Ronga Maria Grazia, Gesualdi Flavia, Bonfrate Anthony, Patriarca Annalisa, Ferrand Régis, Créhange Gilles, Buvat Irène, De Marzi Ludovic
Institut Curie, Radiation Oncology Department, Proton Therapy Centre, PSL Research University, Centre Universitaire, Orsay, France.
Thales Avionics, Vélizy, France.
Med Phys. 2025 Jun;52(6):4775-4784. doi: 10.1002/mp.17700. Epub 2025 Feb 19.
Very high-energy electrons (VHEEs) in radiotherapy may offer several potential advantages over conventional electron beams and other techniques, for example, the fact that they can be used at ultra-high dose rates (UHDRs), therefore enabling FLASH radiotherapy. However, the production of secondary particles at high energies (50-200 MeV) has yet to be studied in detail for this technique currently under development.
The aim of this work was to examine the secondary dose produced by VHEEs, with particular emphasis on bremsstrahlung photons and neutrons, for two beam delivery systems (double scattering [DS] and pencil beam scanning [PBS]).
The electron, X-ray, and neutron doses arising from two beam delivery systems (DS or PBS) were computed using Monte Carlo (MC) simulations in the TOPAS (TOol for PArticle Simulation)/Geant4 toolkit, and a preliminary assessment of the secondary dose for a clinical VHEE treatment was performed using a whole-body phantom. An evaluation of the secondary dose produced by this preliminary design of a VHEE nozzle set in a clinical proton facility was performed, taking into account realistic PBS or DS nozzle configurations.
The mean doses received by a patient undergoing DS-VHEE irradiation were found to be up to 5.3-fold and 6.8-fold higher for in-field or out-of-field organs for photons and neutrons, respectively, compared to the PBS-VHEE plan. The results for the secondary neutron dose in intracranial treatments also demonstrate the characteristic of VHEE compared to proton beams for reducing the out-of-field secondary neutron dose. The dose to the public area that could be delivered to meet regulatory limits surrounding a possible treatment room in a proton therapy facility was assessed. A regulatory limit of 0.5 µSv/h would give a restriction of 49 and 83 Gy per patient and per fraction for DS and PBS, respectively.
This work describes a method to simulate and compare secondary radiation doses resulting from scattered, scanned VHEE or proton therapy treatments. The results indicate that a conventionally shielded proton therapy room results in acceptable public doses for a preliminary VHEE design and could be of interest for radiation protection purposes and for similar setups. Other facilities with differing layouts may, however, lead to different conclusions, requiring further studies.
放射治疗中的超高能电子（VHEEs）相较于传统电子束和其他技术可能具有若干潜在优势，例如，它们可用于超高剂量率（UHDRs），从而实现FLASH放射治疗。然而，对于目前正在研发的这项技术，高能（50 - 200 MeV）下二次粒子的产生尚未得到详细研究。
本研究的目的是针对两种束流传输系统（双散射[DS]和笔形束扫描[PBS]），研究VHEEs产生的二次剂量，特别关注轫致辐射光子和中子。
使用TOPAS（粒子模拟工具）/Geant4工具包中的蒙特卡罗（MC）模拟计算两种束流传输系统（DS或PBS）产生的电子、X射线和中子剂量，并使用全身体模对临床VHEE治疗的二次剂量进行初步评估。考虑到实际的PBS或DS喷嘴配置，对临床质子设施中设置的VHEE喷嘴的初步设计产生的二次剂量进行了评估。
发现接受DS - VHEE照射的患者，其场内或场外器官接受的光子和中子平均剂量分别比PBS - VHEE计划高出5.3倍和6.8倍。颅内治疗中二次中子剂量的结果也表明了VHEE与质子束相比在降低场外二次中子剂量方面的特性。评估了为满足质子治疗设施中可能的治疗室周围的监管限制而可向公共区域输送的剂量。0.5 μSv/h的监管限制分别会使DS和PBS每位患者每次分割的剂量限制为49 Gy和83 Gy。
本研究描述了一种模拟和比较散射、扫描的VHEE或质子治疗产生的二次辐射剂量的方法。结果表明，对于VHEE的初步设计，传统屏蔽的质子治疗室产生的公共剂量是可接受的，这对于辐射防护目的和类似设置可能具有意义。然而，其他布局不同的设施可能会得出不同的结论，需要进一步研究。
