Modelling of a double-scattering proton therapy nozzle using the FLUKA Monte Carlo code and analysis of linear energy transfer in patients treated for prostate cancer

IF 2 4区医学 Q3 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Journal of Applied Clinical Medical Physics Pub Date : 2025-03-19 DOI:10.1002/acm2.70032

Rasmus Klitgaard, Lars Fredrik Fjæra, Camilla Hanquist Stokkevåg, Perry Johnson, Mark Artz, Nancy Price Mendenhall, Curtis Bryant, Ludvig Paul Muren

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引用次数: 0

Abstract

Background

The dose-averaged linear energy transfer (LET_D) in proton therapy (PT) has in pre-clinical studies been linked to the relative biological effectiveness (RBE) of protons. Until recently, the most common PT delivery method in prostate cancer has been double-scattered PT, with LET_D only available through dedicated Monte Carlo (MC) simulations. However, as most studies of the relationship between LET_D and RBE in double scattered PT have been focused on the head and neck region, existing MC implementations have not been capable of calculating LET_D for the longer field ranges used, for example, in the pelvic region.

Purpose

The initial aim of this study was to implement a MC code allowing for LET_D calculations in double-scattered PT of prostate cancer. Additionally, we explored LET_D profiles and LET_D as a function of field configuration, by performing MC calculations for a large prostate cancer cohort treated with double-scattered PT.

Methods

The components of a passive scattered clinical treatment nozzle used for delivery of extended field ranges, with two associated modulation wheels, were implemented into an existing FLUKA MC framework for LET_D calculations. The code was validated to spread out Bragg peak (SOBP) measurements conducted using the treatment nozzle with 11 different range and modulation width configurations. After validation, LET_D distributions were calculated on the planning computed tomographies of 582 prostate cancer patients treated with two-field double-scattered PT. All patients had symmetric field configurations with respect to the sagittal plane, with one pair of posterior oblique, lateral opposing, or anterior oblique fields. Dose and LET_D volume parameters and the mean LET_D ratio between the bladder and rectum were compared across the three groups.

Results

The range differences were below 1 mm for all SOBP scenarios used for calibration. For 9 of 11 SOBP scenarios, the modulation width differences were below 2 mm. For the patient simulations, the mean gamma pass rates (3 mm/3%) were at least 98% in the PTV, bladder, and rectum. Comparing anterior to posterior field configurations, the mean LET_D in the bladder increased within both the 10 and 70 Gy iso-dose regions, and conversely, the mean LET_D decreased for the rectum. There was a marked difference in the mean bladder-to-rectum LET_D ratios between anterior oblique, lateral opposing and posterior oblique field configurations.

Conclusion

A MC code allowing for accurate calculations of dose and LET_D in double-scattered PT of prostate cancer was implemented and validated. The LET_D distributions in the rectum and bladder showed a systematic dependence on the field configuration.

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利用FLUKA蒙特卡罗代码建立双散射质子治疗喷嘴的模型并分析前列腺癌患者的线性能量转移。

背景：质子治疗（PT）中的剂量平均线性能量转移（LETD）在临床前研究中与质子的相对生物学有效性（RBE）有关。直到最近，前列腺癌中最常见的PT给药方法是双分散PT， LETD只能通过专门的蒙特卡罗（MC）模拟来实现。然而，由于大多数关于双散射PT中LETD和RBE之间关系的研究都集中在头颈部区域，现有的MC实现无法计算较长视场范围的LETD，例如在骨盆区域。目的：本研究的最初目的是实现一个MC代码，允许在前列腺癌的双分散PT中计算LETD。此外，我们通过对双分散pt治疗的大型前列腺癌队列进行MC计算，探索了LETD剖面和LETD作为视场配置的函数。方法：用于提供扩展视场范围的被动分散临床治疗喷嘴的组件，以及两个相关的调制轮，被实现到现有的FLUKA MC框架中用于LETD计算。经过验证，该代码可以分散使用11种不同范围和调制宽度配置的处理喷嘴进行的Bragg峰（SOBP）测量。验证后，计算582例双视野双散射PT治疗前列腺癌患者的计划计算机断层上的LETD分布。所有患者的视野构型相对于矢状面对称，有一对后斜、侧对或前斜视野。比较三组患者的剂量、LETD容积参数及膀胱和直肠平均LETD比值。结果：用于校准的所有SOBP场景的范围差异均小于1 mm。在11个SOBP场景中，有9个场景的调制宽度差异低于2毫米。对于患者模拟，PTV、膀胱和直肠的平均γ及格率（3mm /3%）至少为98%。与前后场构型相比，膀胱的平均LETD在10 Gy和70 Gy等剂量区域均有所增加，相反，直肠的平均LETD则有所下降。在前斜、侧对位和后斜场构型中，平均膀胱-直肠LETD比值有显著差异。结论：实现并验证了一种能够精确计算前列腺癌双分散放射治疗剂量和LETD的MC代码。直肠和膀胱的LETD分布与场构型有系统的依赖性。

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

Journal of Applied Clinical Medical Physics 医学-核医学

CiteScore

3.60

自引率

19.00%

发文量

331

审稿时长

3 months

期刊介绍： Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission. JACMP will publish: -Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500. -Review Articles: Reviews of major areas or sub-areas in the field of clinical medical physics. These articles may be of any length and are peer reviewed. -Technical Notes: These should be no longer than 3000 words, including key references. -Letters to the Editor: Comments on papers published in JACMP or on any other matters of interest to clinical medical physics. These should not be more than 1250 (including the literature) and their publication is only based on the decision of the editor, who occasionally asks experts on the merit of the contents. -Book Reviews: The editorial office solicits Book Reviews. -Announcements of Forthcoming Meetings: The Editor may provide notice of forthcoming meetings, course offerings, and other events relevant to clinical medical physics. -Parallel Opposed Editorial: We welcome topics relevant to clinical practice and medical physics profession. The contents can be controversial debate or opposed aspects of an issue. One author argues for the position and the other against. Each side of the debate contains an opening statement up to 800 words, followed by a rebuttal up to 500 words. Readers interested in participating in this series should contact the moderator with a proposed title and a short description of the topic