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Development and implementation of mesh ripple filter for multi-ion therapy
https://repo.qst.go.jp/records/2002916
https://repo.qst.go.jp/records/200291626ad025c-fffb-4177-9457-91c64414a902
| アイテムタイプ | 会議発表用資料 / Presentation(1) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 公開日 | 2026-02-27 | |||||||||
| タイトル | ||||||||||
| タイトル | Development and implementation of mesh ripple filter for multi-ion therapy | |||||||||
| 言語 | ja | |||||||||
| 言語 | ||||||||||
| 言語 | jpn | |||||||||
| 資源タイプ | ||||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||||||
| 資源タイプ | conference presentation | |||||||||
| 著者 |
田中 創大
× 田中 創大
× 稲庭 拓
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| 抄録 | ||||||||||
| 内容記述 | [Purpose] In scanned charged-particle therapy with heavy ions, e.g. He, C, O, and Ne ions, the Bragg peak width is broadened by a ripple filter to reduce the number of energy layers. A conventional ripple filter has a ridge-and-groove structure with approximately 1 mm intervals. The ridge-and-groove structure may cause lateral dose inhomogeneity at a patient surface, especially for heavy ions like Ne ions due to their low scattering power. The purpose of this study was to develop and verify a multi-layered mesh ripple filter (mRiFi), which broadens the Bragg peak width without surface dose inhomogeneity, for clinical trials of the multi-ion therapy with He-, C-, O-, and Ne-ion beams. [Methods] A mRiFi was fabricated by stacking mesh sheets at random positions and angles. The random microstructure broadens the Bragg peak width without surface dose inhomogeneity. The width of the broadened Bragg peak is determined by the wire material, wire diameter, wire interval, and the number of mesh sheets. Aluminum alloy was selected as a wire material with low atomic number for suppressing the lateral beam spread. To effectively broaden the Bragg peak width, the wire diameter and wire interval were determined to be 0.29 mm and 1.27 mm, respectively. The number of mesh sheets were determined to be 25 to achieve clinically required Bragg peak width of ~1.5 mm. To evaluate the developed mRiFi, we conducted experiments using He-, C- O- and Ne-ion beams. The integrated depth doses (IDDs) of the ion beams with various energies broadened by the mRiFi were measured using an in-house parallel plane ionization chamber with a diameter of 15 cm in water. The in-air beam sizes of the ion beams were measured using a fluorescence screen and a camera. The measured beam data were then modeled and registered to the TPS. The spread-out Bragg peak (SOBP) plans of the four ion beams were made with the TPS and delivered to the water tank. The dose distributions measured with a Markus chamber and pinpoint ionization chambers were compared with the plan distributions. [Results] The Bragg peaks of pristine He-, C-, O-, and Ne-ion beams were broadened by the developed mRiFi into a normal distribution shape with the standard deviations σ of 1.45, 1.47, 1.44, and 1.43 mm, respectively. For all SOBP plans, measured dose distributions were consistent with the planned dose distributions within 2%. [Conclusion] We developed and verified a mRiFi, which broadens the Bragg peak width of scanned charged-particle beams without surface dose inhomogeneity. The mRiFi was implemented in the clinical irradiation system at the QST and has been used in ongoing clinical trials of multi-ion therapy with He-, C-, O-, and Ne-ion beams. | |||||||||
| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||||||
| 内容記述 | 第129回日本医学物理学会学術大会 | |||||||||
| 発表年月日 | ||||||||||
| 日付 | 2025-04-10 | |||||||||
