两种调强放疗计划设计模式的比较

目的分步设计和直接子野优化是设计静态调强放疗计划的两种模式,本研究比较两种计划模式的特点。方法采用两种模式分别设计10例前列腺癌和10例鼻咽癌患者的调强计划。在射野方向和优化条件相同、最终目标函数值相近的前提下,比较两种计划设计模式下的剂量体积直方图(DVH)、靶区和危及器官的剂量、子野数、机器跳数(MU)、以及治疗时间。结果两种计划设计模式制定的计划均满足临床要求,剂量分布基本一致,DVH相似。与分步设计模式相比,直接子野优化模式使前列腺癌计划的子野数减少34%,MU减少23%,治疗时间缩短32%(即3.5 min);在鼻咽癌计划中,使总子野数减少59%,但MU增加9%,节省治疗时间49%(即13.8 min)。结论与分步模式相比,直接子野优化模式可显著减少子野数目,缩短治疗时间,降低机器磨损。但该模式MU的变化与治疗部位有关。

Comparison of two planning modes for intensity-modulated radiation therapy

Objective To compare two planning modes,multiple-step(MS)and direct machine pa- rameter optimization(DMPO)modes,for intensity-modulated radiation therapy.Methods Ten patients with prostate cancer and ten patients with nasopharyngeal carcinoma were alloted.Their plans were designed in both modes with Pinnacle~3 treatment planning system(Philips/Adac).Under the condition that beam di- rections being the same,optimization parameters also the same,the final objective values having a difference of less than 1%,the dose volume histogram(DVH),number of segments,number of monitor units(MU), and treatment delivery time were compared between these two modes.Results The plans designed in both modes satisfied all clinical requirements.They both had similar dose distributions and similar DVH curves. Compared with the MS,DMPO reduced 34% of the segments by average and 23% MU by average for prostate cancer,and consequently shortened the treatment delivery time by 32% (i.e.,3.5 minutes).For nasopha- ryngeal carcinoma,the number of segments decreased by 59%whereas the number of MU increased by 9%, and consequently the treatment delivery time decreased by 49% (i.e.,13.8 minutes).Conclusions In comparison with multiple-step mode,direct machine parameter optimization(DMPO)mode reduces the num- ber of segments,shortens the treatment delivery time,and relieves the wearing of multileaf collimator signifi- cantly.But the variation of multiple step monitor units(MU) for this mode depends on treatment site.