Busch Kia, Muren Ludvig P, Thörnqvist Sara, Andersen Andreas G, Pedersen Jesper, Dong Lei, Petersen Jørgen B B
Department of Medical Physics, Aarhus University Hospital/Aarhus University, Aarhus, Denmark.
Department of Physics and Technology, University of Bergen, Norway.
Phys Imaging Radiat Oncol. 2018 Dec 19;9:7-13. doi: 10.1016/j.phro.2018.11.009. eCollection 2019 Jan.
Proton therapy (PT) of extra-cranial tumour sites is challenged by density changes caused by inter-fractional organ motion. In this study we investigate dose-guided PT (DGPT) to account inter-fractional target motion, exemplified by internal motion in the pelvis.
On-line DGPT involved re-calculating dose distributions with the isocenter shifted up to 15 mm from the position corresponding to conventional soft-tissue based image-guided PT (IGPT). The method was applied to patient models with simulated prostate/seminal vesicle target motion of ±3, ±5 and ±10 mm along the three cardinal axes. Treatment plans were created using either two lateral (gantry angles of 90°/270°) or two lateral oblique fields (gantry angles of 35°/325°). Target coverage and normal tissue doses from DGPT were compared to both soft-tissue and bony anatomy based IGPT.
DGPT improved the dose distributions relative to soft-tissue based IGPT for 39 of 90 simulation scenarios using lateral fields and for 50 of 90 scenarios using lateral oblique fields. The greatest benefits of DGPT were seen for large motion, e.g. a median target coverage improvement of 13% was found for 10 mm anterior motion with lateral fields. DGPT also improved the dose distribution in comparison to bony anatomy IGPT in all cases. The best strategy was often to move the fields back towards the original target position prior to the simulated target motion.
DGPT has the potential to better account for large inter-fractional organ motion in the pelvis than IGPT.
颅外肿瘤部位的质子治疗（PT）受到分次间器官运动引起的密度变化的挑战。在本研究中，我们研究了剂量引导质子治疗（DGPT）以应对分次间靶区运动，以骨盆内部运动为例。
在线 DGPT 涉及将等中心从对应于传统基于软组织的图像引导质子治疗（IGPT）的位置向上移动至 15 毫米，重新计算剂量分布。该方法应用于模拟前列腺/精囊靶区沿三个坐标轴有±3、±5 和±10 毫米运动的患者模型。使用两个侧野（机架角度为 90°/270°）或两个侧斜野（机架角度为 35°/325°）创建治疗计划。将 DGPT 的靶区覆盖情况和正常组织剂量与基于软组织和骨骼解剖结构的 IGPT 进行比较。
对于使用侧野的 90 个模拟场景中的 39 个以及使用侧斜野的 90 个场景中的 50 个，DGPT 相对于基于软组织的 IGPT 改善了剂量分布。对于大运动，DGPT 的益处最为明显，例如，使用侧野时，向前运动 10 毫米，靶区覆盖的中位数改善了 13%。与基于骨骼解剖结构的 IGPT 相比，DGPT 在所有情况下也改善了剂量分布。最佳策略通常是在模拟靶区运动之前将射野向原始靶区位置移动。
与 IGPT 相比，DGPT 有可能更好地应对骨盆中较大的分次间器官运动。
