title: A Review of NIST Primary Activity Standards for (18)F: 1982 to 2013.
abstract: The new NIST activity standardization for (18)F, described in 2014 in Applied Radiation and Isotopes (v. 85, p. 77), differs from results obtained between 1998 and 2008 by 4 %. The new results are considered to be very reliable; they are based on a battery of robust primary measurement techniques and bring the NIST standard into accord with other national metrology institutes. This paper reviews all ten (18)F activity standardizations performed at NIST from 1982 to 2013, with a focus on experimental variables that might account for discrepancies. We have identified many possible sources of measurement bias and eliminated most of them, but we have not adequately accounted for the 1998-2008 results.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Denis E
authors.initials: DE
authors.lastname: Bergeron
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Cessna
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Bert M
authors.initials: BM
authors.lastname: Coursey
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Ryan
authors.initials: R
authors.lastname: Fitzgerald
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Zimmerman
keywords: F-18; anticoincidence; discrepancy; ionization chamber; liquid scintillation counting; primary standard