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Abstract：
OBJECTIVE: The objective of this study was to investigate the dosimetric impact of range uncertainty in a large cohort of patients receiving passive scatter proton therapy.
METHODS: A cohort of 120 patients were reviewed in this study retrospectively, of which 61 were brain, 39 lung, and 20 prostate patients. Range uncertainties of ±3.5% (overshooting and undershooting by 3.5%, respectively) were added and recalculated on the original plans, which had been planned according to our clinical planning protocol while keeping beamlines, apertures, compensators, and dose grids intact. Changes in the coverage on CTV and DVH for critical organs were compared and analyzed. Correlation between dose change and minimal distance between CTV and critical organs were also investigated.
RESULTS: Although CTV coverages and maximum dose to critical organs were largely maintained for most brain patients, large variations over 5% were still observed sporadically. Critical organs, such as brainstem and chiasm, could still be affected by range uncertainty at 4 cm away from CTV. Coverage and OARs in lung and prostate patients were less likely to be affected by range uncertainty with very few exceptions.
CONCLUSIONS: The margin recipe in modern TPS leads to clinically acceptable OAR doses in the presence of range uncertainties. However, range uncertainties still pose a noticeable challenge for small but critical serial organs near tumors, and occasionally for large parallel organs that are located distal to incident proton beams.
METHODS: A cohort of 120 patients were reviewed in this study retrospectively, of which 61 were brain, 39 lung, and 20 prostate patients. Range uncertainties of ±3.5% (overshooting and undershooting by 3.5%, respectively) were added and recalculated on the original plans, which had been planned according to our clinical planning protocol while keeping beamlines, apertures, compensators, and dose grids intact. Changes in the coverage on CTV and DVH for critical organs were compared and analyzed. Correlation between dose change and minimal distance between CTV and critical organs were also investigated.
RESULTS: Although CTV coverages and maximum dose to critical organs were largely maintained for most brain patients, large variations over 5% were still observed sporadically. Critical organs, such as brainstem and chiasm, could still be affected by range uncertainty at 4 cm away from CTV. Coverage and OARs in lung and prostate patients were less likely to be affected by range uncertainty with very few exceptions.
CONCLUSIONS: The margin recipe in modern TPS leads to clinically acceptable OAR doses in the presence of range uncertainties. However, range uncertainties still pose a noticeable challenge for small but critical serial organs near tumors, and occasionally for large parallel organs that are located distal to incident proton beams.
摘要：
目的：本研究的目的是研究在接受被动散射质子治疗的大型队列患者中范围不确定性的剂量学影响。
方法：本研究回顾性分析了120例患者的队列，其中61个是大脑，39肺，和20名前列腺患者。范围不确定性为±3.5%(过冲和下冲3.5%，分别)在原计划上添加和重新计算，这是根据我们的临床规划方案规划的，同时保留波束线，光圈,补偿器,剂量网格完好无损。比较并分析了关键器官的CTV和DVH覆盖率的变化。还研究了剂量变化与CTV和关键器官之间的最小距离之间的相关性。
结果：尽管大多数脑部患者的CTV覆盖率和对关键器官的最大剂量基本保持不变，仍然偶尔观察到超过5%的大变化。关键器官,比如脑干和交叉，仍然可能受到距离CTV4厘米的范围不确定性的影响。肺和前列腺患者的覆盖率和OAR不太可能受到范围不确定性的影响，只有极少数例外。
结论：在存在范围不确定性的情况下，现代TPS的边际配方导致临床上可接受的OAR剂量。然而,范围的不确定性仍然对肿瘤附近的小但关键的连续器官构成了明显的挑战，偶尔用于位于入射质子束远端的大型平行器官。
方法：本研究回顾性分析了120例患者的队列，其中61个是大脑，39肺，和20名前列腺患者。范围不确定性为±3.5%(过冲和下冲3.5%，分别)在原计划上添加和重新计算，这是根据我们的临床规划方案规划的，同时保留波束线，光圈,补偿器,剂量网格完好无损。比较并分析了关键器官的CTV和DVH覆盖率的变化。还研究了剂量变化与CTV和关键器官之间的最小距离之间的相关性。
结果：尽管大多数脑部患者的CTV覆盖率和对关键器官的最大剂量基本保持不变，仍然偶尔观察到超过5%的大变化。关键器官,比如脑干和交叉，仍然可能受到距离CTV4厘米的范围不确定性的影响。肺和前列腺患者的覆盖率和OAR不太可能受到范围不确定性的影响，只有极少数例外。
结论：在存在范围不确定性的情况下，现代TPS的边际配方导致临床上可接受的OAR剂量。然而,范围的不确定性仍然对肿瘤附近的小但关键的连续器官构成了明显的挑战，偶尔用于位于入射质子束远端的大型平行器官。
