Significant changes in yields of 7-hydroxy-coumarin-3-carboxylic acid produced under FLASH radiotherapy conditions.
Significant changes in yields of 7-hydroxy-coumarin-3-carboxylic acid produced under FLASH radiotherapy conditions.
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DOI：
10.1039/d0ra07999e
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发表时间：
2020-10-15
期刊：
影响因子：
3.9
通讯作者：
Kodaira, Satoshi
中科院分区：
文献类型：
--
作者：
Kusumoto, Tamon;Kitamura, Hisashi;Hojo, Satoru;Konishi, Teruaki;Kodaira, Satoshi
FLASH放射治疗似乎通过超高剂量率（>40戈伊s-1）的照射杀死肿瘤细胞，同时保留健康组织。本研究的目的是从辐射化学的角度阐明质子辐照在FLASH条件下的节约效应的机制。为此，我们评估7-羟基-香豆素-3-羧酸（7 OH-C3 CA）的辐射化学产率（G值），这是由水辐解使用香豆素-3-羧酸（C3 CA）溶液作为羟基自由基的自由基清除剂。我们以0.05 ~ 160戈伊s-1的剂量率发射27.5 MeV的质子。产生的羟基自由基的重组过程之后，通过改变C3 CA的浓度从0.2到20 mM，这对应于从7.1到714 ns的清除时间尺度。在相同的清除时间尺度上，产生的7 OH-C3 CA的G值随剂量率的增加而减小。此外，在100 ns的清除时间尺度下归一化的相对G值的趋势，其中自由基-自由基反应消退，在检查的剂量率范围内是一致的。这一发现意味着，由于氧耗尽，产生的7 OH-C3 CA的G值随着剂量率的增加而降低。我们的实验表明，由于氧气的耗尽，即使在FLASH条件下使用质子束，也会看到对健康组织的节省效果。与0.05戈伊s-1的常规条件相比，在剂量率>40戈伊s-1的FLASH条件下，7-羟基-香豆素-3-羧酸（7 OH-C3 CA）的产率显著降低，这是由于溶液中的氧耗尽。
FLASH radiotherapy appears to kill off tumor cells while sparing healthy tissues, by irradiation at ultra high dose rate (>40 Gy s−1). The present study aims to clarify the mechanism of the sparing effect by proton irradiation under the FLASH conditions from a viewpoint of radiation chemistry. To do so, we evaluate radiation chemical yields (G values) of 7-hydroxy-coumarin-3-carboxylic acid (7OH–C3CA), which is produced by water radiolysis using coumarin-3-carboxylic acid (C3CA) solution as a radical scavenger of hydroxyl radicals. We shoot 27.5 MeV protons in the dose rate ranging from 0.05 to 160 Gy s−1. The recombination process of hydroxyl radicals produced is followed by varying the concentration of C3CA from 0.2 to 20 mM, which corresponds to the scavenging time scale from 7.1 to 714 ns. The G value of 7OH–C3CA produced decreases with increasing dose rate on the same scavenging time scale. Additionally, the trend of the relative G value normalized at a scavenging time scale of 100 ns, where radical–radical reaction subsides, is consistent in the examined dose rate range. This finding implies that G values of 7OH–C3CA produced reduce with increasing dose rate due to the oxygen depletion. We experimentally present that the sparing effect for healthy tissues would be seen even with a proton beam under the FLASH conditions due to the depletion of oxygen. Yield of 7-hydroxy-coumarin-3-carboxylic acid (7OH–C3CA) significantly decreases at FLASH condition with the dose rate of >40 Gy s−1, compared to that at conventional condition of 0.05 Gy s−1, due to the oxygen depletion in the solution.
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影响因子：
3.7
作者：
Seki, S;Tsukuda, S;Tagawa, S
通讯作者：
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影响因子：
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作者：
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作者：
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通讯作者：
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作者：
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通讯作者：
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