Effects of Partial-Body, Continuous/Pulse Irradiation at Dose Rates from FLASH to Conventional Rates on the Level of...

Area of Science:

• Radiation biology
• Mathematical modeling
• Radiobiology

Background:

• Understanding the impact of radiation dose rates on lymphocyte survival is crucial for radiation protection and therapy.
• Previous models did not fully capture the complex dynamics of pulsed irradiation across a range of dose rates.

Purpose of the Study:

• To develop and validate mathematical models predicting blood lymphocyte survival under various irradiation conditions.
• To investigate the dose rate effects on lymphocyte sparing in humans and mice, including FLASH and conventional rates.

Main Methods:

• Development of mathematical models based on established approaches for pulsed irradiation.
• Simulation of partial-body, two-pulse, and multiple-pulse irradiation scenarios.
• Comparison of model predictions with experimental data on lymphocyte and crypt survival.

Main Results:

• Models predict increased lymphocyte survival with higher dose rates, approaching an upper limit (1-vR).
• Optimal lymphocyte sparing observed at dose rates >= 40 Gy/s (humans) and >= 400 Gy/s (mice).
• Multiple-pulse irradiation showed decreased survival at lower rates, while two-pulse irradiation exhibited cyclical changes.

Conclusions:

• The developed models accurately describe lymphocyte sparing under different irradiation regimes.
• A correlation was found between blood lymphocyte survival and crypt survival in mice after abdominal irradiation.
• The study provides insights into optimizing radiation protocols for minimizing lymphocyte-induced toxicity.