Standards for radioiodines.

Abstract

The National Institute of Standards and Technology, NIST (formerly National Bureau of Standards), is the nation's standards laboratory for civilian technology. NIST develops and maintains the nation's physical measurement standards for medical therapy and diagnostics. For the past 50 years, NIST has developed radioactivity Standard Reference Materials (SRMs) for radioiodines as well as decay-scheme data and test methods for use by the radiopharmaceutical manufacturers in their quality assurance and quality control at the point of manufacture. Methods of standardizing radioiodines include 4 pi beta-gamma coincidence counting (131I), 4 pi beta-gamma anti-coincidence counting (129I), 4 pi(e,x)-gamma coincidence counting (123I), and x-gamma sum peak coincidence counting (125I). NIST also uses sources standardized by these techniques to calibrate re-entrant ionization chambers (dose calibrators) and scintillation counters. SRMs of 131I and 125I are now available on an annual basis, and the long-lived 129I has recently been reissued.