Ga-68 Unit of Activity: Traceability to the Russian National Primary Radionuclide Activity Standard

Questions on the use of the radionuclide Ga-68 in the medical institutions of the Russian Federation for diagnosis of malignant tumors were examined. The task of precise measurement of Ga-68 activity in order to decrease dose loads for patients and enhance the effectiveness of the diagnosis is very important. Calibration of the mobile RIS-3A reference dose calculator to Ga-68 activity was studied. Various methods of calibration, ensuring traceability to the National Primary Standard of the units of radionuclide activity, the specific activity of radionuclides, and the stream of alpha and beta particles and photons of radionuclide sources in GET 6-2016 are: the method of direct comparison with a UeA-7 installation from GET 6-2016, using a sample of Ga-68 solution; and the use of a gamma spectrometer and sources based on other radionuclides with traceability of the unit of radionuclides to GeT 6-2016. The expanded uncertainty budgets of the calibration coefficient are presented for both calibration procedures, using the UeA-7 installation from GET 6-2016, and a gamma spectrometer with F-18. The convergence of the measurement results of Ga-68 activity on the reference dose calibrator, with calibration coefficients obtained by different methods, was evaluated. The results obtained confirm the applicability of the various calibration methods. The results of the study may find application in ensuring the traceability to GET 6-2016 of the units of activity of other promising radionuclides introduced into medical practice.