Organ dose conversion factors for murine galactic cosmic ray irradiation

Area of Science:

• Space radiation physics
• Radiation biology
• Astrobiology

Background:

• Galactic cosmic rays (GCR) pose significant radiation exposure risks for astronauts on deep space missions.
• Accurate prediction of radiation doses and biological impacts is essential for astronaut safety and mission planning, especially for Mars exploration.
• The GCRsim facility at NASA Space Radiation Laboratory simulates deep space radiation conditions for radiobiology studies.

Purpose of the Study:

• To introduce a series of Dose Conversion Factors (DCFs) for calculating absorbed radiation doses in mice irradiated at the GCRsim facility.
• To enable rigorous absorbed dose calculations for radiobiology studies relevant to astronaut radiation safety.

Main Methods:

• Developed a formalism for calculating organ-level and voxel-level radiation dose to a mouse phantom.
• Quantified DCFs for different GCRsim beam components and irradiation orientations.
• Utilized the PHITS Monte Carlo code to compute DCFs in units of Gy∙cm²∙ion^-1.

Main Results:

• Derived a library of murine DCFs using the PHITS Monte Carlo code for six irradiation orientations.
• Calculated absorbed doses to the murine total body and compared them with ion chamber measurements.
• Achieved agreement within 10% between calculated absorbed doses and physical measurements.

Conclusions:

• Developed and validated a library of DCFs for mouse irradiation at GCRsim against physical measurements.
• DCFs account for organ-specific dose variations from different GCRsim beam components.
• Enables improved assessments of radiogenic effects, enhancing astronaut safety for future deep space missions.