Proton-FLASH: effects of ultra-high dose rate irradiation on an in-vivo mouse ear model.
Sarah Rudigkeit, Thomas E Schmid, Annique C Dombrowsky, Jessica Stolz, Stefan Bartzsch, Ce-Belle Chen, Nicole Matejka, Matthias Sammer, Andreas Bergmaier, Günther Dollinger, Judith Reindl
Author Information
Sarah Rudigkeit: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany.
Thomas E Schmid: Institute of Radiation Medicine (IRM), Helmholtz Zentrum München, Neuherberg, Germany.
Annique C Dombrowsky: Institute of Radiation Medicine (IRM), Helmholtz Zentrum München, Neuherberg, Germany.
Jessica Stolz: Institute of Radiation Medicine (IRM), Helmholtz Zentrum München, Neuherberg, Germany.
Stefan Bartzsch: Institute of Radiation Medicine (IRM), Helmholtz Zentrum München, Neuherberg, Germany.
Ce-Belle Chen: Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore, Singapore.
Nicole Matejka: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany.
Matthias Sammer: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany.
Andreas Bergmaier: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany.
Günther Dollinger: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany.
Judith Reindl: Institute of Applied Physics and Measurement Technologies, Universität der Bundeswehr München, Neubiberg, Germany. judith.reindl@unibw.de.
FLASH-radiotherapy may provide significant sparing of healthy tissue through ultra-high dose rates in protons, electrons, and x-rays while maintaining the tumor control. Key factors for the FLASH effect might be oxygen depletion, the immune system, and the irradiated blood volume, but none could be fully confirmed yet. Therefore, further investigations are necessary. We investigated the protective (tissue sparing) effect of FLASH in proton treatment using an in-vivo mouse ear model. The right ears of Balb/c mice were irradiated with 20 MeV protons at the ion microprobe SNAKE in Garching near Munich by using three dose rates (Conv = 0.06 Gy/s, Flash9 = 9.3 Gy/s and Flash930 = 930 Gy/s) at a total dose of 23 Gy or 33 Gy. The ear thickness, desquamation, and erythema combined in an inflammation score were measured for 180 days. The cytokines TGF-β1, TNF-α, IL1α, and IL1β were analyzed in the blood sampled in the first 4 weeks and at termination day. No differences in inflammation reactions were visible in the 23 Gy group for the different dose rates. In the 33 Gy group, the ear swelling and the inflammation score for Flash9 was reduced by (57 ± 12) % and (67 ± 17) % and for Flash930 by (40 ± 13) % and (50 ± 17) % compared to the Conv dose rate. No changes in the cytokines in the blood could be measured. However, an estimation of the irradiated blood volume demonstrates, that 100-times more blood is irradiated when using Conv compared to using Flash9 or Flash930. This indicates that blood might play a role in the underlying mechanisms in the protective effect of FLASH.
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