Division of Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Faculty of Physics and Astronomy, Ruprecht-Karls-University, Heidelberg, Germany.
Med Phys. 2021 Jul;48(7):3982-3990. doi: 10.1002/mp.14917. Epub 2021 May 27.
To investigate experimentally, if FLASH irradiation depletes oxygen within water for different radiation types such as photons, protons, and carbon ions.
This study presents measurements of the oxygen consumption in sealed, 3D-printed water phantoms during irradiation with x-rays, protons, and carbon ions at varying dose rates up to 340 Gy/s. The oxygen measurement was performed using an optical sensor allowing for noninvasive measurements.
Oxygen consumption in water only depends on dose, dose rate, and linear energy transfer (LET) of the irradiation. The total amount of oxygen depleted per 10 Gy was found to be 0.04% atm - 0.18% atm for 225 kV photons, 0.04% atm - 0.25% atm for 224 MeV protons, and 0.09% atm - 0.17% atm for carbon ions. Consumption depends on dose rate by an inverse power law and saturates for higher dose rates because of self-interactions of radicals. Higher dose rates yield lower oxygen consumption. No total depletion of oxygen was found for clinical doses.
FLASH irradiation does consume oxygen, but not enough to deplete all the oxygen present. For higher dose rates, less oxygen was consumed than at standard radiotherapy dose rates. No total depletion was found for any of the analyzed radiation types for 10 Gy dose delivery using FLASH.
实验研究不同辐射类型（如光子、质子和碳离子）的 FLASH 照射是否会耗尽水中的氧气。
本研究在不同剂量率（高达 340 Gy/s）下，通过对密封的 3D 打印水模型进行 X 射线、质子和碳离子照射，测量了氧消耗。氧测量使用允许非侵入性测量的光学传感器进行。
水中的氧消耗仅取决于辐照的剂量、剂量率和线性能量传递（LET）。每 10 Gy 耗氧量为 0.04% atm-0.18% atm，用于 225 kV 光子；0.04% atm-0.25% atm，用于 224 MeV 质子；0.09% atm-0.17% atm，用于碳离子。消耗率与剂量率呈反比关系，并且由于自由基的自相互作用，高剂量率下会饱和。较高的剂量率会导致较低的氧气消耗。对于临床剂量，未发现氧气完全耗尽。
FLASH 照射确实会消耗氧气，但不足以耗尽所有存在的氧气。对于较高的剂量率，与标准放射治疗剂量率相比，消耗的氧气更少。对于分析的任何辐射类型，在使用 FLASH 进行 10 Gy 剂量输送时，均未发现总耗竭。
