title: A new NIST primary standardization of 18F.
abstract: A new primary standardization of (18)F by NIST is reported. The standard is based on live-timed beta-gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST (3)H efficiency tracing; (ii) triple-to-double coincidence ratio (TDCR) counting; and (iii) NaI integral counting and HPGe γ-ray spectrometry. The results are reported as calibration factors for NIST-maintained ionization chambers (including some "dose calibrators"). The LS-based methods reveal evidence for cocktail instability for one LS cocktail. Using an ionization chamber to link this work with previous NIST results, the new value differs from the previous reports by about 4%, but appears to be in good agreement with the key comparison reference value (KCRV) of 2005.
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA. Electronic address: ryan.fitzgerald@nist.gov.
authors.forename: R
authors.initials: R
authors.lastname: Fitzgerald
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA.
authors.forename: B E
authors.initials: BE
authors.lastname: Zimmerman
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Bergeron
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Cessna
authors.affiliation: Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, MD 20899, USA.
authors.forename: L
authors.initials: L
authors.lastname: Pibida
authors.affiliation: Laboratório Nacional de Metrologia das Radiações Ionizantes, Comissão Nacional de Energia Nuclear, Avenida Salvador Allende, s/n, Recreio dos Bandeirantes, CEP 22783-127 Rio de Janeiro, RJ, Brazil.
authors.forename: D S
authors.initials: DS
authors.lastname: Moreira
keywords: Anticoincidence; CIEMAT/NIST; Dose calibrator; F-18; Fluorine-18; TDCR