Proton FLASH effects on mouse skin at different oxygen tensions.

Area of Science:

• Radiation Oncology
• Biophysics
• Dermatology

Background:

• FLASH radiotherapy utilizes ultra-high dose rates (>40 Gy/s) for potential normal tissue sparing.
• The underlying mechanisms, particularly oxygen's role, require further investigation.
• Previous studies observed the FLASH effect with various radiation types, including protons.

Purpose of the Study:

• To investigate the protective effect of FLASH proton irradiation on skin.
• To determine the influence of varying oxygen concentrations on the FLASH effect in skin.

Main Methods:

• Mouse skin was irradiated using a proton beam at FLASH (~130 Gy/s) and conventional (~0.4 Gy/s) dose rates.
• Skin oxygen levels were manipulated by administering pure oxygen or restricting blood flow.
• Skin contraction was measured by tracking tattooed dots over time.

Main Results:

• FLASH proton irradiation reduced skin contraction by 15% compared to conventional dose rates.
• Long-term protective effects were indicated by reduced epidermis thickness and collagen deposition post-FLASH irradiation.
• Altering oxygen concentration eliminated the dose-rate-dependent difference in skin response.

Conclusions:

• FLASH proton irradiation demonstrates a protective effect on skin, reducing contraction and tissue alterations.
• The oxygen-dependence of the FLASH effect supports the hypothesis of rapid oxygen depletion during irradiation.
• These findings highlight the potential of FLASH radiotherapy for improved clinical outcomes.