An adaptive proton FLASH therapy using modularized pin ridge filter

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

Medical physics Pub Date : 2025-09-12 DOI:10.1002/mp.18109

Ahmal Jawad Zafar, Xiaofeng Yang, Zachary Diamond, Tian Sibo, David Yu, Pretesh R. Patel, Jun Zhou

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Abstract

Background

In our previous study, we developed a modular pin ridge filter (pRF) design framework to streamline assembly, enabling the fast manufacture of custom filters optimized for single-energy proton FLASH planning.

Purpose

In this paper, we propose a method to optimize adaptive proton FLASH therapy (ADP-FLASH) using modularized pRFs by recycling module pins from the initial plan while reducing pRF adjustments in adaptive FLASH planning.

Methods

Initially, single energy (250 MeV) FLASH-pRF plans were created using pencil beam directions (PBDs) from initial IMPT plans on the planning CT (pCT). PBDs are classified as new/changed (ΔE > 5 MeV) or unchanged by comparing spot maps for targets between pCT and re-CT. We used an iterative least-square regression model to identify recyclable PBDs with minimal relative changes to spot MU weighting. Two PBDs with the least square error were retrieved per iteration and added to the background plan, and the remaining PBDs were reoptimized for the adaptive plan in subsequent iterations. The method was validated on three liver SBRT cases (50 Gy in five fractions) by comparing various dosimetric parameters across initial pRF plans on pCT, re-CT, and the ADP-FLASH-pRF plans on re-CT.

Results

V₁₀₀ for initial-pRF plans on pCT, re-CT, and ADP-FLASH-pRF plans for the three cases were as follows: (93.7%, 89.2%, 91.4%), (93.5%, 60.2%, 91.7%), and (97.3%, 69.9%, 98.8%). We observe a decline in plan quality when applying the initial pRF to the re-CT, whereas the ADP-FLASH-pRF approach restores quality comparable to the initial pRF on the pCT. FLASH effect of the initial pRF and ADP pRF plans were evaluated with a dose and dose rate threshold of 1 and 40 Gy/s, respectively, using the FLASH effectiveness model. The proposed method recycled 91.2%, 71%, and 64.7% of PBDs from initial pRF plans for the three cases while maintaining all clinical goals and preserving FLASH effects.

Conclusion

This study validated a method for recycling the pRFs in single-energy proton FLASH planning for SBRT cases. This framework offers a scalable solution for adaptive proton therapy, balancing clinical effectiveness and practicality.

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采用模块化针脊滤波器的自适应质子闪蒸治疗

在我们之前的研究中，我们开发了一个模块化的引脚脊滤波器（pRF）设计框架，以简化组装，实现针对单能量质子FLASH规划优化的定制滤波器的快速制造。在本文中，我们提出了一种利用模块化的pRF来优化自适应质子FLASH治疗（ADP-FLASH）的方法，通过从初始计划中回收模块引脚，同时减少自适应FLASH计划中的pRF调整。方法首先，在规划CT （pCT）上使用铅笔束方向（pbd）从初始IMPT计划创建单能量（250 MeV） FLASH-pRF计划。通过比较pCT和re-CT之间的目标点图，pbd被分为新的/改变的（ΔE > 5 MeV）或未改变的。我们使用迭代最小二乘回归模型来识别具有最小相对变化的可回收pbd。每次迭代提取两个最小二乘误差的pbd，并将其添加到后台方案中，其余pbd在后续迭代中针对自适应方案进行重新优化。通过比较pCT、re-CT的初始pRF计划和re-CT的ADP-FLASH-pRF计划的不同剂量学参数，该方法在3例肝脏SBRT病例（5组50 Gy）中得到验证。结果3例患者pCT、re-CT和ADP-FLASH-pRF方案的初始prf方案V100分别为（93.7%、89.2%、91.4%）、（93.5%、60.2%、91.7%）和（97.3%、69.9%、98.8%）。我们观察到将初始pRF应用于re-CT时，计划质量下降，而ADP-FLASH-pRF方法恢复的质量与pCT上的初始pRF相当。使用FLASH有效性模型，分别以1 Gy/s和40 Gy/s的剂量和剂量率阈值评估初始pRF和ADP pRF计划的FLASH效果。该方法在保持所有临床目标和FLASH效果的同时，回收了最初pRF计划中91.2%、71%和64.7%的pbd。结论本研究验证了在SBRT病例的单能量质子FLASH计划中回收pRFs的方法。该框架为自适应质子治疗提供了可扩展的解决方案，平衡了临床有效性和实用性。

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.