PDF(Pubmed)
Abstract：
UNASSIGNED: The purpose of this study is to evaluate the potential of the flattening filter free (FFF) mode of a linear accelerator for patients with hippocampal avoidance whole-brain radiotherapy (HA-WBRT) by comparison with flattened beams (FF) technique in the application of volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) using dosimetric and radiobiological indexes based on the volume of hippocampus and target.
UNASSIGNED: 2 VMAT- and 2 IMRT- plans were optimized in Eclipse planning system with 2 different delivery modes (6 MV standard vs. 6 MV FFF) for each of 25 patients. Dose distributions of the target and organs at risk (OARs), normal tissue complication probability (NTCP) of the hippocampus, monitor units, treatment time and quality assurance results were evaluated to compare the normal and FFF beam characteristics by Wilcoxon matched-pair signed-rank test with a significance level of 0.05.
UNASSIGNED: VMAT-FFF provided the significantly best homogeneity and conformity of the target, delivered the lowest dose to hippocampus and the other OARs, and led to the lowest NTCP of the hippocampus among all modalities, which has the potential to alleviate neurocognitive decline after WBRT. IMRT-FFF reduced the dose to the lens with similar dose distributions of the target compared with IMRT-FF, whereas the lower dose to the hippocampus was achieved using the conventional beams. The monitor units were obviously increased by 19.2% for VMAT and 33.8% for IMRT, when FFF beams w ere used. The removal of flattening filter for IMRT resulted in a 26% reduction in treatment time, but VMAT had the similar treatment time for the two modes owing to the limitation of gantry rotation speed. Gamma analysis showed an excellent agreement for all plans at 3%/2 mm, and no statistical differences were found between FF and FFF.
UNASSIGNED: In conclusion, this study suggests that FFF mode is feasible and advantageous in HA-WBRT and VMAT-FFF is the optimal solution in terms of dose distribution of the target, OARs sparing, NTCP of the hippocampus and delivery efficiency compared to the other three techniques. Additionally, the advantages of the FFF technique for VMAT are more prominent in cases with small hippocampal volumes.
UNASSIGNED: 2 VMAT- and 2 IMRT- plans were optimized in Eclipse planning system with 2 different delivery modes (6 MV standard vs. 6 MV FFF) for each of 25 patients. Dose distributions of the target and organs at risk (OARs), normal tissue complication probability (NTCP) of the hippocampus, monitor units, treatment time and quality assurance results were evaluated to compare the normal and FFF beam characteristics by Wilcoxon matched-pair signed-rank test with a significance level of 0.05.
UNASSIGNED: VMAT-FFF provided the significantly best homogeneity and conformity of the target, delivered the lowest dose to hippocampus and the other OARs, and led to the lowest NTCP of the hippocampus among all modalities, which has the potential to alleviate neurocognitive decline after WBRT. IMRT-FFF reduced the dose to the lens with similar dose distributions of the target compared with IMRT-FF, whereas the lower dose to the hippocampus was achieved using the conventional beams. The monitor units were obviously increased by 19.2% for VMAT and 33.8% for IMRT, when FFF beams w ere used. The removal of flattening filter for IMRT resulted in a 26% reduction in treatment time, but VMAT had the similar treatment time for the two modes owing to the limitation of gantry rotation speed. Gamma analysis showed an excellent agreement for all plans at 3%/2 mm, and no statistical differences were found between FF and FFF.
UNASSIGNED: In conclusion, this study suggests that FFF mode is feasible and advantageous in HA-WBRT and VMAT-FFF is the optimal solution in terms of dose distribution of the target, OARs sparing, NTCP of the hippocampus and delivery efficiency compared to the other three techniques. Additionally, the advantages of the FFF technique for VMAT are more prominent in cases with small hippocampal volumes.
摘要：
■这项研究的目的是通过与基于海马和靶标体积的剂量学和放射生物学指标的体积调制电弧疗法（VMAT）和强度调制放射疗法（IMRT）的应用相比，评估线性加速器的无平坦滤波（FFF）模式对海马回避全脑放射治疗（HA-WBRT）患者的潜力。
■在Eclipse规划系统中优化了2个VMET-和2个IMRT-计划，具有2种不同的交付模式（6MV标准与6MVFFF）为25名患者。目标和危险器官（OAR）的剂量分布，海马的正常组织并发症概率（NTCP），监测单位,对治疗时间和质量保证结果进行了评估，以通过Wilcoxon配对对符号秩检验比较正常和FFF波束特征，显著性水平为0.05。
■VMAT-FFF提供了目标的最佳均匀性和一致性，将最低剂量输送到海马体和其他OAR，并导致所有模式中海马的NTCP最低，有可能缓解WBRT后的神经认知能力下降。与IMRT-FF相比，IMRT-FFF减少了目标剂量分布相似的晶状体剂量。而较低剂量的海马是使用常规束实现的。VMAT监测单位明显增加19.2%,IMRT监测单位明显增加33.8%,当使用FFF梁时。去除用于IMRT的平坦化过滤器导致治疗时间减少26%，但是由于机架转速的限制，VMAT对两种模式的处理时间相似。伽马分析显示，所有计划在3%/2毫米时都有很好的一致性，FF和FFF之间无统计学差异。
■总而言之，这项研究表明，FFF模式在HA-WBRT中是可行和有利的，VMAT-FFF是目标剂量分布方面的最佳解决方案，OARssparing,海马NTCP的给药效率比拟其他三种技巧。此外,在海马体积较小的病例中，FFF技术用于VMAT的优势更为突出。
■在Eclipse规划系统中优化了2个VMET-和2个IMRT-计划，具有2种不同的交付模式（6MV标准与6MVFFF）为25名患者。目标和危险器官（OAR）的剂量分布，海马的正常组织并发症概率（NTCP），监测单位,对治疗时间和质量保证结果进行了评估，以通过Wilcoxon配对对符号秩检验比较正常和FFF波束特征，显著性水平为0.05。
■VMAT-FFF提供了目标的最佳均匀性和一致性，将最低剂量输送到海马体和其他OAR，并导致所有模式中海马的NTCP最低，有可能缓解WBRT后的神经认知能力下降。与IMRT-FF相比，IMRT-FFF减少了目标剂量分布相似的晶状体剂量。而较低剂量的海马是使用常规束实现的。VMAT监测单位明显增加19.2%,IMRT监测单位明显增加33.8%,当使用FFF梁时。去除用于IMRT的平坦化过滤器导致治疗时间减少26%，但是由于机架转速的限制，VMAT对两种模式的处理时间相似。伽马分析显示，所有计划在3%/2毫米时都有很好的一致性，FF和FFF之间无统计学差异。
■总而言之，这项研究表明，FFF模式在HA-WBRT中是可行和有利的，VMAT-FFF是目标剂量分布方面的最佳解决方案，OARssparing,海马NTCP的给药效率比拟其他三种技巧。此外,在海马体积较小的病例中，FFF技术用于VMAT的优势更为突出。
