Van Hoey Olivier, Stolarczyk Liliana, Lillhök Jan, Eliasson Linda, Mojzeszek Natalia, Liszka Malgorzata, Alkhiat Ali, Mares Vladimir, Trompier François, Trinkl Sebastian, Martínez-Rovira Immaculada, Romero-Expósito Maite, Domingo Carles, Ploc Ondrej, Harrison Roger, Olko Pawel
Belgian Nuclear Research Center (SCK CEN), Institute for Environment, Health and Safety (EHS), Mol, Belgium.
Danish Centre for Particle Therapy, Aarhus University Hospital (AUH), Aarhus, Denmark.
Front Oncol. 2022 Sep 8;12:903537. doi: 10.3389/fonc.2022.903537. eCollection 2022.
Out-of-field patient doses in proton therapy are dominated by neutrons. Currently, they are not taken into account by treatment planning systems. There is an increasing need to include out-of-field doses in the dose calculation, especially when treating children, pregnant patients, and patients with implants. In response to this demand, this work presents the first steps towards a tool for the prediction of out-of-field neutron doses in pencil beam scanning proton therapy facilities. As a first step, a general Monte Carlo radiation transport model for simulation of out-of-field neutron doses was set up and successfully verified by comparison of simulated and measured ambient neutron dose equivalent and neutron fluence energy spectra around a solid water phantom irradiated with a variation of different treatment plan parameters. Simulations with the verified model enabled a detailed study of the variation of the neutron ambient dose equivalent with field size, range, modulation width, use of a range shifter, and position inside the treatment room. For future work, it is planned to use this verified model to simulate out-of-field neutron doses inside the phantom and to verify the simulation results by comparison with previous in-phantom measurement campaigns. Eventually, these verified simulations will be used to build a library and a corresponding tool to allow assessment of out-of-field neutron doses at pencil beam scanning proton therapy facilities.
质子治疗中射野外患者剂量主要由中子构成。目前，治疗计划系统并未将其纳入考量。在剂量计算中纳入射野外剂量的需求日益增加，尤其是在治疗儿童、孕妇以及植入物患者时。为响应这一需求，本研究朝着开发一种用于预测笔形束扫描质子治疗设施中射野外中子剂量的工具迈出了第一步。第一步，建立了一个用于模拟射野外中子剂量的通用蒙特卡罗辐射传输模型，并通过比较在不同治疗计划参数变化下照射固体水模体周围模拟和测量的环境中子剂量当量及中子注量能谱，成功验证了该模型。使用经过验证的模型进行模拟，能够详细研究中子环境剂量当量随射野大小、射程、调制宽度、使用射程移位器以及治疗室内位置的变化情况。对于未来的工作，计划使用该经过验证的模型模拟模体内的射野外中子剂量，并通过与之前模体内测量活动的结果进行比较来验证模拟结果。最终，这些经过验证的模拟将用于构建一个库和相应的工具，以评估笔形束扫描质子治疗设施中的射野外中子剂量。
