TY - JOUR T1 - Standards for Cu-64 activity: a new national standard for the USA, links to international standards, and dose calibrator factors. JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1299 LP - 1299 VL - 58 IS - supplement 1 AU - Denis Bergeron AU - Jeffrey Cessna AU - Harrison Jacobs AU - Brian Zimmerman Y1 - 2017/05/01 UR - http://jnm.snmjournals.org/content/58/supplement_1/1299.abstract N2 - 1299Objectives: Copper-64 decays by positron emission, beta decay, and electron capture with a half-life just over 12 h. Interest in 64Cu stems mostly from its promise as a theranostic radionuclide. Copper nimbly coordinates to an assortment of complexing agents, allowing specific chemical targeting of biologically active sites. Its β- branch (≍ 38.5 %) provides significant local therapeutic dose (Eβmax ≍ 580 keV) while its β+ branch (≍ 17.5 %) allows for quantitative imaging by positron emission tomography (PET). To achieve meaningful quantitative imaging data requires standardization of data acquisition and analysis. Ideally, activity measurements are traceable to a national standard. The National Institute of Standards and Technology (NIST) has now established an activity standard for this important radionuclide.Methods: The large electron capture branch (≍ 44.0 %) makes the standardization of 64Cu challenging. The primary activity standardization was realized by live-timed anticoincidence counting (LTAC), with confirmatory measurements by two liquid scintillation counting techniques. The LTAC standardization achieved a 0.51 % total combined uncertainty on the activity. Through ionization chamber calibrations and participation in a comparison exercise, NIST established links to international standards. In addition, measurements were carried out to link radionuclide activity calibrator (i.e., “dose calibrator”) and well counter calibrations to the new standard.Results: The NIST activity standard for 64Cu agrees with the standard from the National Physical Laboratory (NPL; the national metrology institute for the United Kingdom) to 0.32 % ± 0.51 %. It agrees with the reference value established in a European intercomparison to within stated uncertainties. NIST determined dial settings for 5 commercial dose calibrators maintained at NIST, finding that measurements using the manufacturer-recommended dial settings returned activities that were 1.5 % to 2.4 % high.Conclusion: NIST reports a new activity standard for 64Cu. NIST-determined dose calibrator dial settings are reported. Measurements made with the manufacturers’ recommended dial settings for 64Cu return activities that are uniformly higher than the NIST standard activities, but agree to within the expanded (k = 2) uncertainties. NIST strives to disseminate accurate standards to increase confidence in clinical measurements, reduce measurement uncertainties, and facilitate standardization and intercomparability in quantitative molecular imaging. Research Support: ER -