Determination of the ¹⁶¹Tb half-life

Area of Science:

• Nuclear physics
• Radiochemistry
• Medical physics

Background:

• Terbium-161 (¹⁶¹Tb) is a promising radioisotope for targeted cancer therapy and diagnosis due to its decay properties.
• The current evaluated half-life of ¹⁶¹Tb (6.89(2) d) has significant uncertainty and has been recently challenged by new measurements.
• Accurate half-life determination is crucial for applications in nuclear medicine and nuclear forensics.

Purpose of the Study:

• To precisely measure the half-life of the ¹⁶¹Tb ground state decay.
• To address discrepancies in previously reported half-life values.
• To provide an accurate value for ¹⁶¹Tb half-life for improved applications.

Main Methods:

• Measurements were conducted at three independent laboratories in the UK and USA.
• Six independent determinations were performed using three distinct techniques: gamma-ray spectrometry, ionization chamber measurement, and liquid scintillation counting.
• Data analysis focused on precise determination of the decay rate over time.

Main Results:

• The measured half-life for ¹⁶¹Tb is 6.9637(29) days.
• This result confirms the 1% increase in half-life observed in recent studies.
• A significant difference (ζ-score = 3.1) was found between the results of this work and the IRA measurements.

Conclusions:

• The new half-life value of 6.9637(29) days for ¹⁶¹Tb is established.
• This refined value will improve the accuracy of activity calculations for ¹⁶¹Tb in therapeutic and diagnostic applications.
• Further investigation into the discrepancies between measurement techniques and laboratories may be warranted.