A technique for achieving arbitrary machine dose rates via MLC leaf motion modulation using fixed-gantry IMRT delivery mode

IF 3.2 2区 医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Medical physics Pub Date : 2025-04-25 DOI:10.1002/mp.17835
Xin Wu, Dongrong Yang, Qingrong Jackie Wu, Yang Sheng, Anna E. Rodrigues, Joseph P. Kowalski, Qiuwen Wu
{"title":"A technique for achieving arbitrary machine dose rates via MLC leaf motion modulation using fixed-gantry IMRT delivery mode","authors":"Xin Wu,&nbsp;Dongrong Yang,&nbsp;Qingrong Jackie Wu,&nbsp;Yang Sheng,&nbsp;Anna E. Rodrigues,&nbsp;Joseph P. Kowalski,&nbsp;Qiuwen Wu","doi":"10.1002/mp.17835","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Background</h3>\n \n <p>The medical linear accelerator (Linac) typically operates at a constant but discrete dose rate for both 3D conformal fields and intensity modulation radiotherapy (IMRT) fields. However, in certain clinical and radiobiological scenarios, such as total body irradiation (TBI), an arbitrary dose rate outside the preset values may be desired.</p>\n </section>\n \n <section>\n \n <h3> Purpose</h3>\n \n <p>This study aims to achieve arbitrary machine dose rates in photon delivery through modulation of MLC leaf motion, providing flexibility for specific needs.</p>\n </section>\n \n <section>\n \n <h3> Method</h3>\n \n <p>The desired effective dose rate is achieved by precisely programming the motion of unused MLC leaves outside the field boundary set by the jaws, while keeping the MLC leaves within the jaw boundary same as originally planned. Between control points, the leaf speed is adjusted by multiplying the permissible limit by the ratio of the current dose rate to the desired value. During delivery, the dose rate is reduced so that the MLC leaves arrive at the expected position for the expected monitor units (MU). Two schemes were designed for different application scenarios and successfully delivered and verified. A circular 3D conformal field, a 40 cm × 40 cm TBI field, and a head-and-neck (H&amp;N) IMRT DMLC field were modified for dose rates between 600 and 1 MU/min. These plans were successfully delivered on Varian TrueBeam, and Clinac Linacs with modulated dose rates. Trajectory log analysis and portal dosimetry QA (PDQA) were utilized to verify the accuracy.</p>\n </section>\n \n <section>\n \n <h3> Results</h3>\n \n <p>Both schemes achieved stable and accurate dose rates, with mean deviations from the desired values remaining below 0.5% across the range from 600 to 1 MU/min. Fluctuations, represented by relative standard deviations, increased monotonically as the desired dose rate decreased. For clinically relevant dose rates above 100 MU/min, fluctuations remained below 0.5%. At lower dose rates, the thresholds for fluctuations reaching 1% and 10% were approximately 50 and 7 MU/min, respectively. Trajectory log file analysis confirmed agreement between planned and actual values of various treatment parameters, such as leaf position, speed, and MU. PDQA analysis showed 99% gamma pass rate with criteria of 3%/2 mm. For Scheme 1 with step-and-shoot, a 50% increase in delivery time due to the temporary beam-hold during step-and-shoot was both expected and observed.</p>\n </section>\n \n <section>\n \n <h3> Conclusion</h3>\n \n <p>A technique has been developed and validated to achieve arbitrary machine dose rates in photon delivery through the modulation of MLC leaf motion.</p>\n </section>\n </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 6","pages":"3595-3610"},"PeriodicalIF":3.2000,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Medical physics","FirstCategoryId":"3","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/mp.17835","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING","Score":null,"Total":0}
引用次数: 0

Abstract

Background

The medical linear accelerator (Linac) typically operates at a constant but discrete dose rate for both 3D conformal fields and intensity modulation radiotherapy (IMRT) fields. However, in certain clinical and radiobiological scenarios, such as total body irradiation (TBI), an arbitrary dose rate outside the preset values may be desired.

Purpose

This study aims to achieve arbitrary machine dose rates in photon delivery through modulation of MLC leaf motion, providing flexibility for specific needs.

Method

The desired effective dose rate is achieved by precisely programming the motion of unused MLC leaves outside the field boundary set by the jaws, while keeping the MLC leaves within the jaw boundary same as originally planned. Between control points, the leaf speed is adjusted by multiplying the permissible limit by the ratio of the current dose rate to the desired value. During delivery, the dose rate is reduced so that the MLC leaves arrive at the expected position for the expected monitor units (MU). Two schemes were designed for different application scenarios and successfully delivered and verified. A circular 3D conformal field, a 40 cm × 40 cm TBI field, and a head-and-neck (H&N) IMRT DMLC field were modified for dose rates between 600 and 1 MU/min. These plans were successfully delivered on Varian TrueBeam, and Clinac Linacs with modulated dose rates. Trajectory log analysis and portal dosimetry QA (PDQA) were utilized to verify the accuracy.

Results

Both schemes achieved stable and accurate dose rates, with mean deviations from the desired values remaining below 0.5% across the range from 600 to 1 MU/min. Fluctuations, represented by relative standard deviations, increased monotonically as the desired dose rate decreased. For clinically relevant dose rates above 100 MU/min, fluctuations remained below 0.5%. At lower dose rates, the thresholds for fluctuations reaching 1% and 10% were approximately 50 and 7 MU/min, respectively. Trajectory log file analysis confirmed agreement between planned and actual values of various treatment parameters, such as leaf position, speed, and MU. PDQA analysis showed 99% gamma pass rate with criteria of 3%/2 mm. For Scheme 1 with step-and-shoot, a 50% increase in delivery time due to the temporary beam-hold during step-and-shoot was both expected and observed.

Conclusion

A technique has been developed and validated to achieve arbitrary machine dose rates in photon delivery through the modulation of MLC leaf motion.

一种通过MLC叶片运动调制实现任意机器剂量率的技术,采用固定龙门IMRT递送模式。
背景:医用直线加速器(Linac)通常以恒定但离散的剂量率工作,用于三维适形场和强度调制放疗(IMRT)场。然而,在某些临床和放射生物学情况下,如全身照射(TBI),可能需要在预设值之外的任意剂量率。目的:本研究旨在通过调节MLC叶片运动实现任意机器剂量率的光子传递,为特定需求提供灵活性。方法:通过精确编程未使用的MLC叶片在颌骨设定的场边界外的运动,同时保持颌骨边界内的MLC叶片与原计划相同,实现所需的有效剂量率。在控制点之间,通过将允许限值乘以当前剂量率与期望值的比值来调节叶片速度。在给药过程中,降低剂量率,使MLC叶片到达预期监测单位(MU)的预期位置。针对不同的应用场景设计了两种方案,并成功交付和验证。圆形三维适形场、40 cm × 40 cm TBI场和头颈部(H&N) IMRT DMLC场的剂量率在600 ~ 1 MU/min之间。这些计划成功地在Varian TrueBeam和Clinac Linacs上进行了调制剂量率。利用轨迹测井分析和门脉剂量测定QA (PDQA)来验证其准确性。结果:两种方案均获得稳定准确的剂量率,在600 ~ 1 MU/min范围内,与期望值的平均偏差保持在0.5%以下。以相对标准偏差表示的波动随着所需剂量率的降低而单调增加。对于100 MU/min以上的临床相关剂量率,波动保持在0.5%以下。在较低的剂量率下,波动达到1%和10%的阈值分别约为50和7 μ MU/min。轨迹日志文件分析证实了各种处理参数(如叶片位置、速度和MU)的计划值与实际值之间的一致性。PDQA分析显示99%的伽玛通过率,标准为3%/ 2mm。对于步进射击方案1,由于步进射击期间的临时波束保持,预计和观察到的交付时间增加了50%。结论:已经开发并验证了一种通过调制MLC叶片运动来实现任意机器剂量率光子传递的技术。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
Medical physics
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.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:604180095
Book学术官方微信