The National Institute of Standards and Technology (NIST) performed new
standardization measurements for 64Cu. As part of this work the
photon emission probabilities for the main gamma-rays and the half-life were
determined using several high purity germanium (HPGe) detectors. Half-life
determinations were also carried out with a NaI(Tl) well counter and two
pressurized ionization chambers.
The International Atomic Energy Agency (IAEA) has organized an international comparison to assess Single Photon Emission Computed Tomography (SPECT) image quantification capabilities in 12 countries. Iodine-131 was chosen as the radionuclide for the comparison because of its wide use around the world, but for logistical reasons solid 133Ba sources were used as a long-lived surrogate for 131I. For this study, we designed a set of solid cylindrical sources so that each site could have a set of phantoms (having nominal volumes of 2 mL, 4 mL, 6 mL, and 23 mL) with traceable activity calibrations so that the results could be properly compared. We also developed a technique using two different detection methods for individually calibrating the sources for 133Ba activity based on a National standard. This methodology allows for the activity calibration of each 133Ba source with a standard uncertainty on the activity of 1.4 % for the high-level 2-, 4-, and 6-mL sources and 1.7 % for the lower-level 23 mL cylinders. This level of uncertainty allows for these sources to be used for the intended comparison exercise, as well as in other SPECT image quantification studies.
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