Using oxygen dose histograms to quantify voxelised ultra-high dose rate (FLASH) effects in multiple radiation...

Area of Science:

• Radiation oncology
• Radiobiology
• Medical physics

Background:

• Pulsed ultra-high dose rate radiation, like FLASH-radiotherapy, shows promising tissue sparing effects.
• Predicting these effects requires understanding complex biological responses to radiation dose and oxygen levels.
• Current models may not fully capture the dynamic interplay of oxygen and dose in pulsed exposures.

Purpose of the Study:

• To develop and validate a methodology for predicting tissue sparing in pulsed ultra-high dose rate radiation exposures.
• To integrate this methodology into dose-effect prediction or treatment planning systems.
• To illustrate the system's utility using established experimental data.

Main Methods:

• Formalization of oxygen level variability using an oxygen dose histogram (ODH).
• Application of the oxygen fixation concept to quantify DNA-damage induction relative to hypoxic conditions.
• Estimation of radiation effects considering multiple pulses, partial, and spatial oxygen depletion.

Main Results:

• The proposed system predicts that FLASH effects are contingent upon initial oxygenation, total dose, pulse length, and repetition rate.
• The system accurately represents cell culture data and shows a highly significant correlation (p < 0.01) with pre-clinical cognitive effect experiments.
• The magnitude of the FLASH effect demonstrates a redundant system behavior, yielding consistent values across different parameter combinations.

Conclusions:

• A system based on oxygen-related effects can quantify many observed FLASH-radiation effects.
• The ODH methodology provides a robust framework for predicting tissue sparing in pulsed high-dose-rate exposures.
• This approach has the potential to enhance the precision and efficacy of advanced radiotherapy techniques.