Chen Hungcheng, Wu Andrew, Brandner Edward D, Heron Dwight E, Huq M Saiful, Yue Ning J, Chen Wen-Cheng
Department of Radiation Oncology, Helen F Graham Cancer Center Christiana Care Health System, Newark, Delaware 19713, USA.
Med Phys. 2009 Mar;36(3):893-903. doi: 10.1118/1.3070542.
The interplay between a mobile target and a dynamic multileaf collimator can compromise the accuracy of intensity-modulated radiation therapy (IMRT). Our goal in this study is to investigate the dosimetric effects caused by the respiratory motion during IMRT. A moving phantom was built to simulate the typical breathing motion. Different sizes of the gating windows were selected for gated deliveries. The residual motions during the beam-on period ranged from 0.5 to 3 cm. An IMRT plan with five treatment fields from different gantry angles were delivered to the moving phantom for three irradiation conditions: Stationary condition, moving with the use of gating system, and moving without the use of gating system. When the residual motion was 3 cm, the results showed significant differences in dose distributions between the stationary condition and the moving phantom without gating beam control. The overdosed or underdosed areas enclosed about 33% of the treatment area. In contrast, the dose distribution on the moving phantom with gating window set to 0.5 cm showed no significant differences from the stationary phantom. With the appropriate setting of the gating window, the deviation of dose from the respiratory motion can be minimized. It appeals that limiting the residual motion to less than 0.5 cm is critical for the treatments of mobile structures.
移动靶区与动态多叶准直器之间的相互作用可能会影响调强放射治疗（IMRT）的准确性。本研究的目的是探讨IMRT过程中呼吸运动引起的剂量学效应。构建了一个移动体模来模拟典型的呼吸运动。选择不同大小的门控窗口进行门控照射。射束开启期间的残余运动范围为0.5至3厘米。针对三种照射条件，将具有五个来自不同机架角度的治疗野的IMRT计划施用于移动体模：静止状态、使用门控系统移动以及不使用门控系统移动。当残余运动为3厘米时，结果显示静止状态与无门控射束控制的移动体模之间的剂量分布存在显著差异。剂量过量或不足的区域约占治疗区域的33%。相比之下，门控窗口设置为0.5厘米的移动体模上的剂量分布与静止体模无显著差异。通过适当设置门控窗口，可以将呼吸运动引起的剂量偏差降至最低。对于移动结构的治疗，将残余运动限制在小于0.5厘米至关重要。
