Optimization of the ICRP 67 and NCRP 156 Transfer Rates Applied to Nonhuman Primates Intramuscularly Injected With...

Area of Science:

• Radiological Protection
• Biokinetics
• Nuclear Medicine

Background:

• Established models (ICRP 67, NCRP 156) with default parameters showed limitations in predicting americium (Am) biokinetics in nonhuman primates.
• Previous studies indicated default transfer rates explained early Am(NO3)3 behavior but failed for long-term retention due to physiological differences.

Purpose of the Study:

• To develop and validate new transfer rate parameters for wound and systemic models to improve americium biokinetic predictions in nonhuman primates.
• To address discrepancies observed between predicted and experimental data for intake and skeleton retention.

Main Methods:

• Utilized International Commission on Radiological Protection Report 67 and National Council on Radiation Protection and Measurements Report 156 models.
• Employed Integrated Modules for Bioassay Analysis (IMBA) software and its Uncertainty Analyzer companion program.
• Estimated new transfer rates using nonhuman primate experimental data from Durbin studies.

Main Results:

• Optimized transfer rate parameters successfully predicted americium intake in 66% of tested nonhuman primates.
• Skeleton retention predictions showed significant improvement, with differences between predicted and measured activity less than 20% in most cases.

Conclusions:

• The developed transfer rate parameters enhance the accuracy of biokinetic models for americium in nonhuman primates.
• These improved parameters are vital for more precise radiation dose assessments and understanding americium's behavior in primate models.