Potential improvements in brain dose estimates for internal emitters.

Area of Science:

• Radiological Sciences
• Biokinetics
• Dosimetry

Background:

• Element-specific biokinetic models are crucial for internal emitter dose reconstruction.
• Current models often aggregate diverse tissues, including the brain, into an "Other tissue" compartment.
• There is a growing need to enhance brain dosimetry due to increased interest in radiation effects on the brain.

Purpose of the Study:

• To evaluate the impact of explicitly modeling brain kinetics versus the "Other tissue" approach on internal emitter dosimetry.
• To assess potential improvements in brain dose estimation by incorporating specific brain biokinetic data.

Main Methods:

• Compared two versions of the International Commission on Radiological Protection (ICRP) biokinetic models for 10 elements.
• One version treated the brain as part of "Other tissue"; the modified version used explicit brain kinetics based on published data.
• Calculated injection dose coefficients for long-lived radioisotopes of each element using both model versions.

Main Results:

• Ratios of dose coefficients (explicit brain model vs. "Other tissue" model) varied significantly across radionuclides (e.g., 0.13 for 241Am to 3.3 for 210Pb).
• These findings demonstrate that neglecting explicit brain modeling can lead to substantial under- or overestimation of radiation dose.
• The accuracy of explicit brain dosimetry is contingent upon the quality of available brain-specific biokinetic data.

Conclusions:

• Explicitly modeling the brain in biokinetic models is recommended for more accurate dosimetry.
• This approach is particularly important for epidemiological studies investigating adverse effects of ionizing radiation on the brain.
• Prioritizing the inclusion of explicit brain compartments in radiation protection models is essential.