Abstract：
OBJECTIVE: Respiratory motion and patient setup error both contribute to the dosimetric uncertainty in radiotherapy of lung tumors. Managing these uncertainties for free-breathing treatments is usually done by margin-based approaches or robust optimization. However, breathing motion can be irregular and concerns have been raised for the robustness of the treatment plans. We have previously reported the dosimetric effects of the respiratory motion, without setup uncertainties, in lung tumor photon radiotherapy using free-breathing images. In this study, we include setup uncertainty.
METHODS: Tumor positions from cine-CT images acquired in free-breathing were combined with per-fraction patient shifts to simulate treatment scenarios. A total of 14 patients with 300 tumor positions were used to evaluate treatment plans based on 4DCT. Four planning methods aiming at delivering 54 Gy as median tumor dose in three fractions were compared. The planning methods were denoted robust 4D (RB4), isodose to the PTV with a central higher dose (ISD), the ISD method normalized to the intended median tumor dose (IRN) and homogeneous fluence to the PTV (FLU).
RESULTS: For all planning methods 95% of the intended dose was achieved with at least 90% probability with RB4 and FLU having equal CTV D50% values at this probability. FLU gave the most consistent results in terms of CTV D50% spread and dose homogeneity.
CONCLUSIONS: Despite the simulated patient shifts and tumor motions being larger than observed in the 4DCTs the dosimetric impact was suggested to be small. RB4 or FLU are recommended for the planning of free-breathing treatments.
METHODS: Tumor positions from cine-CT images acquired in free-breathing were combined with per-fraction patient shifts to simulate treatment scenarios. A total of 14 patients with 300 tumor positions were used to evaluate treatment plans based on 4DCT. Four planning methods aiming at delivering 54 Gy as median tumor dose in three fractions were compared. The planning methods were denoted robust 4D (RB4), isodose to the PTV with a central higher dose (ISD), the ISD method normalized to the intended median tumor dose (IRN) and homogeneous fluence to the PTV (FLU).
RESULTS: For all planning methods 95% of the intended dose was achieved with at least 90% probability with RB4 and FLU having equal CTV D50% values at this probability. FLU gave the most consistent results in terms of CTV D50% spread and dose homogeneity.
CONCLUSIONS: Despite the simulated patient shifts and tumor motions being larger than observed in the 4DCTs the dosimetric impact was suggested to be small. RB4 or FLU are recommended for the planning of free-breathing treatments.
摘要：
目的：呼吸运动和患者设置错误都会导致肺部肿瘤放疗的剂量不确定性。管理自由呼吸治疗的这些不确定性通常通过基于边缘的方法或鲁棒优化来完成。然而,呼吸运动可能是不规则的,并且已经引起了对治疗计划的鲁棒性的关注。我们以前报道过呼吸运动的剂量学效应，没有设置不确定性，在肺肿瘤光子放射治疗中使用自由呼吸图像。在这项研究中,我们包括设置不确定性。
方法：将自由呼吸中采集的cine-CT图像中的肿瘤位置与患者每个分数的移位相结合，以模拟治疗方案。共14例300个肿瘤位置的患者用于基于4DCT评价医治计划。比较了四种计划方法，目的是在三个部分中提供54Gy作为中位肿瘤剂量。规划方法表示为鲁棒4D(RB4)，等剂量的PTV与中心高剂量（ISD），ISD方法标准化为预期的中位肿瘤剂量(IRN)和对PTV的均匀注量(FLU)。
结果：对于所有计划方法，以至少90％的概率实现了95％的预期剂量，RB4和FLU在此概率下具有相等的CTVD50％值。就CTVD50%扩散和剂量均匀性而言,FLU给出了最一致的结果。
结论：尽管模拟的患者移位和肿瘤运动比在4DCT中观察到的更大，但剂量影响被认为是小的。建议将RB4或FLU用于计划自由呼吸治疗。
方法：将自由呼吸中采集的cine-CT图像中的肿瘤位置与患者每个分数的移位相结合，以模拟治疗方案。共14例300个肿瘤位置的患者用于基于4DCT评价医治计划。比较了四种计划方法，目的是在三个部分中提供54Gy作为中位肿瘤剂量。规划方法表示为鲁棒4D(RB4)，等剂量的PTV与中心高剂量（ISD），ISD方法标准化为预期的中位肿瘤剂量(IRN)和对PTV的均匀注量(FLU)。
结果：对于所有计划方法，以至少90％的概率实现了95％的预期剂量，RB4和FLU在此概率下具有相等的CTVD50％值。就CTVD50%扩散和剂量均匀性而言,FLU给出了最一致的结果。
结论：尽管模拟的患者移位和肿瘤运动比在4DCT中观察到的更大，但剂量影响被认为是小的。建议将RB4或FLU用于计划自由呼吸治疗。
