A development project for hypo-fractionated multi-ion therapy has been initiated at the National Institute of Radiological Sciences in Japan. In the treatment, helium, carbon, oxygen, and neon ions will be used as primary beams with pencil beam scanning. A ripple filter (RiFi), consisting of a thin plastic or aluminum plate with a fine periodic ridge and groove structure, has been used to broaden the Bragg peak of heavy-ion beams in the beam direction. To sufficiently broaden the Bragg peak of helium-, carbon-, oxygen-, and neon-ion beams with suppressed lateral scattering and surface dose inhomogeneity, in this study, we tested a plate made of a lung substitute material, Gammex LN300, as the RiFi. The planar integrated dose distribution of a 183.5 MeV u⁻¹ neon-ion beam was measured behind a 3 cm thick LN300 plate in water. The Bragg peak of the pristine beam was broadened following the normal distribution with the standard deviation σ value of 1.29 mm, while the range of the beam was reduced by 8.8 mm by the plate. To verify the LN300 performance as the RiFi in multi-ion therapy, we measured the pencil beam data of helium-, carbon-, oxygen- and neon-ion beams penetrating the 3 cm thick LN300 plate. The data were then modeled and used in a treatment planning system to achieve a uniform 10% survival of human undifferentiated carcinoma cells within a cuboid target by the beam for each of the different ion species. The measured survival fractions were reasonably reproduced by the planned ones for all the ion species. No surface dose inhomogeneity was observed for any ion species even when the plate was placed close to the phantom surface. The plate made of lung substitute material, Gammex LN300, is applicable as the RiFi in multi-ion therapy with helium-, carbon-, oxygen- and neon-ion beams.

日本国立放射科学研究所已经启动了大分割多离子治疗的开发项目。在治疗中，氦、碳、氧和氖离子将用作铅笔束扫描的主束。波纹滤波器 (RiFi) 由具有精细周期性脊和凹槽结构的薄塑料或铝板组成，已用于在光束方向上加宽重离子束的布拉格峰。为了充分展宽氦离子、碳离子、氧离子和氖离子束的布拉格峰，抑制横向散射和表面剂量不均匀性，在本研究中，我们测试了由肺替代材料 Gammex LN300 制成的板，作为日菲。^{183.5 MeV u -1}的平面积分剂量分布在水中 3 cm 厚的 LN300 板后面测量氖离子束。原始光束的布拉格峰按照正态分布展宽，标准偏差为σ值 1.29 毫米，而光束的范围被板减少了 8.8 毫米。为了验证 LN300 在多离子治疗中作为 RiFi 的性能，我们测量了穿透 3 cm 厚 LN300 板的氦离子、碳离子、氧离子和氖离子束的笔形束数据。然后将数据建模并用于治疗计划系统，以通过每个不同离子种类的束在长方体目标内实现人未分化癌细胞的均匀 10% 存活。对于所有离子种类，计划的存活分数合理地再现了测量的存活分数。即使将板放置在模型表面附近，也没有观察到任何离子种类的表面剂量不均匀性。由肺替代材料 Gammex LN300 制成的板可用作多离子治疗中的 RiFi，包括氦、碳、