Monte Carlo study of out-of-field exposure in carbon-ion radiotherapy: Organ doses in pediatric brain tumor treatment
Monte Carlo study of out-of-field exposure in carbon-ion radiotherapy: Organ doses in pediatric brain tumor treatment
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DOI：
10.1002/mp.13864
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发表时间：
2019-10-29
期刊：
影响因子：
3.8
通讯作者：
Bolch, Wesley E.
中科院分区：
文献类型：
--
作者：
Matsumoto, Shinnosuke;Yonai, Shunsuke;Bolch, Wesley E.
目的评估小儿小脑室管膜瘤碳离子放疗（CIRT）的场外剂量。方法考虑到CIRT的场外剂量取决于光束参数，我们在前人研究的基础上设定了治疗典型儿童小脑室管膜瘤的剂量。然后使用粒子和重离子传输编码系统与蒙特卡罗模拟和佛罗里达大学开发的计算幻影来估计儿童小脑室管膜瘤CIRT期间的场外剂量。根据模拟结果，计算了被动束和主动扫描束CIRT剂量当量的场外剂量，并与被动束CIRT和质子治疗的二次中子当量剂量进行了比较。结果外场剂量当量从甲状腺的1.45 mSv/Gy（相对生物效应- RBE）下降到膀胱的0.06 mSv/Gy (RBE)，证实随着距离治疗目标的增加而衰减。相对于被动束质子治疗，被动束CIRT在器官内的场外中子当量剂量较低。此外，主动扫描束CIRT的每规定剂量的场外器官剂量当量低于被动扫描束CIRT。结论主动扫描束CIRT治疗小儿小脑室管膜瘤在场外照射方面有较好的前景，优于对比放疗。
Purpose To estimate out-of-field doses during carbon-ion radiotherapy (CIRT) for pediatric cerebellar ependymoma. Methods Given that the out-of-field dose of CIRT depends on beam parameters, we set them for treatment of typical pediatric cerebellar ependymoma based on a previous study. The out-of-field dose during CIRT for pediatric cerebellar ependymoma was then estimated using the Particle and Heavy-Ion Transport code System with Monte Carlo simulations and a computational phantom developed at the University of Florida. From the simulation results, out-of-field doses at dose equivalents of passive beam and active scanning beam CIRT were calculated and compared to the secondary neutron-equivalent dose of passive beam CIRT and proton therapy. Results The out-of-field dose equivalent decreases from 1.45 mSv/Gy (relative biological effectiveness - RBE) at the thyroid to 0.06 mSv/Gy (RBE) at the bladder, verifying decay as the distance from the treatment target increases. The out-of-field neutron-equivalent dose in organs per prescribed dose for passive beam CIRT is lower than that for passive beam proton therapy. Moreover, the out-of-field organ dose equivalent per prescribed dose for the active scanning beam CIRT is lower than that for the passive beam CIRT. Conclusions Active scanning beam CIRT is promising for pediatric cerebellar ependymoma regarding out-of-field exposure, outperforming the comparison radiotherapy modalities.