两种调强放疗计划设计模式的比较

关莹 戴建荣 金大伟 章众

中国医科院肿瘤医院放射治疗科

摘 要

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。

材料与方法：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）、以及治疗时间的差别。

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33.8%，MU减少23.2%，治疗时间缩短32.4%(即3.5分钟)；在鼻咽癌计划中，使总子野数减少59.3%，但MU增加9.4%，节省治疗时间48.8%(即13.8分钟)。

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。

关键字：IMRT，直接子野优化，分步设计，前列腺癌、鼻咽癌

Comparison of two planning modes

for intensity-modulated radiation therapy

GUAN Ying DAI Jianrong ZHANG Zhong JIN Dawei

Cancer Institute (Hospital)

Chinese Academy of Medical Sciences

(Peking Union Medical College)

Corresponding author: Dai Jianrong

Email: dai_jianrong@yahoo.com.cn

Abstract

Purpose: To compare two planning modes for intensity-modulated radiation therapy. The two modes are multiple-step （MS）mode and direct machine parameter optimization （DMPO）.

Material and Methods: Ten patients with prostate cancer and ten patients with nasopharyngeal carcinoma were enrolled in this study. Plans were designed in both modes with Philips ADAC Pinnacle³ treatment planning system (Philips/Adac). Under the condition that beam directions were the same, optimization parameters were the same, and the final objective values had a difference of less than 1%, , the DVH (Dose Volume Histogram), number of segments, number of monitor units (MU), and treatment delivery time were compared between two modes.

Results: Plans designed in both modes satisfied all clinical requirements. They both had similar dose distributions and similar DVH curves. Comparing with the traditional multiple-step mode，, DMPO reduced the number of segments averagely by 33. 8%, and the number of MUs averagely by 23.2% for prostate cancer, and consequently shortened the treatment delivery time by 32.4% (i.e., 3.5 minutes). For nasopharyngeal carcinoma, the number of segments decreased by 59.3% whereas the number of MUs increased by 9.4%, and consequently the treatment delivery time decreased by 48.8% (i.e.,13.8 minutes).

Conclusions: In Comparison with MS mode, DMPO mode reduces the number of segments, shortens treatment delivery time, relieve wearing of multileaf collimator, significantly. But the variation of MUs for this mode depends on treatment site.

Key words: IMRT; Direct machine parameter optimization; Multiple-step mode; Prostate cancer; Nasopharyngeal cancer.