Organ dose conversion coefficients based on a voxel mouse model and MCNP code for external photon irradiation

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Computational Biology

Background:

• Accurate organ absorbed dose estimation is vital for radiation effect evaluation.
• Existing models may not fully capture species-specific anatomical differences.
• Development of detailed computational models is essential for precise dosimetry.

Purpose of the Study:

• To present organ dose conversion coefficients from kerma free-in-air for external photon beams in a mouse model.
• To evaluate the impact of photon energy, irradiation geometry, and body size on organ absorbed dose.
• To provide data for improved radiation risk assessment in preclinical studies.

Main Methods:

• Development of a 3D voxel mouse model from cryosection images, segmenting 14 organs.
• Implementation of the voxel model in the Monte Carlo N-particle (MCNP) code.
• Monte Carlo simulations for calculating organ dose conversion coefficients across 22 photon energies and 5 geometries.

Main Results:

• Organ dose conversion coefficients were calculated for a range of photon energies (10 keV to 10 MeV) and irradiation conditions.
• Comparison with rat model data revealed similar trends for most organs, with notable differences in bone and skin.
• Organ dose sensitivity to body size and weight was observed, particularly at photon energies below 0.1 MeV.

Conclusions:

• The developed voxel mouse model provides valuable organ dose conversion coefficients for radiation research.
• Photon energy and body size significantly influence organ absorbed dose, especially at lower energies.
• These findings contribute to more accurate radiation effect evaluations and risk assessments in mice.