@misc{oai:repo.qst.go.jp:00075995,
 author = {Matsumoto, Shinnosuke and Yonai, Shunsuke and Matsumoto, Shinnosuke and Yonai, Shunsuke},
 month = {May},
 note = {Introduction
Ion-beam radiotherapy can reduce the entrance dose because of their physical characteristics called the Bragg peak. In addition, CIRT offers physical and biological advantages over proton beams. These advantages in CIRT lead to high-dose localization in the target volume with minimal damage to the normal tissue, thereby indicating favorable outcomes. Meanwhile, the radiation-induced second cancer risk of patients receiving radiotherapy is a major concern, especially in children, as is increasing the effectiveness of the radiotherapy and extending life expectancy. The second cancer risk depends on the volumes of both the high-dose region in the irradiation field and the low-dose region outside the field. The aim of the study is to use Monte Carlo simulations with an anthropomorphic phantom to estimate the secondary dose in CIRT with the beam parameters of a typical pediatric brain tumor treatment.
Methods The target disease of this study was pediatric cerebellar ependymoma. We estimate the out-of-field organ absorbed dose, dose equivalent and equivalent dose for each radiation type during CIRT for typical pediatric cerebellar ependymoma treatment using Monte Carlo simulations using the Particle and Heavy-Ion Transport Code System (PHITS). Because the CIRT out-of-field dose depends on the beam parameters, the typical values of the parameters were used. Both methods of passive beam and active scanning beam ware calculated.
Results The results showed that the dose equivalent decreased with distance from the target, ranging from 1.3 mSv/Gy(RBE) in the thyroid to 0.05 mSv/Gy(RBE) in the bladder. The neutron equivalent doses per treatment dose in organ were lower than passive scatter proton therapy. When increasing distance from the target volume, contribution from external secondary charged particles decreases and contribution from external neutrons increases.
Conclusions The typical out-of-field organ dose during CIRT in pediatric cerebellar ependymoma were shown., The 3rd International Conference on Dosimetry and its Applications (ICDA-3)},
 title = {Monte Carlo study of out-of-field exposure in carbon-ion radiotherapy: Organ doses in pediatric brain tumor treatment.},
 year = {2019}
}