Activity standardisation of ¹⁶¹Tb.

Area of Science:

• Nuclear physics
• Radiochemistry
• Medical physics

Background:

• Terbium-161 (161Tb) is a radionuclide of increasing interest for targeted radiopharmaceutical therapy and medical imaging due to its advantageous decay properties.
• Accurate standardization of 161Tb is crucial for its reliable application in clinical settings and research.

Purpose of the Study:

• To standardize a 161Tb solution using multiple techniques to ensure accuracy and reliability.
• To assess the presence of 160Tb impurities in the 161Tb solution.

Main Methods:

• Standardization was performed using the beta-gamma coincidence counting technique with both analogue and digital electronics.
• The Triple-to-Double Coincidence Ratio (TDCR) method was also employed, with efficiency variations achieved through defocusing, grey filtering, and quenching.
• Monte Carlo simulations were utilized to calculate detection efficiencies for the measurements.

Main Results:

• The 161Tb solution contained 4.5 × 10^-3% of 160Tb impurities.
• Coincidence measurements using analogue electronics and TDCR methods showed good consistency.
• Results from analogue coincidence measurements and TDCR were compatible with digital coincidence results within experimental uncertainties.

Conclusions:

• The applied standardization methods confirm the reliable activity concentration of the 161Tb solution.
• The consistency across different measurement techniques validates the accuracy of the standardization.
• The standardized 161Tb solution is suitable for use as a reference material and in further medical research.