Dose conversion coefficients based on the Chinese mathematical phantom and MCNP code for external photon irradiation

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Computational Biology

Background:

• Accurate organ dose estimation is crucial for radiation protection.
• Existing conversion coefficients may not fully represent diverse populations, such as the Chinese.
• Mathematical phantoms are essential tools for simulating radiation interactions within the human body.

Purpose of the Study:

• To calculate organ-absorbed dose conversion coefficients specific to the Chinese population.
• To develop a Chinese mathematical phantom based on established methodologies and population data.
• To compare these new coefficients with existing international recommendations.

Main Methods:

• Development of a whole-body Chinese mathematical phantom.
• Utilizing Monte Carlo simulations with the MCNP code for dose calculations.
• Investigating the impact of physics models and tally types on calculation precision and efficiency.
• Simulating various irradiation geometries (anterior-posterior, posterior-anterior, lateral, rotational, isotropic).

Main Results:

• Conversion coefficients from kerma free-in-air to organ-absorbed dose were generated for photon energies from 10 keV to 10 MeV.
• Overall consistency with ICRP Publication 74 data was observed, with over 60% of values differing by less than 10%.
• Significant deviations were noted for superficial organs (up to 65.9%) and bone surfaces (up to 66%).

Conclusions:

• The Chinese mathematical phantom provides valuable organ dose conversion coefficients for the Chinese population.
• Discrepancies with ICRP74 data, particularly for superficial organs, may stem from kerma approximation at high energies.
• Anatomical differences between populations and calculation methodologies contribute to variations in bone surface dose conversion coefficients.