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Dose rate dependence of yields of 7OH-C3CA under proton and C ion beams: Towards the elucidation of the mechanism of FLASH radiotherapy
https://repo.qst.go.jp/records/85536
https://repo.qst.go.jp/records/85536ff0051da-4fe6-4dfc-8c37-fee7cab8f1b1
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2022-03-22 | |||||
| タイトル | ||||||
| タイトル | Dose rate dependence of yields of 7OH-C3CA under proton and C ion beams: Towards the elucidation of the mechanism of FLASH radiotherapy | |||||
| 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 object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
楠本, 多聞
× 楠本, 多聞× 稲庭, 拓× 水島, 康太× 佐藤, 眞二× 北條, 悟× 北村, 尚× 小平, 聡× Tamon, Kusumoto× Taku, Inaniwa× Kota, Mizushima× Shinji, Sato× Satoru, Hojo× Hisashi, Kitamura× Satoshi, Kodaira |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Abstract By the irradiation above 40 Gy/s, it was reported that tumors were killed while sparing healthy tissues, called FLASH radiotherapy. One of the reasons of the sparing effect for healthy tissues is the suppression of the indirect action under the ultra-high dose rate irradiation. In this study, we evaluate changes in radiation chemical yield (G value) of 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA), which is formed by the reaction of hydroxyl radicals with coumarin-3-carboxilic acid (C3CA), under 140 MeV/u C ions and 30 and 60 MeV protons in a wide dose rate range up to 100 Gy/s. The G value of 7OH-C3CA for 30 MeV protons decreases monotonically with increasing the dose rate (Figure 1). Above 10 Gy/s, the G value of 7OH-C3CA becomes constant. Similar trends are observed under 140 MeV/u C ions and 60 MeV protons. To compare the suppression of the indirect action under C ions with protons, we evaluate the relative G value, which is defined as the G value at each dose rate normalized by that at the conventional (CONV) condition. The relative G values decreases monotonically with increasing dose rate. They become constant above 10 Gy/s. The relative G value under C ions above 10 Gy/s is almost equivalent to that under 30 and 60 MeV protons. This finding implies that the indirect action induced by C ions are suppressed as well as that by protons, meaning that we can expect that the sparing effect even under C ions at ultra-high dose rate. One of the interpretations of the reduction of G value of 7OH-C3CA with dose rate is the reduction of oxygen concentration in the solution. There are two main different pathways from the intermediate OH-adduct radicals to 7OH-C3CA existed, depending on the presence of oxygen. In the case of de-oxygenated condition, the pathway with oxygen is occluded. Therefore, the disproportionation is a key phenomenon for the production of 7OH-C3CA. Two moles of intermediate OH-adduct radicals are necessary for disproportionation to form one mole of 7OH-C3CA. In comparison, under the oxygenated condition, the peroxidation by the presence of oxygen followed by elimination of HO2* is a dominant reaction for producing 7OH-C3CA. Under the ultra-high dose rate irradiation, oxygen could be rapidly consumed, leading the lower G values of 7OH-C3CA. To clarify this view, we evaluate the G value of 7OH-C3CA under the de-oxygenated condition to clarify the mechanism of the reduction of 7OH-C3CA with dose rate. The G value of 7OH-C3CA under de-oxygenated condition is lower than that under the oxygenated condition. Also, the G value of 7OH-C3CA under de-oxygenated condition is higher than those above 10 Gy/s. This result indicates that not only the momentary reduction of the oxygen concentration but also radical-radical reactions between different tracks play important roles to the sparing effect. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 第11回国際放射線神経生物学会大会 | |||||
| 発表年月日 | ||||||
| 日付 | 2022-03-19 | |||||
| 日付タイプ | Issued | |||||
