Purdue School of Engineering Technology, IUPUI, Indianapolis, Indiana 46202.
Med Phys. 2013 Oct;40(10):101708. doi: 10.1118/1.4820534.
To simulate and evaluate the use of dynamic multileaf collimators (dMLC) in respiratory gating to compensate for baseline drift.
Tumor motion tracking data from 30 lung tumors over 322 treatment fractions was analyzed with the finite state model. A dynamic respiratory gating window was established in real-time by determining the average positions during the previous two end-of-expiration breathing phases and centering the dMLC aperture on a weighted average of these positions. A simulated dMLC with physical motion constraints was used in dynamic gating treatment simulations. Fluence maps were created to provide a statistical description of radiation delivery for each fraction. Duty cycle was also calculated for each fraction.
The average duty cycle was 2.3% greater under dynamic gating conditions. Dynamic gating also showed higher fluences and less tumor obstruction. Additionally, dynamic gating required fewer beam toggles and each delivery period was longer on average than with static gating.
The use of dynamic gating showed better performance than static gating and the physical constraints of a dMLC were shown to not be an impediment to dynamic gating.
模拟并评估在呼吸门控中使用动态多叶准直器（dMLC）来补偿基线漂移。
使用有限状态模型对 30 个肺部肿瘤的 322 个治疗分数的肿瘤运动跟踪数据进行分析。通过确定前两个呼气末期呼吸阶段的平均位置，并将 dMLC 孔径中心置于这些位置的加权平均值上，实时建立动态呼吸门控窗口。在动态门控治疗模拟中使用具有物理运动约束的模拟 dMLC。创建通量图以提供每个分数的辐射传递的统计描述。还计算了每个分数的占空比。
动态门控条件下的平均占空比增加了 2.3%。动态门控还显示出更高的通量和更少的肿瘤阻塞。此外，与静态门控相比，动态门控需要更少的波束切换，并且每次输送周期的平均时间更长。
与静态门控相比，动态门控的性能更好，并且 dMLC 的物理限制不会成为动态门控的障碍。
