Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
Phys Med Biol. 2021 Feb 12;66(5). doi: 10.1088/1361-6560/abde99.
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 uneon-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 deviationvalue 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一种低分割多离子治疗的开发项目。在该治疗中，氦、碳、氧和氖离子将被用作原发性射束，并采用铅笔束扫描技术。波纹滤波器（RiFi）由具有精细周期性脊和槽结构的薄塑料或铝板组成，用于在射束方向上拓宽重离子束的布喇格峰。为了充分拓宽氦、碳、氧和氖离子束的布喇格峰，同时抑制侧向散射和表面剂量不均匀性，在这项研究中，我们测试了一种由肺替代材料 Gammex LN300 制成的板作为 RiFi。在水的 3cm 厚 LN300 板后面测量了 183.5MeV 氖离子束的平面积分剂量分布。原始射束的布喇格峰沿正态分布展宽，标准偏差值为 1.29mm，而射束的射程通过该板减少了 8.8mm。为了验证 LN300 在多离子治疗中的 RiFi 性能，我们测量了穿透 3cm 厚 LN300 板的氦、碳、氧和氖离子束的铅笔束数据。然后对数据进行建模，并在治疗计划系统中使用，以使不同离子种类的射束在一个立方靶区内均匀地达到人类未分化癌细胞 10%的存活率。对于所有离子种类，测量的存活分数都可以通过计划的存活分数合理地再现。即使将板放置在接近体模表面的位置，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 制成的板可适用于氦、碳、氧和氖离子的多离子治疗中的 RiFi。
