基于MatriXX系统探讨周期运动靶区调强放疗剂量分布特点

Dose distribution features of periodic motion target based on MatriXX system

目的 基于MatriXX系统,探讨周期运动靶区进行调强放疗时的受照剂量分布特点.方法 用周期运动平台与二维空气电离室矩阵MatriXX系统配合,分别测量静止和周期运动（幅度±1 cm,周期3.5 s）靶区接受调强（Step ＆ shoot和Sliding Window）子野照射的二维剂量分布,然后,对不同状态下所测剂量分布进行两两对比分析.结果 当采用一种调强子野分别对静止和周期运动靶区进行照射时,两种状态下所致等剂量分布有明显的差异,特别是在射野边缘处,偏差高达15%左右,其Gamma分析（3mm,±3%的标准）的符合率较低,约88.0%～92.8%;当靶区只处于某一状态（静止或运动）,而分别采用不同的调强方式的子野照射时,所得剂量分布的差异很小,其Gamma分析的符合率高达96.7%～99.2%.结论 周期运动靶区的实际受照剂量与静态靶区接受的剂量在射野边缘处差异明显,而在中心区域较小.

Objective To investigate the dose distribution features of periodic motion target based on MatriXX system. Methods The static and periodic motion targets were separately irradiated by step and shoot and sliding window intensity modulated radiation therapy （IMRT） beams. The dose distribution was measured by MatfiXX system combined with domestic made periodic motion platform. Then the dose distribu-tions were compared by using the OmniPro I＇mRT software system. Results When the target was irradiated by one type of IMRT beams （step and shoot or sliding window）, the differences of dose distributions between periodic motion target and static were mainly located at the edge of the target, about 15%. When the target （static or motion） was irradiated separately by two types of IMRT beams （step and shoot and sliding window）, the differences of dose distributions between step and shoot and sliding window irradiation were very small. Con-clusions The differences of dose distributions between periodic motion and static target were mainly located at the edge of the fields, and we should pay more attention. In the central area of the target, the dose distribution differences were very small.