下,可明显减少子野数或控制点数和机器跳数、缩短治疗时间、提高治疗效率,具有一定的临床实用价值.

Abstract： Objective To study the influence of the angle of multileaf collimator leaves on segments （control point for sliding windows） number and monitor units in intensity-modulated radiotherapy （IMRT） plan optimization.Methods 10 cases undergone IMRT with rectangle target volume were choosed,2 plan were designed with step and shot technique and sliding windows technique for running direction of collimator with target long axis vertical and parallel respectively,compared the plans with similar optimization parameters for different angle of the collimator.Results The number of segments and monitor units increased by 52.8% and 49.6% more than longitudinal direction of leaf collimator with static IMRT respectively,there appeared significant difference （P =0.000） ; and the number of segments and monitor units increased by 58.2% and 61.9% more than longitudinal direction of leaf collimator with dynamic IMRT respectively,there appeared significant difference （P =0.000）.Conclusions For the optimization of IMRT based on multileaf collimator,the direction of collimator perpendicular to the target long axis,there could be obviously decrease the number of monitor units,shorten the treatment time,improve the treatment efficiency with similar dose distribution.