Correlation Between Exposure Rate and Residual Activity in Felines Undergoing 131I Thyroid Ablation Therapy

Area of Science:

• Veterinary Medicine
• Nuclear Medicine
• Radiation Physics

Background:

• Radioiodine (I-131) therapy is standard for feline hyperthyroidism.
• High gamma-ray emissions necessitate patient isolation post-treatment.
• Current release criteria (≤ 20 μSv/h surface dose rate) don't directly address residual activity limits.

Purpose of the Study:

• To correlate feline thyroid burden and surface dose rates using Monte Carlo simulations.
• To standardize patient isolation time based on predicted residual activity.
• To develop a clinical protocol for estimating residual activity and ensuring regulatory compliance.

Main Methods:

• Monte Carlo computational radiation transport techniques were employed.
• Patient dose rates were measured over time to determine effective half-life.
• Model predictions were validated against experimental measurements.

Main Results:

• An average isolation of 8-9 days reduces residual activity to 3.7 MBq.
• Surface dose rates of ≤ 20 μSv/h correspond to ~925 kBq residual activity.
• A validated protocol was developed for clinical use.

Conclusions:

• The developed protocol aligns surface dose rate release criteria with regulatory limits.
• This standardization ensures patient safety and public health protection.
• The study provides a reliable method for managing radioiodine-treated felines.