Treatment parameters consideration for universal range shifter-based multi-energy proton FLASH-RT

IF 3.2 2区医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Medical physics Pub Date : 2025-09-30 DOI:10.1002/mp.70039

Yiling Zeng, Hong Quan, Qi Zhang, Wei Wang, Xu Liu, Bin Qin, Bo Pang, Muyu Liu, Shuoyan Chen, Kunyu Yang, Yu Chang, Zhiyong Yang

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引用次数: 0

Abstract

Background

Compared to conventional dose rate irradiation, ultra-high dose rate irradiation provides superior normal tissue sparing. Multi-energy proton beams combined with a universal range shifter (URS) and fast energy-switching gantry enable ultra-high dose rate delivery.

Purpose

This study investigates the effects of the URS, planning parameters, and patient selection on multi-energy Bragg peak (MEBP) proton FLASH radiotherapy (FLASH-RT) plans.

Methods

Single-field plans were generated for water phantoms and a brain case, comparing beam setups with and without the URS. Planning parameters, including spot spacing, layer spacing, and beam orientation, were varied. The effects of fractional dose and target size were also assessed. Dose and FLASH-related metrics were analyzed.

Results

The use of a URS increased the spot size, which reduced the number of required spots and energy layers but also resulted in a broader penumbra, a prolonged distal falloff, and a higher D_mean in normal tissue. These effects became more pronounced with greater URS thickness. A spot spacing of 1.5 times the spot size (σ) and a layer spacing of 1.0 times the Bragg peak width (Proximal and Distal R80) improved V_40Gy/s, while effectively maintaining plan quality. Beam orientations with smaller field sizes increased V_40Gy/s. As the fractional dose increased, V_40Gy/s also increased, reaching saturation around 25 GyRBE. Additionally, V_40Gy/s improved with smaller target volumes.

Conclusions

The URS has a significant impact on plan quality, requiring a balance between normal tissue sparing and the FLASH effect in MEBP planning. Although MEBP plan is suitable for treating tumors with complex shapes, careful selection of planning parameters is critical for achieving effective FLASH treatment.

Abstract Image

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基于通用范围移位器的多能质子FLASH-RT处理参数考虑。

背景：与常规剂量率照射相比，超高剂量率照射能更好地保护正常组织。多能质子束与通用范围移位器（URS）和快速能量切换龙门相结合，可以实现超高剂量率的输送。目的：探讨URS、计划参数和患者选择对多能布拉格峰（MEBP）质子FLASH放疗（FLASH- rt）计划的影响。方法：制作水影和脑病例的单场图，比较有URS和没有URS的光束设置。规划参数，包括光斑间距，层间距和光束方向，是不同的。还评估了分数剂量和靶大小的影响。分析剂量和flash相关指标。结果：URS的使用增加了斑点大小，减少了所需斑点和能量层的数量，但也导致了更宽的半影，更长时间的远端脱落，以及正常组织中更高的Dmean。URS厚度越大，这些影响就越明显。当光斑间距为光斑尺寸（σ）的1.5倍和层间距为Bragg峰宽度（近端和远端R80）的1.0倍时，可提高V40Gy/s，同时有效保持平面质量。电场尺寸越小，波束方向增大V40Gy/s。随着分数剂量的增加，V40Gy/s也随之增加，在25 GyRBE左右达到饱和。此外，在更小的目标体积下，V40Gy/s得到了改进。结论：URS对计划质量有显著影响，在MEBP计划中需要平衡正常组织保留和FLASH效应。虽然MEBP计划适用于治疗形状复杂的肿瘤，但仔细选择计划参数对于实现有效的FLASH治疗至关重要。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Medical physics 医学-核医学

CiteScore

6.80

自引率

15.80%

发文量

660

审稿时长

1.7 months

期刊介绍： Medical Physics publishes original, high impact physics, imaging science, and engineering research that advances patient diagnosis and therapy through contributions in 1) Basic science developments with high potential for clinical translation 2) Clinical applications of cutting edge engineering and physics innovations 3) Broadly applicable and innovative clinical physics developments Medical Physics is a journal of global scope and reach. By publishing in Medical Physics your research will reach an international, multidisciplinary audience including practicing medical physicists as well as physics- and engineering based translational scientists. We work closely with authors of promising articles to improve their quality.