NATIONAL RADIOACTIVITY STANDARDS FOR BETA-EMITTING RADIONUCLIDES USEDIN INTRAVASCULAR BRACHYTHERAPY

The uses of beta-particle emitting radionuclides in therapeutic medici ne are rapidly expanding, To ensure the accurate assays of these nucli des prior to administration, radioactivity standards are needed. The N ational Institute of Standards and Technology (NIST), the national met rological standards laboratory for the United States, uses high-effici ency liquid scintillation counting to standardize solutions of such be ta emitters, including P-32, Sr-90/Y-90, and Re-188, Additional measur ements are made on radionuclidic impurities, half lives, and other dec ay-scheme parameters (such as branching decay ratios or gamma-ray abun dances) using HPGe detectors and reentrant ionization chambers. Follow ing such measurements at NIST, standards are disseminated in three way s: Standard Reference Materials (SRMs), calibrations for source manufa cturers, and calibration factors for commercial instruments, Uncertain ties in the activity calibrations for these nuclides are of the order of +/-0.5% (at approximately 1-standard deviation confidence intervals ). (C) 1998 Elsevier Science Inc.