Does FLASH deplete Oxygen? Experimental Evaluation for Photons, Protons and Carbon Ions: https://arxiv.org/abs/2102.12762
Jeannette Jansen (1,2), Jan Knoll (1,2), Elke Beyreuther (3,4), Jörg Pawelke (3,5), Raphael Skuza (1,2), Rachel Hanley (1,2), Stephan Brons (6), Francesca Pagliari (1), Joao Seco (1,2) ((1) Division of Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany, (2) Faculty of Physics and Astronomy, Ruprecht-Karls-University Heidelberg, Germany, (3) OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University, Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, (4) Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany, (5) Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiooncology-OncoRay, Dresden, Germany, (6) Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Germany)
Purpose: To investigate experimentally, if FLASH irradiation depletes oxygen within water for different radiation types such as photons, protons and carbon ions.
Methods: 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 non-invasive measurements.
Results: 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 - 0.18 % atm for 225 kV photons, 0.04 - 0.25 % atm for 224 MeV protons and 0.09 - 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.
Conclusions: 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.
Comments: 23 pages, 7 figures