Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai 201315, China; Shanghai Key Laboratory of radiation oncology（20dz2261000）; Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy.
Biophysics GSI Helmholtz Center for Heavy Ion Research GmbH, Darmstadt, Germany.
Phys Med. 2024 Apr;120:103325. doi: 10.1016/j.ejmp.2024.103325. Epub 2024 Mar 16.
The present study aimed to develop a porous structure with plug-ins (PSP) to broaden the Bragg peak width (BPW, defined as the distance in water between the proximal and distal 80% dose) of the carbon ion beam while maintaining a sharp distal falloff width (DFW, defined as the distance along the beam axis where the dose in water reduces from 80% to 20%).
The binary voxel models of porous structure (PS) and PSP were established in the Monte Carlo code FLUKA and the corresponding physical models were manufactured by 3D printing. Both experiment and simulation were performed for evaluating the modulation capacity of PS and PSP. BPWs and DFWs derived from each integral depth dose curves were compared. Fluence homogeneity of 430 MeV/u carbon-ion beam passing through the PSP was recorded by analyzing radiochromic films at six different locations downstream the PSP in the experiment. Additionally, by changing the beam spot size and incident position on the PSP, totally 48 different carbon-ion beams were simulated and corresponding deviations of beam metrics were evaluated to test the modulating stability of PSP.
According to the measurement data, the use of PSP resulted in an average increase of 0.63 mm in BPW and a decrease of 0.74 mm in DFW compared to PS. The 2D radiation field inhomogeneities were lower than 3 % when the beam passing through a ≥ 10 cm PMMA medium. Furthermore, employing a spot size of ≥ 6 mm ensures that beam metric deviations, including BPW, DFW, and range, remain within a deviation of 0.1 mm across various incident positions.
The developed PSP demonstrated its capability to effectively broaden the BPW of carbon ion beams while maintaining a sharp DFW comparing to PS. The superior performance of PSP, indicates its potential for clinical use in the future.
本研究旨在开发一种具有插件的多孔结构 (PSP)，以拓宽碳离子束的布拉格峰宽度 (BPW，定义为水中近端和远端 80%剂量之间的距离)，同时保持陡峭的远端下降宽度 (DFW，定义为水中剂量从 80%降至 20%的沿束轴的距离)。
在蒙特卡罗代码 FLUKA 中建立了多孔结构 (PS) 和 PSP 的二进制体素模型，并通过 3D 打印制造了相应的物理模型。通过实验和模拟评估了 PS 和 PSP 的调制能力。比较了每个积分深度剂量曲线得出的 BPW 和 DFW。通过在实验中在 PSP 下游的六个不同位置分析放射色迹胶片，记录了 430 MeV/u 碳离子束穿过 PSP 后的通量均匀性。此外，通过改变束斑大小和 PSP 上的入射位置，总共模拟了 48 种不同的碳离子束，并评估了相应的束参数偏差，以测试 PSP 的调制稳定性。
根据测量数据，与 PS 相比，使用 PSP 导致 BPW 平均增加 0.63mm，DFW 减少 0.74mm。当束穿过 ≥ 10cm PMMA 介质时，2D 辐射场不均匀性低于 3%。此外，采用 ≥ 6mm 的光斑尺寸可确保 BPW、DFW 和射程等束参数偏差在各种入射位置保持在 0.1mm 的偏差内。
与 PS 相比，开发的 PSP 表现出有效拓宽碳离子束 BPW 的能力，同时保持陡峭的 DFW。PSP 的卓越性能表明其在未来临床应用中的潜力。
