Wei Long, Shang Haijiao, Jin Fu, Wang Yuenan
School of Computer Science and Technology, Shandong Jianzhu University, Jinan, China.
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, China.
Front Oncol. 2020 Oct 9;10:574605. doi: 10.3389/fonc.2020.574605. eCollection 2020.
The objective of this study was to evaluate the interplay effects in proton-based stereotactic body radiotherapy (SBRT) using 4D robust optimization combined with iso-energy layer repainting techniques for non-small cell lung cancer (NSCLC).
Twelve patients with early-stage NSCLC who underwent 4DCT were retrospectively selected. A robust CTV-based 4D plan was generated for each based on commercial Treatment planning system (TPS), considering patient setup errors, range uncertainties, and organ motion. The 4D static dose (4DSD) and 4D dynamic dose (4DDD) were calculated using a hybrid deformable algorithm and simulated proton delivery system. An index was developed to quantitatively evaluate the interplay effects. The interplay effects of the 4D robust plan and multiple iso-energy layers (3, 4, 5, 6, and 7) of the robust repainting 4D plan were calculated based on to select the optimal times for layer repainting.
Due to the interplay effects, the mean target values D and D increased to 1.28 and 1.01%, and the target values D and D decreased to 2.01 and 1.77%, respectively, for the 4D Robust SBRT plan. After multiple iso-energy repainting times, the interplay effects of the target values D and D tended to migrate, from 2.01 to 0.92% in target value D and from 1.77 to 0.89% in target value D, respectively. Moreover, a positive linear correlation was observed between the optimal interplay effect mitigation and target range of motion.
In proton-based 4D Robust SBRT, the interplay effects degraded the target dose distribution but were mitigated using iso-energy layer repainting techniques. However, there was no significant correlation between the number of repainting layers and improvements in the dose distributions. The optimal layer repainting times based on the interplay effect index were ascertained according to the patient characteristics.
本研究的目的是评估在非小细胞肺癌（NSCLC）的基于质子的立体定向体部放射治疗（SBRT）中，使用4D稳健优化结合等能量层重绘技术的相互作用效果。
回顾性选取12例接受4DCT的早期NSCLC患者。基于商业治疗计划系统（TPS）为每位患者生成基于稳健CTV的4D计划，同时考虑患者摆位误差、射程不确定性和器官运动。使用混合可变形算法和模拟质子输送系统计算4D静态剂量（4DSD）和4D动态剂量（4DDD）。开发了一个指标来定量评估相互作用效果。基于该指标计算4D稳健计划和稳健重绘4D计划的多个等能量层（3、4、5、6和7）的相互作用效果，以选择层重绘的最佳次数。
由于相互作用效果，4D稳健SBRT计划中，平均靶区值D和D分别增加到1.28%和1.01%，靶区值D和D分别降低到2.01%和1.77%。多次等能量重绘后，靶区值D和D的相互作用效果趋于迁移，靶区值D从2.01%降至0.92%，靶区值D从1.77%降至0.89%。此外，在最佳相互作用效果缓解与靶区运动范围之间观察到正线性相关。
在基于质子的4D稳健SBRT中，相互作用效果使靶区剂量分布恶化，但使用等能量层重绘技术可减轻这种影响。然而，重绘层数与剂量分布改善之间无显著相关性。根据患者特征，基于相互作用效果指标确定了最佳层重绘次数。
