Impact of recent change in NIST standard for 18F on the relative response of 68Ge-based mock syringe dose calibrator standards
Brian E. Zimmerman, Denis E. Bergeron, Jeffrey T. Cessna
As a result of a recent change in the National Institute of Standards and Technology (NIST) activity standard for 18F, we have determined new relative response ratios for a 68Ge solid epoxy mock syringe source used in activity calibrators as a long-lived substitute for 18F. New standardized solutions of each radionuclide were used to determine the response ratios while maintaining traceability to national standards. This work updates our previously published data from 2010. Materials and Methods: Following our previously published methodology, solution-filled mock syringe sources, identical in geometry to the solid 68Ge epoxy calibration source currently on the market, were prepared using NIST-calibrated solutions of 68GeCl4 and 18F-FDG and directly compared in several models of activity calibrators to determine empirically the relative response ratios for these two radionuclides. Results: The new relative response ratios measured in this study reflect the change in 18F activity measurements that arise from the recent -4 % change in the NIST activity standard. The results allow the 68Ge activity of the mock syringe source to be expressed in terms of equivalent 18F activity with a relative combined standard uncertainty of about 0.8 % for the activity calibrators used in this study. Conclusion: This work updates our previously-derived relative response ratios for 18F and 68Ge, allowing users of the commercial mock syringe surrogate source to calibrate their activity calibrators in a way that is consistent with the recent change in the NIST 18F standard.
, Bergeron, D.
and Cessna, J.
Impact of recent change in NIST standard for 18F on the relative response of 68Ge-based mock syringe dose calibrator standards, Journal of Nuclear Medicine
(Accessed May 28, 2023)