Institute for Quantum Medical Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, Chiba, 263-8555, Japan.
Phys Med Biol. 2022 Jun 21;67(13). doi: 10.1088/1361-6560/ac762d.
In charged-particle therapy, a ripple filter (RiFi) is used for broadening the Bragg peak in the beam direction. A conventional RiFi consists of plates with a fine ridge and groove structure. The construction of the RiFi has been a time-consuming and costly task. In this study, we developed a simple RiFi made of multi-layered metal mesh (mRiFi), with which the Bragg peak is broadened due to structural randomness, similar to what occurs for the already proposed RiFi with porous material.. The mRiFi was constructed by stacking commercially available metal meshes at random positions and angles. The mRiFi was inexpensive to fabricate due to its high availability and low machining accuracy. The Bragg peak width modulated by the mRiFi can be uniquely determined by the wire material, wire diameter, wire-to-wire spacing of the metal mesh, and the number of mesh sheets. We fabricated four mRiFis consisting of 10, 20, 30, and 40 layers of stainless steel meshes with a wire diameter of 0.1 mm and a wire-to-wire spacing of 0.508 mm.Using the mRiFis consisting of 10, 20, 30, and 40 mesh sheets, we succeeded in broadening the Bragg peak following the normal distribution with the respective standard deviationvalues of 0.83, 1.15, 1.41, and 1.56 mm in water in experimental planar-integrated depth dose measurements with 140.3 MeV ucarbon-ion beams. The effect of range broadening with the mRiFi was independent of its lateral position, and the measurement of the surface dose using radiochromic films showed no severe inhomogeneity with a homogeneity index greater than 0.3 caused by the mRiFis.The developed mRiFi can be used as a RiFi in charged-particle therapy. The mRiFi has three advantages: high supply stability of the material for manufacturing it, easy fabrication, and low cost.
在带电粒子治疗中，使用波纹滤器 (RiFi) 来拓宽射束方向上的布拉格峰。传统的 RiFi 由带有精细脊和槽结构的板组成。RiFi 的构造一直是一项耗时且昂贵的任务。在这项研究中，我们开发了一种由多层金属网制成的简单 RiFi（mRiFi），由于结构的随机性，布拉格峰会因此变宽，类似于已经提出的具有多孔材料的 RiFi。mRiFi 通过随机位置和角度堆叠市售的金属网来构造。由于其高可用性和低加工精度，mRiFi 的制造成本低廉。mRiFi 调制的布拉格峰宽度可以通过金属网的线材材料、线材直径、线材之间的间距以及金属网片的数量来唯一确定。我们制作了四个由 10、20、30 和 40 层不锈钢网组成的 mRiFi，线材直径为 0.1 毫米，线材之间的间距为 0.508 毫米。使用由 10、20、30 和 40 个网片组成的 mRiFi，我们在使用 140.3 MeV u 碳离子束的实验平面集成深度剂量测量中成功地在水中将布拉格峰展宽到正态分布，其各自的标准偏差值为 0.83、1.15、1.41 和 1.56 毫米。mRiFi 引起的射程展宽效应与其横向位置无关，使用光致变色胶片测量表面剂量时，由于 mRiFi 的存在，没有显示出严重的不均匀性，均匀性指数大于 0.3。开发的 mRiFi 可作为带电粒子治疗中的 RiFi 使用。mRiFi 具有三个优点：制造它的材料供应稳定性高、易于制造和成本低。
