On-site standardisation of Tb-149

The development of primary standards of activity of a radionuclide to the SI unit of the bequerel (Bq) is needed to provide confidence to end-users of the accuracy and robustness of their measurements. This is especially true of radionuclides destined for applications in Nuclear Medicine where the accurate activity of the radionuclide is important at the pre-clinical and clinical level for patient safety and treatment efficacy. Within the PRISMAP consortium, new production routes have resulted in the availability of novel radionuclides to researchers at activity and radionuclide purity levels not previously available. To provide confidence in the results that are produced from research being undertaken with these novel radionuclides new standards of activity for each radionuclide are required to enable the dissemination of traceability to national and international standards to these researchers. Whilst many of these novel radionuclides have radioactive half-lives suitable for transportation from production facilities to National Metrology Institutes, where the primary standards can be developed in ideal environments, some have half-lives that restrict the range they can be transported, and a different approach is required. This has required the development of transportable primary standardisation equipment that can be taken to the production facility to perform the standardisation on-site. Terbium-149, with its 4.12 h half-life, produced at the CERN-MEDICIS facility is one such radionuclide. This report details the challenge of the on-site standardisation of Tb-149 and how with the use of a transportable Defined Solid Angle alpha-particle counting system and a HPGe gamma-ray spectrometer the first on-site standardisation of Tb-149 was successfully achieved by the NPL at MEDICIS.