Komori Masataka, Takeuchi Akihiko, Niwa Maiko, Harada Takaomi, Oguchi Hiroshi
Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Japan.
Radiat Prot Dosimetry. 2019 Jul 1;184(1):28-35. doi: 10.1093/rpd/ncy182.
The aim of this work is to optimize an additional collimator in a beam delivery system to reduce neutron exposure to patients in passive carbon-ion therapy. All studies were performed by Monte Carlo simulation assuming the beam delivery system at Heavy-Ion Medical Accelerator in Chiba. We calculated the neutron ambient dose equivalent at patient positions with an additional collimator, and optimized the position, aperture size and material of the collimator to reduce the neutron ambient dose equivalent. The collimator located 125 and 470 cm upstream from the isocenter could reduce the dose equivalent near the isocenter by 35%, while the collimator located 813 cm upstream from the isocenter was ineffective. As for the material of the collimator, iron and nickel could conduct reduction slightly better than aluminum and polymethyl methacrylate. The additional collimator is an effective method for the reduction of the neutron ambient dose equivalent near the isocenter.
这项工作的目的是优化束流传输系统中的附加准直器，以减少被动碳离子治疗中患者所受的中子照射。所有研究均通过蒙特卡罗模拟进行，假设束流传输系统位于千叶重离子医学加速器。我们计算了使用附加准直器时患者位置处的中子周围剂量当量，并优化了准直器的位置、孔径尺寸和材料，以降低中子周围剂量当量。位于等中心上游125和470厘米处的准直器可使等中心附近的剂量当量降低35%，而位于等中心上游813厘米处的准直器则无效。至于准直器的材料，铁和镍在降低剂量当量方面比铝和聚甲基丙烯酸甲酯略好。附加准直器是降低等中心附近中子周围剂量当量的有效方法。
