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内容記述 |
Ultra-high dose rate radiation therapy, commonly known as FLASH, operates at dose rates over 40 Gy/s, which is 1,000 times higher than conventional radiation therapy (approximately 0.03 Gy/s). This method has garnered significant attention due to its potential to reduce side effects on normal tissue while maintaining therapeutic effectiveness. However, the underlying mechanisms of FLASH therapy remain unclear. It is hypothesized that the sparing effect of FLASH may be linked to the yield of water radiolysis products, which contribute to the radiation’s indirect action in causing DNA damage. To experimentally investigate the effects of ultra-high dose rate irradiation, we examined the dose-rate dependence of the yields of radiation-induced decomposition products in water. To support such research, it is crucial to validate dose measurements when the dose rate varies significantly. Additionally, the differences in detector response due to dose rate definitions such as average dose rate, pencil-beam scanning dose rate, and pulsed dose rate should be verified. In this study, we evaluated dose-rate dependences in various types of passive dosimeters, including optically stimulated luminescence dosimeters, Fricke chemical dosimeters, and cellulose triacetate film dosimeters, using 12 MeV electron pulsed beams and 230 MeV proton scanning beams. An extremely high pulsed dose rate of MGy/s, generated by short electron pulses with a width of 2 µs, induced significant saturation. These results provide valuable insights into acceptable dose and dose rate ranges for FLASH dosimetry. |
